A simple prediction rule for all-cause mortality in a cohort eligible for bariatric surgery.
Study Goal
The researchers aimed to assess the importance of BMI as a mortality predictor, identify other mortality predictors, and develop a mortality prediction rule for individuals eligible for bariatric surgery.
Results Summary
The study found that a simple 4-variable prediction rule (age, sex, smoking, and diabetes mellitus) effectively estimated 10-year all-cause mortality in obese individuals eligible for bariatric surgery, while BMI was not a significant predictor. Mortality rates varied across four risk tiers, ranging from 0.2% to 5.2%.
Population
15,394 patients aged 18 to 65 years with BMI ≥35.0 alone or 30.0-34.9 with an obesity-related comorbidity.
Effective Dosage
Not specified
Duration
Mean follow-up duration was 9.9 years.
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
Bariatric surgery | increase | mortality | patients eligible for bariatric surgery | odds ratio, 1.03 per unit | significantly predicted | #1 |
Bariatric surgery | no change | model discrimination or calibration | patients eligible for bariatric surgery | - | did not improve | #2 |
Age | increase | mortality | patients eligible for bariatric surgery | odds ratio, 1.09 per year | predicted | #3 |
Type 2 diabetes mellitus | increase | mortality | patients eligible for bariatric surgery | odds ratio, 2.25 | predicted | #4 |
Current smoking | increase | mortality | patients eligible for bariatric surgery | odds ratio, 1.62 | predicted | #5 |
Male sex | increase | mortality | patients eligible for bariatric surgery | odds ratio, 1.50 | predicted | #6 |
IMPORTANCE: Current eligibility criteria for bariatric surgery use arbitrarily chosen body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) thresholds, an approach that has been criticized as arbitrary and lacking evidence. OBJECTIVES: 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. DESIGN: We 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. We used binary logistic regression to construct a parsimonious model and a clinical prediction rule for 10-year all-cause mortality. SETTING: The United Kingdom General Practice Research Database, a population-representative primary care registry. PARTICIPANTS: Fifteen thousand three hundred ninety-four patients aged 18 to 65 years. EXPOSURE: Bariatric surgery. MAIN OUTCOME AND MEASURE: Ten-year all-cause mortality. RESULTS: 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 mortality was 2.1%, and mean follow-up duration was 9.9 years. The final model, which included age (odds ratio, 1.09 per year [95% CI, 1.07-1.10]), type 2 diabetes mellitus (2.25 [1.76-2.87]), current smoking (1.62 [1.28-2.06]), and male sex (1.50 [1.20-1.87]), had a C statistic of 0.768. Although BMI significantly predicted mortality (odds ratio, 1.03 per unit [95% CI, 1.01-1.05]), it did not improve model discrimination or calibration. We divided clinical prediction rule scoring into 4 tiers. All-cause mortality was 0.2% in tier 1, 0.9% in tier 2, 2.0% in tier 3, and 5.2% in tier 4. CONCLUSIONS AND RELEVANCE: All-cause 10-year mortality in obese individuals eligible for bariatric surgery can be estimated using a simple 4-variable prediction rule based on age, sex, smoking, and diabetes mellitus. Body mass index was not an important mortality predictor. Further work is needed to define low, moderate, and high absolute risk thresholds and to provide external validation.