We’ve known for more than a century that women outlive men. But new research led by Harvard T.H. Chan School of Public Health and University of California, San Francisco, shows that, at least in the United States, the gap has been widening for more than a decade. The trend is being driven by the COVID-19 pandemic and the opioid overdose epidemic, among other factors.

In a research paper, published online Monday in JAMA Internal Medicine, the authors found the difference between how long American men and women live increased to 5.8 years in 2021, the largest it’s been since 1996. This is an increase from 4.8 years in 2010, when the gap was at its smallest in recent history.

The pandemic, which took a disproportionate toll on men, was the biggest contributor to the widening gap from 2019-2021, followed by unintentional injuries and poisonings (mostly drug overdoses), accidents, and suicide.

“There’s been a lot of research into the decline in life expectancy in recent years, but no one has systematically analyzed why the gap between men and women has been widening since 2010,” said first author Brandon Yan, a UCSF internal medicine resident physician and research collaborator at Harvard Chan School.

Life expectancy in the U.S. dropped in 2021 to 76.1 years, falling from 78.8 years in 2019 and 77 years in 2020.

The shortening lifespan of Americans has been attributed in part to so-called “deaths of despair.” The term refers to the increase in deaths from such causes as suicide, drug use disorders, and alcoholic liver disease, which are often connected with economic hardship, depression, and stress.

“While rates of death from drug overdose and homicide have climbed for both men and women, it is clear that men constitute an increasingly disproportionate share of these deaths,” Yan said.

“We have brought insights to a worrisome trend. Future research ought to help focus public health interventions towards helping reverse this decline in life expectancy.”

Brandon Yan, research collaborator at Harvard Chan School

Using data from the National Center for Health Statistics, Yan and fellow researchers from around the country identified the causes of death that were lowering life expectancy the most. Then they estimated the effects on men and women to see how much different causes were contributing to the gap.

Prior to the COVID pandemic, the largest contributors were unintentional injuries, diabetes, suicide, homicide, and heart disease.

But during the pandemic, men were more likely to die of the virus. That was probably due to a number of reasons, including differences in health behaviors, as well as social factors, such as the risk of exposure at work, reluctance to seek medical care, incarceration, and housing instability. Chronic metabolic disorders, mental illness, and gun violence also contributed.

Yan said the results raise questions about whether more specialized care for men, such as in mental health, should be developed to address the growing disparity in life expectancy.

“We have brought insights to a worrisome trend,” Yan said. “Future research ought to help focus public health interventions towards helping reverse this decline in life expectancy.”

Yan and co-authors, including senior author Howard Koh, professor of the practice of public health leadership at Harvard Chan School, also noted that further analysis is needed to see if these trends change after 2021.

“We need to track these trends closely as the pandemic recedes,” Koh said. “And we must make significant investments in prevention and care to ensure that this widening disparity, among many others, do not become entrenched.”

Alan Geller, senior lecturer on social and behavioral sciences at Harvard Chan School, was also a co-author.