People in their 40s and 50s who come out of a long-term relationship may be at particular risk of catching sexually transmitted diseases, doctors warn today.

Sexual health experts in Edinburgh believe that middle aged people may not have had the same quality of sex education as their children receive.

They could therefore be less aware of the dangers of sexually transmitted infections (STIs) such as chlamydia when having unprotected sex, it was claimed.

While previous health campaigns have been geared towards inexperienced young people, a new study aims to find out how widespread the problem is among this "increasingly significant" group.

Dr Gordon Scott, head of department at NHS Lothian's genito-urinary clinic, said: "Sexual health services tend to concentrate on young people, and there is a scarcity of information about the needs of those aged 40 and over, many of whom may be coming out of long-term relationships.

"This survey will hopefully give us valuable insights into this important sector of the sexually active population."

Men and women living in Edinburgh are being invited to fill in an anonymous questionnaire as part of the study.

It is designed to gain fresh insights into an area where little research has been done.

It will investigate the attitudes of the over-40 age group, such as whether sterilised men and women believe they are safe to have unprotected sex.

The survey will also help find out how sexual health services can be geared towards the group in the future.

It is being conducted by fourth-year medical student Bridie Howe, who said there is evidence that the rate of STIs among post-menopausal women has increased in the past decade.

The student said: "Relatives of mine and some family friends split up during their 40s so this is an issue close to my heart.

"I am concerned that they may not realise how at risk they are from STIs and do not consider taking precautions."