We examined the relation between Quetelet's body mass index (BMI) and age-adjusted mortality risk from specific diseases in a 26-year prospective cohort study of 12,576 non-Hispanic white women who had never smoked. To account for effects due to antecedent disease, we focused on women surviving 15–26 years after their report of body weight. High BMI (>27 kg per m2) decreased the risk of fatal respiratory disease (hazard ratios of 0.7 for ages 30–54 years and 0.6 for ages 55–74 years) but increased risk in all other disease categories. Low BMI (<21 kg per m2) increased the risk of fatal respiratory disease (hazard ratios of 2.0 for ages 30–54 years and 1.4 for ages 55–74 years). Among middle-aged women (ages 30–54 years), we found that low BMI also increased the risk of certain fatal cardiovascular diseases (hazard ratios of 1.5 for cerebrovascular death and 2.5 for hypertensive and other cardiovascular deaths), but the increase in the risk of fatal cerebrovascular disease did not remain (hazard ratio of 0.4) after exclusion of subarachnoid and intraparenchymal hemorrhage deaths from the endpoint.
Although the inverse relation between BMI and risk of fatal respiratory disease was also evident in the subset who reported body weight 17 years after baseline, further restriction of this subset to stable-weight women reporting no history of respiratory disease resulted in a U-shaped relation. Data from this subset also indicated that weight loss substantially increased the risk of fatal respiratory disease. These findings implicate high and low BMI as risk factors for fatal respiratory disease but suggest that the risk due to high BMI was obscured by weight loss that followed the onset of disease.
The overall findings support an association between obesity and a higher risk of fatal disease but also raise the possibility that apparently healthy, never-smoking women can experience a higher long-term risk of fatal cardiovascular and respiratory diseases due to a lower body weight. (Epidemiology 1998;9:246–254)
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