Underweight, smoking, exercise and mortality in women

Conflicting findings on the relation between body mass index and/or obesity and mortality have been recently reported. The main purpose of this study is to examine the relationship between being underweight (BMI < 19), as well as behavioral practices and medical conditions, and mortality in women.

Statistical analyses, on data from 5398 college-educated women who participated by responding to a self-administered mailed questionnaire that included questions about medical history, weight and behavioral practices, were carried out to estimate risk ratios for the association of low BMI as well as other factors and mortality.

The mean BMI was 21.60, standard deviation 2.76, the median 21.03. Only 1.5% was obese. In a 15-year follow-up 259 deaths were reported. Underweight women, BMIs less than 19, who comprised 12% of the sample, had higher mortality women than women with BMIs 19 or higher. The age-adjusted odds ratio is: 1.80, 95% CI (1.16, 2.76), p=0.007; the multivariable adjusted OR=1.79, 95% CI (1.17, 2.75), =0.008. Not surprisingly, a major behavioral risk factor associated with mortality was smoking.

These findings show that low BMI is associated with mortality, independent of behavioral practices and medical conditions. Further, currently smoking is a major risk factor for mortality independent of weight or BMI.