25-Hydroxyvitamin D3 Deficiency Independently Predicts Cognitive Impairment in Patients with Systemic Lupus Erythematosus

Sen Hee Tay; Chung Shun Ho; Roger Chun-Man Ho; Anselm Mak

doi:10.1371/journal.pone.0144149

Abstract

Objectives

Cognitive dysfunction has been reported in 20–80% of SLE patients. Converging evidence has indicated the importance of vitamin D as a neuroimmunomodulator for cognitive function. In this study, we evaluated the relationship between vitamin D and cognitive dysfunction.

Methods

Consecutive age- and gender-matched SLE patients and healthy controls (HCs) were administered Automated Neuropsychological Assessment Metrics in this cross-sectional study. The primary outcome was the total throughput score (TTS). Anxiety and depression were measured using the Hospital Anxiety and Depression Scale (HADS). Levels of 25-hydroxyvitamin D [25(OH)D₃ and total 25(OH)D] were measured using Liquid Chromatography-Tandem Mass Spectrometry.

Results

In total, 61 SLE patients and 61 HCs were studied. SLE patients scored significantly lower than HCs in the TTS (p = 0.004). There were no statistically significant differences in 25(OH)D₃ levels, total 25(OH)D levels and total 25(OH)D deficiency between SLE patients and HCs. However, more SLE patients had 25(OH)D₃ deficiency compared to HCs [12 (19.7%) versus 2 (3.3%), p = 0.003]. Deficiency of 25(OH)D₃ (β = -63.667, SE = 27.456, p = 0.025), but not other vitamin D variables, independently predicted worse TTS after adjusting for age, education, gender, ethnicity, HADS-Total, duration of SLE, SELENA-SLEDAI, SLICC/ACR Damage Index and cumulative steroid dose in SLE patients. Age (β = -4.261, SE = 0.866, p < 0.001) was the only predictor of TTS after adjusting for education, gender, ethnicity, HADS-Total, vitamin D levels or status in HCs.

Conclusions

Deficiency of 25(OH)D₃, a potentially modifiable risk factor, independently predicted cognitive impairment in SLE patients.

Citation: Tay SH, Ho CS, Ho RC-M, Mak A (2015) 25-Hydroxyvitamin D₃ Deficiency Independently Predicts Cognitive Impairment in Patients with Systemic Lupus Erythematosus. PLoS ONE 10(12): e0144149. https://doi.org/10.1371/journal.pone.0144149

Editor: Jose Crispin, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, MEXICO

Received: October 16, 2015; Accepted: November 13, 2015; Published: December 4, 2015

Copyright: © 2015 Tay et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Data Availability: The data set cannot be made publicly available for ethical reasons because public availability would compromise participant privacy. Excerpts of data may be available on request from the corresponding author, subject to seeking additional ethical approval for the release of data from NHG Domain Specific Review Board E (reference code: 2011/01764).

Funding: The authors received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Systemic lupus erythematosus (SLE) is a chronic, systemic, relapsing-remitting autoimmune disease of unknown etiology with heterogeneous manifestations, including diverse neuropsychiatric (NP) manifestations [1]. Neurologic and psychiatric syndromes, collectively referred to as neuropsychiatric systemic lupus erythematosus (NPSLE), occur frequently in patients with SLE [2]. Approximately one-third of NP events are directly attributable to SLE, although the attribution rates vary between individual manifestations [2]. Over the past few decades, as the longevity of SLE patients has increased, NPSLE has been identified as one of the important factors negatively affecting of survival of SLE patients over the past 50 years [1, 3]. Among the 19 NPSLE syndromes identified by the American College of Rheumatology (ACR) Ad Hoc Committee on Neuropsychiatric Lupus Nomenclature, cognitive dysfunction is the most prevalent manifestation of NPSLE and has been reported in up to 20–80% of SLE patients [3, 4]. The variability in the frequency of cognitive dysfunction is due to several factors, including bias in selection of patients for study and operational decisions regarding the definition of cognitive dysfunction [5]. Cognitive impairment scores as an item in the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) Damage Index [6]. Accrual of such damage from cognitive dysfunction translates to increased negative impact on health-related quality of life and unemployment rates [7, 8].

Identifying nutritional factors that may mitigate cognitive dysfunction and help preserve higher-level cognitive abilities has significant economic and public health benefits [9]. Epidemiological studies within the general population have demonstrated that vitamin D deficiency is a potential risk factor for cognitive impairment [10, 11]. It has also become recently apparent that vitamin D deficiency contributes to the disease activity and morbidity of SLE [12]. Vitamin D is available in 2 distinct forms, vitamin D₂ (ergocalciferol) and vitamin D₃ (cholecalciferol) [13]. The 2011 Institute of Medicine report concluded that serum 25(OH)D is the most useful marker for vitamin D nutriture, without distinguishing between 25(OH)D₂ and 25(OH)D₃ forms [14]. However, as vitamin D₃ is more effective than vitamin D₂ in raising 25(OH)D concentrations and experimental evidence has revealed that binding of 1,25(OH)₂D₃ to its cognate nuclear vitamin D receptor (VDR) represents an important molecular event, we hypothesize that measurement of 25(OH)D₃ represents a more accurate estimation of in vivo vitamin D status and may thus affect cognitive function in SLE patients [13]. To our knowledge, the relationship between vitamin D and cognitive function in patients with SLE has never been addressed. We undertook this study to evaluate the relationship between 25(OH)D₃, traditional neuropsychological and SLE-specific risk factors and cognitive dysfunction in a multiethnic Asian population living close to the equator.

Patients and Methods

Subjects

Adult SLE patients attending the outpatient clinics of National University Hospital (NUH), Singapore, between 2011 and 2014 who fulfilled at least 4 of the ACR 1997 revised classification criteria were invited to participate in this study [15]. Objectively documented cognitive dysfunction or other NP events were not required for inclusion. Exclusion criteria included the following: (i) patients with known intellectual disability or previous stroke with resultant neuromuscular dysfunction; (ii) subjects who were pregnant; (iii) subjects less than 21 years of age and (iv) subjects who had active infections at the time of recruitment. Community-derived healthy controls (HCs) were recruited using poster advertisement in the hospital or were the nursing staff of NUH. The HCs were selected for the absence of any acute or chronic psychiatric, neurologic or medical conditions. Those who required medications which could alter cognitive function were excluded. All subjects had completed at least primary school education with adequate English fluency. The study was approved by NHG Domain Specific Review Board E (reference code: 2011/01764) and was carried out in accordance with the principles of the Declaration of Helsinki. All subjects gave written informed consent prior to study inclusion.

Study design

The study was cross-sectional in design. Consecutive SLE patients and community-derived HCs matched by age (± 5years) and gender were recruited.

SLE-related disease characteristics

Demographic and relevant clinical data were extracted from the medical records of SLE patients. NP events were compiled by the study rheumatologists (S.H. Tay and A. Mak). Global SLE disease activity and SLE-related disease damage were assessed using the Safety of Estrogens in Lupus Erythematosus National Assessment (SELENA)-modified SLE Disease Activity Index (SLEDAI) and the SLICC/ACR Damage Index, respectively [6, 16].

Psychopathology questionnaire

The Hospital Anxiety and Depression Scale (HADS) was used to assess self-reported symptoms of anxiety and depression. It is a 14-item multiple-choice questionnaire which comprises two 7-item subscales for measuring anxiety (HADS-Anxiety) and depression (HADS-Depression). Scores range from 0–21 for each subscale. A cut-off score of ≥ 8 on either subscale is used to define clinical anxiety and depression [17]. Summing scores across both subscales generates a total psychopathology score (HADS-Total).

Neuropsychological test and definition of cognitive dysfunction

Cognitive function was evaluated using Automated Neuropsychological Assessment Metrics (ANAM), version 4.3 (Vista LifeSciences Inc, Denver, CO, US). The ANAM is a self-administered computer battery of tests to assess neurocognitive efficiency and it is less sensitive to confounding effects of education, English language proficiency and ethnic differences than traditional neuropsychological testing [18]. ANAM tests selected for this study included simple reaction time (neuromuscular response efficiency, 40 trials) and 8 tests: (i) code substitution-learning (learning and recall, 72 trials); (ii) code substitution-immediate (learning and recall, 36 trials); (iii) code substitution-delayed (learning and recall, 36 trials); (iv) spatial processing (visual perception and mental rotation, 20 trials); (v) matching to sample (short-term memory, attention and visual-spatial discrimination, 20 trials); (vi) running memory continuous performance test (CPT) (sustained attention, 80 trials); (vii) mathematical processing (working memory, 20 trials) and (viii) memory search (working memory, 40 trials). Each ANAM test generates a “throughput” (TP) measure, which is sensitive to cognitive performance, incorporates speed and accuracy in one variable and more closely conforms to a normal distribution than other ANAM measures [19]. The primary outcome of our study was the total throughput score (TTS), which is the total of the throughput scores for each of the 8 ANAM tests [20]. Cognitive dysfunction was defined as TTS < 1.5 SD below the mean of the HCs [20].

