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Why do women live longer than men?

By Layne Weiss     May 15, 2013 in Health
A study conducted by a team of Japanese scientists suggests that women live longer than men partly because their immune systems age more slowly.
In a study of 365 Japanese subjects between the ages of 20 and 90, scientists found that women's immune systems age more slowly than men's. These days men are tending to live longer, the Huff Post notes, but overall, women have a longer life expectancy. On average, the life expectancy for a woman in the United States is 81.1 years of age, while its 76.3 years for a man.
Researchers looked at the subjects' blood and found that the number of white cells decreased with age for both genders, different types of white cells decreased or increased at a slower or faster rate in women than in men. For example, T-Cells and B-Cells declined slower in women than in men. CD4+T Cells and NK Cells increased for both men and women, but they increased at a higher rate for women. Another type of white cells, IL-6 and IL-10, decreased faster for men.
Women have more estrogen which seemingly protects them more from cardiovascular diseases until menopause, The Daily Mail notes. Sex hormones also affect the immune system, especially certain types of lymphocytes.
"Age related changes in various immunological parameters differ between men and women," Prof Katsuiku Hirokawa and his colleagues reported in the online journal Immunity and Ageing.
"Our findings indicate that the slower rate of decline in these immunological parameters in women than in men is consistent with the fact that women live longer than do men."
Prof. Tim Kirkwood of the Institute of Ageing and Health commented that the findings were valuable, but not particularly surprising, BBC News reports.
"It's likely that the slower aging in the immune system of women reflects a generally slower rate of intinsic aging rather than that the immune itself is setting the pace."
Dr. Donald Palmer, senior lecturer in Immunology at the Royal Veterinary College said studies in mice have shown similar results.
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