Social participation and coronary heart disease risk in a large prospective study of UK women

BACKGROUND Participation in social activities is thought to prevent heart disease, but evidence is inconclusive. DESIGN We assessed whether participating in social activities reduces the risk of coronary heart disease (CHD) in a large prospective study of 735,159 middle-aged UK women. METHODS Women reported their participation in eight social activities (religious group, voluntary work, adult education, art/craft/music, dancing, sports club, yoga, bingo) and were followed for first CHD event (hospital admission or death) over the next 8.6 years. Cox regression models were used to estimate relative risks for CHD incidence by participation in each and in any of the social activities. RESULTS After adjustment for age and region only, every activity except bingo was associated with a reduced risk of CHD (n = 30,756 cases in total). However, after additional adjustment for 11 factors (deprivation, education, smoking, physical activity, body mass index, alcohol, marital status, self-rated health, happiness, hypertension, diabetes), every relative risk estimate moved close to 1.0. For example, for participation in any of the activities compared with none, the relative risk adjusted for age and region only was 0.83 (99% confidence interval 0.81-0.86), but changed to 1.06 (99% confidence interval 1.02-1.09) after additional adjustment. Adjustment for education, self-rated health, smoking and physical activity attenuated the associations most strongly. Residual confounding and other unmeasured factors may well account for any small remaining associations. CONCLUSIONS Associations between participation in various social activities and CHD risk appear to be largely or wholly due to confounding by personal characteristics of the participants.