Assay of 25(OH)D₃ and definition of vitamin D deficiency

Quantitative determination of serum 25(OH)D₃ was performed at an external laboratory (Prince of Wales Hospital, Hong Kong SAR, China) using liquid chromatography-tandem mass spectrometry (LC-MS/MS) as the candidate reference method to measure both 25(OH)D₃ and total 25(OH)D [25(OH)D₂ + 25(OH)D₃] [21]. Processed serum was stored at -80°C until retrieval for analyses. Total 25(OH)D was also measured using the Roche Elecsys vitamin D total assay immediately after collection at the local laboratory of NUH. Vitamin D status was operationally defined as deficiency < 10 ng/mL, insufficient 10–29 ng/mL and sufficient ≥ 30 ng/mL as per the clinical laboratory reference ranges of NUH.

Study procedures

For each subject, HADS, ANAM, and if applicable, SELENA-SLEDAI and SLICC/ACR Damage Index were assessed on the day when serum samples were collected.

Statistical methods

As most of the published normative data are for young men (because ANAM was developed by the US Department of Defense) and since SLE patients could not be their own controls in a cross-sectional study; therefore, a control group was required to assess (i) prevalence of cognitive dysfunction and (ii) the association of vitamin D deficiency with cognitive impairment in SLE patients [22, 23]. 25(OH)D₃ and total 25(OH)D levels were examined as continuous variables and also as deficient, insufficient and sufficient categorical variables. Multiple linear regression was used to identify independent predictors for TTS and to test for group differences in the TTS while adjusting for potential confounders. In all models, we controlled for baseline confounders including age, education, gender, ethnicity and HADS-Total. In the fully adjusted model, we adjusted for SLE-specific variables that have been identified as potential confounders in studies of cognition: duration of SLE, SELENA-SLEDAI, SLICC/ACR Damage Index and cumulative steroid dose. To ascertain the validity of the regression equations, only independent variables of tolerance > 0.4 were accepted into the final regression model. Statistical significance was defined as a two-tailed p value of < 0.05. All statistical analyses were performed with SPSS, version 23.0 (IBM Corp, Armonk, NY, US).

Results

Characteristics of SLE patients and healthy controls

In total, 61 SLE patients and 61 HCs were studied. The SLE patients and HCs were comparable in terms of age, gender and body mass index (Table 1). However, there were statistically significant differences in ethnicity and duration of education [SLE patients: 12.0 years (Q1; Q3 10.0; 15.0) versus HCs: 16.0 years (Q1; Q3 14.0; 18.0), p < 0.001]. SLE patients had the following characteristics: 83.6% female; median age 36.0 (Q1; Q3 26.0; 48.5); SLE duration 6.0 years (Q1; Q3 0.0; 12.0); SELENA-SLEDAI 4.0 (Q1; Q3 2.0; 5.0) and SLICC/ACR Damage Index 0.0 (Q1; Q3 0.0; 1.0) (Tables 1 and 2). Fifty-six (91.8%) of the 61 SLE patients were taking prednisolone [median dosage 7.5 mg/day (Q1; Q3 4.5; 16.3)] with a cumulative prednisolone dose of 15.9 gm (Q1; Q3 7.4; 26.9) (Table 2). Twelve (19.7%) of the 61 SLE patients had at least 1 NP event but no patient had documented cognitive dysfunction (Table 2). Psychopathology parameters which included HADS-Anxiety, HADS-Depression and HADS-Total were significantly higher in SLE patients than those of HCs [HADS-Anxiety: 8.0 (Q1; Q3 4.5; 9.0) versus 5.0 (Q1; Q3 2.5; 8.0), p = 0.001; HADS-Depression: 3.0 (Q1; Q3 2.0; 6.0) versus 2.0 (Q1; Q3 1.0; 3.0), p < 0.001; HADS-Total: 11.0 (Q1; Q3 7.5; 15.0) versus 7.0 (Q1; Q3 3.0; 10.5), p < 0.001] (Table 1). Significantly more SLE patients had clinical anxiety (50.8% versus 26.2%, p = 0.005) and depression (14.8% versus 1.6%, p = 0.008) than HCs (Table 1).

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Table 1. Demographics, clinical and psychological characteristics of SLE patients versus healthy controls.

Data are no./no. assessed (%) or median (interquartile range).

https://doi.org/10.1371/journal.pone.0144149.t001

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Table 2. Cumulative clinical features of SLE patients at time of study recruitment.

Data are no./no. assessed (%) or median (interquartile range).

https://doi.org/10.1371/journal.pone.0144149.t002

Vitamin D levels and status

The levels and status of vitamin D in patients with SLE and HCs are shown in Table 1. SLE patients were more likely than HCs to use any vitamin D supplements (93.4% versus 19.7%, p < 0.001), particularly vitamin D₂ supplements (13.1% versus 0.0%, p < 0.001). Total 25(OH)D levels were similar using LC-MS/MS and Roche Elecsys vitamin D total assay methods and did not differ between SLE patients and HCs. There was no significant difference in 25(OH)D₃ levels between SLE patients and HCs. The prevalence of total 25(OH)D deficiency was similar in SLE patients and HCs (8.2% versus 3.3%, p = 0.224). However, significantly more SLE patients than HCs had 25(OH)D₃ deficiency (19.7% versus 3.3%, p = 0.003).

Group differences in performance on ANAM testing

Throughput scores for each of the ANAM tests and TTS for SLE patients and HCs are summarized in Table 3. After adjusting for age, education, gender, ethnicity and HADS-Total, SLE patients scored significantly lower than HCs in 4 of the ANAM tests (code substitution-learning, p = 0.013; code substitution-immediate, p = 0.012; code substitution-delayed, p = 0.025; matching to sample, p = 0.026) and in the TTS (p = 0.004) (Fig 1). Simple reaction time and running memory CPT did not differ significantly between both groups. Twenty-one (34.4%) of the 61 SLE patients were identified as having cognitive dysfunction by ANAM in comparison with 1 (1.6%) of 61 HCs (p < 0.001).

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Fig 1. Mean throughput scores in SLE patients and HCs.

Higher scores represent better performance. The individual test data points for each group are connected for illustration purposes only. *P<0.05; **P<0.01.

https://doi.org/10.1371/journal.pone.0144149.g001

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Table 3. Comparison of ANAM throughput scores for SLE patients and healthy controls.

Data are no./no. assessed (%) or mean (standard deviation).

https://doi.org/10.1371/journal.pone.0144149.t003

Vitamin D deficiency and cognitive function

Multiple linear regression models were constructed for all subjects, and for HCs and SLE patients which were analyzed separately (Tables 4, 5 and 6). Age and SLE status were negative predictors for cognitive function in the regression model for all subjects, and age (β = -4.261, SE = 0.866, p < 0.001) was the only predictor for cognitive function in the HC group. Deficiency of 25(OH)D₃, but not other vitamin D variables, independently predicted worse cognitive function in the final regression models for all subjects (β = -46.977, SE = 21.949, p = 0.035) and SLE patients (β = -63.667, SE = 27.456, p = 0.025). Mean TTS varied significantly by 25(OH)D₃ status in SLE patients (one-way ANOVA, F(2,52) = 3.73, p = 0.031) (Fig 2). Chinese ethnicity was significantly associated with higher TTS in the SLE group. Age, education, HADS-Total and 25(OH)D₃ levels did not differ significantly amongst the different ethnicities in the SLE group (one-way ANOVA, p > 0.05). The study sample was also analyzed for potential associations between cognitive performance and other clinical characteristics. There was no significant association between SLE patients with cognitive dysfunction and anti-dsDNA levels, stroke or antiphospholipid antibodies. Levels of 25(OH)D₃ correlated negatively with the SLICC/ACR Damage Index (r = -0.326, p = 0.015) but not with the SELENA-SLEDAI.

