Americans may be aging more slowly than they were two decades ago. A new study by University of Southern California and Yale University researchers suggests that at least part of the gains in life expectancy over recent decades may be due to a change in the rate of biological aging, rather than simply keeping ailing people alive. “This is the first evidence we have of delayed ‘aging’ among a national sample of Americans,” said senior author Eileen M. Crimmins, University Professor and AARP Professor of Gerontology at the USC Leonard Davis School of Gerontology. As noted in the study by Crimmins and lead author Morgan E. Levine, assistant professor at the Yale Center for Research on Aging: “A deceleration of the human aging process, whether accomplished through environment or biomedical intervention, would push the timing of aging-related disease and disability incidence closer to the end of life.”

Using data from the National Health and Nutrition Examination Survey (NHANES) III (1988-19994) and NHANES IV (2007-2010), the researchers examined how biological age, relative to chronological age, changed in the U.S. while considering the contributions of health behaviors. Biological age was calculated using several indicators for metabolism, inflammation, and organ function, including levels of hemoglobin, total cholesterol, creatinine, alkaline phosphatase, albumin, and C-reactive protein in blood as well as blood pressure and breath capacity data. While all age groups experienced some decrease in biological age, the results suggest that not all people may be faring the same. Older adults experienced the greatest decreases in biological age, and men experienced greater declines in biological age than females; these differences were partially explained by changes in smoking, obesity, and medication use, Crimmins and Levine explained. Slowing the pace of aging, along with increasing life expectancy, has important social and economic implications. The study suggests that modifying health behaviors and using prescription medications does indeed have significant impact on the health of the population.