WASHINGTON, Nov. 2 (UPI) -- In the United States today, black residents overall can expect to live six fewer years than their white counterparts, and the main culprits are cardiovascular disease, cancer and diabetes, which together account for about two thirds of the gap.
External factors explain a great deal of why blacks are more likely to die of those diseases. Lower socioeconomic status, a less healthy and more dangerous environment, and lifestyle-related factors like obesity explain a majority -- but not all -- of the difference in life expectancy.
Thus, medical researchers are increasingly looking into the role that inherent physiological characteristics of populations play in determining health outcomes. The end result, some experts predict, will be a more personalized form of medicine where treatments, especially drugs, are tailored to each person's specific needs.
In 1998, the Food and Drug Administration acknowledged the need to take into account the physiological differences among various populations when it issued guidelines for drug trials designed to encourage testing on a diverse range of groups.
"We always try to encourage people to go out of their way to include different racial groups," FDA spokesperson Megan Moynahan told United Press International. "We also ask -- if racial data is available for a study -- that that information be included."
More recently, in June 2005, the agency took that racial awareness a step further by approving BiDil, a drug for treating African American heart attack patients that is the first medicine specifically intended for a racial or ethnic group.
David Cutler, a professor of health policy at Harvard University is currently working on a project looking for possible causes of the racial disparities in health outcomes that cannot be accounted for by external factors.
"At the end of the day, 35 percent of the (health disparity) is left to explain," Cutler said at a recent research presentation at the Brookings Institution.
One of the possible explanations he has put forth stems from an observed medical mystery. African Americans have a higher rate of high blood pressure than whites, but lower cholesterol.
This has left researchers looking for potential causes of high blood pressure aside from high cholesterol and one such potential cause dates back to Africans' journey to the Americas via the transatlantic slave trade.
African Americans have a higher level of salt sensitivity -- a reduced ability of the body to process salt -- than both white Americans and Africans currently living in west Africa from where most slaves were taken.
Cutler thinks that may be due to the fact that salt sensitivity helps individuals retain water -- something that could be crucial to survival in dehydrating conditions of slave ships. If more individuals with salt-sensitivity were able to survive, it could explain the higher incidence of the trait among African Americans.
"Salt sensitivity is something that helps you when water is scarce, but hurts you in a salt-rich environment like the U.S.," he said.
The research could be years from being complete because crucial evidence on things like the heritability of salt sensitivity is lacking, Cutler cautions. It is also not clear what the precise effects of salt-sensitivity are on blood pressure.
But preliminary evidence suggests the salt sensitivity gap could account for as much as a third of the racial mortality gap, given the fact that 54 percent of blacks are salt sensitive compared to 38 percent of whites, and that people who are salt sensitive were shown in one study to have a 73 percent higher mortality rate over a 27-year period, Cutler said.
Others caution, however, that stopping at racial groups is not enough in the quest to make medicine better fit patients. Brian Smedley, who served as research director of a seminal 2002 Institute of Medicine report on the racial health divide, warns that while different populations have different needs, the concept of race is more cultural than biological, thus making it a poor basis on which to target drugs.
