I have no proof, only whispers
Pretty sure things like the flu, cholera, pneumonia, infections, cancer, asthma, hypertension, heart attacks, aneurysms and so on were a thing.the thing is the women also have a lower life expectancy due to the same cause of infant mortality which is giving birth, once you factor that out its near the same, so other than giving birth better we haven't improved much, infact we have less healthy foods nowadays/ worse physical exercise causing many of these modern illnesses that never existed in the first place anyways, so modern medicine is really mostly curing modern problems that wouldn't have existed at the time like say diabetes
As for healthy eating and exercise, I agree. Those who have good life habits tend to live long. It's weird though, there are a lot of old people who smoke a lot, drink and don't eat healthy yet they make it to 80-100.