Having sex at least once a week slows aging in women - even if they do not enjoy being intimate.Being active between the sheets increases the length of women's telomeres.

Researchers believe sex may aid ageing in women by dampening stress and boosting their immune system.

'Over time, shortened telomeres may contribute to chronic degenerative diseases and premature mortality.

'Sexual intimacy may dampen the effects of stress by down-regulating stress response systems and up-regulating immune response.

'Over time, these patterns of stress function should result in longer telomere length

The effects of regular sex in men are unclear.