Prospective study of intentionality of weight loss and mortality in older women: the Iowa Women's Health Study.

Several epidemiologic investigations have suggested that weight loss is associated with increased mortality risk but have not examined whether the weight loss was intentional or unintentional. The authors examined whether the association between weight loss and mortality differs by whether the weight loss was intentional or unintentional as part of the Iowa Women's Health Study, a prospective cohort study of health risk factors in postmenopausal women. Women aged 55-69 years completed questions about intentional and unintentional weight losses since age 18 years via mail survey in 1992 and were followed through 1995. One or more intentional weight loss episodes of 20 or more pounds (> or =9.1 kg) during adulthood was not significantly associated with higher total or cardiovascular disease mortality risk compared with never losing > or =20 pounds. One or more unintentional weight loss episodes of 20 or more pounds was associated with a 26-57% higher total mortality risk and a 51-114% higher cardiovascular disease mortality risk, compared with never losing 20 or more pounds. Associations between unintentional weight loss and increased mortality risk were confined mostly to women with prevalent disease, hypertension, or diabetes. Patterns of association did not vary by overweight status. These findings suggest that the association between weight loss and increased mortality risk observed in epidemiologic studies may be due to unintentional weight loss that reflects existing disease and not due to intentional weight loss.