But this is the overall the result of an "anthropological reversal", meaning the society switch its focus on older generations rather than the younger ones.
Most policies in the last decades had the goal of favoring the silent and boomer generations ("boomers always win": ZIPR, assets inflation, etc.).
Millennials and Gen Z got wreaked, plus they know they might have to pay the debt left by the previous generations one way or another. So why not just dying, it is easier.
A 40 year old is federally protected from age discrimination (for being too old) and can have children which are legally adults. No one is calling this age group "early adults".
"legal"/"federally protected" adulthood - 21 - can vote, drink, etc.
"biological" adulthood - brain is not fully developed until ~25, and takes a few years to "activate/realize" those "powers", so ~30 for "actual, mature" adult processes to start taking place. ~40 seems appropriate within that as an outer boundary of "early" adulthood.
But this story could be about more recent environmental pathogens like micro-plastics that trigger inflammation and auto-immune responses that progress into disease and/or cancer. Cancer rates in that generation is markedly higher than for previous generations at that age, and not just a case of better detection but hospital admissions and death.
They may not have had the free-roaming childhood of many Gen-Xers where you spent all day out riding bikes and playing ball games in the street, but they seem more aware of the risk of sitting at an office job through the day, and then sitting in front of the TV in the evening.
