Class informs everything from the circumstances of patients’ heart attacks to the emergency care each receives, the households they return to and the jobs they hope to resume. It shapes their understanding of their illness, the support they get from their families, their relationships with their doctors. It helps define their ability to change their lives and shapes their odds of getting better. 

Class is a powerful force in health and longevity in the United States. The more education and income people have, the less likely they are to have and die of heart disease, strokes, diabetes and many types of cancer. Upper-middle- class Americans live longer and in better health than middle-class Americans, who live longer and better than those at the bottom. And the gaps are widening, say people who have researched social factors in health. 

As advances in medicine and disease prevention have increased life expectancy in the United States, the benefits have disproportionately gone to people with education, money, good jobs and connections. They are almost invariably in the best position to learn new information early, modify their behavior, take advantage of the latest treatments and have the cost covered by insurance. 

Many risk factors for chronic diseases are now more common among the less educated than the better educated. Smoking has dropped sharply among the better educated, but not among the less. Physical inactivity is more than twice as common among high school dropouts as among college graduates. Lower-income women are more likely than other women to be overweight, though the pattern among men may be the opposite. 

There may be subtler differences. Some researchers now believe that the stress involved in so-called high-demand, low-control jobs further down the occupational scale is more harmful than the stress of professional jobs that come with greater autonomy and control. Others are studying the health impact of job insecurity, lack of support on the job, and employment that makes it difficult to balance work and family obligations. 

Then there is the issue of social networks and support, the differences in the knowledge, time and attention that a person’ s family and friends are in a position to offer. What is the effect of social isolation? Neighborhood differences have also been studied: How stressful is a neighborhood? Are there safe places to exercise? What are the health effects of discrimination? 

“In the last 20 years, there have been enormous advances in rescuing patients with heart attack and in knowledge about how to prevent heart attack, ” said Ichiro Kawachi, a professor of social epidemiology at the Harvard School of Public Health. “It’ s like diffusion of innovation: whenever innovation comes along, the well-to-do are much quicker at adopting it. On the lower end, various disadvantages have piled onto the poor. Diet has gotten worse. There’ s a lot more work stress. People have less time, if they’ re poor, to devote to health maintenance behaviors when they are juggling two jobs. Mortality rates even among the poor are coming down, but the rate is not anywhere near as fast as for the well-to-do. So the gap has increased. ”