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Fig 2. Total throughput scores in relation to 25(OH)D₃ status in SLE patients.

Box represents 25^th and 75^th percentiles, horizontal line represents the median, error bars show the 5^th and 95^th percentile and outside values are shown as dots. F(2,52) = 3.73, p = 0.031.

https://doi.org/10.1371/journal.pone.0144149.g002

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Table 4. Results of multiple linear regression analysis between total throughput score and demographic, neuropsychological and clinical variables for 61 SLE patients and 61 healthy controls.

https://doi.org/10.1371/journal.pone.0144149.t004

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Table 5. Results of multiple linear regression analysis between total throughput score and demographic, neuropsychological and clinical variables for 61 healthy controls.

https://doi.org/10.1371/journal.pone.0144149.t005

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Table 6. Results of multiple linear regression analysis between total throughput score and demographic, neuropsychological and clinical variables for 61 SLE patients.

https://doi.org/10.1371/journal.pone.0144149.t006

Discussion

The current study demonstrated that 25(OH)D₃ deficiency independently predicted worse cognitive function, irrespective of the measured potential confounders. The association between cognitive function and 25(OH)D₃ but not with total 25(OH)D is in accordance with our hypothesis that 25(OH)D₃ represents a more accurate estimation of in vivo vitamin D status to affect cognitive function. Our study also confirmed that SLE patients had poorer cognitive performance on ANAM assessment compared to HCs [5, 22]. Some notable points of our study include: (i) SLE patients in the current study were not selected based on the presence and absence of NP manifestations; (ii) SLE patients had mild disease activity and disease-related damage and (iii) the absence of difference between groups in simple reaction time and running memory CPT mitigated differential effects on fatigue and inattentiveness on ANAM performance between the two groups. Thus, the inferior cognitive performance amongst the SLE patients compared to HCs in this study sample is particularly striking. While a single pattern of SLE-attributed cognitive dysfunction has not been found, commonly reported cognitive domains which are abnormal in patients with SLE include overall cognitive slowing, decreased attention, executive dysfunction and impaired working memory to suggest subcortical brain involvement reminiscent of white matter dementias; whereas, vitamin D has been associated with associated with several beneficial measures on cognitive domains associated with subcortical function, such as processing speed, attention and executive function [3, 9, 24].

Recent evidence has suggested a link between low vitamin D levels and impaired brain functioning. 25(OH)D₃ crosses the blood-brain barrier to reach VDRs which are present on neurons and glial cells of the central nervous system (CNS), often co-localized in cells expressing 1α-hydroxylase [25, 26]. There is conversion of 25(OH)D₃ to the biologically active 1,25(OH)₂D₃ in the CNS, qualifying vitamin D as a neurosteroid [27, 28]. The physiological properties of neurosteroids are diverse and differ temporally and regionally within the brain [27]. In line with this, neonatal rats exposed to vitamin D deficiency during brain development show changes in brain structure and neurochemistry [29]. 1,25(OH)₂D₃ has effects on neurotrophic function, neuroprotection and neuroimmunomodulation in vitro [10, 30]. 1,25(OH)₂D₃ upregulates synthesis of nerve growth factor, neurotropin 3 and low-affinity p75_NTR receptors [10, 30]. It regulates the intra-neuronal calcium homeostasis via voltage-gated calcium channels and exhibits neuroprotective properties against glutamate toxicity through antioxidant effects [30, 31]. Lastly, 1,25(OH)₂D₃ inhibits the expression of major histocompatibility complex class II proteins and sensitizes inflammatory cells to apoptotic signals [10, 30]. Functionally, the substantial expression of VDRs in the cortex and hippocampus suggests a potentially significant impact of 25(OH)D₃ on cognition [32]. Therefore, these observations support the pharmacological potential of 25(OH)D₃ in neuroimmunological and neurodegenerative disease management strategies [30]. Two recent meta-analyses of observational studies have concluded the potential positive effects of vitamin D in cognitive function [10, 11]. Herein, we argue that the use of vitamin D₂ in some of the earlier studies to be study weaknesses as vitamin D₂ administration may lead to reduction of 25(OH)D₃ [33].

Vitamin D has a spectrum of immunoregulatory actions, many of which have been found to oppose the observed immunological aberrations in SLE [34, 35]. VDRs are expressed on immune cells of the innate and adaptive immune systems, including monocytes, macrophages,dendritic cells and lymphocytes [36]. These immune cells express 1α-hydroxylase to convert vitamin D to its biologically active form, 1,25(OH)₂D₃, for paracrine or autocrine signaling in the local immunologic milieu [36, 37]. 1,25(OH)₂D₃ binds to the VDR which acts as a transcription factor to determine a genomic response that regulates the transcription of 229 genes [38]. These VDR binding sites are significantly enriched near autoimmune genes identified from genome-wide association studies [38]. 1,25(OH)₂D₃ promotes chemotaxis and phagocytosis of macrophages which are important for the clearance of apoptotic cells [34]. 1,25(OH)₂D₃ potently inhibits type I IFN-mediated pathway of monocyte differentiation into dendritic cells [39]. By modulating the activation, maturation and survival of dendritic cells, 1,25(OH)₂D₃ affects the phenotype and function of interacting T cells by skewing the T cell compartment to a more anti-inflammatory and regulatory state, leading to the inhibition of Th1 and Th17 cells and induction of Th2, natural killer T and T regulatory cells [12, 40]. 1,25(OH)₂D₃ induces apoptosis in activated B cells and inhibits the generation of plasma cells and memory B cells [41]. Isolated peripheral blood mononuclear cells from SLE patients incubated with 1,25(OH)₂D₃ significantly reduced cell proliferation, as well as polyclonal and anti-dsDNA immunoglobulin production [42]. In sum, the in vitro data suggests a potential role of vitamin D in mitigating the pro-inflammatory pathogenic pathways of autoimmune diseases such as SLE.

Vitamin D deficiency is common in patients with SLE. It is estimated that between 8–30% of SLE patients have vitamin D deficiency during the course of the disease [12]. As Singapore lies 1° north of the equator and receives 12 hours of sunlight a day throughout the year, this study population provides a unique opportunity to evaluate vitamin D status in the absence of seasonal variation in ultraviolet B (UVB) exposure [43]. Although a single 20 min exposure of the summer sun of a fair-skinned individual can help synthesize 20,000 units of vitamin D₃, 8.2% of SLE patients in this study were deficient in vitamin D despite supplementation [37]. This may be due to use of photo-protection, urinary loss of total 25(OH)D, medications and anti-vitamin D antibodies [35, 44]. SLE patients with active disease or cognitive dysfunction may be less inclined to spend time outdoors, as an example of reverse causality. However, most of our patients were in good health at the time of assessment with low SELENA-SELDAI scores. A recent randomized, placebo-controlled trial with vitamin D₃ failed to diminish the interferon signature in SLE patients with total 25(OH)D levels ≤ 20 ng/mL [36]. Nonetheless, a modest improvement of SELENA-SLEDAI in the presence of higher total 25(OH)D levels has been demonstrated in SLE patients with total 25(OH)D levels < 40 ng/mL in a cohort study [45]. The larger sample size of the study by Petri et al. might explain why we were unable to find a relationship between 25(OH)D₃ levels and SELENA-SLEDAI in our study [45].

More work is required to address the clinical relevance of and potential relationship between vitamin D deficiency and cognitive dysfunction in SLE patients. T2-weighted white matter hyperintensities localized to the periventricular and subcortical white matter on magnetic resonance imaging (MRI) of the brain have been described in subjects with vitamin D deficiency and SLE-attributed cognitive dysfunction [3, 46]. The clinical relevance of these T2-weighted white matter hyperintensities is related to the disruption of cortico-subcortical white matter tracts that connect brain regions important for subserving cognitive function [46]. Newly diagnosed SLE patients with no focal neurological symptoms who underwent ¹⁸F-fluorodeoxyglucose (¹⁸FDG) positron emission tomography had increased ¹⁸FDG uptake in the white matter, indicative of inflammatory activity [47]. This suggests that cognitive dysfunction in SLE might result from white matter inflammation as an inciting pathology with subsequent white matter tract damage [3]. The capabilities of sophisticated MRI techniques such as diffusion-tensor imaging (DTI) and spectroscopy which detect microstructural and metabolic abnormalities respectively may assist to further the understanding of hypovitaminosis D-related cognitive dysfunction in SLE [48]. The positive association with vitamin D levels and the integrity of white fibers using DTI can potentially explain our findings of higher SLICC/ACR Damage Index in SLE patients with lower 25(OH)D₃ levels [49].

