Have recent changes in public health spending influenced community health? An instrumental variables analysis

OBJECTIVES: Public health activities are supported through a patchwork of funding streams that vary considerably across communities and fluctuate over time. This instability in spending may have important consequences for community health, but measuring these effects is complicated by the fact that spending levels may be shaped by factors that also influence health, including a community's socioeconomic status (via the tax base) and its underlying health needs (via grant funding formulae). The objectives of this analysis are to: (1) examine how local public health spending levels have changed over the past decade; and (2) determine whether changes in public health spending are associated with changes in community health status and disease burden.

METHODS: A longitudinal cohort design is used to analyze changes in spending patterns and community health within service areas of the nation's 2900 local public health agencies between 1993 and 2005. The National Association of County and City Health Officials (NACCHO) collected data on these agencies through census surveys fielded in 1993, 1997, and 2005 (response rates 72-88%). We linked these data with contemporaneous information on community and state characteristics, federal and state spending, and disease burden from other data sources. Multivariate, hierarchical regression models for panel data are estimated to test for changes in spending patterns over time and differences across communities defined by demographic, economic, organizational and geographic characteristics. Instrumental-variables methods are used to identify associations between spending levels and community health while controlling for unmeasured factors that jointly influence spending and health.

RESULTS: Local public health spending increased from a median of $27 per capita in 1993 to $29 in 2005 (constant dollars), indicating an annual growth rate of less than 1%. Larger increases in spending were observed among agencies serving metropolitan areas, communities with higher per-capita income, and agencies governed by local boards of health (p<0.01), even after adjusting for other agency and community differences. After controlling for these differences, increases in spending were associated with significant improvements in several key measures of community health, including infant mortality and case rates for clamydia, gonorrhea, hepatitis, and tuberculosis (p<0.05). Instrumental-variables estimates indicate that these spending effects are even larger after accounting for unmeasured characteristics that jointly influence spending and health.

CONCLUSIONS: Differences in spending may contribute to differences in community health status. Efforts to improve local public health resources and infrastructure may help to address disparities in health status across communities.