Does Vitamin D Deficiency Cause Chronic Low Back Pain: A Case-Control Study

Background: Chronic low back pain (CLBP) is an important cause of morbidity worldwide and is routinely treated by vitamin D supplementation alongwith other measures. Whether vitamin D deficiency is responsible for CLBP, is a matter of debate. The aim of this case-control study is to find out weather vitamin d deficiency is associated with CLBP. Objective: The objective of the study to find out whether hypovitaminosis D causes CLBP. Methods: This case-control study was conducted in the Department of Surgery and Medicine of Aero Hospital Wahcantt from 2ndMay 2022 to 31May 2023 after ethical approval from IMC vide letter No 44(33)/2023-IMC. 195 cases of CLBP and an equal number of controls were selected through non-probability convenience sampling. After matching confounding factors between the two groups, their vitamin D levels were recorded. The null hypothesis that there is no difference between the mean vitamin D level of cases and controls was tested by applying an independent sample t-test. Taking vitamin D levels below 20ng/ml as hypovitaminosis D, the odds ratio was calculated as well. Results: Both groups, cases, and controls had an equal number of males (n=63, 32.3%) and females (n=132, 67.7%). The mean age of cases was 44.6 years with SD ± 13.54 while the mean age of controls was 45.2 years with SD ± 13.46 years. The mean level of vitamin D of patients was 23.22 ng/ml with SD ± 17.76 while the mean vitamin D level of controls was 26.48ng/ml with SD ± 20.64. Independent sample t-test showed that there is no statistical significant difference between the mean vitamin D levels of the two groups (p-value > 0.05). The odds ratio was 1.31 showing no or very weak correlation between hypovitaminosis D and CLBP. Conclusion: There is no causal relationship between CLBP and hypovitaminosis D.


Introduction
C hronic low back pain (CLBP) is defined as low back pain that lasts for more than 03 months or 1-3 that recurs frequentlyduring06 months or beyond.
CLBP causes significant morbidity, abstinence from work, and poor quality of life both in men and women 4 across the globe .Multiple visits to outpatient departments and indoor admissions due to CLBP burdens the 7,8 dysfunction, failed back surgery, and malignancy, but in a majority of patients clinicians label the pain as nonspecific or mechanical as no obvious pathology 9,10 can be found.Optimum levels of vitamin D are essential for musculo-11, 12 skeletal health.The prevalence of Vitamin D defi-13 ciency is high in Pakistan and other South Asian countries.A serum level of vitamin D less than 20ng/ml is considered a deficiency of vitamin D, while a level between 12, 13 20-30ng/ml is considered insufficient.According to many studies hypovitaminosis D is associated with 12, 14 CLBP, however, this association is not established and evidence is lacking.Many studies do not support a causal relationship between hypovitaminosis D and 15 CLBP.The objective of this case-control study is to find out the association between hypovitaminosis D and CLBP.This study will determine whether a causal relationship exists between vitamin D deficiency and CLBP.If hypovitaminosis D is found to be the cause of CLBP, correction of vitamin D levels in CLBP patients will benefit and improve this chronic, debilitating disease.

Methods
This case-control study was conducted in the Department of Surgery and Medicine of Aero Hospital Wahcantt nd from 2 May 2022 to 31May 2023 after ethical approval from IMC vide letter no44(33)/2023-IMC.Aero Hospital has a total patient load of approximately 100,000.Taking chronic low back pain (CLBP) prevalence as high as 50% based on the reference study conducted by Shetty GM6 in India, the population size of CLBP patients was assumed as 50,000.With 5% margin of error, 95% confidence interval and population size of 50,000,the sample size was calculated using Raosoft 16 calculator and it turned out to be 382.We included 195 cases of CLBP and 195 controls not having CLBP.Our null hypothesis was that there is no association between chronic low back pain and hypovitaminosis D. If the null hypothesis is true, there will be no significant difference between means of vitamin D levels of cases and controls, and the odds ratio will be equal to or less than 01.Our alternate or research hypothesis was that there is an association between chronic low back pain and hypovitaminosis D. In this case there will be a significant difference between means of vitamin D levels of cases and controls and the odds ratio will be more than 01.Cases and controls were selected through non probability convenience sampling technique.All patients above 12 years of age presenting with CLBP in the medicine and surgery department were advised on vitamin D levels.Patients with spinal disc disease, fractures, and infections of the spine like tuberculosis and spinal tumors were excluded.Controls were selected from the same hospital.These were either healthy attendants of patients who opted for vitamin D levels voluntarily or patients with problems other than CLBP.Cases and controls were matched in terms of confounding factors like age, gender, and sun exposure.Both cases and controls were advised vitamin D levels on a venous sample in a non-fasting state from the same laboratory and the results recorded after arrival of reports.For data entry and statistical analysis, windows compatible SPSS version 25 was used.Descriptive statistics were represented as mean, median, mode, and standard deviation.An Independent sample t-test was applied to compare the means of vitamin D levels of cases and controls.T-test was also applied to see whether there was a statistically significant difference between vitamin D levels of males and females.Taking vitamin D less than 20ng/ml as hypovitaminosis D, the odds ratio was calculated using a classic 2×2 table for case-control studies.P value less than 0.05 was set as statistically significant.