The current study has several limitations. First, the study sample was not matched for potential confounders of education and ethnicity. However, more stringent specifications would lead to a smaller sample size, but inclusion of both variables in the multiple regression models for all analyses would partially compensate for this. Second, traditional neuropsychological testing was not performed to look for clinical behavioral correlates of the abnormalities found on ANAM testing. ANAM has been validated for use in SLE to assess cognitive function and demonstrates both good sensitivity (76.2%) and specificity (82.8%) in classifying SLE patients with probable versus no impairment on traditional neuropsychological testing [18, 50]. Although ANAM does not measure complex aspects of memory, language and visuospatial functions, factor analyses have demonstrated that both ANAM and traditional neuropsychological tests measure similar underlying cognitive domains, including processing speed, working memory and resistance to interference [50, 51]. Further, ANAM provides more sensitive assessment of information processing speed and complex attention functions, which are not well assessed with traditional neuropsychological testing [18]. More importantly for this study, each ANAM test can be computer scored to yield a summary statistic, the total throughput score (TTS), to assess overall neurocognitive efficiency as a surrogate of overall cognitive impairment (i.e. brain health) of SLE patients [5, 20]. This summary statistic allowed for multiple linear regression for us to identify 25(OH)D₃ deficiency as an independent negative predictor for TTS. On the other hand, the ACR neuropsychological battery is composed of different instruments assessing domains of simple attention, complex attention, reasoning and/or problem solving, executive functions, memory, visual-spatial processing and psychomotor speed [52]. These instruments were developed by different agencies and the scores from different instruments cannot be combined into a single summary statistic. As a result, outputs from traditional neuropsychological testing are not compatible with such analysis. The Cognitive Symptom Inventory (CSI) has been recommended as a screening tool for SLE patients suspected of having cognitive impairment in research and clinical settings; however, later studies indicated that the CSI alone is insufficient to accurately determine the likelihood of significant cognitive impairment [52, 53]. Rather, cognitive complaints reported in the CSI are influenced by the presence of anxiety and depression [53]. Lastly, although we did not have baseline levels of 25(OH)D₃ in our subjects before study entry, a one-time assessment of total 25(OH)D levels has been shown to moderately reflect vitamin D status of individuals over an approximately 5-year period [54].

To our knowledge, this study is the first report which addressed the potential relationship between vitamin D levels and cognitive function in SLE patients. The association between 25(OH)D₃ deficiency and cognitive impairment in SLE is novel and may provide further insights into the pathophysiological impact of vitamin D on cognitive dysfunction. The effects of the VDR likely depend on adequate concentrations of 25(OH)D₃ as a substrate, which makes vitamin D levels or status a crucial factor in the normal functioning of the nervous and immune systems. Further prospective studies are warranted to clarify if SLE patients with 25(OH)D₃ deficiency are more likely to experience cognitive dysfunction and whether the correction of 25(OH)D₃ deficiency with vitamin D₃ supplementation could improve or even prevent the process of cognitive dysfunction amongst SLE patients.

Acknowledgments

The authors wish to express their appreciation to the following individuals: Tung Lin Lee for helping with the study assessments; Nien Yee Kow for technical assistance in the laboratory; Hung Chew Wong for statistical support; and finally, the patients and controls who participated in this study.

Author Contributions

Conceived and designed the experiments: SHT RCH AM. Performed the experiments: SHT CSH AM. Analyzed the data: SHT AM. Contributed reagents/materials/analysis tools: CSH. Wrote the paper: SHT CSH RCH AM.

