- Higher BMI was associated with an increased risk of both mild and severe diverticulitis
- The associations did not differ according to age, smoking, physical activity or BMI in early adulthood
- Weight gain since early adulthood was also associated with increased risk of diverticulitis
- These findings underscore the scientific rationale for maintaining a healthy weight throughout adulthood
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Several studies have consistently demonstrated an association between higher body mass index (BMI) and increased risk of severe diverticulitis. However, evidence about how adiposity and weight change influence the risk of more common, milder presentations of diverticulitis is sparse, especially among women.
To address this knowledge gap, Massachusetts General Hospital researchers Wenjie Ma, MBBS, ScD, research fellow, Andrew T. Chan, MD, MPH, director of the Gastroenterology Training Program, and colleagues analyzed data from the Nurses' Health Study, a large prospective study in which U.S. female registered nurses have answered health questionnaires every two years since 1976. The researchers found a consistent association between BMI and risk of diverticulitis, independent of other lifestyle risk factors.
Their groundbreaking report, published in Gastroenterology, was selected as one of the publication's "Hot Papers From New Investigators"—an accolade awarded for original articles from gastroenterologists early in their careers who publish what the journal editors consider high-impact research.
BMI as a Risk Factor
Between 2008 and 2014, the researchers documented 1,084 incident cases of diverticulitis. They found a linear, significant association between increasing BMI and an increased risk for diverticulitis.
After adjustment for various lifestyle and dietary risk factors, compared to women in the reference group (BMI <22.5 kg/m2), the hazard ratios were:
- 1.31 (95% CI, 1.09–1.59) for women with BMI 25.0–27.4
- 1.35 (95% CI, 1.09–1.68) for women with BMI 27.5–29.9
- 1.51 (95% CI, 1.23–1.86) for women with BMI 30.0–34.9
- 1.42 (95% CI, 1.08–1.85) for women with BMI ≥35.0
Age, smoking status and extent of physical activity did not appear to affect the association of BMI with diverticulitis. The association included both cases that were treated with antibiotics in the outpatient setting and more severe cases that led to hospitalization or surgery.
Waist Measurements as Risk Factors
Waist circumference (WC) and waist-to-hip ratio (WHR) did not seem to be independent of BMI in this study. Yet when BMI and WHR were assessed jointly, WHR appeared to play a role in determining diverticulitis among women who were overweight or obese.
The researchers note that although WC and WHR indirectly measure total abdominal fat, these measurements are thought to be better markers of visceral fat than BMI. Visceral fat is metabolically more active than subcutaneous fat and is suggested to promote systemic inflammation that may affect the pathogenesis of diverticulitis.
Weight Gain as a Risk Factor
Women who had gained ≥20 kg since age 18 had a 73% increased risk of diverticulitis (95% CI, 27%–136%), compared with those who had maintained their weight. Short-term weight gain during the past four years was not a risk factor for diverticulitis.
Given the increasing prevalence of diverticulitis and the lack of known modifiable risk factors, the findings have important implications for preventing diverticulitis and provide an additional reason for adults to maintain a healthy weight.
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