Next, the research team compared Medicare claims data with census data for a complete national sample of more than 7 million men throughout the United States and arrived at similar results (for technical reasons, the study was unable to evaluate results for women who outnumbered men at sexual maturity).

Much attention has been paid to the deleterious social effects of gender imbalances in countries such as China and India, where selective abortion, internal migration and other factors have in some areas resulted in men outnumbering women by up to twenty percent. Such an environment, already associated with a marked increase in violence and human trafficking, appears to shorten life as well.

The researchers have not investigated mechanisms that might account for this phenomenon, but Christakis suspects that it arises from a combination of social and biological factors. After all, finding a mate can be stressful, and stress as a contributor to health disorders has been well documented.

Says Christakis, "We literally come to embody the social world around us, and what could be more social than the dynamics of sexual competition?"

Source: Harvard Medical School