Do Mortality Differentials Associated with Body Mass Decline over Age? An Age-Period-Cohort Analysis and Evidence of Cohort Distortions in the U.S.

Yan Yu, Australian National University

Excess mortality due to overweight or obesity was found to decline over cross-sectional age groups, which has been interpreted as a declining age effect in the public health literature. This finding is susceptible to cohort and period distortions because the age groups belong to different birth cohorts, and their mortality is observed over a considerably long period of time. In addition, prior research used time since baseline as analysis time, making it impossible to evaluate age-specific mortality. This paper conducts an age-period-cohort analysis of mortality differentials by body mass for US men and women who were born in 1901-57, using the 1988-94 National Health and Nutrition Examination Survey. The body mass-mortality association strengthens across cohort but changes little over age or the study period. As excess overweight or obese mortality has been increasing from earlier to later cohorts, failing to account for cohort differences leads to a declining age pattern.