Analysis of Body Mass Index and Mortality in Patients with Colorectal Cancer Using Causal Diagrams
Research JAMA Oncology | Original Investigation Analysis of Body Mass Index and Mortality in Patients With Colorectal Cancer Using Causal Diagrams Candyce H. Kroenke, ScD; Romain Neugebauer, PhD; Jeffrey Meyerhardt, MD; Carla M. Prado, PhD; Erin Weltzien, BA; Marilyn L. Kwan, PhD; Jingjie Xiao, MS; Bette J. Caan, DrPH Editorial page 1127 IMPORTANCE Physicians and investigators have sought to determine the relationship Supplemental content between body mass index (BMI [calculated as weight in kilograms divided by height in meters squared]) and colorectal cancer (CRC) outcomes, but methodologic limitations including sampling selection bias, reverse causality, and collider bias have prevented the ability to draw definitive conclusions. OBJECTIVE To evaluate the association of BMI at the time of, and following, colorectal cancer (CRC) diagnosis with mortality in a complete population using causal diagrams. DESIGN, SETTING, AND PARTICIPANTS This retrospective observational study with prospectively collected data included a cohort of 3408 men and women, ages 18 to 80 years, from the Kaiser Permanente Northern California population, who were diagnosed with stage I to III CRC between 2006 and 2011 and who also had surgery. EXPOSURES Body mass index at diagnosis and 15 months following diagnosis. MAIN OUTCOMES AND MEASURES Hazard ratios (HRs) for all-cause mortality and CRC-specific mortality compared with normal-weight patients, adjusted for sociodemographics, disease severity, treatment, and prediagnosis BMI. RESULTS This study investigated a cohort of 3408 men and women ages 18 to 80 years diagnosed with stage I to III CRC between 2006 and 2011 who also had surgery. At-diagnosis BMI was associated with all-cause mortality in a nonlinear fashion, with patients who were underweight (BMI <18.5; HR, 2.65; 95% CI, 1.63-4.31) and patients who were class II or III obese (BMI Ն35; HR, 1.33; 95% CI, 0.89-1.98) exhibiting elevated mortality risks, compared with patients who were low-normal weight (BMI 18.5 to <23).
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