Gina Kolata Via Brad DeLong
I would like to present an alternative hypothesis. The article basically makes a claim of fact -- that people develope Arthritis, heart disease and chronic lung disease at a much older age -- and presents a hypothesis -- that this is due to better health in early childhood, infancy and in the womb. The natural experiement of the Spanish flu provides direct evidence.
The basic reason for the long delayed costs of ill health very early in life (or just before) is that the diseases are not prevented by medical interventions (such as vaccination) and are not believed to have an infectious cause which could be blocked before we know about it by sanitation including water purification, sewage treatment etc. (I really did just delete two ceteras for space)
All very interesting, but I think the diseases in question might have infectious causes so the explanation might be sanitation.
Consider an example: stomach cancer. Over the past century, deaths due to stomach cancer have declined as dramatically as deaths due to lung cancer have increased. This was a mystery until it was discovered that stomach ulcers and stomach cancers are largely caused by helicobacter pilori, an infectious agent. Better sanitation thus explains the decline in stomach cancer (in developed countries).
Rheumatoid arthritis was unknown in the old world before 1492 (they had osteo arthritis but these are different syndromes and the diagnosis can be made from bones). It is very possible that it has an infectious cause brought from the Western hemisphere (syphillis in contrast is definitely an old world disease even if it was introduced to Europe from North Africa about then).
Heart disease can be caused the Streptococcus. More generally, heart disease seems to have something to do with inflamation which might have something to do with an infectious agent.
If the causes are infectious, it is at least possible that the agents will be found implying an even more dramatic improvement in the future.
This is just an effort to provoke thought. I don't really hope to take a heart disease vaccine before I die.