Social capital, income inequality, and mortality.
OBJECTIVE
Recent studies have demonstrated that income inequality is related to mortality rates. It was hypothesized, in this study, that income inequality is related to reduction in social cohesion and that disinvestment in social capital is in turn associated with increased mortality.


METHODS
In this cross-sectional ecologic study based on data from 39 states, social capital was measured by weighted responses to two items from the General Social Survey: per capita density of membership in voluntary groups in each state and level of social trust, as gauged by the proportion of residents in each state who believed that people could be trusted. Age-standardized total and cause-specific mortality rates in 1990 were obtained for each state.


RESULTS
Income inequality was strongly correlated with both per capita group membership (r = -.46) and lack of social trust (r = .76). In turn, both social trust and group membership were associated with total mortality, as well as rates of death from coronary heart disease, malignant neoplasms, and infant mortality.


CONCLUSIONS
These data support the notion that income inequality leads to increased mortality via disinvestment in social capital.
Kawachi
I
I
Department of Health and Social Behavior, Harvard School of Public Health, Boston, MA 02115, USA.
Kennedy
B P
BP
Lochner
K
K
Prothrow-Stith
D
D
D003327:Coronary Disease / Q000401:mortality*; D003430:Cross-Sectional Studies; D004644:Emotions; D006801:Humans; D007182:Income / Q000706:statistics & numerical data; D007226:Infant Mortality; D007231:Infant, Newborn; D007398:Interpersonal Relations; D009309:National Center for Health Statistics, U.S.; D009369:Neoplasms / Q000401:mortality*; D011203:Poverty; D012923:Social Class; D014481:United States / Q000453:epidemiology