Social capital, mortality, cardiovascular events and cancer: a systematic review of prospective studies.

BACKGROUND Social capital is considered to be an important determinant of life expectancy and cardiovascular health. Evidence on the association between social capital and all-cause mortality, cardiovascular disease (CVD) and cancer was systematically reviewed. METHODS Prospective studies examining the association of social capital with these outcomes were systematically sought in Medline, Embase and PsycInfo, all from inception to 8 October 2012. We categorized the findings from studies according to seven dimensions of social capital, including social participation, social network, civic participation,social support, trust, norm of reciprocity and sense of community, and pooled the estimates across studies to obtain summary relative risks of the health outcomes for each social capital dimension. We excluded studies focusing on children, refugees or immigrants and studies conducted in the former Soviet Union. RESULTS Fourteen prospective studies were identified. The pooled estimates showed no association between most social capital dimensions and all-cause mortality, CVD or cancer. Limited evidence was found for association of increased mortality with social participation and civic participation when comparing the most extreme risk comparisons. CONCLUSIONS Evidence to support an association between social capital and health outcomes is limited. Lack of consensus on measurements for social capital hinders the comparability of studies and weakens the evidence base.