Estimating population attributable fractions to quantify the health burden of obesity

Abstract

Purpose Obesity is a highly prevalent condition in the US and elsewhere and is associated with increased mortality and morbidity. Here we discuss some issues involved in quantifying the health burden of obesity using population attributable fraction (PAF) estimates and provide examples. Methods We searched PubMed for articles reporting attributable fraction estimates for obesity. We reviewed eligible articles to identify methodological concerns and tabulated illustrative examples of PAF estimates for obesity relative to cancer, diabetes, cardiovascular disease and all-cause mortality. Results There is considerable variability among studies regarding the methods used for PAF calculation and the selection of appropriate counterfactuals. The reported estimates ranged from 5% to 15% for all-cause mortality, −0.2% to 8% for all-cancer incidence, 7% to 44% for cardiovascular disease incidence, and 3% to 83% for diabetes incidence. Conclusions To evaluate a given estimate, it is important to consider whether the exposure and outcome were defined similarly for the PAF and for the relative risks, whether the relative risks were suitable for the population at hand, and whether PAF was calculated using correct methods. Strong causal assumptions are not necessarily warranted. In general PAFs for obesity may be best considered as indicators of association.

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