Results
Both groups, cases, and controls had an equal number of males (n=63, 32.3%) and females(n=132, 67.7% as shown in the pie charts (figure 1).Both groups were also comparable with reference to age.The mean age of cases was 44.6 years with SD ± 13.54 while the mean age of controls was 45.2 years with SD ± 13.46 years.The minimum age of cases was 14 years while that of control was 13 years.The maximum age of cases was 91 years while of controls was 85 years.The mean level of vitamin D of patients was 23.22 ng/ml with SD ± 17.76 while the mean vitamin D of controls was 26.48ng/ml ± 20.64 as shown in Table 1.An Independent sample t-test was applied to compare the means of vitamin D levels of cases and controls.Although the vitamin D levels of cases were lower than controls the difference was statistically insignificant.The p-value turned out to be 0.095 (non-significant).Hence null hypothesis cannot be rejected as shown in Table 2.

Figure 1. Gender Distribution of Cases and Controls
Our sample had overall 32.3% (n=126) males and 67.7% (n=264) females.The mean vitamin D levels of males were 23.57ng/ml SD ± 18.41 while of females was 25.47 ng/ml SD ± 19.72 as shown in Table 3.The mean vitamin D level of males and females was compared by applying independent sample t-test.Although the mean vitamin D level of females was higher than males (25.47>23.57), the difference was not significant p-value = 0.354.Taking values less than 20ng/ml as hypovitaminosis D, the odds ratio was calculated by using a classic 2×2 table of case-control studies as shown in Table 4.
Odds ratio = 1.31 The odds ratio was noted as 1.31 showing no or very weak correlation between hypovitaminosis d and CLBP.

Discussion
Chronic low back pain (CLBP) is the most common complaint by which patients present to the surgical outpatient department of any hospital5,6.Vitamin D

11,12
deficiency is thought to be related to CLBP.We seldom see any prescription for a patient of CLBP without heavy doses of vitamin D and calcium supplements whether rationale exists or not.This case-control study was intended to determine any causal relationship between CLBP and hypovitaminosis D.
Vitamin D is necessary for musculoskeletal health and its optimum levels are important for normal bone and  The strength of our study is its case control design which significantly determines the causal relationship between cause and effect.Also, the matching of both cases and controls concerning confounding factors was done well.The limitation noted in our study was that the majority of cases and controls belong to the same socioeconomic status.So further studies are needed across various socioeconomic classes to achieve uniformity of results.

Conclusion
Although the deficiency of vitamin D is highly prevalent in our society, there is no causal relationship between hypovitaminosis D and CLBP.The null hypothesis that there is no significant difference between the mean vitamin D level of cases and controls cannot be rejected.Also, the odds ratio was

Table 1 :
Mean vitamin D levels of cases and controls

Table 2 :
Independent sample t-test to compare vitamin D means of cases and controls

Table 3 :
Comparison of vitamin D levels of males and females

Table 4 :
Odds ratio calculation 19of cases and controls can not be rejected.Al Tair A in his cross-sectional study of 760 adult school boys in Kuwait also had similar results and found no significant difference between vitamin D levels of CLBP patients and 1.31 which does not support a causal relationship between hypovitaminosis D and CLBP.Conception and design, data drafting and final approval of the version