Treating many women with estrogen to relieve the discomforts of menopause is not "cost effective" because the hormone does not increase the average lifespan, a study concludes.

However, the report, which attempts to calculate the value of estrogen to society, notes that women usually take estrogen to feel better, not live longer. And when this is taken into account, using the drug may be worthwhile, it said.

The study, conducted by a researcher at the Harvard School of Public Health, found that estrogen is not cost effective for women who have not had hysterectomies, do not have brittle bones and do not suffer the ill effects of menopause. When they take estrogen, their life expectancies actually decrease by about two days.

Dr. Milton C. Weinstein's report was published in Thursday's issue of the New England Journal of Medicine.

Studies have show that estrogen will relieve the unpleasant effects of menopause and help keep bones from becoming brittle. But it also increases the risk of uterine cancer and gall bladder disease.

The report calculated that if all American women took estrogen between the ages of 50 and 65, the hormone would cause 27,000 cases of cancer, 28,000 gall bladder operations and 60,000 dilation and curettage operations each year. It also would prevent 55,000 hip fractures.

But, Weinstein said, "The analysis suggests that estrogen treatment of such patients probably confers a small net loss of life expectancy and imposes a modest net burden on medical resources, but that relief of symptons may well be sufficent to make treatment a cost-effective intervention."