(C-030) Obesity and obesity-related metabolic factors and incident diverticulitis risk in a US cohort of women

Background: Diverticulitis is a painful gastrointestinal disease that can be complicated by abscesses or perforations in the bowel. Obesity is a risk factor for diverticulitis. While the mechanism is unclear, metabolic syndrome may also play a role.

Objectives: To elucidate associations of obesity and metabolic factors with incident diverticulitis in women. We hypothesize that obesity and metabolic syndrome are associated with increased risk.

Methods: We analyzed data from 29,831 eligible participants in the Sister Study, a prospective cohort of 50,884 U.S. women aged 35-74 years. At enrollment (2003-2009), participants completed detailed questionnaires and underwent anthropometric and blood pressure (BP) measurements. We excluded women with inflammatory bowel disease, diverticulitis, or cancer prior to enrollment. Metabolic exposures were hypertension (high BP or antihypertensive medication use), dyslipidemia (self-reported high cholesterol/ triglycerides or cholesterol-lowering medication use), type 2 diabetes (self-reported diabetes diagnosis at age ≥30 years), waist circumference ≥88 cm, and metabolic syndrome (≥3 of the previous factors). Obesity exposures were body mass index (kg/m^2), waist circumference, and waist to hip ratio (WHR). The primary outcome was incident diverticulitis, defined as a first diverticulitis episode after enrollment. Multivariable Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) adjusted for demographic, clinical, and medication variables.

Results: We identified 1,533 cases of incident diverticulitis over 440,626 person-years of follow up (mean=14.8 years). Hypertension [HR 1.40, 95% CI: (1.26, 1.56)], dyslipidemia [1.23 (1.10, 1.37)], and central obesity [1.47, (1.32, 1.63)] were associated with increased diverticulitis risk. The HR for diabetes’ association with diverticulitis was 1.14 (0.88, 1.50). Metabolic syndrome was also associated with increased diverticulitis risk [1.38, (1.20, 1.59)], with HR increasing from 1.48 (1.29, 1.70) to 1.75 (1.51, 2.03), 1.98 (1.66, 2.51), and 2.01 (1.39, 2.92) for 1-4 metabolic factors respectively. Among obesity measures, WHR ≥ 0.85 (vs. < 0.85)) was associated with higher diverticulitis risk [1.46 (1.30, 1.62)] as was increasing waist circumference [1.38 (1.20, 1.58) for ≥80-88cm and 1.67 (1.48, 1.88) for ≥88cm vs. < 80cm]. Higher BMI categories (vs normal BMI of 18.5-24.9 kg/m2) were also associated with incident diverticulitis [1.35 (1.19, 1.52) for 25.0-29.9 kg/m^2 and 1.64 (1.44, 1.87) for ≥ 30 kg/m^2].

Conclusions: Obesity and metabolic factors are associated with higher risk of incident diverticulitis in women. Future studies should evaluate the mechanisms underlying these associations.