There is a growing disparity between healthy and sick Americans born after 1980, caused by various factors, including a widening income gap, obesity which tends to hit certain income and ethnic groups more, access to health care services, and some other factors, researchers from Ohio State University wrote in American Sociological Review.
The authors added that the difference in the health of people gets wider as they approach and reach middle age, before closing during old age.
This being the case, the researchers predict that over the next couple of decades, as younger generations get older and replace existing ones, differences will widen.
Lead Hui Zheng, said:
"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."
The trend has been for disparities to widen - a future widening gap will obviously depend on whether this trend continues.
"If that trend continues, as I expect it will, health disparities in the whole population will increase in the coming decades."
The researchers explain that the health disparity has not always been widening. In fact, during the first half of the 20th century the health gap closed decade after decade. From the late 1960s the gap started widening, and then progressively faster after 1980.
The authors say their study is one of the most comprehensive yet to illustrate clearly and compellingly how wide health disparities have become in the USA. They say it is because of "a methodological innovation".
They combined two statistical models which let them see how health disparities are, in the long-term, affected by three factors - people's age, when they were born, and when their health was assessed.
"We have never before been able to look at all three of these factors together and see how each interacts with the others to affect changes in health disparities."
The researchers gathered data from the National Health Interview Survey over a 24-year span (1984-2007). Approximately thirty-thousand people were added to the database each year.
In the survey, respondents were asked to rate their health on a scale from one to five - with five being "excellent".
They factored in elements which may influence their results, such as race, gender, marital status, income, education and work status.
The authors found that those born between 1955 and 1964 - the late baby boomers - appeared to enjoy better health than any other age group. They also found that overall self-rated health has deteriorated considerably since the end of the 1990s.
The largest gap in people's state of health exists in Americans who were born from 1980 onwards.
This study was not designed to find out why health disparities got worse, the authors explained. Zheng says additional research is required in this area.
Some factors are probably linked to the widening health gap, such as income inequality, which has got progressively worse in America during the last thirty years. Income inequality impacts on access to health care and other resources which affect health. For example, eating junk or fast foods is generally cheaper than fresh fruit and vegetables and wholesome products.
Other factors include obesity rates across all age groups, as well as an increase in the immigrant population (documented and undocumented).
Access to medical and health information has changed considerably over the last three decades, because of the emergence of the Internet. There is a growing digital divide in the country, i.e. one part of the population is moving ahead in leaps and bounds as their access to medical and health information explodes, while another part is not.
If current young adults have a widening health gap, in the years to come this gap will grow as they reach middle age and replace current middle agers whose health gap is smaller.
Zheng said that most young people enjoy better health compared to older age groups - this fact keeps disparities to a minimum. People develop diseases, conditions and other health problems as they get older, resulting in more disparity. After middle age, disparities become narrower - this is partly because a higher percentage of sick people die, while the healthier ones remain.
Another reason for narrower disparities in old age is the similarity of health conditions and illnesses in this age group - older people have similar risk factors and frailties. Also, Medicare covers Americans over the age of 65, making access to health care for this age group more equal across the spectrum of society.
Zheng and team also report that during early adulthood males tend to enjoy better health than females of the same age. The disparity gradually narrows until the age of 61 years, when chronic conditions afflict the male population more.
Their study focused on health, Zhen said. However, the data they gathered and analyzed could also be used for studies on gaps in education, wealth and income.
"This model provides a powerful framework to identify and study the evolution of inequalities across age, period and cohorts."
Written by Christian Nordqvist