SOCIOECONOMIC STATUS: Unmasking the Stress, Health Link
Long overlooked as an explanation for disease, socioeconomic status -- which unleashes very real physiological effects -- is gaining acceptance as a driving force behind some illnesses, not just a correlative factor, according to hundreds of researchers convened at the New York Academy of Sciences' SES conference May 10-12. Chronic stress to the body -- such as insufficient nutrition or substance abuse -- accumulates, plays out in health- related behaviors and ultimately translates into physical illness, such as cardiovascular disease and diabetes. In short, it is not just dramatic stress events that take their toll on the body, according to Dr. Bruce McEwen, director of the laboratory of neuroendocrinology at Rockefeller University. While short- term stress can jump start the immune system and actually enhance immune response, McEwen said, long-term exposure can jam up the body's stress system and damage normal immune response. The accumulation of daily stress factors into the body's allostatic load -- an indicator of the strain produced by the repeated ups and downs of physiologic responses. Some of the most potent stressors, which in turn promote damage to the immune system, are incurred by less well-off members of society and those who are vying to move up. Indeed, McEwen said, social ordering in human society precipitates health gradients, with an increasing frequency of mortality, cardiovascular disease and type II diabetes among those at the lower end of the SES scale.
Health disparities follow a continuum from low status all the way to those at the high end of the scale, as determined by income, education and occupation. Accordingly, researchers said, health status disparities are the widest where socioeconomic inequalities are the greatest. And SES appears to have lasting effects: status early in life is a potent predictor of health later in life, with people who rise from low status as children less likely to be healthy adults than those who started life at a higher level, according to Dr. Michael Marmot of the University College London. However, Marmot notes that the stress of an income drop -- even for a highly educated, upper level employee with a good salary -- can impact mortality. According to one study, he said, people who made $70,000 a year with no drop in income had a mortality rate lower than that of their counterparts making $70,000 but had incurred an income drop.
Multiple levels of risk factors come into play, said George Kaplan of the University of Michigan School of Public Health, pointing to social and economic policies, communities, work, family, social groups, culture, diet, hostility and biological effects, to name a few. And while most studies have not pitted one risk factor against another, the social environment predicts morbidity and mortality even when individual SES characteristics are held constant.
No Magic Bullets
Although programs such as those that aim to curb smoking certainly have some benefits in decreasing individual disease risk factors, researchers agree, they are not magic bullets for eliminating health disparities. Other risk factors persist, said Dr. Nancy Adler of the University of California-San Francisco, noting that because SES exposes people to a host of stressors, eliminating one, such as smoking, will prove only marginally helpful. "People deal with stress by smoking; if you take smoking away, they may have other maladaptive ways of dealing with stress," she said. In addition, health promotion programs are disproportionately favored by the more affluent, which can actually exacerbate health disparities. Alder noted that when the surgeon general's report revealed that smoking caused health problems, the "higher SES people ... had more access to the information and more support for stopping." The same holds for expanding access to health care, Adler said, noting that while access is crucial for sick patients, "more of the action is in preventing. Access will help, but for many of the diseases, health care has a small impact, but much more of the action is why you got the disease in the first place."
Finally, because of the heavy influence of social environment, says Ichiro Kawachi of the Harvard School of Public Health, "intervening to reduce socioeconomic disparities in health requires that we focus on the characteristics of places as well as people" (Allison Morgan, American Health Line). Look for part two in tomorrow's California Healthline.