Immune system decay linked to shorter life expectancy in men

Women live longer than men partly because their immune systems age more slowly, a study suggests.

As their body defences weaken with the passing years, the increasing susceptibility of men to disease shortens their lives, it is claimed.

Life expectancy in the UK is 79 years for men and 82 for women, according to the World Health Organisation. In Japan, where the research took place, the average lifespan of men is the same, but women live to 85.5.

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The study involved examining blood samples from healthy volunteers with a wide range of ages.

Scientists tested the blood of 356 men and women aged between 20 and 90 looking at levels of white blood cells and immune system signalling molecules called cytokines.

In both sexes, the number of white blood cells per person decreased with age, but closer study revealed striking differences between men and women.

The rate of decline of most T-cell and B-cell lymphocytes, two key elements of the immune system, was faster in men. Similarly, men showed a more rapid age-related decline in the two cytokines IL-6 and IL-10.

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Two specific types of immune system cell that actively destroy foreign invaders, CD4 T-cells and natural killer (NK) cells, increased in number with age. In this case, the rate of increase was higher in women than in men.

NK cells are believed to be one of the body’s first lines of defence against cancer.

The research, led by Professor Katsuiku Hirokawa, from Tokyo Medical & Dental University, appears in the online journal Immunity & Ageing.

Immune system mechanisms protect the body from infection and cancer, but can also cause disease when not properly regulated. Inflammation is a potentially damaging response that contributes to heart and artery disease and may play a role in dementia.