Methods Matter: Investigating Causation & Correlation Are Local Health Department Expenditures Related to Racial Disparities in Mortality? David Grembowski University of Washington Funded by the Robert Wood Johnson Foundation & Changes in Health Care Financing and Organization

Outline Write the question Apply a conceptual model Choose a study design Identify data sources Measure mortality disparities Identify control variables in conceptual model Link mortality & control variables Adjust for baseline mortality differences Address variation in covariates over time Deal with reverse causation Data analysis & results Assess external validity Limitations

Write the Question Are local health department expenditures related to racial disparities in mortality? - or - What is the effect of local health department expenditures on racial disparities in mortality?

Apply a Conceptual Model Physical & Social Environment Behavior Human Biology Population Health & Disparities Medical Care Public Health

Can Local Public Health Reduce Racial/Ethnic Disparities?  Yes!  Population-based interventions that influence everyone have the potential to reduce health disparities Water fluoridation, highway safety improvements Raising the health of the worst off fastest  No!  Population-based interventions that depend on voluntary participation may increase disparities because people with more resources are more likely to take advantage of them  Goal of improving population health may conflict with goal of reducing health disparities Link & Phelan 2005; Mechanic 2002

Choose a Study Design: Internal Validity Longitudinal (randomized) experiment Longitudinal observational data Cross-sectional observational data

Choose a Study Design Time-Trend Ecologic Study Design Test whether changes in LHD spending per capita are associated with changes in Black & White mortality rates (Temporal rather than causal effects)

Identify Data Sources LHD expenditures 1990 & 1997 National Profiles of Local Health Departments from the National Association of County and City Health Officials (NACCHO) 1990 & 1997 Black and White mortality rates from CDC County Sociodemographic and Government Characteristics from U.S. Census & Area Resource File County Medicare expenditures from Centers for Medicare and Medicaid Services Rural/urban county commuting codes from Department of Agriculture

Measure Mortality Disparities Population Health Paradox Population health has increased in many developed countries Disparities in population health have increased in many developed countries

Absolute Change vs. Relative Disparity in Infant Mortality by Racial/Ethnic Group 2002-Absolute Change Black White B/W Rate Ratio * bigger gap * 1950 Black/White Rate Ratio = 44/27 = 1.63 Infant mortality rate: rate of deaths in children less than 1 year old per 1,000 live births Health, United States, 2007

Absolute Change in All-Cause Black Mortality Rates in Local Areas

Change in Black/White Rate Ratios in Local Areas

Identify Observed & Unobserved Control Variables in Conceptual Model Social EnvironmentBiology Education Female Income Income inequality Physical Environment White collar occupation Rural/Urban Unemployment Household size Medical Care Single female household Medicare expenditures Percent Black Hospital beds Foreign residents Physicians English speaking VeteransBehavior Home values Drive to work People in mental institutions People in correctional institutions

Link Mortality & Control Variables Black mortality = f(Black income per capita) White mortality = f(White income per capita) Black/White = f(Black/White income per capita) rate ratio

Adjust for Baseline Differences in Mortality BM 97 – BM 90 = f((LHD$ 97 – LHD$ 90 ), Covariates) - or - BM 97 – BM 90 = f(BM 90, (LHD$ 97 – LHD$ 90 ), Covariates) BM: Black mortality rate LHD$: Local health department spending per capita

Address Time-Invariant & Time-Variant Covariates Time-Invariant Covariates (?) Smoking is Unobserved (no county data) WM = White mortality rate WM 90 = f(Education 90, Smoking 90 ) WM 97 = f(Education 90, Smoking 90 ) WM 97 – WM 90 = f((Education 90 – Education 90 ), (Smoking 90 - Smoking 90 )) Time-Variant Covariates (?) WM 97 – WM 90 = f((Education 97 – Education 90 ), (Smoking 97 - Smoking 90 ))

Deal with Reverse Causation Physical & Social Environment Behavior Human Biology Population Health & Disparities Medical Care Public Health Spending Instrumental Variable

Deal with Reverse Causation  1990 Cross-Sectional Analyses  Endogeneity tests significant  Instrumental variables for 1990 LHD spending  County government revenue per capita  Average county home value Longitudinal Change in Mortality Endogeneity tests mostly not significant No IV identified for changes in health department spending

Data Analysis & Results  General Estimating Equations (GEE) 40 binary (0,1) State variables to control for State-level influences on local areas Standard errors adjusted for clustering of local areas by Federal Region Hausman-Durbin-Wu test for 2-way causation between LHD spending and mortality

Results Per capita LHD expenditures generally not related to disparities in all-cause, all- age Black and White mortality rates and infant mortality rates We also are analyzing whether LHD services are related to Black/White disparities in mortality

Assess External Validity Mortality Rates & 1990/1997 Profile Surveys Areas Areas withwithout ProfileProfile SurveysSurveys Both YrsBoth Yrsp-value Absolute Change Black mortality White mortality Black infant mortality White infant mortality ___________________________________________________________________________________

Limitations Study design Omitted variables (e.g., population-level smoking, medical care rates) No data for LHDs without Profile Surveys No data for how LHDs spent funds in 1990/97 Profile Surveys No data for public health spending by other community agencies Black county populations often too small to calculate cause of death mortality rates (by gender and by age group) Only 2 racial/ethnic groups

Are Local Health Department Expenditures Related to Racial Disparities in Mortality? David Grembowski Douglas Conrad Betty Bekemeier William Kreuter Eric Darst University of Washington Funded by the Robert Wood Johnson Foundation & Changes in Health Care Financing and Organization