Growing US disparities in health not inevitable

In the public health field, there is an ongoing debate as to whether improvement in the overall health of the population is linked to increases or decreases in social inequities in health, that is, the inequities between higher-income and lower-income groups or people of different race/ethnicities.

In the most comprehensive study to date addressing this debate, researchers at the Harvard School of Public Health (HSPH) found that, as overall health improved (as measured by a decline in mortality rates), inequities in health both shrank and widened between 1960 and 2002. The study demonstrates that the recent trend of growing U.S. disparities in health status is not inevitable.

“Our papers refutes the argument, currently gaining ground, that as overall population health improves, it is inevitable that socioeconomic disparities in health will increase, allegedly because the better-off more quickly take advantage of health-promoting resources,” said Nancy Krieger, professor of society, human development and health at HSPH and the study's lead author. “Instead, we clearly show that this argument is flawed because, in the period from 1966 to 1980, socioeconomic disparities declined in tandem with a decline in mortality rates.”

Journalists can preview the paper here: http://www.plos.org/press/plme-05-02-krieger.pdf. The study will be published in the February 26, 2008 issue of the open-access journal PLoS Medicine. At that time, the paper will be freely available here: http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0050046

Krieger and her co-authors set out to test the hypothesis that health inequities widen—or shrink—in a context of declining mortality rates. Prior studies had typically gone back only to the 1980s and had found evidence chiefly of growing health disparities. The HSPH researchers looked at two measures of population health--rates of premature mortality (dying before the age of 65) and rates of infant death (dying before the age of 1)--during the period from 1960 to 2002. They measured both absolute and relative inequities. U.S. county mortality rates were ranked for different county income levels and for the total population as well as for U.S. whites and U.S. people of color.

The results showed that mortality rates declined among all county income groups. Between 1966 and 1980, absolute and relative inequities in premature mortality shrank, especially for people of color. After 1980, relative inequities increased, while absolute inequities stayed flat. The same trends were apparent for the inequities in infant death rates.

Quantifying the burden of socioeconomic and racial/ethnic inequities in premature mortality, the authors found that from 1960 to 2002, 14% of the white premature deaths and fully 30% of the premature deaths among people of color would not have occurred had all persons experienced the same yearly age-specific premature mortality rates as whites living in the most affluent counties.

By providing a more complete picture of the trends in mortality and disparities, the researchers are able to hypothesize about the findings. One possible explanation is that health inequities narrowed in the earlier period because of the positive effect of social programs in the 1960s, such as the “War on Poverty,” the establishment of Medicare, Medicaid and community health centers, and civil rights legislation. Starting in the 1980s, there was a general rollback in public health and antipoverty programs in the U.S., which would explain the widening and persistence of health disparities beginning in the 1980s.

The results are important, say the authors, because it provides an empirical basis to the view that health inequities can be lessened in a context of declining mortality rates. “The public health implication is that, while death is inevitable, premature mortality is not, and neither are social inequities in premature mortality,” said Krieger. “It is our job to ascertain what changed in the U.S. to produce these differing trends. A good place to start is examining the differential health impact of major U.S. policies regarding socioeconomic and racial/ethnic inequality that were enacted in the mid-1960s versus those enacted since the 1980s,” she said.