Vital and Health Statistics Series

Series 3, No. 42. Excess Deaths Associated With Underweight, Overweight, and Obesity: An Evaluation of Potential Bias

Previous analyses of mortality data from the National Health and Nutrition Examination Survey published in 2005 found that relative to the normal weight category of body mass index (BMI), defined as a BMI of 18.5–24.9, underweight (BMI less than 18.5) and obesity (BMI greater than or equal to 30) were associated with excess mortality, and overweight (BMI 25–29.9) was associated with reduced mortality, after adjusting for sex, smoking status, race–ethnicity group, and alcohol consumption. Possible sources of bias in those analyses include residual confounding due to imperfect adjustment for smoking and prevalent illness at baseline. This report presents an evaluation of these sources of bias.

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