New York City's average life expectancy may have dipped by 5 years due to the coronavirus. Here's how that compares to past epidemics.

• Coronavirus deaths from March to May caused New York City's life expectancy to decline by 5 years, according to a recent analysis.
• By comparison, the 1918 flu pandemic resulted in a 12-year decline in life expectancy in the US.
• Life expectancies can rebound quickly after an epidemic, depending on the length of the outbreak.

The coronavirus pandemic has killed more than 20,000 people in New York City — enough to lower the life expectancy among the city's residents.

A recent analysis from Resolve to Save Lives, a nonprofit initiative led by former CDC director Tom Frieden, found that excess deaths reported in New York City from March 11 to May 14 likely decreased the city's life expectancy by five years.

A decline in life expectancy isn't an indicator of when residents will die — rather, it's a marker of the general health of the population. When the mortality rate (the proportion of the city's population that passed away over a given period of time) goes up, the life expectancy consequently drops.

New York City saw a sharp increase in its mortality rate from March 11 to May 2. The city's health department reported 24,000 excess deaths during that time period — including 19,000 linked to the coronavirus. The remaining 5,000 excess deaths "might have been directly or indirectly attributable to the pandemic," the department estimated.

This caused the city's life expectancy to drop from 83 years, on average, to 78 years, according to the analysis from Resolve to Save Lives.

Official figures suggest that New York City's life expectancy is around 81 years, but that data is a projection based on figures from the 2010 census. So the team at Resolve to Save Lives used 2017 mortality figures and 2018 population data to calculate the city's current life expectancy with and without COVID-19 deaths.

"Since deaths from COVID-19 will likely continue throughout the rest of 2020, we expect that our work represents an underestimate and the actual difference in life expectancy will be greater," the analysis reads.

For now, the decline in New York City's life expectancy doesn't compare to the effects of the 1918 Spanish flu in the US or the HIV epidemic in South Africa, which caused life expectancies to decline by more than 10 years.

Life expectancies can rebound after a pandemic

Prior to the pandemic, New York City's life expectancy was higher than the US average, which is around 79 years. That national number declined for three straight years from 2014 to 2017, primarily because of deaths linked to drug overdoses, suicides, and alcohol-related diseases.

The pandemic now puts New York City on par with the US's overall life expectancy, which is lower than many other wealthy nations.

The 2014 Ebola epidemic had a similar effect on life expectancy in West African countries like Sierra Leone and Liberia. A 2015 study found that the outbreak caused Sierra Leone's life expectancy to decline by up to five years, and Liberia's life expectancy to decline by up to six from 2013 to 2014. Those two countries already had relatively short life expectancies compared to other nations as of 2013— around 58 years for Sierra Leone and 63 for Liberia.

Life expectancies can bounce back quickly after an outbreak. The Spanish flu pandemic, for instance, resulted in a 12-year decline in life expectancy in the US from 1917 to 1918. But by 1919, the nation's average life expectancy was around four years higher than it was in 1917, at nearly 55 years.

In other cases, the effects of an epidemic are more long-lasting. The HIV outbreak in South Africa resulted in a 10-year decline in life expectancy from 1990 to 2004. Babies born there in 1990 had an average life expectancy of 63 years compared to just 53 years in 2004.

As it stands, the coronavirus pandemic temporarily reversed the gains in life expectancy that New York City made over the last 20 years. But that could change as the city continues to contain its outbreak.

Read the original article on Business Insider