Effects of depressive symptoms and coronary heart disease and their interactive associations on mortality in middle-aged adults: the Whitehall II cohort study

Background Depression and mortality have been studied separately in patients with coronary heart disease (CHD) and in populations healthy at study inception. This does not allow comparisons across risk-factor groups based on the cross-classification of depression and CHD status. Objective To examine effects of depressive symptoms and CHD and their interactive associations on mortality in middle-aged adults followed over 5.6 years. Design and setting A prospective population-based cohort study of 5936 middle-aged men and women from the British Whitehall II study. We created four risk-factor groups based on the cross-classification of depressive symptoms and CHD status. Results The age-adjusted and sex-adjusted hazard ratios for death from all causes were 1.67 (p<0.05) for participants with only CHD, 2.10 (p<0.001) for those with only depressive symptoms and 4.99 (p<0.001) for those with both CHD and depressive symptoms when compared to participants without either condition. The two latter risk-factor groups remained at increased risk after adjustments for relevant confounders. The relative excess risk due to the interaction between depressive symptoms and CHD for all-cause mortality was 3.58 (95% CI-0.09 to 7.26), showing some evidence of an additive interaction. A similar pattern was also observed for cardiovascular death. Conclusions This study provides evidence that depressive symptoms are associated with an increased risk of all-cause and cardiovascular death and that this risk is particularly marked in depressive participants with co-morbid CHD.