Exploring smoking, mental health and smoking-related disease in a nationally representative sample of older adults in Ireland – A retrospective secondary analysis
Introduction
General population smoking prevalence has reached an all-time low of 19% in the UK and 19.5% in Ireland [1], [2]. Mental health difficulties (MHD) as identified via various indicators including diagnostic or clinical interview, medical records, current psychiatric treatment, reported doctor diagnosed conditions or medication use, are consistently associated with higher smoking prevalences with rates cited ranging from 25.5 to 59% [3], [4], [5], [6], [7], [8], [9]. These increased smoking rates are most pronounced in those with substance use disorders and more severe mental illness (SMI) diagnoses such as bipolar disorder, schizophrenia or psychosis [6], [7], [10], [11], [12], [13]. In general, those with MHD tend to smoke more heavily than other smokers [7] and also appear to be less likely to quit smoking [7]. While those with schizophrenia appear to be less likely to quit smoking [14], common mental illnesses such as anxiety or depression also seem to affect quitting behaviour [15]. For instance, meta-analyses have shown that in patients with chronic respiratory conditions or coronary heart disease patients with depressive symptoms are less likely to quit smoking than those without such depressive symptoms [16], [17].
This higher prevalence of smoking has been associated with significant health consequences in those with MHD. People with mental health conditions die on average 10 to 20 years younger than the general population [18], [19], [20], [21], [22] and smoking has been reported as the largest contributor to this premature mortality [23], [24]. In the US, Callaghan et al. found significantly heightened patterns of tobacco-related mortality in terms of respiratory disease, smoking-related cancers and cardiovascular disease in patients with schizophrenia (standardised mortality ratio [SMR] 2.45 95% CI 2.41–2.48), bipolar disorder (SMR 1.57 95% CI 1.53–1.62) and depression (SMR 1.95 95% CI 1.93–1.98) [25]. Earlier studies have also shown increased risk of death from cardiovascular disease [4], [22], [26], [27] and cancer [22], [26]. Morbidity studies have also shown those with SMI have a significantly higher prevalence of pulmonary illness [3], [28], [29], [30], [31], [32], [33], cancer [28] and cardiovascular diseases (including stroke, congestive heart failure, angina and myocardial infarction) [28], [29], [30] compared to matched samples or general population counterparts [28], [29], [30], [31], [32]. While smoking is thought to account for the majority of morbidity and mortality in these populations, studies have also found associations between mental illness and respiratory disease, cardiovascular disease and risk of death from cardiovascular disease which seems to persist after adjustment for smoking [4], [28], [34]. However, the literature is limited by the range of conditions investigated, and the samples used are not always generalisable. For example, many of these studies focus on schizophrenia-related disorders and psychosis, though some have also included affective disorder diagnoses [28], [32]. Partti et al.'s study of respiratory disease was population-based but only explored psychosis [3], while other studies were based on clinical populations with some reliant on small samples ranging from 80 to 100 [28], [30], [32]. The last study to address the impact of smoking on the physical health of those with MHD in Ireland is now over 30 years old, was specific to schizophrenia and was not population-based [35]. More generally, morbidity and mortality studies have tended to rely upon one or two indicators, such as structured clinical interviews, medical records, medical service claims or scale scores, but never more than two indicators when identifying those with MHD [3], [4], [25], [27], [29], [34]. The use of a number of different methods is preferable to enhance the reliability of the findings.
In addition, chronic diseases such as cardiovascular disease and cancers usually occur later in life. Most cancer diagnoses occur in individuals older than 65 years [36] and CHD risk increases in both men and women after age 55 [37]. In spite of this, some studies of smoking prevalence in those with MHD have been limited to younger samples with age ceilings of 54 and 64 [7], [10] and there are almost no studies of smoking or smoking-related morbidity or mortality specific to older populations. To our knowledge only one study exploring excess mortality in those with MHD concerns those aged 65 and older [27]. The impact of smoking on the physical health of older adults with MHD therefore remains unclear.
In summary, few population studies have explored smoking-related morbidity in older individuals with MHD and there are no recent studies addressing the health impacts of smoking in those with MHD in Ireland. This study had two aims. Firstly, to determine whether there is a higher prevalence of smoking and of smoking-related disease in older adults with mental health problems. Secondly, to assess whether smoking mediates or moderates the relationship between mental health difficulties and smoking-related disease at a population level. Given the absence of diagnostic interviews, several indicators were used both individually and in combination to reliably identify those with MHD. We hypothesized that persons with MHD would be more likely to have higher levels of smoking-related diseases, which would be explained by a higher rate of smoking.
Section snippets
The Irish Longitudinal Study on Ageing (TILDA)
TILDA provides a stratified clustered nationally representative sample of community dwelling adults aged 50 and over living in Ireland [38]. Private residential dwellings were assigned to clusters stratified by geography and socioeconomic group to produce a population representative sample. Across households where it was possible to make contact to confirm eligibility a response rate of 62% was achieved [39]. Population weighting was employed to counteract bias introduced by differential
Sample description
This analysis of TILDA included 8175 participants aged 50 years and over. As described above, due to missing values related to issues such as health assessment attendance and completion of the HADS-A the analytic sample ranged from 5024 to 8158. Sample sizes for each model are included below (Table 2, Table 3, Table 4).
Overall 18.24% of respondents were current smokers and 38.1% were former smokers. The prevalence of MHD ranged from 1.60% (self-reported alcohol or substance use problem) to 9.49%
Discussion
We reported a number of important findings in a population-based dataset of older people, using multiple indicators of MHD to ensure robustness of findings. MHD, as evidenced by self-reported doctor diagnosed problems, psychiatric medication use and scores on anxiety and depression scales, was associated with smoking status in community living adults aged 50 and over in Ireland. MHD was also associated with the presence of a smoking-related disease i.e. respiratory disease, cardiovascular
Strengths and limitations
Strengths of the current study include the large nationally representative sample of older adults. The TILDA study with its robust methodology provides a detailed and rich population weighted dataset and the necessary power to adjust for many confounders. This large representative sample means results can be generalised to the population [39]. This study also included multiple measures of MHD from self-reported doctor diagnosed conditions to medication use to standardised scales.
This study was
Conclusion
Among older community living adults in Ireland indicators of MHD was associated with a higher prevalence of current smoking and self-reported doctor diagnosed cardiovascular disease, respiratory diseases and smoking-related cancers. This increased risk of smoking-related disease remained even after adjusting for smoking status.
Funding
This work was supported by the Health Research Board of Ireland (HRB) through the HRB Structured PhD in Population Health and Health Services Research (SPHeRE) programme (SPHeRE/2013/01).
Declaration of interests
The authors declare no conflicts of interest.
Acknowledgments
The authors would like to thank Dr. Mark Ward (Research Fellow at The Irish Longitudinal Study on Ageing) for his comments on a previous version of this manuscript and Ms. Siobhan Scarlett (Research Assistant and Data manager at The Irish Longitudinal Study on Ageing) for her guidance on data cleaning.
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