After 83, blacks may live longest, census finds

December 08, 1992|By Boston Globe

Demographers are puzzling over a persistent riddle in federal census data: Blacks compose only 14 percent of the U.S. population but 19 percent of people over age 100, even though they generally have less access to medical care and face greater obstacles to survival.

Black infant mortality, for instance, is twice that of whites. Blacks are seven times more likely than whites to die of homicide and three times more likely to die of acquired immune deficiency syndrome. Of the 15 leading causes of death, all but two are higher for blacks at all ages, said Sandy Smith, a spokeswoman for the National Center for Health Statistics.

Yet a curious thing happens at roughly age 83, federal figures show. Life expectancy -- the number of years a person probably has left -- becomes equal for blacks and whites, a moment demographers called the "mortality crossover" point.

After age 84, life expectancy is higher for blacks than for whites -- and no one really knows why.

The most intriguing explanation, said demographer Charles Nam, associate director of the Center for the Study of Population at Florida State University, is that very old black people may be examples of a selective "survivor effect," unusually hardy individuals who manage to avoid most of the medical threats that kill their peers.

Take Minnie Belle Ward, for instance, the daughter of a Tennessee Baptist minister who, she said, preached back "in slavery time." Ms. Ward, a former schoolteacher who is 107, has outlived not only her husband, a Baptist minister in Boston, but also siblings and some of her children.

So has Gladys Olivia Washington Pinderhughes, now a widow for nearly a quarter-century. At 100, she still does her knee bends every morning in her son's Boston home and presides graciously over her large and accomplished clan.

(She also is an aunt of the former Baltimore school superintendent, Alice G. Pinderhughes, and a great-aunt of Baltimore attorney Alice Pinderhughes. Ms. Pinderhughes, the attorney, said that she sees her great-aunt at reunions and that she remains "very alert. She knows what's going on.")

Mr. Nam said the mortality crossover phenomenon has been observed not just between blacks and whites in America but also around the world in comparisons of different socio-economic groups.

As members of any disadvantaged group go through life, he said, only the hardiest manage to avoid the myriad of accidents and diseases that lie in wait. In later life, these hardy few have a better-than-average chance of reaching 100 or more.

In contrast, he said, an advantaged group by midlife consists of many individuals who are actually quite frail, alive only through the grace of medical intervention. By late life, the latent frailty of some members of this group overcomes their advantages.

Appealing as the survivor theory is, there is another, more mundane theory for overrepresentation of blacks among the nation's 36,000 centenarians: It may not be real.

Virtually all demographers agree that federal census data contain many errors in age reporting among the nation's oldest citizens.

The error rate may be higher among blacks because they "were born disproportionately in the South, and the South was the last region to have birth registration," said Sam Preston, a University of Pennsylvania demographer.

Indeed, Mr. Preston has found error rates as high as 40 percent when age information from Social Security files is correlated with age data on death certificates.

Besides, he argues, it simply does not make sense that a population group that has faced tougher survival odds throughout life will suddenly have better survival rates later in life.

Ansley Coale, a demographer emeritus from Princeton University New Jersey, agrees, citing studies showing a correlation between high infant mortality and higher mortality throughout the lifespan.

In fact, Mr. Coale said, as age reporting and census-taking have become more accurate over the years, the number of documented black centenarians has been dropping. But Mr. Coale has not thrown out the notion of particularly hardy black survivors altogether. He tried to correct statistically for errors in age reporting and found that, although most of the difference in survivalrates disappeared, it didn't vanish.

Enter Kenneth Manton, a demographer at Duke University in Durham, N.C., who decided not to use questionable census data at all; instead, he used data from two longitudinal health studies in which black and white participants' ages were verified and each patient was followed for years.

These two large studies convinced Mr. Manton that the hardy survivor effect "is real for several reasons," among them the fact that diseases that disproportionately kill blacks, such as hypertension, tend to cause death earlier in the life cycle than the diseases that kill whites disproportionately, such as atherosclerosis.

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