To Örebro University

BACKGROUND & AIMS: Obesity promotes intestinal inflammation and might contribute to the pathogenesis of inflammatory bowel disease. We examined the association between obesity and risk of microscopic colitis in a prospective cohort study.

METHODS: We collected data from 192,101 women enrolled in the Nurses' Health Study (NHS) (from 1986 through 2014) or the NHSII (from 1991 through 2015). Anthropomorphic and lifestyle information were self-reported biennially. Obesity was defined using body mass index (BMI). Microscopic colitis was confirmed by review of medical records. We used Cox proportional hazard models to estimate adjusted hazard ratios (aHRs) and 95% CIs.

RESULTS: Among the participants in the NHS and NHSII, we confirmed 244 cases of microscopic colitis during 4,223,868 person-years of follow-up evaluation. Higher BMI was associated inversely with risk of microscopic colitis (Ptrend < .001). Compared with women with BMIs ranging from 18.5 to 20.9 kg/m(2), the aHRs were 0.61 (95% CI, 0.41-0.91) for overweight women (BMI, 2529.9 kg/m(2)) and 0.50 (95% CI, 0.32-0.79) for obese women (BMI >= 30 kg/m(2)). The aHR for each 5-kg/m(2) increase in BMI was 0.79 (95% CI, 0.69-0.90). Weight gain since early adulthood (age, 18 y) also was associated inversely with risk of microscopic colitis (Ptrend = .001). The aHR for each 10-kg weight gain since early adulthood was 0.85 (95% CI, 0.77-0.94). The associations were not modified by age, cohort, physical activity, or smoking status (all Pinteraction >= .26).

CONCLUSIONS: Unlike many other immune- and metabolic-related disorders, obesity and weight gain since early adulthood were associated with a lower risk of microscopic colitis, based on an analysis of participants in the NHS and NHSII.