Social relations in late adolescence and incident coronary heart disease: a 38-year follow-up of the Swedish 1969-1970 Conscription Cohort

Objectives Increasing evidence suggests that low social support is associated with an elevated risk of coronary heart disease (CHD). Earlier studies in this field were conducted in predominantly middle-aged or older samples; thus, the associations reported previously may have been confounded by subclinical manifestations of the disease. We investigated whether social relationships in late adolescence, that is, well before symptoms of subclinical disease manifest, are associated with CHD during a 38-year follow-up. Setting Sweden. Participants Men born 1949–1951 and conscripted for military service in Sweden during 1969–1970 (n=49 321). At conscription, participants completed questionnaires about social relationships, lifestyle and health-related factors and underwent a medical examination. Primary and secondary outcome measures CHD, acute myocardial infarction (AMI). Results We found no relationship between having no confidant and frequency of confidential discussions with friends and the risk of CHD or AMI in the first 30 years of follow-up. However, after 30 years, men with no confidant at baseline had increased CHD and AMI risks relative to those having a confidant; the childhood socioeconomic status-adjusted HR and 95% CIs (CI) were 1.25 (1.10 to 1.41) and 1.27 (1.08 to 1.49), respectively. The frequency of confidential discussions with friends had an inverse U-shaped relationship with the outcomes after 30 years; the HR (95% CI) for ‘sometimes’ versus ‘quite often’ was 1.16 (1.04 to 1.29) for CHD and 1.16 (1.01 to 1.33) for AMI. These associations persisted after adjusting for mental ill-health, lifestyle factors and systolic blood pressure. A low number of friends in late adolescence was not related to an increased CHD or AMI risk. Conclusions Not having a confidant in late adolescence was associated positively, while the frequency of confidential discussions with friends had an inverse U-shaped relationship with CHD and AMI after 30 years of follow-up, suggesting that these associations are not due to subclinical disease manifestations