(23-05-13) Association of All-Cause Mortality With Overweight and Obesity Using Standard Body Mass Index Categories

Association of All-Cause Mortality With Overweight and Obesity Using Standard Body Mass Index Categories
A Systematic Review and Meta-analysis
Katherine M. Flegal, PhD
Brian K. Kit, MD
Heather Orpana, PhD
Barry I. Graubard, PhD
Importance Estimates of the relative mortality risks associated with normal weight,
overweight, and obesity may help to inform decision making in the clinical setting.
Objective To perform a systematic review of reported hazard ratios (HRs) of allcause
mortality for overweight and obesity relative to normal weight in the general
population.
Data Sources PubMed and EMBASE electronic databases were searched through
September 30, 2012, without language restrictions.
Study Selection Articles that reported HRs for all-cause mortality using standard body
mass index (BMI) categories from prospective studies of general populations of adults were
selected by consensus among multiple reviewers. Studies were excluded that used nonstandard
categories or that were limited to adolescents or to those with specific medical
conditions or to those undergoing specific procedures. PubMed searches yielded 7034
articles, of which 141 (2.0%) were eligible. An EMBASE search yielded 2 additional articles.
After eliminating overlap, 97 studies were retained for analysis, providing a combined
sample size of more than 2.88 million individuals and more than 270 000 deaths.
Data Extraction Data were extracted by 1 reviewer and then reviewed by 3 independent
reviewers. We selected the most complex model available for the full sample
and used a variety of sensitivity analyses to address issues of possible overadjustment
(adjusted for factors in causal pathway) or underadjustment (not adjusted for at least
age, sex, and smoking).
Results Random-effects summary all-cause mortality HRs for overweight (BMI of
25-_30), obesity (BMI of _30), grade 1 obesity (BMI of 30-_35), and grades 2 and
3 obesity (BMI of _35) were calculated relative to normal weight (BMI of 18.5-_25).
The summary HRs were 0.94 (95% CI, 0.91-0.96) for overweight, 1.18 (95% CI, 1.12-
1.25) for obesity (all grades combined), 0.95 (95% CI, 0.88-1.01) for grade 1 obesity,
and 1.29 (95% CI, 1.18-1.41) for grades 2 and 3 obesity. These findings persisted
when limited to studies with measured weight and height that were considered to be
adequately adjusted. The HRs tended to be higher when weight and height were selfreported
rather than measured.
Conclusions and Relevance Relative to normal weight, both obesity (all grades)
and grades 2 and 3 obesity were associated with significantly higher all-cause mortality.
Grade 1 obesity overall was not associated with higher mortality, and overweight
was associated with significantly lower all-cause mortality. The use of predefined
standard BMI groupings can facilitate between-study comparisons.


Source: Source: JAMA. 2013;309(1):71-82 www.jama.com

©2013 American Medical Association. All rights reserved. JAMA, January 2, 2013—Vol 309, No. 1 71
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