Los Angeles Times
September 20, 2010
Attention 20-year-old men: Look at the people around you. Are most of them women? If so, you're in for a longer life (statistically speaking). On the other hand, if the men outnumber the women, you might want to consider moving somewhere like Hartford, Ga.; St. Joseph, Minn.; Bryn Mawr, Pa.; or Dugway, Utah (all cities where more than two-thirds of residents are female).
It may sound crazy, but the preponderance of males in places where men live when they reach marriageable age influences how long they will live, according to a study published in the August issue of the journal Demography.
Researchers from China and the United States looked at the link between sex ratios and life expectancy and found that they mattered for men, but not for women. It turned out that guys who lived in areas where there was more competition for women wound up dying younger.
The researchers began by analyzing data from the Wisconsin Longitudinal Study, which tracked thousands of people who graduated from the state's high schools in 1957. The researchers were able to compare the proportion of boys in each man's graduating class to their age when they died (if they had). In this sample, the men who went to schools where boys outnumbered girls by more than 3-to-2 were about 40% more likely to have died by age 65 than men who went to schools where girls outnumbered boys by a similar margin.
Next, the researchers turned to Medicare and Social Security records for 12.7 million elderly white men. The researchers calculated the sex ratio among men and women of marriageable age (18-27 for men and 15-24 for women) in every state for each year from 1933 to 1948. They used that information to figure out how male-dominated each elderly man's environment was when he turned 20. Then they matched that up with their "survival in old age" and looked for a correlation, according to the study.
What they found was that those who came of age in states that were 52% male were slightly more likely to have died than men who came of age in states that were only 47% male. The difference amounted to shaving three months off the life expectancy of 65-year-old men, according to the study.
Dr. Nicholas Christakis of Harvard Medical School, who led the study, said there are at least three possible reasons why men who were surrounded by lots of other men might die younger:
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