Primary care, infant mortality, and low birth weight in the states of the USA.

STUDY OBJECTIVE

The study tests the extent to which primary care physician supply (office based primary care physicians per 10 000 population) moderates the association between social inequalities and infant mortality and low birth weight throughout the 50 states of the USA.

DESIGN

Pooled cross sectional, time series analysis of secondary data. Analyses controlled for state level education, unemployment, racial/ethnic composition, income inequality, and urban/rural differences. Contemporaneous and time lagged covariates were modelled.

SETTING

Eleven years (1985-95) of data from 50 US states (final n = 549 because of one missing data point).

MAIN RESULTS

Primary care was negatively associated with infant mortality and low birth weight in all multivariate models (p<0.0001). The association was consistent in contemporaneous and time lagged models. Although income inequality was positively associated with low birth weight and infant mortality (p<0.0001), the association with infant mortality disappeared with the addition of sociodemographic covariates.

CONCLUSIONS

In US states, an increased supply of primary care practitioners-especially in areas with high levels of social disparities-is negatively associated with infant mortality and low birth weight.