Since about 1890, women in the U.S. have, on average, lived longer than men. There are many reasons why — both biological and sociological — this is the case. A new study finds that the life expectancy gap is growing. On average, men now live nearly six years less than women.

Life expectancy in general is declining in the U.S., according to the new study which was published in JAMA Internal Medicine. For the study, researchers examined mortality data, including causes of death, in the country from 2010 to 2021. They found that from 2019 to 2021, average life expectancy dropped from 78.8 to 76.1 years.

As of 2021, women’s life expectancy is 79.3 years and men’s life expectancy is 73.5 years. That means there’s a 5.8 year difference between the two — the largest gap since 1996 and up from a low of 4.8 years difference in 2010.

“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,” first author Brandon Yan, M.D., an internal medicine resident physician at the University of California, San Francisco, and a research collaborator at Harvard T.H. Chan School of Public Health, said in a press release.

Historically, two of the biggest factors that have contributed to women living longer than men were the difference in cardiovascular-related deaths and deaths from lung cancer. Men are more at risk of some heart problems because they tend to have unhealthier habits — for example, they’re worse at handling stress — and they don’t experience the protection that estrogen and progesterone offer to premenopausal cisgender women’s hearts. Men also smoke more than women, leading to more lung cancer deaths.

Before the pandemic hit in 2020, the causes of death that were contributing to the longevity gap the most were drug overdoses, unintentional injuries, diabetes, suicide, homicide, and heart disease. “The increase in overdose deaths, homicide, and suicide underscore twin crises of deaths from despair and firearm violence,” the study authors wrote. The biggest factor in the longevity gap was drug overdoses, especially from opioids. Helping men utilize mental health treatment could help decrease this, Yan said.

This increasing gap was offset by deaths due to several causes, including Alzheimer’s and cancer, increasing more in women than men.

In recent years, the COVID-19 pandemic was primarily responsible for driving a larger longevity gap between men and women. In nine years, from 2010 to 2019, the life expectancy gap increased by 0.23 years. But in just two years during the pandemic, from 2019 to 2021, it increased by 0.70 years.

Social reasons play a part in why men were more likely to die from COVID-19, including that they’re more likely to be incarcerated and have pre-existing conditions and less likely to wear a mask and social distance. Biological factors also play a role, such as differences in immune response based on sex.

In regards to these stark numbers, senior author Howard Koh, M.D., a professor of the practice of public health leadership at the Harvard Chan School said, “We need to track these trends closely as the pandemic recedes. And we must make significant investments in prevention and care to ensure that this widening disparity, among many others, do not become entrenched.”

For the study, federal health expectancy data was only available through 2021. But provisional estimates for 2022 have since been released — and they’re slightly more positive.

From 2021 to 2022, life expectancy increased by 1.1 years to 77.5 years, largely due to a decrease in COVID-19 deaths. Life expectancy in 2022 was 74.8 years for men, an increase in 1.3 years in 2021. For women in 2022, it was 80.2 years, a 0.9 year increase from the year prior. As such, the longevity gap between men and women decreased to 5.4 years — a small silver lining.