Life expectancy is a measure of the health and wellbeing of a population. Widespread or sustained declines in life expectancy may signal problems in a nation's social and economic conditions or in the provision or quality of its healthcare services, researchers write in The BMJ.

The first study looked at trends across 18 high-income countries and found that most countries experienced declines in life expectancy in 2015. This is the first time in recent decades that so many high-income countries simultaneously experienced declines in life expectancy for both men and women.

Out of 18 countries in the study, 12 experienced life expectancy declines among men and 11 experienced life expectancy declines among women.