Sexually transmitted infections are on the increase in people aged over 45, with menopausal women most at risk, according to a report out today.

The report from the American Center for Disease Control (CDC) and the UK's Health Protection Agency shows that infections of STIs, particularly HIV, are rising steadily among older people.

CDC figures show that 18% of people with HIV infection are over 45 and the risk of heterosexual transmission in older adults is increasing, partly due to the lack of relevant prevention programmes.

Older patients often acquire infection through heterosexual contact, the report says, but they are "universally omitted from prevention programmes" and menopausal women have "largely been ignored within the field of sexual health".

Menopausal women are still wrongly seen as being at low risk of infection, based on an assumption that they are in monogamous heterosexual relationships and are relatively sexually inactive.

Prevention programmes haven't yet recognised the fact that older women are beginning new sexual relationships and don't use condoms, since pregnancy is no longer an issue. Erectile dysfunction also makes condom use more difficult for older couples, the study notes.

A "gradual decline of immune function" and the presence of other diseases in older women is also believed to contribute to their predisposition to HIV and other STIs.