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A Significant Link to Mortality and BMI

Body mass index was the least predictive risk factor for mortality over 10 years in obese patients who were eligible for bariatric surgery….

In this study, the authors aimed to verify the importance of BMI as a mortality predictor, to identify other important mortality predictors, and to construct a mortality prediction rule in a population eligible for bariatric surgery. The authors studied individuals from a population-representative register who met contemporary eligibility criteria for bariatric surgery (BMI, ≥35.0 alone or 30.0-34.9 with an obesity-related comorbidity) from January 1, 1988, through December 31, 1998. An age cutoff of 65 years was chosen because very few bariatric procedures are performed in patients older than 65 years. Hypertension, dyslipidemia, heart failure, type 2 diabetes mellitus, sleep apnea, osteoarthritis, coronary artery disease, and cerebrovascular disease (CVD) were obesity-related comorbidities used to define eligibility. The primary outcome, 10-year all-cause mortality, was ascertained by linking with the mortality records of the UK Office of National Statistics.

Mean (SD) age was 46.9 (11.9) years, BMI was 36.2 (5.5), and 63.2% of the patients were women. All-cause 10-year mortality was 2.1% (n = 330). Mortality within age strata did not differ significantly between BMI classes (P > .05). Age, type 2 diabetes mellitus, male sex, smoking, BMI, coronary artery disease, and CVD were significant predictors of all-cause mortality, with age and diabetes having the largest impact. Exclusion of other variables not significantly associated with all-cause mortality had minimal effect. Although their association with the outcome was statistically significant, established CVD and BMI did not contribute materially to the mortality prediction in the primary analysis.

Based on these results, the authors conclude that factors other than BMI are important in predicting the risk of death in patients eligible for bariatric surgery and that, of the obesity-related comorbidities, type 2 diabetes mellitus is the most important mortality predictor. Given that diabetes mellitus is highly amenable to surgical treatment, a strong case could be made for prioritizing it over BMI or other comorbidities.

Practice Pearls:
  • Age, type 2 diabetes mellitus, male sex, smoking, BMI, coronary artery disease, and CVD were significant predictors of all-cause mortality.
  • Age and diabetes had the largest impact on all-cause mortality.
  • Established CVD and BMI did not contribute materially to the mortality prediction in the primary analysis.

JAMA Surgery, October 2013