The Body Mass Index-Mortality Link across the Life Course: Two Selection Biases and Their Effects

Hui Zheng, Ohio State University
Jonathan Dirlam, Ohio State University

This study investigated two selection biases that may affect the obesity-mortality link over the life course: mortality selection and healthy participant effects. We used data from the National Health and Nutrition Examination Survey 1988-2004 with linked mortality files from 1988-2006. We employed weighted Cox models to test and adjust for these two selection biases. We also used complementary log-log models, adjusted for a normal distribution of frailty, to test for mortality selection effects; accelerated failure-time models to mitigate the mortality selection effect; and ordinary least squares regression to test for healthy participant effects. The link between class II/III obesity and mortality weakens at older ages. We did not find evidence for significant mortality selection or healthy participant effects. Therefore, neither of these selection biases explains the diminishing effect of class II/III obesity on mortality over the life course.