Why Do Women Live Longer Than Men?

May 11, 2006 -- Women generally outlive men, and researchers are exploring the reasons why.

Evolution may play a role, researchers note in the journal Human Nature. But other factors also work in women's favor, and it's possible for anyone -- male or female -- to work toward a longer, healthier life.

First, take a look at the latest snapshot of U.S. life expectancy. In 2004, the most recent year for which such statistics are available, life expectancy from birth was 77.9 years. In 2004, life expectancy for U.S. women was 5.2 years longer than men.

Women don't just outlive men in the U.S. In April, researchers in England predicted that 2006 may be the year in which women outlive men all over the world, even in the world's poorest countries.

Vying for Attention

Here's the short version of the study, published in Human Nature: Male animals often have to compete for female attention -- witness the male peacock's showy tail and the male moose's battle-ready antlers; vying against other suitors can be risky.

The University of Michigan's Daniel Kruger, PhD, and Randolph Nesse, MD, wrote the paper. They argue that men are much more likely than women to engage in risky and sometimes violent behavior, ultimately raising men's death rate.

More men than women die in car accidents, other types of accidents, homicides, and suicides, the researchers note. They add that in the U.S., the gender gap in death rates peaks in young adulthood and is mainly due to behavior.

Daredevil Appeal?

Kruger and Nesse took a big-picture look at how evolution may contribute to male-female death rates.

They don't claim that all men engage in risky behavior to impress women, or that all women look at daredevils and think, "I'd like him to father my children." They also don't dismiss women's health risks.

However, Kruger and Nesse note that men, particularly those experiencing uncertainty or deprivation, "may develop riskier life strategies, leading to higher mortality rates." Of course, many men may not act that way when facing uncertainty or harsh conditions.

The male-female gap in death rates may be a sign of male-male competition in a society, the researchers also suggest.