Income inequality, primary care, and health indicators.
BACKGROUND
The significant association of income inequality with a variety of health indicators is receiving increasing attention. There has also been increasing evidence of a link between primary care and improved health status. We examined the joint relationship between income inequality, availability of primary care, and various health indicators to determine whether primary care has an impact on health indicators by modifying the adverse effect of income inequality.


METHODS
Our ecologic study used the US states as the units of analysis. In analyzing the data, we looked at the associations among income inequality, primary care, specialty care, smoking, and health indicators, using Pearson's correlation coefficients for intercorrelations and the adjusted multiple regression procedure. To examine the effect of inequality and primary care on health outcome indicators, we conducted path analyses according to a causal model in which inequality affects health both directly and indirectly through its impact on primary care.


RESULTS
Our study indicates that both primary care and income inequality exerted a strong and significant direct influence on life expectancy and total mortality (P <.01). Primary care also exerted a significant direct influence on stroke and postneonatal mortality (P <.01). Although levels of smoking are also influential, the effect of income inequality and primary care persists after controlling for smoking. Primary care serves as one pathway through which income inequality influences population-level mortality and at least some other health outcome indicators.


CONCLUSIONS
It appears possible that a primary care orientation may, in part, overcome the severe adverse effects on health of income inequalities.
Shi
L
L
Department of Health Policy and Management, Johns Hopkins School of Public Health & Hygiene, Baltimore, MD 21205-1996, USA. lshi@jhsph.edu
Starfield
B
B
Kennedy
B
B
Kawachi
I
I
D002561:Cerebrovascular Disorders; D006297:Health Services Accessibility / Q000191:economics; D006302:Health Services Research / Q000379:methods; D006305:Health Status Indicators; D006801:Humans; D007182:Income; D007226:Infant Mortality; D007231:Infant, Newborn; D008017:Life Expectancy; D009026:Mortality; D010821:Physicians, Family / Q000600:supply & distribution; D011320:Primary Health Care / Q000706:statistics & numerical data*; D012044:Regression Analysis; D012907:Smoking / Q000453:epidemiology; D012935:Social Justice; D014481:United States / Q000453:epidemiology; D000078329:Workforce