Previous studies have shown the association of new onset depressive symptoms with major adverse cardiac events and mortality. However, previously which factors are associated with new onset depressive symptoms had not been thoroughly examined. Therefore, the current study provides insights into the factors associated with post heart event new onset depressive symptoms. The findings of this study show the factors that are statistically significantly associated with new onset depressive symptoms are higher total number of comorbidities, increased weight, high HADS anxiety symptoms, physical inactivity and variety of comorbidities. Additionally, in terms of demographics, patients with new onset depressive symptoms were more likely to be male, single and from areas with higher social deprivation.
One finding is that patients with new onset depressive symptoms have a higher number of total comorbidities compared to patients with absence of depressive symptoms after their heart event. Likewise, higher number of comorbidities was associated with increased odds of having new onset depressive symptoms at the start of CR after accounting for other covariates (OR: 1.029, CI: 1.008, 1.051). In addition, a range of comorbidities including angina, arthritis, diabetes, rheumatism, stroke, osteoporosis, chronic bronchitis, emphysema, asthma, anxiety, claudication, and chronic back problems were found to be more prevalent in patients with new onset depressive symptoms. However, a prior RCT data driven study of Vitinius et al. [24] was not able to find an association between comorbidities and depressive symptoms. This may be due to their population being younger (mean age 59.1 ± 19.8) in comparison to ours (65.79 ± 11.14). RCTs are known to recruit a younger population, therefore recommendations have been made for RCTs to be more inclusive of older aged, multi-morbid populations [6]. Additionally, patients with multiple comorbidities are less likely to be referred to or uptake CR which creates challenges for services and health care providers [25, 26]. Increased numbers of comorbidities may limit cardiac patients’ physical functioning and thereby increase their depression levels [27]. However, patients with multiple comorbidities may benefit from attending CR which improves their functional capacity and psychosocial conditions [26, 28].
Diabetes is one of the most prevalent comorbid condition in patients with new onset depression in our sample. In addition, the current study has shown that diabetes was associated with 29% increased odds of having new onset depressive symptoms in CR attenders (OR: 1.297 95% CI: 1.209, 1.392). At the start of CR, diabetic patients presented with more cardiovascular risk factors and had reduced physical fitness [29]. The positive impact of CR in patients with diabetes has been investigated by previous studies in terms of mortality [30, 31]. Due to having a greater cardiac risk profile and lower programme uptake rate, CR programmes are recommended to target patients with diabetes [32,33,34]. Given that the prevalence of diabetes is continuing to rise [35], the medical management of diabetes may be relevant and lead to a reduction in depressive symptoms.
For each percent increase in the proportion of patients with stroke comorbidity, the odds of being in the new onset depressive symptoms category increases by a factor of 1.543 compared to absence of new onset depressive symptoms. The presence of stroke comorbidity is associated with a lower likelihood of a patient being referred to [25], and uptake CR [26]. Yet, stroke patients can benefit from CR programmes in terms of improvements in their cardiovascular fitness and functional capacity [36], therefore involvement of these patients into CR can be of benefit.
Our study has shown that respiratory related conditions such as chronic bronchitis, emphysema and asthma were associated with new onset depressive symptoms in baseline univariate analysis. Patients with CVD and COPD experience problems of breathlessness and disability, therefore cardiac rehabilitation services are recommended to provide sufficient flexibility to be inclusive of patients with COPD [37]. The comorbidities of arthritis, rheumatism, osteoporosis and back pain were also associated with increased depressive symptoms after heart event. The findings of a cohort study has shown that, at baseline CR assessments, patients having these comorbid conditions had a poorer health profile such as lack of physical activity and fitness than those who do not present with these comorbidities [38] which may be responsible from their increased levels of depression. Indeed, in the current study, the comorbidity of chronic back pain was associated with increased odds of having new onset depressive symptoms in patients commencing CR (OR 1.095, 95%CI: 1.000, 1.198). This study is the first to shed a light upon the variety of comorbidities and their association with new onset depressive symptoms among patients attending CR.
