In the first half of the 20th Century war was the leading cause of a great many men and some women dying in their 20s and 30s .. and to a lesser degree at later ages (if in occupied territories, etc).

Dying young drags "life expectancy" figures (especially those calculated "from birth") but doesn't necessarily impact the likelihood of dying (say) "within the next 5 years" if you're already (say) 55.

Eg. Many people that survived war in the early 20th Cent still managed to live to a ripe old age past their 60s.

The boomers quit smoking decades ago.

I grew up mostly in a rural town, unwittingly away from lead gasoline fumes.