(CNN) Life expectancy in the United States dropped for the second consecutive year in 2021, falling to the lowest it has been since 1996, according to final mortality data published Thursday by the US Centers for Disease Control and Prevention's National Center for Health Statistics.
Covid-19 was a major contributor to the decline in life expectancy, which is now nearly two and a half years shorter than it was at the start of the pandemic. After a drop of 1.8 years in 2020, another cut of 0.6 years last year brought US life expectancy down to 76.4 years in 2021.
"What we're seeing in terms of the patterns of mortality, it's being driven, I think, largely by the pandemic," said Robert Anderson, chief of mortality statistics at the National Center for Health Statistics. The drop isn't necessarily surprising, but it is "substantial."
The final mortality data is less severe than earlier estimates predicted; provisional data suggested life expectancy might have dropped nearly a full year in 2021. But it is still historic -- life expectancy typically only changes by 0.1 or 0.2 years.
Nearly 1 in 8 deaths in 2021 were due to Covid-19, up from about 1 in 10 deaths in 2020. It was again the third leading cause of death. Heart disease remained the leading cause of death, followed by cancer. About half of all deaths last year were from these three causes.
Drug overdose deaths also increased significantly throughout the pandemic, reaching record levels in 2021. Nearly 107,000 people died of a drug overdose in 2021, driving the age-adjusted death rate for overdoses up more than 14% in one year and 50% over the past two years.
"These data are very tragic but not surprising," said Dr. Nora Volkow, director of the National Institute on Drug Abuse. "The pandemic had a magnifying effect on an already-devastating overdose crisis, and exacerbated many of the stressors in society that make people more vulnerable to taking drugs."
The final CDC mortality data shows that between 2020 and 2021, overall death rates increased for all age groups except infants younger than one year. But the largest increase was among those ages 35 to 44, a group that was most affected by drug overdose deaths.
"We also know that substance use is more dangerous than it has ever been, as fentanyl has continued to permeate the illicit drug supply, increasing the risk for overdoses among both people with substance use disorders as well as those who use drugs occasionally," Volkow said.
Deaths involving synthetic opioids such as fentanyl increased by a marked 22% in 2021, according to the CDC data. Deaths involving cocaine and psychostimulants such as methamphetamine were also significantly more frequent, while those involving heroin decreased.
Overall, life expectancy for women was nearly six years longer than it was for men in 2021, a gap similar to that in 2020. Age-adjusted death rates were lowest among Asian men and women, while they were highest -- and increased significantly -- among American Indian and Alaska Native men.
The death rate for Black men declined slightly in 2021, but was still the second highest among the demographic groups.
"Anytime the death rate drops, it's a good thing," Anderson said. That drop aligns with patterns in the pandemic, as Covid-19 death disparities narrowed in 2021, he said.
But 2021 life expectancy data broken out by race and ethnicity has not yet been finalized, and it's possible that life expectancy for Black men may have fallen even through death rates improved.
"If death rates are disproportionately higher at the younger ages than at the older ages, that can have an outsized effect on life expectancy," Anderson said.
White people, however, saw a significant jump in death rates -- up about 7% between 2020 and 2021 among both men and women -- another change that aligns with pandemic trends. Only about half of White people in the US have gotten their initial Covid-19 vaccine, well below the national average, and CDC data estimates that the risk of dying from Covid-19 was about seven times higher for unvaccinated people in December 2021.
There was an extremely mild flu season last year, and influenza and pneumonia dropped out of the 10 leading causes of death in 2021. Along with heart disease, cancer and Covid-19, the other leading causes of death in 2021 were: unintentional injuries, of which drug overdoses represent more than a third; stroke; chronic lower respiratory diseases; Alzheimer's disease; diabetes; chronic liver disease and kidney disease.
Age-adjusted death rates increased for eight of the 10 leading causes of death between 2020 and 2021, changes that are "significant," Anderson said.
While not attributed to Covid-19 directly, many changes in death rates are "almost certainly pandemic-related," he said, pointing to the 3% increase in heart disease and 6% increase in stroke.
"These are the things that need to be watched carefully in the coming years, both in terms of surveillance data and in terms of final data as well," he said. "They need to be monitored to see how things are progressing post-pandemic."
Long-term, it's hard to know what trends in life expectancy will look like.
"We know it didn't happen in 2022, but for 2023, let's say everything goes back to normal. We could end up with life expectancy going back to where it was, essentially," Anderson said.
"But I think there are enough people who've had (Covid) and enough people who have chronic problems that Covid has caused whose life expectancy is likely to be shortened in the long run, which may mean higher death rates."
The opioid epidemic could hinder progress, too.
"We have treatments and tools available, but we must prioritize taking them off the shelf and using them to their full potential," Volkow said. "To curb the overdose crisis, it is crucial that we put this same urgency and infrastructure into action to accelerate discoveries in addiction science, provide treatment and support for people with substance use disorders, and deploy prevention interventions to save lives."
Anderson said there are still a substantial number of Covid-19 deaths occurring in the US, but it's a lot better than it was.
"I'd like to think that we will go back to at least a trend of increasing life expectancy. But, how long it will take for us to get back to 2019, it's hard to know," he said.