BMI was statistically significantly higher among patients with new onset depressive symptoms group with difference of 0.79 compared to patients with absence of new onset depressive symptoms, whereas they were in the same range of being overweight (BMI 29.00 vs 28.21). However, this statistically significant finding have not been observed in a USA based CR study [28], the reason for this might be that this American study have not factored in the patients with new onset depressive symptoms whose characteristics may be different. Patients with new onset depressive symptoms had also increased weight by 1.13 kilogrammes compared to patients with absence of new depressive symptoms group in the current study. In addition, in multivariate analysis, weight measurement remained to be significantly associated with new onset depressive symptoms after adjusting for other covariates.
The association of anxiety with depressive symptoms is confirmed by this study. The mean HADS anxiety scores were both statistically significant and clinically meaningfully higher in patients with new onset depressive symptoms group compared to absence of new onset depression (MD:5.38 (95%CI 5.33 to 5.44)). A recent study of Lemay et al. 2019 has shown that minimum clinically important difference in HADS is 1.7 for CR patients [39]. The mean difference among these groups were more than threefold higher than the minimal clinically important difference.
One clinically relevant finding was that smoking and physical inactivity were two of the modifiable cardiac risk factors that were associated with new onset depression. These results support previous systematic reviews conducted in the general population which show the prospective association between physical activity and smoking with depression [40, 41], and some cohort studies that were unable to differentiate new onset depressive symptoms in cardiac populations [42,43,44]. Our findings have added that at baseline CR assessments patients who present with new onset post heart event depression are more likely to smoke and be physically inactive compared to patients with absence of new onset depression. In addition in multivariable analysis physical inactivity was statistically significantly associated with 87% increased odds of having new onset depressive symptoms at baseline CR (OR 1.870, 95% CI: 1.761, 1.985). However, smoking was unable to reach the statistical significance in the regression model.
The patient demographics associated with new onset depressive symptoms were being single, which was in line with previous studies [45], male gender and being older. The English Index of Multiple Deprivation (IMD) was also one of the demographic measures included in the current study. A recent USA based study has shown that lower neighbourhood socioeconomic context, measured by neighbourhood deprivation index, was associated with reduced likelihood of CR uptake [46]. However, our study used the IMD measure and is the first to show that patients with new onset depressive symptoms attending CR were more likely to be from areas with higher levels of social deprivation. This association of increased social deprivation with new onset depressive symptoms remained significant after adjusting for other covariates by having 27% increased odds of presenting with new onset depressive symptoms (OR 1.270, 95%CI: 1.169, 1.378). Deprivation is associated with poor health behaviours such as smoking and physical inactivity [47] which might be responsible for their depressive symptoms initiation. Patients from areas with greater deprivation can be more disadvantaged naturally and experience barriers to attending CR [46] therefore strategies for inclusion of this patient group appears to be a natural next step. In addition, screening depressive symptoms in patients from areas of higher levels of deprivation that attend CR may be of benefit for early detection of the patients with high risks which perhaps could be investigated in the future studies.
Our findings are in line with the European Society of Cardiology (ESC) Position statement on psychosocial aspects of cardiac rehabilitation supporting that patients with low socioeconomic status or from areas of higher deprivation are more likely to have depressive symptoms which may lead to poor prognosis of their CVD [48]. We agree that it is important for CR programmes to identify patients with new onset depressive symptoms or other psychosocial risk factors and offer tailored interventions to these patients by a trained health care professionals [48].
Limitations
Our population excluded patients with prior history of depression. This is because we aimed to investigate the factors associated with new onset depressive symptoms. However, when we examined the characteristics of our sample, it was representative of all available patients during the study time period ((n = 277,521), mean age was 65.79 compared to 65.06, 26% female compared to 27%, and this proportion did not differ by more than 4% for other variables). The study sample was nationally representative of patients with new onset depressive symptoms in the UK. The use of an observational approach enabled us to generate real world understanding by analysing routinely collected clinical data. The data included more patients with multi-comorbidities and higher female proportion than prior RCTs [6]. However, due to the nature of an observational study, causal conclusions cannot be drawn.