The statement that our friend, the hammer, probably referred to was one in which the idea that 40 used to be “old age” was trashed as being a misunderstanding of statistical expression.
Because “life expectancy” is given as around 30 - 35 during the Roman Empire (and lower during the medieval period), folks tend to think that that was the normal age at death. Instead, life expectancy indicates the average number of years that a child born at a specific time may expect to live. Since infant mortality ran as high as 20% in those ancient times (and mortality for children under the age of 5 ran to almost 30%) (Source: EB, “Population: Mortality”), the effective death of 44% of the population before age 6 means that people surviving the first five years of life had to live quite a while to bring the average up to 32 years.
People have been living longer, recently. However, the notion that a 35 year old person in 70 CE or a 40 year old person in 800 CE was considered a living fossil by his or her fast-aging 25-year-old contemporaries does get quite a bit of abuse on this MB.
Regarding the OP: it is also true (to what extent, I don’t know) that a certain number of diseases of the aged are 20th century phenomena. Hypertension/high blood pressure has a lot of triggers in the latter half of the 20th century that did not used to be there. More people suffer from it now, because more people have it. (It is also true that more people have it because we do keep sufferers alive longer, rather than letting them die of strokes, but the number of instances within the population is higher than it was 100 years ago.)