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Thursday, 19 September, 2002, 17:57 GMT 18:57 UK
Secrets of women's longer lives
Women at bingo
Women on average live at least five years more than men
Men may have shorter lives than women because they are naturally less able to fight off bacterial infections, suggests research.

This key difference appears to exist in many types of animals, including many mammals, according to a study carried out at the University of Stirling.

Currently, women tend to live approximately five to six years longer than men in the UK.

Men currently live to an average age of 75 while women are in make it on average to 79.9 years.

This differential has not closed in recent years despite advances in medical science.

Worldwide, men on average live to 65 and women to 70.

More infections

The research, which looked at various types of animal, found that males suffered a disproportionate level of "parasitic" infection compared with females.

This included infection with bacteria as well as more conventional parasites such as ticks and worms.

It was previously thought that the excess death risk for men in the animal kingdom was mainly due to males taking more risks - but the researchers, writing in the journal Science, believe that this vulnerability could be another factor.

Dr Ian Owens, of Imperial College London, said that it was already known that in the US, UK and Japan, men are approximately twice as vulnerable as women to "parasite-induced" death.

In other countries, he said, the risk was even higher for men.

He said that the way men's bodies worked tended to reduce the efficiency of their immune systems.

Cutting off risk

He said: "The classic explanation for low immunocompetence in male mammals is that masculinization depends on the male sex hormone testosterone - an immunosuppressant.

"Long-term comparisons between castrated and 'intact' males show that the former outlive the latter by up to 15 years."

He said that the precise reasons why testosterone had this effect will still unknown.

But he said that it was possible that males suffered more simply because they tended to be bigger than females - offering a "bigger target" to infection.

The fact that they needed to eat more food to stay that way might also put them at greater risk.

See also:

18 Jul 02 | Health
21 Jun 02 | Science/Nature
14 Jun 02 | Science/Nature
05 May 02 | Health
12 Jul 01 | UK
28 Feb 01 | Asia-Pacific
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