Education and longevity

A Gina Kolata NYT article reviews the link between education and health.

The article keys off research by economist Adriana Lleras-Muney, who examined historical records to find whether increases in the length of compulsory education in different states had significant effects on lifespan:

"The idea was, when a state changed compulsory schooling from, say, six years to seven years, would the people who were forced to go to school for six years live as long as the people the next year who had to go for seven years," Dr. Lleras-Muney asked.
All she would have to do was to go back and find the laws in the different states and then use data from the census to find out how long people lived before and after the law in each state was changed.
"I was very excited for about three seconds," she says. Then she realized how onerous it could be to comb through the state archives.

After describing the results of this and other studies (all show education has a significant impact, increasing lifespan), the article discusses the interesting scientific problem -- just how does education have this effect?

There's really no answer, and the article discusses other factors like social networks and wealth, which are themselves not so easy to explain.

It's a mystery.