An examination of black/white differences in the rate of age-related mortality increase.

BACKGROUNDThe rate of mortality increase with age among adults is typically used as a measure of the rate of functional decline associated with aging or senescence. While black and white populations differ in the level of mortality, mortality also rises less rapidly with age for blacks than for whites, leading to the well-known black/white mortality "crossover".OBJECTIVEThis paper investigates black/white differences in the rate of mortality increase with age for major causes of death in order to examine the factors responsible for the black/white crossover.METHODSThe analysis considers two explanations for the crossover: selective survival and age misreporting. Mortality is modeled using a Gompertz model for 11 causes of death from ages 50-84 among blacks and whites by sex.RESULTSMortality increases more rapidly with age for whites than for blacks for nearly all causes of death considered. The all-cause mortality rate of mortality increase is nearly two percentage points higher for whites. The analysis finds evidence for both selective survival and age misreporting, although age misreporting is a more prominent explanation among women.CONCLUSIONSThe black/white mortality crossover reflects large differences in the rate of age-related mortality increase. Instead of reflecting the impact of specific causes of death, this pattern exists across many disparate disease conditions, indicating the need for a broad explanation.(ProQuest: ... denotes formulae omitted.)1. IntroductionHuman mortality rates begin to increase with advancing age starting around age 20 in most populations. Especially at older ages, age-related increases in the observed mortality rate are thought to reflect functional decline and processes associated with physiological aging. Gompertz (1825) originally noted that adult mortality increases exponentially as a function of age with remarkable consistency. That is, age-specific death rates increase at a nearly constant exponential rate for each year of age. Gompertz' model has enjoyed success as the most heavily used model of adult mortality, and remains a quintessential tool for demographers and gerontologists. Among the many attractive characteristics of the Gompertz model is an estimate of the percentage increase in mortality for each additional year of age, the Rate of Mortality Increase (RMI). Although this measure is assumed to be a species-typical indicator of physiological aging, human population subgroups exhibit significant differences in the rate of mortality increase (Horiuchi et al. 2003). Group differences in the rate of age- related mortality increase may reflect differences in accumulated risk over the life course or in the timing of the onset of specific diseases (Carey and Liedo 1995; Horiuchi and Wilmoth 1997; Luder 1993). In examining life course trajectories of mortality, comparing group differences in the rate of increase with age can supplement our understanding of differences in the level of mortality. One important comparison is blacks and whites in the United States. Although the vast majority of research on this topic focuses on black/white differences in the level of mortality, blacks and whites also differ in the slope of age-related increase (Elo and Drevenstedt 2004; Geronimus et al. 1996; Hayward et al. 2000). This leads to categorically distinct trajectories of mortality in the adult age range.Mortality profiles for the black and white populations in the United States differ considerably; blacks and whites experiences differences in the level and age-pattern of mortality and in the relative contribution of specific diseases. Studies examining the black mortality disadvantage throughout the life course also find that mortality increases more rapidly with age for whites than for blacks. Death rates for the two populations converge at older ages and mortality for whites begins to exceed that of blacks at the oldest ages (Manton et al. …