Obesity and Mortality Rate: Are the Risks Declining? Evidence from 18 Prospective Studies in U.S.

• Activity Number: 581
• Type: Contributed
• Date/Time: Wednesday, August 1, 2012 : 2:00 PM to 3:50 PM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Tapan Mehta*+ and Kevin Fontaine and Scott W Keith and Sai Santosh Bangalore and Gustavo de los Campos and Nicholas Pajewski and Alfred Bartolucci and David B. Allison
• Companies: and The Johns Hopkins University School of Medicine and Thomas Jefferson University and The University of Alabama at Birmingham and The University of Alabama at Birmingham and Wake Forest University Health Sciences and The University of Alabama at Birmingham and The University of Alabama at Birmingham
• Keywords: obesity ; meta-regression ; length of follow-up ; mortality rate ; calendar time

Abstract

In this study we evaluate whether the reduction in the detrimental association of obesity with mortality rate (MR) over calendar time, reported in previous analyses of the NHANES, is supported by data from an additional 18 US prospective studies. Prospective studies with at least 2 assessments of body mass index (BMI, kg/m2) at different calendar years (2 waves) were used. Log hazard ratios (HRs) were estimated by BMI category (i.e., underweight : < 18.5, normal weight: 18.5 to < 25, overweight: 25 to < 30, grade 1 obesity: 30 to < 35, grade 2-3 obesity: 35 or greater) separately for 2 waves of each study using a Cox regression. These log HRs were then pooled as a response in a weighted random effects meta-regression to test for interactions between BMI categories and calendar time after controlling for length of follow-up. From 1960 to 1990, the deleterious association of grade 1 obesity decreased by 10.5% (p=0.19) while that of grade 2-3 obesity increased by 25.1% (p=0.06). Our results suggest that after controlling for length of follow-up, there was no consistent and statistically significant reduction in the deleterious association of obesity with MR over calendar time.