摘要：Objectives. We tested the association between the availability of primary care and income inequality on several categories of mortality in US counties. Methods. We used cross-sectional analysis of data from counties (n=3081) in 1990, including analysis of variance and multivariate ordinary least squares regression. Independent variables included primary care resources, income inequality, and sociodemographics. Results . Counties with higher availability of primary care resources experienced between 2% and 3% lower mortality than counties with less primary care. Counties with high income inequality experienced between 11% and 13% higher mortality than counties with less inequality. Conclusions. Primary care resources may partially moderate the effects of income inequality on health outcomes at the county level. There is strong theoretical and empirical evidence for the association between strong national primary care systems and improved health indicators. 1– 4 US ecological studies have demonstrated an association between the primary care physician-to-population ratio and various health outcomes. Better health outcomes were found in states with higher primary care physician-to-population ratios after sociodemographic measures (elderly populations, urban residents, minority populations, education, income, unemployment, pollution) and lifestyle factors (seatbelt usage, obesity, and smoking) were controlled for. 5 Geographic areas with more family and general physicians had lower hospitalization rates for conditions preventable with good primary care. 6 Individual-level and state-level measures of primary care resources were also significantly associated with lower heart disease and cancer mortality rates. 7– 11 Although many of the previous studies controlled for both environmental and individual-level determinants of health, a new appreciation of the role of contextual-level determinants of population health emerged during the past decade. In particular, there is an ongoing debate over the role of the distribution of income as a determinant of population health, with evidence both supporting and refuting what has become known as the relative income hypothesis —the proposition that the greater the gap in income between the rich and the poor in a given area, the worse the health status for the overall population of that area. 12– 15 Although international and cross-country studies of the relative income hypothesis have resulted in conflicting conclusions, 16– 18 there is considerable evidence that, at least within the United States, income inequality is associated with poorer population health. 19– 21 The pathways through which income inequality might affect health are still unknown, and hypotheses include psychosocial and material pathways. 12, 19 In this study, we use income inequality as a proxy for social inequalities regardless of their cause. We include the measure of unequal income distribution as a measure of underlying social inequalities in order to test whether primary care resources might be one strategy to help remedy the poorer-than-expected health profile seen in communities that suffer from income and other social inequalities. Our previous studies suggested that the availability of primary care partially attenuates the adverse effects of other community-level risk factors for poorer health, such as income inequality. Shi and colleagues 22 found that the supply of primary care services had an independent and positive impact on health indicators, and that in multivariate models when demographic, income, and health system covariates were controlled for, a higher supply of primary care services actually reduced the magnitude of the deleterious impact of income inequality on health outcomes. Using a multilevel model that included individual, community, and state-level variables, Shi and Starfield 23 found that even when they controlled for all covariates, an increase of 1 primary care physician per 10000 population was associated with a 2% increase in the odds of reporting excellent/good health. Although previous studies have examined the relation between income inequality, primary care, and health outcomes, questions remain about the level of aggregation in which contextual effects occur. This study tests the extent to which these effects are present at a smaller level of analysis: US counties. We chose counties because they represent distinct political and geographic units, are an important unit of local decisionmaking, and are used by health and social services organizations to plan and provide many (but not all) public health and other social programs.
