LONDON -- The COVID-19 pandemic has caused US males' life expectancy at birth in 2020 to drop by 2.2 years from the 2019 level, the largest among the 29 countries involved in a paper published Sunday by the Oxford University.

As many as 27 countries analyzed saw life expectancy losses, with losses of longer than one year in 11 countries for males and 8 for females, it found.

For western European countries, "the last time such large magnitudes of declines in life expectancy at birth were observed in a single year was during WWII," said Jose Manuel Aburto, a co-lead author.

The research was led by scientists at Oxford's Leverhulme Center for Demographic Science and explores COVID-19's impacts on life expectancy in most European countries, Chile and the United States.

In the United States, increases in mortality at working-age (under 60) contributed most to the life expectancy decline, while in most European countries, the above-60 group contributed most, the research said, adding that despite having a younger population, the Unites States also has "higher co-morbidities in these age groups."

Other factors, such as "unevenness in healthcare access in the working-age population" and "structural racism," also contributed to the mortality increase, said the research, citing a recent US research showing that "socially disadvantaged populations," including Blacks and Latinos, witnessed higher life expectancy losses.