BOSTON, Mass. (Aug 9, 2010) "Love stinks!" the J. Geils band told the world in 1980, and while you can certainly argue whether or not this tender and ineffable spirit of affection has a downside, working hard to find it does. It may even shorten your life.
A new study shows that ratios between males and females affect human longevity. Men who reach sexual maturity in a context in which they far outnumber women live, on average, three months less than men whose competition for a mate isn't as stiff. The steeper the gender ratio (also known as the operational sex ratio), the sharper the decline in lifespan.
"At first blush, a quarter of a year may not seem like much, but it is comparable to the effects of, say, taking a daily aspirin, or engaging in moderate exercise," says Nicholas Christakis, senior author on the study and professor of medicine and medical sociology at Harvard Medical School as well as professor of sociology at Harvard University's Faculty of Arts and Sciences. "A 65-year-old man is typically expected to live another 15.4 years. Removing three months from this block of time is significant."
These results are published in the August issue of the journal Demography.
An association between gender ratios and longevity had been established through studies of animals before, but never in humans. To search for a link in people, Christakis collaborated with researchers from the Chinese University of Hong Kong, the University of Wisconsin and Northwestern University. The researchers looked at two distinct datasets.
First, they examined information from the Wisconsin Longitudinal Study, a long-term project involving individuals who graduated from Wisconsin high schools in 1957. The researchers calculated the gender ratios of each high-school graduating class, then ascertained how long the graduates went on to live. After adjusting for a multitude of factors, they discovered that, 50 years later, me
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Harvard Medical School