References

1. Jeltsch-David H, Muller S. Neuropsychiatric systemic lupus erythematosus: pathogenesis and biomarkers. Nat Rev Neurol. 2014;10:579–96. pmid:25201240
- View Article
- PubMed/NCBI
- Google Scholar
2. Hanly JG, Su L, Urowitz MB, Romero-Diaz J, Gordon C, Bae SC, et al. Mood Disorders in Systemic Lupus Erythematosus: Results From an International Inception Cohort Study. Arthritis Rheumatol. 2015;67:1837–47. pmid:25778456
- View Article
- PubMed/NCBI
- Google Scholar
3. Tay SH, Mak A. Anti-NR2A/B Antibodies and Other Major Molecular Mechanisms in the Pathogenesis of Cognitive Dysfunction in Systemic Lupus Erythematosus. Int J Mol Sci. 2015;16:10281–300. pmid:25955648
- View Article
- PubMed/NCBI
- Google Scholar
4. The American College of Rheumatology nomenclature and case definitions for neuropsychiatric lupus syndromes. Arthritis Rheum. 1999;42:599–608. pmid:10211873
- View Article
- PubMed/NCBI
- Google Scholar
5. Hanly JG, Omisade A, Su L, Farewell V, Fisk JD. Assessment of cognitive function in systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis by computerized neuropsychological tests. Arthritis Rheum. 2010;62:1478–86. pmid:20155829
- View Article
- PubMed/NCBI
- Google Scholar
6. Gladman D, Ginzler E, Goldsmith C, Fortin P, Liang M, Urowitz M, et al. The development and initial validation of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology damage index for systemic lupus erythematosus. Arthritis Rheum. 1996;39:363–9. pmid:8607884
- View Article
- PubMed/NCBI
- Google Scholar
7. Panopalis P, Julian L, Yazdany J, Gillis JZ, Trupin L, Hersh A, et al. Impact of memory impairment on employment status in persons with systemic lupus erythematosus. Arthritis Rheum. 2007;57:1453–60. pmid:18050187
- View Article
- PubMed/NCBI
- Google Scholar
8. Tam LS, Wong A, Mok VC, Zhu YE, Kwok LW, Li TK, et al. The relationship between neuropsychiatric, clinical, and laboratory variables and quality of life of Chinese patients with systemic lupus erythematosus. J Rheumatol. 2008;35:1038–45. pmid:18464308
- View Article
- PubMed/NCBI
- Google Scholar
9. Buell JS, Scott TM, Dawson-Hughes B, Dallal GE, Rosenberg IH, Folstein MF, et al. Vitamin D is associated with cognitive function in elders receiving home health services. J Gerontol A Biol Sci Med Sci. 2009;64:888–95. pmid:19377013
- View Article
- PubMed/NCBI
- Google Scholar
10. Etgen T, Sander D, Bickel H, Sander K, Forstl H. Vitamin D deficiency, cognitive impairment and dementia: a systematic review and meta-analysis. Dement Geriatr Cogn Disord. 2012;33:297–305. pmid:22759681
- View Article
- PubMed/NCBI
- Google Scholar
11. Balion C, Griffith LE, Strifler L, Henderson M, Patterson C, Heckman G, et al. Vitamin D, cognition, and dementia: a systematic review and meta-analysis. Neurology. 2012;79:1397–405. pmid:23008220
- View Article
- PubMed/NCBI
- Google Scholar
12. Yap KS, Morand EF. Vitamin D and systemic lupus erythematosus: continued evolution. Int J Rheum Dis. 2015;18:242–9. pmid:25522756
- View Article
- PubMed/NCBI
- Google Scholar
13. Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr. 2006;84:694–7. pmid:17023693
- View Article
- PubMed/NCBI
- Google Scholar
14. Institute of Medicine Committee to Review Dietary Reference Intakes for Vitamin D, Calcium. The National Academies Collection: Reports funded by National Institutes of Health. In: Ross AC, Taylor CL, Yaktine AL, Del Valle HB, editors. Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US) National Academy of Sciences.; 2011.
15. Hochberg MC. Updating the American College of Rheumatology revised criteria for the classification of systemic lupus erythematosus. Arthritis Rheum. 1997;40:1725.
- View Article
- Google Scholar
16. Petri M, Kim MY, Kalunian KC, Grossman J, Hahn BH, Sammaritano LR, et al. Combined oral contraceptives in women with systemic lupus erythematosus. N Engl J Med. 2005;353:2550–8. pmid:16354891
- View Article
- PubMed/NCBI
- Google Scholar
17. Tay SH, Cheung PP, Mak A. Active disease is independently associated with more severe anxiety rather than depressive symptoms in patients with systemic lupus erythematosus. Lupus. 2015;24:1392–9. pmid:26085594
- View Article
- PubMed/NCBI
- Google Scholar
18. Holliday SL, Navarrete MG, Hermosillo-Romo D, Valdez CR, Saklad AR, Escalante A, et al. Validating a computerized neuropsychological test battery for mixed ethnic lupus patients. Lupus. 2003;12:697–703. pmid:14514133
- View Article
- PubMed/NCBI
- Google Scholar
19. Brunner HI, Klein-Gitelman MS, Zelko F, Thomas EC, Hummel J, Nelson SM, et al. Validation of the Pediatric Automated Neuropsychological Assessment Metrics in childhood-onset systemic lupus erythematosus. Arthritis Care Res (Hoboken). 2013;65:372–81.
- View Article
- Google Scholar
20. Antonchak MA, Saoudian M, Khan AR, Brunner HI, Luggen ME. Cognitive dysfunction in patients with systemic lupus erythematosus: a controlled study. J Rheumatol. 2011;38:1020–5. pmid:21459946
- View Article
- PubMed/NCBI
- Google Scholar
21. Ong L, Saw S, Sahabdeen NB, Tey KT, Ho CS, Sethi SK. Current 25-hydroxyvitamin D assays: do they pass the test? Clin Chim Acta. 2012;413:1127–34. pmid:22465235
- View Article
- PubMed/NCBI
- Google Scholar
22. Petri M, Naqibuddin M, Carson KA, Sampedro M, Wallace DJ, Weisman MH, et al. Cognitive function in a systemic lupus erythematosus inception cohort. J Rheumatol. 2008;35:1776–81. pmid:18634154
- View Article
- PubMed/NCBI
- Google Scholar
23. Annweiler C, Allali G, Allain P, Bridenbaugh S, Schott AM, Kressig RW, et al. Vitamin D and cognitive performance in adults: a systematic review. Eur J Neurol. 2009;16:1083–9. pmid:19659751
- View Article
- PubMed/NCBI
- Google Scholar
24. Hanly JG. Diagnosis and management of neuropsychiatric SLE. Nat Rev Rheumatol. 2014;10:338–47. pmid:24514913
- View Article
- PubMed/NCBI
- Google Scholar
25. Pardridge WM, Sakiyama R, Coty WA. Restricted transport of vitamin D and A derivatives through the rat blood-brain barrier. J Neurochem. 1985;44:1138–41. pmid:3838342
- View Article
- PubMed/NCBI
- Google Scholar
26. Eyles DW, Smith S, Kinobe R, Hewison M, McGrath JJ. Distribution of the vitamin D receptor and 1 alpha-hydroxylase in human brain. J Chem Neuroanat. 2005;29:21–30. pmid:15589699
- View Article
- PubMed/NCBI
- Google Scholar
27. McGrath J, Feron F, Eyles D, Mackay-Sim A. Vitamin D: the neglected neurosteroid? Trends Neurosci. 2001;24:570–2. pmid:11576669
- View Article
- PubMed/NCBI
- Google Scholar
28. Johansson P, Almqvist EG, Johansson JO, Mattsson N, Andreasson U, Hansson O, et al. Cerebrospinal fluid (CSF) 25-hydroxyvitamin D concentration and CSF acetylcholinesterase activity are reduced in patients with Alzheimer's disease. PloS one. 2013;8:e81989. pmid:24312390
- View Article
- PubMed/NCBI
- Google Scholar
29. Burne TH, Becker A, Brown J, Eyles DW, Mackay-Sim A, McGrath JJ. Transient prenatal Vitamin D deficiency is associated with hyperlocomotion in adult rats. Behav Brain Res. 2004;154:549–55. pmid:15313044
- View Article
- PubMed/NCBI
- Google Scholar
30. Annweiler C, Schott AM, Berrut G, Chauvire V, Le Gall D, Inzitari M, et al. Vitamin D and ageing: neurological issues. Neuropsychobiology. 2010;62:139–50. pmid:20628264
- View Article
- PubMed/NCBI
- Google Scholar
31. Annweiler C, Fantino B, Parot-Schinkel E, Thiery S, Gautier J, Beauchet O. Alzheimer's disease—input of vitamin D with mEmantine assay (AD-IDEA trial): study protocol for a randomized controlled trial. Trials. 2011;12:230. pmid:22014101
- View Article
- PubMed/NCBI
- Google Scholar
32. Stewart A, Wong K, Cachat J, Elegante M, Gilder T, Mohnot S, et al. Neurosteroid vitamin D system as a nontraditional drug target in neuropsychopharmacology. Behav Pharmacol. 2010;21:420–6. pmid:20571365
- View Article
- PubMed/NCBI
- Google Scholar
33. Przybelski R, Agrawal S, Krueger D, Engelke JA, Walbrun F, Binkley N. Rapid correction of low vitamin D status in nursing home residents. Osteoporos Int. 2008;19:1621–8. pmid:18421544
- View Article
- PubMed/NCBI
- Google Scholar
34. Mok CC, Birmingham DJ, Ho LY, Hebert LA, Song H, Rovin BH. Vitamin D deficiency as marker for disease activity and damage in systemic lupus erythematosus: a comparison with anti-dsDNA and anti-C1q. Lupus. 2012;21:36–42. pmid:21993384
- View Article
- PubMed/NCBI
- Google Scholar
35. Mok CC, Birmingham DJ, Leung HW, Hebert LA, Song H, Rovin BH. Vitamin D levels in Chinese patients with systemic lupus erythematosus: relationship with disease activity, vascular risk factors and atherosclerosis. Rheumatology (Oxford). 2012;51:644–52.
- View Article
- Google Scholar
36. Aranow C, Kamen DL, Dall'Era M, Massarotti EM, Mackay MC, Koumpouras F, et al. Randomized, Double-Blind, Placebo-Controlled Trial of the Effect of Vitamin D3 on the Interferon Signature in Patients With Systemic Lupus Erythematosus. Arthritis Rheumatol. 2015;67:1848–57. pmid:25777546
- View Article
- PubMed/NCBI
- Google Scholar
37. Amital H, Szekanecz Z, Szucs G, Danko K, Nagy E, Csepany T, et al. Serum concentrations of 25-OH vitamin D in patients with systemic lupus erythematosus (SLE) are inversely related to disease activity: is it time to routinely supplement patients with SLE with vitamin D? Ann Rheum Dis. 2010;69:1155–7. pmid:20439290
- View Article
- PubMed/NCBI
- Google Scholar
38. Ramagopalan SV, Heger A, Berlanga AJ, Maugeri NJ, Lincoln MR, Burrell A, et al. A ChIP-seq defined genome-wide map of vitamin D receptor binding: associations with disease and evolution. Genome Res. 2010;20:1352–60. pmid:20736230
- View Article
- PubMed/NCBI
- Google Scholar
39. Gauzzi MC, Purificato C, Donato K, Jin Y, Wang L, Daniel KC, et al. Suppressive effect of 1alpha,25-dihydroxyvitamin D3 on type I IFN-mediated monocyte differentiation into dendritic cells: impairment of functional activities and chemotaxis. J Immunol. 2005;174:270–6. pmid:15611249
- View Article
- PubMed/NCBI
- Google Scholar
40. Haroon M, Fitzgerald O. Vitamin D and its emerging role in immunopathology. Clin Rheumatol. 2012;31:199–202. pmid:22020389
- View Article
- PubMed/NCBI
- Google Scholar
41. Ritterhouse LL, Crowe SR, Niewold TB, Kamen DL, Macwana SR, Roberts VC, et al. Vitamin D deficiency is associated with an increased autoimmune response in healthy individuals and in patients with systemic lupus erythematosus. Ann Rheum Dis. 2011;70:1569–74. pmid:21586442
- View Article
- PubMed/NCBI
- Google Scholar
42. Linker-Israeli M, Elstner E, Klinenberg JR, Wallace DJ, Koeffler HP. Vitamin D(3) and its synthetic analogs inhibit the spontaneous in vitro immunoglobulin production by SLE-derived PBMC. Clin Immunol. 2001;99:82–93. pmid:11286544
- View Article
- PubMed/NCBI
- Google Scholar
43. Robien K, Butler LM, Wang R, Beckman KB, Walek D, Koh WP, et al. Genetic and environmental predictors of serum 25-hydroxyvitamin D concentrations among middle-aged and elderly Chinese in Singapore. Br J Nutr. 2013;109:493–502. pmid:22583563
- View Article
- PubMed/NCBI
- Google Scholar
44. Robinson AB, Thierry-Palmer M, Gibson KL, Rabinovich CE. Disease activity, proteinuria, and vitamin D status in children with systemic lupus erythematosus and juvenile dermatomyositis. J Pediatr. 2012;160:297–302. pmid:21924736
- View Article
- PubMed/NCBI
- Google Scholar
45. Petri M, Bello KJ, Fang H, Magder LS. Vitamin D in systemic lupus erythematosus: modest association with disease activity and the urine protein-to-creatinine ratio. Arthritis Rheum. 2013;65:1865–71. pmid:23553077
- View Article
- PubMed/NCBI
- Google Scholar
46. Annweiler C, Annweiler T, Bartha R, Herrmann FR, Camicioli R, Beauchet O. Vitamin D and white matter abnormalities in older adults: a cross-sectional neuroimaging study. Eur J Neurol. 2014;21:1436–e95. pmid:25041065
- View Article
- PubMed/NCBI
- Google Scholar
47. Ramage AE, Fox PT, Brey RL, Narayana S, Cykowski MD, Naqibuddin M, et al. Neuroimaging evidence of white matter inflammation in newly diagnosed systemic lupus erythematosus. Arthritis Rheum. 2011;63:3048–57. pmid:21618460
- View Article
- PubMed/NCBI
- Google Scholar
48. Sarbu N, Alobeidi F, Toledano P, Espinosa G, Giles I, Rahman A, et al. Brain abnormalities in newly diagnosed neuropsychiatric lupus: systematic MRI approach and correlation with clinical and laboratory data in a large multicenter cohort. Autoimmun Rev. 2015;14:153–9. pmid:25461835
- View Article
- PubMed/NCBI
- Google Scholar
49. Buell JS, Dawson-Hughes B. Vitamin D and neurocognitive dysfunction: preventing "D"ecline? Mol Aspects Med. 2008;29:415–22. pmid:18579197
- View Article
- PubMed/NCBI
- Google Scholar
50. Roebuck-Spencer TM, Yarboro C, Nowak M, Takada K, Jacobs G, Lapteva L, et al. Use of computerized assessment to predict neuropsychological functioning and emotional distress in patients with systemic lupus erythematosus. Arthritis Rheum. 2006;55:434–41. pmid:16739211
- View Article
- PubMed/NCBI
- Google Scholar
51. Kozora E, Hanly JG, Lapteva L, Filley CM. Cognitive dysfunction in systemic lupus erythematosus: past, present, and future. Arthritis Rheum. 2008;58:3286–98. pmid:18975345
- View Article
- PubMed/NCBI
- Google Scholar
52. Mikdashi JA, Esdaile JM, Alarcon GS, Crofford L, Fessler BJ, Shanberg L, et al. Proposed response criteria for neurocognitive impairment in systemic lupus erythematosus clinical trials. Lupus. 2007;16:418–25. pmid:17664232
- View Article
- PubMed/NCBI
- Google Scholar
53. Hanly JG, Su L, Omisade A, Farewell VT, Fisk JD. Screening for cognitive impairment in systemic lupus erythematosus. J Rheumatol. 2012;39:1371–7. pmid:22660804
- View Article
- PubMed/NCBI
- Google Scholar
54. Meng JE, Hovey KM, Wactawski-Wende J, Andrews CA, Lamonte MJ, Horst RL, et al. Intraindividual variation in plasma 25-hydroxyvitamin D measures 5 years apart among postmenopausal women. Cancer Epidemiol Biomarkers Prev. 2012;21:916–24. pmid:22523182
- View Article
- PubMed/NCBI
- Google Scholar

