Women’s immune systems hold the secret to longer life
Women may live longer, healthier lives than men because their immune systems age more slowly, researchers have found. A new study has shown that levels of key white blood cells, which are responsible for fighting off infections, become lower in men as they get older compared to women.The average life expectancy for men in the UK is 79 years old, while for women it is 82 years old. In some parts of the world, such as Japan, the gap is even larger, with women living on average nearly six years longer.
There have been a number of theories for why this may be, including a recent finding that the tiny “power cells” that produce energy for their cells tend to have fewer faults than in men.
Scientists in Japan have now uncovered another reason after finding that the levels of white blood cells and other parts of the immune system called cytokines decline faster in men.
They believe this might be because female sex hormones such as oestrogen can boost the immune system’s response to infections.
The work could now help scientists predict the “biological age” of people based on the state of their immune system.
Professor Katsuiku Hirokawa, who led the research at Tokyo Medical & Dental University, said: “Because people age at different rates, a person’s immunological parameters could be used to provide an indication of their true biological age.”
The scientists, whose research is published in the journal Immunity and Ageing, examined the blood of 356 men and women aged between 20 and 90 years old.
They looked at levels of white blood cells and cytokines, which help to carry messages in the immune system.
In both sexes the number of white blood cells decreased with age, but two key elements – known as the T-cell and B-cell lymphocytes, declined faster in men.
Both of these white blood cells are involved in fighting off bacterial infections.
They also found that another type of cell that tackles viruses and tumours increased with age, with women having a higher rate of increase than men.
They also found that men showed a decline in two types of cytokines that help to keep the immune system under control and prevent inflammation from damaging surrounding tissue.
Professor Hirokawa added: “It is well known that ageing is associated with a decline in the normal function of the immune system, leading to increased susceptibility to various diseases and shortened longevity.
“However, specific dysfunctions in the immune system directly responsible for this have yet to be identified.
“Among the important factors, T cells are central to the immune response, and their function is significantly altered with increasing age.”