Causal impact of cardiovascular disease on depression: loneliness and social isolation as mediators

Abstract Background Cardiovascular disease (CVD) increases the risk of depression, but the mechanisms underlying this relationship are unclear. Loneliness and social isolation are known risk factors for physical and mental health conditions; however, their role in linking CVD to depression is poorly understood. We investigated whether loneliness and/or social isolation mediate the relationship between CVD and depression. Methods We analysed data from the English Longitudinal Study of Ageing, a cohort study of adults aged 50 and older in the UK. The exposure was newly-reported CVD at wave seven (angina, heart attack, heart failure, heart murmur, abnormal heart rhythm, and stroke). We assessed loneliness and social isolation at wave eight as potential mediators. The outcome depressive symptom severity was measured at wave nine. We examined associations between CVD, loneliness, social isolation, and depression using multivariate regression models. Results Preliminary analyses included 6,448 participants (mean age = 66.11), of whom 382 had newly reported CVD at baseline. Loneliness (B = 0.07, 95% CI: 0.05, 0.09) and social isolation (B = 0.11, 95% CI: 0.08, 0.14), measured in 2016-2017, were each significantly associated with more severe depressive symptoms two years years later. However, we found no evidence that CVD at wave seven was associated with loneliness or social isolation at wave weight, or with depressive symptoms at wave nine. Conclusions Our findings suggest that loneliness and social isolation do not mediate the relationship between CVD and depression among older adults. While CVD was not directly associated with depression, loneliness and social isolation emerged as potentially important targets for interventions aimed at reducing depression in mid-to-later life. Future research should explore alternative mediating or moderating pathways and broader mental health outcomes to better understand the psychological impact of CVD. Key messages • Loneliness and social isolation were linked to later depression, but did not mediate the relationship between cardiovascular disease and depression in older adults. • Interventions targeting loneliness and social isolation may help reduce depression in mid-to-later life, even without a direct link to cardiovascular disease.