[ref1] 1. Jeltsch-David H, Muller S. Neuropsychiatric systemic lupus erythematosus: pathogenesis and biomarkers. Nat Rev Neurol. 2014;10:579–96. pmid:25201240
View Article
PubMed/NCBI
Google Scholar

[2] View Article

[3] PubMed/NCBI

[4] Google Scholar

[ref2] 2. Hanly JG, Su L, Urowitz MB, Romero-Diaz J, Gordon C, Bae SC, et al. Mood Disorders in Systemic Lupus Erythematosus: Results From an International Inception Cohort Study. Arthritis Rheumatol. 2015;67:1837–47. pmid:25778456
View Article
PubMed/NCBI
Google Scholar

[6] View Article

[7] PubMed/NCBI

[8] Google Scholar

[ref3] 3. Tay SH, Mak A. Anti-NR2A/B Antibodies and Other Major Molecular Mechanisms in the Pathogenesis of Cognitive Dysfunction in Systemic Lupus Erythematosus. Int J Mol Sci. 2015;16:10281–300. pmid:25955648
View Article
PubMed/NCBI
Google Scholar

[10] View Article

[11] PubMed/NCBI

[12] Google Scholar

[ref4] 4. The American College of Rheumatology nomenclature and case definitions for neuropsychiatric lupus syndromes. Arthritis Rheum. 1999;42:599–608. pmid:10211873
View Article
PubMed/NCBI
Google Scholar

[14] View Article

[15] PubMed/NCBI

[16] Google Scholar

[ref5] 5. Hanly JG, Omisade A, Su L, Farewell V, Fisk JD. Assessment of cognitive function in systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis by computerized neuropsychological tests. Arthritis Rheum. 2010;62:1478–86. pmid:20155829
View Article
PubMed/NCBI
Google Scholar

[18] View Article

[19] PubMed/NCBI

[20] Google Scholar

[ref6] 6. Gladman D, Ginzler E, Goldsmith C, Fortin P, Liang M, Urowitz M, et al. The development and initial validation of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology damage index for systemic lupus erythematosus. Arthritis Rheum. 1996;39:363–9. pmid:8607884
View Article
PubMed/NCBI
Google Scholar

[22] View Article

[23] PubMed/NCBI

[24] Google Scholar

[ref7] 7. Panopalis P, Julian L, Yazdany J, Gillis JZ, Trupin L, Hersh A, et al. Impact of memory impairment on employment status in persons with systemic lupus erythematosus. Arthritis Rheum. 2007;57:1453–60. pmid:18050187
View Article
PubMed/NCBI
Google Scholar

[26] View Article

[27] PubMed/NCBI

[28] Google Scholar

[ref8] 8. Tam LS, Wong A, Mok VC, Zhu YE, Kwok LW, Li TK, et al. The relationship between neuropsychiatric, clinical, and laboratory variables and quality of life of Chinese patients with systemic lupus erythematosus. J Rheumatol. 2008;35:1038–45. pmid:18464308
View Article
PubMed/NCBI
Google Scholar

[30] View Article

[31] PubMed/NCBI

[32] Google Scholar

[ref9] 9. Buell JS, Scott TM, Dawson-Hughes B, Dallal GE, Rosenberg IH, Folstein MF, et al. Vitamin D is associated with cognitive function in elders receiving home health services. J Gerontol A Biol Sci Med Sci. 2009;64:888–95. pmid:19377013
View Article
PubMed/NCBI
Google Scholar

[34] View Article

[35] PubMed/NCBI

[36] Google Scholar

[ref10] 10. Etgen T, Sander D, Bickel H, Sander K, Forstl H. Vitamin D deficiency, cognitive impairment and dementia: a systematic review and meta-analysis. Dement Geriatr Cogn Disord. 2012;33:297–305. pmid:22759681
View Article
PubMed/NCBI
Google Scholar

[38] View Article

[39] PubMed/NCBI

[40] Google Scholar

[ref11] 11. Balion C, Griffith LE, Strifler L, Henderson M, Patterson C, Heckman G, et al. Vitamin D, cognition, and dementia: a systematic review and meta-analysis. Neurology. 2012;79:1397–405. pmid:23008220
View Article
PubMed/NCBI
Google Scholar

[42] View Article

[43] PubMed/NCBI

[44] Google Scholar

[ref12] 12. Yap KS, Morand EF. Vitamin D and systemic lupus erythematosus: continued evolution. Int J Rheum Dis. 2015;18:242–9. pmid:25522756
View Article
PubMed/NCBI
Google Scholar

[46] View Article

[47] PubMed/NCBI

[48] Google Scholar

[ref13] 13. Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr. 2006;84:694–7. pmid:17023693
View Article
PubMed/NCBI
Google Scholar

[50] View Article

[51] PubMed/NCBI

[52] Google Scholar

[ref14] 14. Institute of Medicine Committee to Review Dietary Reference Intakes for Vitamin D, Calcium. The National Academies Collection: Reports funded by National Institutes of Health. In: Ross AC, Taylor CL, Yaktine AL, Del Valle HB, editors. Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US) National Academy of Sciences.; 2011.

