Original Article
International Journal of Obesity (2007) 31, 1449–1455; doi:10.1038/sj.ijo.0803615; published online 1 May 2007
Putative biases in estimating mortality attributable to obesity in the US population
J A Greenberg1, K Fontaine2 and D B Allison3
- 1Department of Health and Nutrition Sciences, Brooklyn College of the City University of New York, Brooklyn, NY, USA
- 2Division of Rheumatology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
- 3Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL, USA
Correspondence: Professor JA Greenberg, Department of Health and Nutrition Sciences, Brooklyn College of the City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA. E-mail: jamesg@brooklyn.cuny.edu
Received 7 August 2006; Revised 31 December 2006; Accepted 7 January 2007; Published online 1 May 2007.
Abstract
Background:
A recent analysis concluded that there were fewer excess deaths attributable to obesity in the US population than previously believed. This analysis may not have fully corrected for two putative biases, the regression-dilution and the reverse-causation biases. It is not presently known whether correcting for these biases would increase estimates of excess deaths attributable to obesity.
Methods:
All-cause mortality hazard ratios (HRs) for different body mass index (BMI) categories were calculated and adjusted for confounding factors, using data from the prospective Atherosclerosis Risk in Communities Study. The analysis was based on 12 457 individuals aged 51–70 years and 606 all-cause deaths during a 5.3-year follow-up. The HRs were corrected for the regression-dilution and reverse-causation biases, and compared with data from a previously published study to evaluate the effects of correcting for these putative biases on estimates of excess deaths attributable to obesity in the US population.
Results:
The uncorrected all-cause mortality HR for obesity (BMI
30) was 1.26 (95% confidence interval (95% CI)=1.01–1.58), using the 21–25 kg/m2 as ideal-weight category. Correcting for regression dilution increased the HR to 1.46 (95% CI=1.17–1.83). Correcting for both putative biases increased it further to 2.70 (95% CI=1.31–5.57). Such increases in HRs are consonant with increases of several hundred percent in estimates of deaths attributable to obesity in the US.
Conclusions:
Correcting for putative biases yielded increases in all-cause mortality HRs for obesity that correspond to substantial increases in estimates of excess deaths attributable to obesity in the US population.
Keywords:
body mass index, excess mortality, regression-dilution bias, reverse causation, ARIC, attributable fraction
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