It's common knowledge that women tend to live longer than men. Although men are living longer these days, a woman's life expectancy is 81.1 years compared to 76.3 years for men in the United States. But what's behind women's longevity? A new study may have found an answer.
In a study of 365 Japanese subjects between the ages of 20 and 90, researchers found that women's immune systems age more slowly than men's, according to a study published in the journal Immunity and Ageing.
"Our findings indicate that the slower rate of decline in these immunological parameters in women than that in men is consistent with the fact that women live longer than do men," reads the study's provisional abstract.
Researchers looked at participants' blood and found that while the number of white blood cells (which fight infections in your body) decreased with age across both genders, different types of white blood cells either decreased at a slower rate or increased overall in women than men. For example, T-cells (responsible for various immune functions) and B-cells (which produce antibodies, our immune system's security guards) declined slower in women than in men. CD4+ T cells and NK cells increased for both sexes, but women had a higher rate of increase, while another type of white blood cells -- IL-6 and IL-10 -- decreased faster for men.
The study also noted an age-related decline in red blood cells for men that didn't exist for women.
Professor Katsuiku Hirokawa from the Tokyo Medical & Dental University Open Laboratory explained the difference between the way women and men age in the press release:
"The process of aging is different for men and women for many reasons. Women have more oestrogen than men which seems to protect them from cardiovascular disease until menopause. Sex hormones also affect the immune system, especially certain types of lymphocytes. Because people age at different rates a person's immunological parameters could be used to provide an indication of their true biological age."