Women are going through the menopause 18 months later than their mothers did, according to new research.

On average they embark on "the change" at the age of 50 years and six months. Women of their mothers' generation experienced the same thing at 49, say scientists. Women born in 1915 went through the menopause an average of 17 months earlier than women born in 1939.

The scientists calculated that the risk of premature death goes down by 2 per cent with each year that passes before the menopause starts. The report said: "Heart disease mortality is lower. Although the risk of death from uterine or ovarian cancer is increased by 5 per cent, the net effect is an increased lifespan."

The scientists were unable to come up with one single reason why women are reaching the menopause later: "No one hypothesis has gained widespread support. Potential delays may be associated with genetic, social, environmental or hormonal factors. Women born [later] were more likely to... receive a college education, to have a greater body mass index and to use oral contraceptives."

Professor John Studd of the British Menopause Society said: "If menopause is delayed it is because of better health, less smoking and less drinking."