Geographic and racial variation in premature mortality in the U.S.: analyzing the disparities

Abstract

Life expectancy at birth, estimated from United States period life tables, has been shown to vary systematically and widely by region and race. We use the same tables to estimate the probability of survival from birth to age 70 (S(70)), a measure of mortality more sensitive to disparities and more reliably calculated for small populations, to describe the variation and identify its sources in greater detail to assess the patterns of this variation. Examination of the unadjusted probability of S(70) for each US county with a sufficient population of whites and blacks reveals large geographic differences for each race-sex group. For example, white males born in the ten percent healthiest counties have a 77 percent probability of survival to age 70, but only a 61 percent chance if born in the ten percent least healthy counties. Similar geographical disparities face white women and blacks of each sex. Moreover, within each county, large differences in S(70) prevail between blacks and whites, on average 17 percentage points for men and 12 percentage points for women. In linear regressions for each race-sex group, nearly all of the geographic variation is accounted for by a common set of 22 socio-economic and environmental variables, selected for previously suspected impact on mortality; R(2) ranges from 0.86 for white males to 0.72 for black females. Analysis of black-white survival chances within each county reveals that the same variables account for most of the race gap in S(70) as well. When actual white male values for each explanatory variable are substituted for black in the black male prediction equation to assess the role explanatory variables play in the black-white survival difference, residual black-white differences at the county level shrink markedly to a mean of -2.4% (+/-2.4); for women the mean difference is -3.7% (+/-2.3).

Figure 1. Probability of survival to age 70 for white males.

Probability of S₇₀ for white males by county, based on mortality rates 1999–2001. Small counties have been aggregated into Public Use Microdata Areas of >100,000 persons (N = 957).

Figure 2. Probability of survival to age 70 for black males.

Probability of S₇₀ for black males by county, based on mortality rates 1999–2001. Same method as for Figure 1 for counties with sufficient black deaths, N = 510; other counties are blank. Note the different scale from 1.

Figure 3. Absolute difference in survival to age 70 by county.

Absolute difference in S₇₀ by county between values depicted in Figure 2 (black) and Figure 1 (white). Note: Values of all differences appearing in color are negative.

Figure 4. Age and distribution of deaths before age 70.

The distribution of age at death for all deaths before age 70 for each subpopulation for all US in the year 2000.

Figure 5. Frequency distribution (kernel plot) for S₇₀.

Frequency distribution (kernel plot) of survival to age 70 county for each subpopulation, 1999–2001.

Figure 6. Correlation globes for the predictor and outcome variables for each of the four subpopulations, white males (A), white females (B), black males (C) and black females (D).

All correlations with (absolute value) r>.36 are shown. Black lines denote a positive correlation; red negative. The thickness of the line is proportional to the absolute magnitude of the correlation.

Figure 7. Actual S₇₀ (y-axis) vs. predicted (x-axis) for each subpopulation.

Note that circle size is proportional to county population (weight).

Figure 8. T-statistics (by sign and magnitude) for each significant predictor variable.

Test statistics from the four weighted OLS regressions. Note that five variables are omitted altogether from the figure because they produced significant associations for none of the four subgroups: PROPVALUE, PARTMETRO, GROWTH, SOUTH and PM_2.5.

Figure 9. Percent of counties with actual and predicted race differences (black-white) in S₇₀ for men (A) and women (B).

Red and blue bars represent percent of counties (N = 510) with actual and predicted race differences (black-white) in S₇₀ for men. The green bars on each panel represent the hypothetical black-white difference in predicted S₇₀ if blacks in each county were assigned the comparable white value for each predictor variable.