[ref15] 15. Hochberg MC. Updating the American College of Rheumatology revised criteria for the classification of systemic lupus erythematosus. Arthritis Rheum. 1997;40:1725.
View Article
Google Scholar

[55] View Article

[56] Google Scholar

[ref16] 16. Petri M, Kim MY, Kalunian KC, Grossman J, Hahn BH, Sammaritano LR, et al. Combined oral contraceptives in women with systemic lupus erythematosus. N Engl J Med. 2005;353:2550–8. pmid:16354891
View Article
PubMed/NCBI
Google Scholar

[58] View Article

[59] PubMed/NCBI

[60] Google Scholar

[ref17] 17. Tay SH, Cheung PP, Mak A. Active disease is independently associated with more severe anxiety rather than depressive symptoms in patients with systemic lupus erythematosus. Lupus. 2015;24:1392–9. pmid:26085594
View Article
PubMed/NCBI
Google Scholar

[62] View Article

[63] PubMed/NCBI

[64] Google Scholar

[ref18] 18. Holliday SL, Navarrete MG, Hermosillo-Romo D, Valdez CR, Saklad AR, Escalante A, et al. Validating a computerized neuropsychological test battery for mixed ethnic lupus patients. Lupus. 2003;12:697–703. pmid:14514133
View Article
PubMed/NCBI
Google Scholar

[66] View Article

[67] PubMed/NCBI

[68] Google Scholar

[ref19] 19. Brunner HI, Klein-Gitelman MS, Zelko F, Thomas EC, Hummel J, Nelson SM, et al. Validation of the Pediatric Automated Neuropsychological Assessment Metrics in childhood-onset systemic lupus erythematosus. Arthritis Care Res (Hoboken). 2013;65:372–81.
View Article
Google Scholar

[70] View Article

[71] Google Scholar

[ref20] 20. Antonchak MA, Saoudian M, Khan AR, Brunner HI, Luggen ME. Cognitive dysfunction in patients with systemic lupus erythematosus: a controlled study. J Rheumatol. 2011;38:1020–5. pmid:21459946
View Article
PubMed/NCBI
Google Scholar

[73] View Article

[74] PubMed/NCBI

[75] Google Scholar

[ref21] 21. Ong L, Saw S, Sahabdeen NB, Tey KT, Ho CS, Sethi SK. Current 25-hydroxyvitamin D assays: do they pass the test? Clin Chim Acta. 2012;413:1127–34. pmid:22465235
View Article
PubMed/NCBI
Google Scholar

[77] View Article

[78] PubMed/NCBI

[79] Google Scholar

[ref22] 22. Petri M, Naqibuddin M, Carson KA, Sampedro M, Wallace DJ, Weisman MH, et al. Cognitive function in a systemic lupus erythematosus inception cohort. J Rheumatol. 2008;35:1776–81. pmid:18634154
View Article
PubMed/NCBI
Google Scholar

[81] View Article

[82] PubMed/NCBI

[83] Google Scholar

[ref23] 23. Annweiler C, Allali G, Allain P, Bridenbaugh S, Schott AM, Kressig RW, et al. Vitamin D and cognitive performance in adults: a systematic review. Eur J Neurol. 2009;16:1083–9. pmid:19659751
View Article
PubMed/NCBI
Google Scholar

[85] View Article

[86] PubMed/NCBI

[87] Google Scholar

[ref24] 24. Hanly JG. Diagnosis and management of neuropsychiatric SLE. Nat Rev Rheumatol. 2014;10:338–47. pmid:24514913
View Article
PubMed/NCBI
Google Scholar

[89] View Article

[90] PubMed/NCBI

[91] Google Scholar

[ref25] 25. Pardridge WM, Sakiyama R, Coty WA. Restricted transport of vitamin D and A derivatives through the rat blood-brain barrier. J Neurochem. 1985;44:1138–41. pmid:3838342
View Article
PubMed/NCBI
Google Scholar

[93] View Article

[94] PubMed/NCBI

[95] Google Scholar

[ref26] 26. Eyles DW, Smith S, Kinobe R, Hewison M, McGrath JJ. Distribution of the vitamin D receptor and 1 alpha-hydroxylase in human brain. J Chem Neuroanat. 2005;29:21–30. pmid:15589699
View Article
PubMed/NCBI
Google Scholar

[97] View Article

[98] PubMed/NCBI

[99] Google Scholar

[ref27] 27. McGrath J, Feron F, Eyles D, Mackay-Sim A. Vitamin D: the neglected neurosteroid? Trends Neurosci. 2001;24:570–2. pmid:11576669
View Article
PubMed/NCBI
Google Scholar

[101] View Article

[102] PubMed/NCBI

[103] Google Scholar

[ref28] 28. Johansson P, Almqvist EG, Johansson JO, Mattsson N, Andreasson U, Hansson O, et al. Cerebrospinal fluid (CSF) 25-hydroxyvitamin D concentration and CSF acetylcholinesterase activity are reduced in patients with Alzheimer's disease. PloS one. 2013;8:e81989. pmid:24312390
View Article
PubMed/NCBI
Google Scholar

[105] View Article

[106] PubMed/NCBI

[107] Google Scholar

[ref29] 29. Burne TH, Becker A, Brown J, Eyles DW, Mackay-Sim A, McGrath JJ. Transient prenatal Vitamin D deficiency is associated with hyperlocomotion in adult rats. Behav Brain Res. 2004;154:549–55. pmid:15313044
View Article
PubMed/NCBI
Google Scholar

[109] View Article

[110] PubMed/NCBI

[111] Google Scholar

[ref30] 30. Annweiler C, Schott AM, Berrut G, Chauvire V, Le Gall D, Inzitari M, et al. Vitamin D and ageing: neurological issues. Neuropsychobiology. 2010;62:139–50. pmid:20628264
View Article
PubMed/NCBI
Google Scholar

[113] View Article

[114] PubMed/NCBI

[115] Google Scholar

[ref31] 31. Annweiler C, Fantino B, Parot-Schinkel E, Thiery S, Gautier J, Beauchet O. Alzheimer's disease—input of vitamin D with mEmantine assay (AD-IDEA trial): study protocol for a randomized controlled trial. Trials. 2011;12:230. pmid:22014101
View Article
PubMed/NCBI
Google Scholar

[117] View Article

[118] PubMed/NCBI

[119] Google Scholar

[ref32] 32. Stewart A, Wong K, Cachat J, Elegante M, Gilder T, Mohnot S, et al. Neurosteroid vitamin D system as a nontraditional drug target in neuropsychopharmacology. Behav Pharmacol. 2010;21:420–6. pmid:20571365
View Article
PubMed/NCBI
Google Scholar

[121] View Article

[122] PubMed/NCBI

[123] Google Scholar

[ref33] 33. Przybelski R, Agrawal S, Krueger D, Engelke JA, Walbrun F, Binkley N. Rapid correction of low vitamin D status in nursing home residents. Osteoporos Int. 2008;19:1621–8. pmid:18421544
View Article
PubMed/NCBI
Google Scholar

[125] View Article

[126] PubMed/NCBI

[127] Google Scholar

[ref34] 34. Mok CC, Birmingham DJ, Ho LY, Hebert LA, Song H, Rovin BH. Vitamin D deficiency as marker for disease activity and damage in systemic lupus erythematosus: a comparison with anti-dsDNA and anti-C1q. Lupus. 2012;21:36–42. pmid:21993384
View Article
PubMed/NCBI
Google Scholar

[129] View Article

[130] PubMed/NCBI

[131] Google Scholar

[ref35] 35. Mok CC, Birmingham DJ, Leung HW, Hebert LA, Song H, Rovin BH. Vitamin D levels in Chinese patients with systemic lupus erythematosus: relationship with disease activity, vascular risk factors and atherosclerosis. Rheumatology (Oxford). 2012;51:644–52.
View Article
Google Scholar

[133] View Article

[134] Google Scholar

[ref36] 36. Aranow C, Kamen DL, Dall'Era M, Massarotti EM, Mackay MC, Koumpouras F, et al. Randomized, Double-Blind, Placebo-Controlled Trial of the Effect of Vitamin D3 on the Interferon Signature in Patients With Systemic Lupus Erythematosus. Arthritis Rheumatol. 2015;67:1848–57. pmid:25777546
View Article
PubMed/NCBI
Google Scholar

