A research team from the Tokyo Medical & Dental University Open Laboratory is looking into the causes of why women generally live longer than men in Japan. Their findings and research data suggest that woman’s immune systems age more slowly than those of men, and this slower aging may contribute to women living longer.
Information on the human immune system is generally taken from measurements of blood serum and blood cells. To test their hypothesis that age-related changes in the immune system differ between men and women, the researcher team analyzed the blood of healthy Japanese men and women – all volunteers – ranging from 20 and 90 years old. In both genders, the total number of white blood cells per person decreased with age, including the number of neutrophils. Neutrophils are white blood cells responsible for the body’s protection against infection, produced mainly in the bone marrow and released into the bloodstream. Lymphocytes, another type of white blood cell associated with immunity, also decreased in men and increased in women. Lymphocytes are divided into B cells and T cells – where B cells work by secreting antibodies into the body’s fluids, T cells attack the objects in the bloodstream marked by antibodies as harmful.
Generally, younger men have higher levels of lymphocytes than similarly aged women – the reason for that still unclear – but as people age, the number of lymphocytes becomes relatively equal across genders. However, researchers have discovered that the rate of decline in T cells and B cells was slower in women than in men. Other types of lymphocytes – including cells that kill viruses and infected cells in the bloodstream – multiplied with age, and the rate of increase was higher in women than in men. Similarly, an age-related decline in signaling molecules for in cell communication was steeper in men. There was also an age-dependent decrease in red blood cells found in men, but not in women.
Because of these, researchers have commented that this could be the explanation of why various age-related immune system problems are more pronounced in men than in women. “The process of aging is different for men and women for many reasons,” explained Katsuiku Hirokawa, part of the research team. “Women have more estrogen than men which seems to protect them from cardiovascular disease until menopause. Sex hormones also affect the immune system, especially certain types of lymphocytes.” In Japan, life expectancy for men is 79 years, while women are expected to reach 86 years, according to data from the World Health Organization. Globally, women live six to eight years longer than men. “Because people age at different rates, a person’s immunological parameters could be used to provide an indication of their true biological age,” said Hirokawa.
[via Medical Daily]