According to a new study, older adults are more likely to have a greater number of chronic health conditions than the generations that preceded them.

The study was published in the journal, The Journals of Gerontology'.The increasing frequency of reporting multiple chronic health conditions - or multimorbidity -- represents a substantial threat to the health of ageing populations.

This may place increased strain on the well-being of older adults, as well as medical and federal insurance systems, adults older than age 65 are projected to grow by more than 50 per cent by 2050.

Steven Haas, associate professor of sociology and demography at Penn State, said the results fit with other recent research that suggests the health of more recent generations in the US is worse than that of their predecessors in a number of ways.

"Even before the COVID-19 pandemic, we were beginning to see declines in life expectancy among middle-aged Americans, a reversal of more than a century-long trend," Haas said.

"Furthermore, the past 30 years have seen population health in the U.S. fall behind that in other high-income countries, and our findings suggest that the US is likely to continue to fall further behind our peers," he added.

For the study, the researchers examined data about adults aged 51 years and older from the Health and Retirement Study, a nationally representative survey of ageing Americans.

The study measured multimorbidity using a count of nine chronic conditions: heart disease, hypertension, stroke, diabetes, arthritis, lung disease, cancer (excluding skin cancer), high depressive symptoms and cognitive impairment. The researchers also explored variation in the specific conditions driving generational differences in multimorbidity.

They found that more recently born generations of older adults are more likely to report a greater number of chronic conditions and experience the onset of those conditions earlier in life.

"For example, when comparing those born between 1948-65 - referred to as Baby Boomers -- to those born during the later years of the Great Depression (between 1931 and 1941) at similar ages," Haas said.

"Baby Boomers exhibited a greater number of chronic health conditions. Baby Boomers also reported two or more chronic health conditions at younger ages," he added.

The researchers also found that sociodemographic factors such as race and ethnicity, whether the person was born in the U.S., childhood socioeconomic circumstances, and childhood health affected the risk of multimorbidity for all generations.

Among adults with multimorbidity, arthritis and hypertension were the most prevalent conditions for all generations, and there was evidence that high depressive symptoms and diabetes contributed to the observed generational differences in multimorbidity risk.

Nicholas Bishop, assistant professor at Texas State University, said there could be multiple explanations for the findings. "Later-born generations have had access to more advanced modern medicine for a greater period of their lives, therefore we may expect them to enjoy better health than those born to prior generations," Bishop said.

"Though this is partially true, advanced medical treatments may enable individuals to live with multiple chronic conditions that once would have proven fatal, potentially increasing the likelihood that any one person experiences multimorbidity," he added.

He added that older adults in more recently born generations have also had greater exposure to health risk factors such as obesity, which increases the likelihood of experiencing chronic disease. Medical advances have also been accompanied by better surveillance and measurement of disease, leading to the identification of chronic conditions which once may have gone undiagnosed.

The researchers said future studies could try to find explanations for these differences in multimorbidity between generations.