Health disparities among young American adults born after 1980 have grown substantially, according to a new study led by
Hui Zheng, assistant professor of sociology at Ohio State University, that is published in the December issue of the American
Zheng and colleagues also found that the gaps tend to widen as people reach middle age, and then narrow again as they reach old age.
They suggest this is because most young people are generally healthy, and at this stage, disparities stay low. But as they age, some develop health problems and diseases, so disparities grow. But these fall off again in old age as sicker people die and healthy ones remain. In old age there may also be an effect from older people sharing similar health risk factors due to frailty, and there may also be an equalizing effect from health care usage and protection through Medicare coverage for the elderly.
The implication of these two findings is that the overall gap between the healthiest and the least healthy Americans will get bigger and bigger for the next ten or even twenty years, as the younger adults get older and replace previous generations.
Zheng told the press:
"As young people today reach middle age and preceding cohorts with a smaller health gap die off, we expect health disparities in the whole population to grow even larger."
Much of this prediction depends on whether the trend of large health disparities will continue in future generations, as we see now in the present baby boomer generation. Zheng expects it will, bringing wider gaps in the coming decades.
This has not always been the case, say the authors: before the baby boomer generation, health disparities were getting smaller, for those born in the early part of the 20th century. But from the baby boomers onwards, they widened again.
Baby boomers are people born during the surge in births that followed World War II. Today, the oldest baby boomers are in their mid-60s, and the youngest are in their late 40s and early 50s.
Zheng said the fact they used an innovative new method, means the study gives one of the clearest and most comprehensive accounts ever of health disparities in the US.
Their method combines two statistical models (the Variance Function Regression model and the Hierarchical Age-Period-Cohort model) allowing them, for the first time, to disintangle three factors that influence health disparity over time.
The three factors are: how old people are, when they were born, and when their health is assessed (the cohort they belong to). Zheng said this was the first time they had been able to look at the effect of these factors together, and also see how each interacts with the other two to influence the gaps in health.
For their study they used data covering 1984 to 2007 from the National Health Interview Survey, which every year, asks about 30,000 people to rate their own health on a five-point scale from poor to excellent.
Although the data is based on self-report, a method that usually attracts criticism because it is not based on objective assessments, Zheng says it is actually a good indicator of objective health. For instance, there is plenty of evidence that self-reported health is a better predictor of mortality among the elderly than doctor assessments, said Zheng.
Zheng and colleagues adjusted their findings to rule out potential influence from other factors known to affect health, such as race, gender, marital status, education, income level and employment status.
The results showed that:
- Self-rated health has declined significantly since the late 1990s.
- Overall, late baby boomers, that is those born between 1955 and 1964, reported enjoying better health than any other age group.
- A large gap opened for people born since 1980 (showing a wider spread among the five health categories from poor to excellent).
For example, income inequality has widened significantly in the last 30 years in the US. This could affect access to health care and other resources important to good health, such as food and recreational facilities.
Another reason could be the increase in the immigrant population, which affects the distribution of health ratings, while the rising obesity epidemic adds to those in poor health.
A third reason could be the growing "digital divide" with those who are able easily to access medical and health information in the digital age at a greater advantage than those who are not able to do so.
But Zheng says the main driver of health disparity in the overall population in the coming decades is the result of what is happening with young adults born after 1980. Because they have a wider gap in health disparities than previous generations, when you add that to the fact that disparity goes up and then down again anyway from young adulthood into middle age and then old age, you have a widening of disparities as the younger generation replaces the older ones.
The researchers also found health differences between men and women as they go from young adults through middle age into their final decades. There is quite a large gap in early adulthood, with men reporting better health than women, but this narrows until around age 61, as men are the sex more likely to have the more serious chronic diseases such as heart disease. Then, as the sicker men die off, the gap widens again because the men that remain are healthier, while there is a relatively larger proportion of women with poorer health who remain alive into old age.
Zheng said their model could also be used to unravel and compare the effects of age, period and cohorts in other types of inequality such as income, wealth and education.
Written by Catharine Paddock PhD