Here's some good news for women approaching 40. Although their "bodies may be in decline", they are more likely to have sexual fantasies at this age, according to a study reported in today's Telegraph, because they sense that their fertility is declining. 

Their instinctual reaction is an increased appetite for sex, the researchers said, an explanation which could explain the rise of the "cougar" – a woman who seeks out flings with younger partners.

The survey of nearly 900 women divided respondents into three groups: those at their most fertile (aged 19 to 26), those whose fertility was declining (aged 27 to 45) and those who were approaching or had reached the menopause.

Those in the middle group were significantly more sexually driven, engaging in sex and having sexual fantasies more often than their older and younger counterparts and being more likely to have flings.

Professor David Buss said: "Results indicate women with declining fertility have greater sexual motivations and increased sexual behaviours than do women with relatively high fertility.

The research, by academics from the University of Texas, was published in the journal "Personality And Individual Differences".