Causes of Life-Expectancy Gap Between Races, Education Levels ID’d

UCLA researchers for the first time have identified and ranked which diseases contribute most to the life-expectancy gap between races and between education levels. The top four contributors to the life-expectancy disparity between blacks and whites are hypertension, HIV, homicide and diabetes. The top six contributors of mortality differences between education levels are all smoking-related diseases.

The most comprehensive study of its kind, reported in the Nov. 14 issue of the New England Journal of Medicine, the study will help better target public health interventions to help close these life-expectancy differences. This study examines national data on the health and mortality of adults in the United States and accounts for the very latest trends in HIV/AIDS mortality.

Previous studies have shown that blacks and those who never completed high school live an average of six fewer years than whites and high school graduates, respectively. Federal and state public health officials have made the elimination of these health disparities a primary goal. Until now, no study has ever identified which specific diseases and conditions account for these life-span differences.

“Health disparities are pervasive and exist for many diseases ? making it difficult to focus public health interventions,” said Dr. Mitchell Wong, lead investigator and assistant professor, UCLA Division of General Internal Medicine and Health Services Research.

“This new research is a step toward pinpointing the factors that influence life expectancy the most. In turn, these factors might suggest how to intervene to reduce disparities in health and mortality,” said Richard M. Suzman, associate director of the National Institute on Aging for the Behavioral and Social Research Program, one of the funders of the study.

UCLA researchers estimated risk of death from specific causes from a national sample of approximately 600,000 adults, age 18 and older. The data was taken from the 1986?94 National Health Interview Survey, an annual poll of U.S. households, and from the Centers for Disease Control surveillance data on HIV trends in mortality. Using advanced techniques in mathematical modeling, the researchers were able to construct a detailed picture of disparities in life expectancy.

Researchers identified hypertension as the leading contributor to the life-expectancy gap between blacks and whites ? accounting for 15 percent of the gap. HIV accounted for 11 percent of the gap ? more than heart attacks, strokes and all types of cancer, combined. Diabetes and homicide each accounted for 8 percent.

“These results identify achievable goals for public health efforts since the top contributor ? hypertension ? can be easily screened for and treated, and HIV is, in theory, entirely preventable,” Wong said. “Public health efforts should clearly be most effective in reducing disparities in life expectancy by focusing more interventions to improve screening and treatment for conditions such as hypertension, diabetes and HIV in targeted populations.”

According to Wong, previous studies had focused heavily on racial and socioeconomic differences in treatment for heart attacks and cancer. Wong said that the new study found that heart attacks only account for 6 percent of the total difference in mortality for blacks compared to whites, while all cancers combined only account for 3 percent. “This constitutes a major change from previous studies and should help redirect public health efforts.”

Wong also noted that researchers expected the life-expectancy gap between races to narrow with the introduction of more effective HIV treatment in 1996. Wong estimated that before 1996, HIV accounted for 18 percent of the racial difference in life expectancy. The new study showed that number dropped to 11 percent after 1996, which is still very high. Wong noted that the use of newer HIV treatment medications has been lower among blacks than among whites ? resulting in HIV mortality improving more for whites than for blacks. If the mortality trend had been equal, the study estimates, HIV would have dropped even further to 6 percent.

Researchers also identified the top six diseases contributing to the life-expectancy gap between high school graduates and those who didn’t finish high school. Heart attacks were responsible for 12 percent of the gap, followed by lung cancer accounting for 8 percent, stroke at 6 percent, and pneumonia, congestive heart failure and chronic lung disease, each responsible for 5 percent of the gap. Together, these conditions account for about 40 percent of the total mortality disparity according to education levels ? and all six diseases are smoking-related.

Previous studies have indicated that smoking does not completely account for socioeconomic disparities in life expectancy. Wong noted that this conclusion, though correct, may have taken too much focus away from smoking. “Smoking is clearly harmful and an important contributor to health disparities. Our study suggests that public health efforts targeting smoking might substantially reduce the educational differences in life expectancy,” Wong said

The next step, according to Wong, is more research to find out how and why these conditions and diseases cause mortality disparities. Wong noted that insurance coverage, accessibility of health care, quality of care, health behaviors and other factors may play a role.

The analysis by Wong and colleagues was supported as part of the University of Southern California-UCLA Center on the Demography of Aging, funded by the National Institute on Aging. The center is one of 11 across the United States that provide research on the health, economic and social issues presented by an aging population.

The study was also funded by an Institutional National Research Service Award from the Health Resources and Services Administration, the UCLA Department of Medicine STAR program, the Irving and Mary Lazar Program in Health Services Research, and an EXCEED grant from the Agency for Healthcare Research and Quality.