NEW YORK: Women who smoke are more likely to begin menopause before the age of 45 years, which puts them at increased risk of osteoporosis and heart disease, Norwegian researchers report.

Among a group of 2,123 women 59 to 60 years old, those who currently smoked were 59% more likely than non-smokers to have undergone early menopause, Dr Thea F Mikkelsen of the University of Oslo and her colleagues found. For the heaviest smokers, the risk of early menopause was nearly doubled.

However, women who were smokers, but quit at least 10 years before menopause, were substantially less likely than current smokers to have stopped menstruating before age 45.

There is evidence that smoking later in life makes a woman more likely to have early menopause, while smokers who quit before middle age may not be affected, Mikkelsen and her team note in the online journal BMC Public Health. They investigated the relationship further and determined if exposure to second-hand smoke might also influence the timing of menopause.

The researchers found that nearly 10% of the women went through menopause before age 45. About 25% were current smokers, 28.7% were ex-smokers and 35.2% reported current passive exposure to smoke.

Compared with married women, widows were also at increased risk of early menopause, as were women who said they were in poor health. More educated women were less likely to go into menopause early, but they were also less likely to be smokers.