Researchers have long noted the connection between health and wealth. People with higher incomes tend to be healthier and live longer than poor people.
But why this is so has puzzled experts for as long as the connection has been known. Evidence has been thin to nonexistent to support the most intuitive reasons: access to health care, income inequality and environmental factors.
A recent study appears to shed new light on this quandary, and its conclusions suggest that behaviors – smoking, diet and exercise – are the most important factors driving health disparities.
The research, published this month in the Journal of the American Medical Association, examined more than 7 million deaths over a 15-year period, along with geography and numbers on the factors most often suspected of contributing to the health gap between rich and poor.
The study confirmed that, in general, wealthier people live longer than poor people. Adjusted for race and ethnicity, the average 40-year-old in the lowest quarter of the income distribution can expect to live to be 79. A person in the top quarter of the income range typically lives to be 86.
But the real news is that this life expectancy gap is not universal. Low-income people in some places live longer than poor people elsewhere.
California is one place where poor people do better. Of the 100 U.S. communities examined in the study, six of the 10 places where life expectancy for low-income people was highest were in California: Santa Barbara, San Jose, Los Angeles, San Diego, San Francisco and Santa Rosa.
So what’s going on?
Health advocates know that in some places, low-income people have more access to better health care. So researchers looked at the number of uninsured; spending on Medicaid, the government health program for the poor; and two measures of quality for primary care and hospitals. But none of these factors explained the gap.
Next the researchers looked at environmental factors. They examined whether low-income people living in more segregated communities and more likely to be exposed to toxins died sooner. They found the opposite. Poor people in more segregated places actually lived longer than low-income people in more integrated communities.
What about income inequality? It’s one of the most contentious issues in politics and policy and is often blamed for health disparities. Again, the researchers found no correlation.
Finally, the researchers found that labor market conditions – unemployment and changes in the size of the labor force – had no significant impact on life expectancy.
The researchers did find positive connections between life expectancy and the fraction of immigrants in a community, median home prices, local government spending, population density and the proportion of college graduates.
But the most significant variables the researchers found were rates of smoking, obesity and exercise.
“The strongest pattern in the data,” the researchers concluded, “was that low-income individuals tend to live longest (and have more healthful behaviors) in cities with highly educated populations, high incomes, and high levels of government expenditures.”
And that’s true even if those areas – including New York, Los Angeles and San Francisco – also have high levels of income inequality.
Speculating about why this might be so, the researchers suggested that these areas might have more aggressive public health campaigns and more effective social services to support low-income people.
But they couldn’t say for sure, and that will likely be a focus of future research. The sooner we find the answer, the sooner society will be able to reduce, and hopefully eliminate, those disparities.
Daniel Weintraub is editor of the California Health Report. He can be contacted at Daniel.firstname.lastname@example.org.