Early menopause before the age of 45 is associated with an increased risk for cardiovascular disease and death, a review of studies has found.

The average age at onset of menopause is 51 but some women start much earlier. Premature menopause is defined as onset before age 40, while early-onset menopause occurs before the age of 45.

Researchers in the Netherlands pooled data from 32 studies of premature menopause and early-onset menopause that included more than 310,000 women.

Compared with women who reached menopause after 45, those who reached menopause earlier had a 50 percent increased risk of coronary heart disease and a 23 percent increased risk of stroke. They had no increased risk of stroke mortality, but did have a 19 percent increased risk for death from cardiovascular disease and a 12 percent increased risk for overall mortality.

The study, online in JAMA Cardiology, also found that compared with women who were younger than 50 at menopause, those who experienced menopause at 50 to 54 had a 13 percent lower risk of fatal cardiovascular disease, but no difference in risk of stroke.

The reason early menopause is associated with more health risks is not clear, but earlier loss of ovarian function may cause hormonal changes that lead to inflammation and vascular damage.

“Women who reach menopause early should be screened for medical conditions such as hypertension, hyperlipidemia and diabetes,” said the lead author, Dr. Taulant Muka, a physician and postdoctoral researcher at Erasmus University. “Treating these disorders early reduces the risk.”