When women breast-feed their infants for a year, there are lasting health benefits for both mother and infant, according to a new study.

In the study, researchers found evidence that increased duration of breast-feeding may lower the mother's risk of high blood pressure, diabetes, high cholesterol, and cardiovascular disease after menopause.

The finding, reported in the May issue of the medical journal Obstetrics and Gynecology, stem from data on nearly 140,000 mothers who breast-fed their infants.

According to Dr. Eleanor Bimla Schwarz of the University of Pittsburgh and associates, the beneficial effect of breast-feeding on cardiovascular risk factors appeared to be "dose-dependent" — the longer the duration of breast-feeding, the greater the benefits — even after adjusting for social, demographic and lifestyle variables, family history, and body weight.

Women with a lifetime history of more than 12 months of breast-feeding were significantly less likely than women who never breast-fed to have high blood pressure, diabetes, high cholesterol, and heart disease.

Schwarz and colleagues speculate that breast-feeding "does more than simply reduce a woman's fat stores," and propose that the effects on cardiovascular risk profiles may be due to hormonal effects of breast-feeding.