[136] View Article

[137] PubMed/NCBI

[138] Google Scholar

[ref37] 37. Amital H, Szekanecz Z, Szucs G, Danko K, Nagy E, Csepany T, et al. Serum concentrations of 25-OH vitamin D in patients with systemic lupus erythematosus (SLE) are inversely related to disease activity: is it time to routinely supplement patients with SLE with vitamin D? Ann Rheum Dis. 2010;69:1155–7. pmid:20439290
View Article
PubMed/NCBI
Google Scholar

[140] View Article

[141] PubMed/NCBI

[142] Google Scholar

[ref38] 38. Ramagopalan SV, Heger A, Berlanga AJ, Maugeri NJ, Lincoln MR, Burrell A, et al. A ChIP-seq defined genome-wide map of vitamin D receptor binding: associations with disease and evolution. Genome Res. 2010;20:1352–60. pmid:20736230
View Article
PubMed/NCBI
Google Scholar

[144] View Article

[145] PubMed/NCBI

[146] Google Scholar

[ref39] 39. Gauzzi MC, Purificato C, Donato K, Jin Y, Wang L, Daniel KC, et al. Suppressive effect of 1alpha,25-dihydroxyvitamin D3 on type I IFN-mediated monocyte differentiation into dendritic cells: impairment of functional activities and chemotaxis. J Immunol. 2005;174:270–6. pmid:15611249
View Article
PubMed/NCBI
Google Scholar

[148] View Article

[149] PubMed/NCBI

[150] Google Scholar

[ref40] 40. Haroon M, Fitzgerald O. Vitamin D and its emerging role in immunopathology. Clin Rheumatol. 2012;31:199–202. pmid:22020389
View Article
PubMed/NCBI
Google Scholar

[152] View Article

[153] PubMed/NCBI

[154] Google Scholar

[ref41] 41. Ritterhouse LL, Crowe SR, Niewold TB, Kamen DL, Macwana SR, Roberts VC, et al. Vitamin D deficiency is associated with an increased autoimmune response in healthy individuals and in patients with systemic lupus erythematosus. Ann Rheum Dis. 2011;70:1569–74. pmid:21586442
View Article
PubMed/NCBI
Google Scholar

[156] View Article

[157] PubMed/NCBI

[158] Google Scholar

[ref42] 42. Linker-Israeli M, Elstner E, Klinenberg JR, Wallace DJ, Koeffler HP. Vitamin D(3) and its synthetic analogs inhibit the spontaneous in vitro immunoglobulin production by SLE-derived PBMC. Clin Immunol. 2001;99:82–93. pmid:11286544
View Article
PubMed/NCBI
Google Scholar

[160] View Article

[161] PubMed/NCBI

[162] Google Scholar

[ref43] 43. Robien K, Butler LM, Wang R, Beckman KB, Walek D, Koh WP, et al. Genetic and environmental predictors of serum 25-hydroxyvitamin D concentrations among middle-aged and elderly Chinese in Singapore. Br J Nutr. 2013;109:493–502. pmid:22583563
View Article
PubMed/NCBI
Google Scholar

[164] View Article

[165] PubMed/NCBI

[166] Google Scholar

[ref44] 44. Robinson AB, Thierry-Palmer M, Gibson KL, Rabinovich CE. Disease activity, proteinuria, and vitamin D status in children with systemic lupus erythematosus and juvenile dermatomyositis. J Pediatr. 2012;160:297–302. pmid:21924736
View Article
PubMed/NCBI
Google Scholar

[168] View Article

[169] PubMed/NCBI

[170] Google Scholar

[ref45] 45. Petri M, Bello KJ, Fang H, Magder LS. Vitamin D in systemic lupus erythematosus: modest association with disease activity and the urine protein-to-creatinine ratio. Arthritis Rheum. 2013;65:1865–71. pmid:23553077
View Article
PubMed/NCBI
Google Scholar

[172] View Article

[173] PubMed/NCBI

[174] Google Scholar

[ref46] 46. Annweiler C, Annweiler T, Bartha R, Herrmann FR, Camicioli R, Beauchet O. Vitamin D and white matter abnormalities in older adults: a cross-sectional neuroimaging study. Eur J Neurol. 2014;21:1436–e95. pmid:25041065
View Article
PubMed/NCBI
Google Scholar

[176] View Article

[177] PubMed/NCBI

[178] Google Scholar

[ref47] 47. Ramage AE, Fox PT, Brey RL, Narayana S, Cykowski MD, Naqibuddin M, et al. Neuroimaging evidence of white matter inflammation in newly diagnosed systemic lupus erythematosus. Arthritis Rheum. 2011;63:3048–57. pmid:21618460
View Article
PubMed/NCBI
Google Scholar

[180] View Article

[181] PubMed/NCBI

[182] Google Scholar

[ref48] 48. Sarbu N, Alobeidi F, Toledano P, Espinosa G, Giles I, Rahman A, et al. Brain abnormalities in newly diagnosed neuropsychiatric lupus: systematic MRI approach and correlation with clinical and laboratory data in a large multicenter cohort. Autoimmun Rev. 2015;14:153–9. pmid:25461835
View Article
PubMed/NCBI
Google Scholar

[184] View Article

[185] PubMed/NCBI

[186] Google Scholar

[ref49] 49. Buell JS, Dawson-Hughes B. Vitamin D and neurocognitive dysfunction: preventing "D"ecline? Mol Aspects Med. 2008;29:415–22. pmid:18579197
View Article
PubMed/NCBI
Google Scholar

[188] View Article

[189] PubMed/NCBI

[190] Google Scholar

[ref50] 50. Roebuck-Spencer TM, Yarboro C, Nowak M, Takada K, Jacobs G, Lapteva L, et al. Use of computerized assessment to predict neuropsychological functioning and emotional distress in patients with systemic lupus erythematosus. Arthritis Rheum. 2006;55:434–41. pmid:16739211
View Article
PubMed/NCBI
Google Scholar

[192] View Article

[193] PubMed/NCBI

[194] Google Scholar

[ref51] 51. Kozora E, Hanly JG, Lapteva L, Filley CM. Cognitive dysfunction in systemic lupus erythematosus: past, present, and future. Arthritis Rheum. 2008;58:3286–98. pmid:18975345
View Article
PubMed/NCBI
Google Scholar

[196] View Article

[197] PubMed/NCBI

[198] Google Scholar

[ref52] 52. Mikdashi JA, Esdaile JM, Alarcon GS, Crofford L, Fessler BJ, Shanberg L, et al. Proposed response criteria for neurocognitive impairment in systemic lupus erythematosus clinical trials. Lupus. 2007;16:418–25. pmid:17664232
View Article
PubMed/NCBI
Google Scholar

[200] View Article

[201] PubMed/NCBI

[202] Google Scholar

[ref53] 53. Hanly JG, Su L, Omisade A, Farewell VT, Fisk JD. Screening for cognitive impairment in systemic lupus erythematosus. J Rheumatol. 2012;39:1371–7. pmid:22660804
View Article
PubMed/NCBI
Google Scholar

[204] View Article

[205] PubMed/NCBI

[206] Google Scholar

[ref54] 54. Meng JE, Hovey KM, Wactawski-Wende J, Andrews CA, Lamonte MJ, Horst RL, et al. Intraindividual variation in plasma 25-hydroxyvitamin D measures 5 years apart among postmenopausal women. Cancer Epidemiol Biomarkers Prev. 2012;21:916–24. pmid:22523182
View Article
PubMed/NCBI
Google Scholar

[208] View Article

[209] PubMed/NCBI

[210] Google Scholar

Figures

Abstract

Objectives

Methods

Results

Conclusions

Introduction

Patients and Methods

Subjects

Study design

SLE-related disease characteristics

Psychopathology questionnaire

Neuropsychological test and definition of cognitive dysfunction

Assay of 25(OH)D3 and definition of vitamin D deficiency

Study procedures

Statistical methods

Results

Characteristics of SLE patients and healthy controls

Vitamin D levels and status

Group differences in performance on ANAM testing

Vitamin D deficiency and cognitive function

Discussion

Acknowledgments

Author Contributions

References

Assay of 25(OH)D₃ and definition of vitamin D deficiency