Low socioeconomic status and psychological distress as synergistic predictors of mortality from stroke and coronary heart disease.

Background: The purpose of this study was to test whether lower socioeconomic status (SES) augments the effect of psychological distress on mortality from stroke or coronary heart disease (CHD).
Methods: We prospectively linked data from 66,500 participants 35 years or older in the Health Survey for England, selected using stratified random sampling from 1994 to 2004, and free of cardiovascular disease and cancer at baseline, with mortality records. The median follow-up time was 7.9 years. SES was indexed by occupational class, and psychological distress was assessed using the 12-item General Health Questionnaire (GHQ-12).
Results: After adjustment for demographic and clinical variables, both psychological distress and low SES were associated with increased mortality: the hazard ratios (HR) for one-category increase in low SES (three categories in total) were 1.15 for stroke-death (95% confidence interval [CI] = 1.00-1.31, p = .043) and 1.24 for CHD-death (95% CI = 1.09-1.41, p = .001); the HR for one-category increase in GHQ-12 (three categories in total) was 1.18 for stroke-death (95% CI = 1.07-1.30, p = .001) and 1.24 for CHD-death (95% CI = 1.13-1.36, p < .001). In stratified analyses, the strongest associations were found in the lowest SES categories: the HR for GHQ-12 toward stroke-death was 1.15 in high-SES participants (95% CI = 0.97-1.37, p = .107) and 1.31 in low-SES ones (95% CI = 1.13-1.51, p < .001); the HR for GHQ-12 toward CHD-death was 1.10 in high-SES participants (95% CI = 0.97-1.25, p = .129) and 1.33 in low-SES ones (95% CI = 1.19-1.48, p < .001).
Conclusions: People in low socioeconomic circumstances are more vulnerable to the adverse effect of psychological distress. This pattern should be taken into account when evaluating the association between psychosocial variables and health outcomes.