Social integration and mortality in patients with coronary heart disease: findings from the Heart and Soul Study.

OBJECTIVE To determine why lower social integration predicts higher mortality in patients with coronary heart disease (CHD). METHODS The association between social integration and mortality was examined prospectively in 1019 outpatients with stable CHD from the Heart and Soul Study. Baseline social integration was assessed with the Berkman Social Network Index. Cox proportional hazards models were used to determine the extent to which demographic and disease-relevant confounders and potential biological, behavioral, and psychological mediators explained the association between social integration and mortality. RESULTS During a mean (standard deviation) follow-up period of 6.7 (2.3) years, the age-adjusted annual rate of mortality was 6.3% among socially isolated patients and 4.1% among nonisolated patients (age-adjusted hazard ratio [HR] = 1.61, 95% confidence interval [CI] = 1.26-2.05, p < .001). After adjustment for demographic and disease-relevant confounders, socially isolated patients had a 50% greater risk of death than did nonisolated patients (HR = 1.50, 95% CI = 1.07-2.10). Separate adjustment for potential biological (HR = 1.53, CI = 1.05-2.25) and psychological mediators (HR = 1.52, CI = 1.08-2.14) did not significantly attenuate this association, whereas adjustment for potential behavioral mediators did (HR = 1.30, CI = 0.91-1.86). C-reactive protein and hemoglobin A1c were identified as important biological and omega-3 fatty acids, smoking, and medication adherence as important behavioral potential mediators, with smoking making the largest contribution. CONCLUSIONS In this sample of outpatients with baseline stable CHD, the association between social integration and mortality was largely explained by health-related behavioral pathways, particularly smoking.