The new Science study suggests some American health inequalities may shrink as today's children become adults. | Michael Lamberty/ Flickr/ CC BY-NC 2.0
The life expectancy gap between America's rich and poor is shrinking for the young, a new study published in the 29 April issue of Science reports. In fact, life expectancy at birth has been improving for virtually all income groups born in 1990 onward.
"These results are extremely hopeful in that they suggest that today's children are going to grow up into healthier adults with less inequality in health in the future," said lead author Janet Currie, the Henry Putnam Professor of Economics and Public Affairs at Princeton University.
"We were surprised at how large the reductions in mortality have been for younger people," she continued, "and at how these reductions extend all the way into young adulthood; at how extraordinarily large the declines in African-American mortality have been; and finally, at how little attention anyone has paid to this incredible health success story."
The results of Currie and her colleagues suggest that many of the U.S. policies directed at improving the health of the young and the poor in recent decades may have been effective.
Previous research suggests that mortality inequality — differences in how long people live compared to their peers — has grown since the start of the 21st century, with Americans in the top income bracket having gained several years of life expectancy while those at the bottom have gained almost nothing, or have even experienced a decline in life expectancy.
Critically, however, much of this work was based on studies that calculate life expectancy of people starting at age 40 or age 50, ignoring improvements that have been occurring at younger ages — and that have been shown to be important predictors of a group's health and mortality later in life.
"The reason we got interested in this project," Currie said, "was that we knew that there have been tremendous improvements in the health of poor American children over the past 20 years. These improvements are due to specific policies such as expansions of public health insurance, improvements in food and nutrition programs, and expansions of the Earned Income Tax Credit. Yet, the dominant narrative has completely ignored these improvements."
To provide what they believe is a more accurate picture that accounts for those improvements, Currie and colleagues looked at the life expectancy of people from birth. Yet another important difference between their work and previous efforts is that they went beyond looking at life expectancy, instead looking at actual death rates at different ages.
"One thing I hope that people will take away from this study is a sense that inequalities in mortality are not inevitable but rather strongly mediated by policy. Things like health insurance, income support, and anti-tobacco initiatives really do make a noticeable difference at the population level."
"Non-demographers may not realize that all life expectancy rates are based on the assumption that mortality at each age will remain exactly the same as it is now," said Currie. "That is, when you calculate life expectancy starting at age 40, you assume that future mortality rates at ages 50, 60, and 70 for people who are now 40 will be exactly the same as they currently are for people who are currently ages 50, 60, and 70. In an era when mortality is changing, that is not a very good assumption. We argue that is much better to look at the age-specific mortality rates themselves, which is what we do in most of the paper."
Currie and colleagues studied inequality in mortality for all age groups in 1990, 2000, and 2010 in an analysis based on U.S. counties ranked by poverty levels.
They found that while mortality inequality at older ages (above age 75 for men and above age 45 for women) has been increasing (consistent with results from previous studies), mortality inequality for poor children up through poor adults age 20 has actually been declining rapidly. These mortality improvements were most pronounced in poorer counties, the researchers say, suggesting that the life expectancy gap between rich and poor is shrinking notably.
Since these younger groups will form the future adult U.S. population, this research suggests that inequality in old age mortality is likely to decline going forward.
While this study was focused on the United States, Currie said she is interested in comparing trends in mortality inequality in the U.S. to those in other countries that have more comprehensive health safety nets, like Canada. "My hypothesis is that countries that had more robust safety nets to start with will have seen smaller declines in inequality among the young over the period covered in our study," Currie said. She is currently investigating that hypothesis.
"One thing I hope that people will take away from this study," Currie said, "is a sense that inequalities in mortality are not inevitable but rather strongly mediated by policy. Things like health insurance, income support, and anti-tobacco initiatives really do make a noticeable difference at the population level."
"Hence, I hope the results will encourage policy makers to take measures to promote public health," she added. "A very timely example is funding to stop the spread of Zika virus in the U.S., which has been proposed by the CDC but is currently held up in Congress."