Non-paywalled link: https://archive.ph/AfzEs I've heard a lot of theories about what is causing this, the most common being plastics, increased sugar consumption, more people worldwide being overweight/obese, more people worldwide being sedentary/less physically active, exposure to various harmful chemicals, and more. I'd assume it's probably a combination of several factors, but similar to plummeting male testostero…
I'm very curious how large a factor this is. Personally, once I realized how much plastic I used - from water bottles to food containers - I became very concerned and stopped using it.
More intuitive explanations make sense to me, like unhealthy, non-active and stress filled lifestyles.