More frequent bowel movements may be associated with diverticulitis risk

Patients who have more frequent bowel movements may be at higher risk for developing diverticulitis, according to a recent study.

Researchers used data from the Nurses' Health Study and the Health Professionals Follow-up Study, including medical history, lifestyle factors, and diet, to examine the association between bowel movement frequency and diverticulitis risk. The Nurses' Health Study included 121,700 female nurses in 11 U.S. states who were 30 to 55 years of age at inception of the cohort in 1976, while the Health Professionals Follow-up Study included 51,529 U.S. male health professionals ages 40 to 75 years at study enrollment in 1986. Bowel movement frequency was ascertained in 1982 and 2012 in the Nurses' Health Study and in 2000 and 2012 in the Health Professionals Follow-up Study. Cox proportional hazards models were used to calculate hazard ratios and 95% CIs. The study results were published online Jan. 5 by Clinical Gastroenterology and Hepatology.

Overall, 5,214 incident cases of diverticulitis were documented over 23 years and nearly 1.3 million person-years of follow-up in the Nurses' Health Study, and 390 were documented over 14 years and 368,661 person-years of follow-up in the Health Professionals Follow-up Study. A direct correlation was seen between frequency of bowel movements and diverticulitis risk. In the Nurses' Health Study, the hazard ratio was 1.30 (95% CI, 1.19 to 1.42) for women who had bowel movements more than once daily and 0.89 (95% CI, 0.82 to 0.95) for those with less frequent bowel movements compared with women who had one bowel movement a day (P<0.0001 for trend). Among the men in the Health Professionals Follow-up Study, the corresponding hazard ratios were 1.29 (95% CI, 1.04 to 1.59) and 0.61 (95% CI, 0.36 to 1.03), respectively (P=0.003 for trend). The association between bowel movement frequency and diverticulitis did not change when data on age, body mass index, physical activity, laxative use, or fiber intake were considered.

The authors noted that their study was observational, that they could not rule out reverse causation, and that their results might not be generalizable, among other limitations. They concluded that more frequent bowel movements may be a risk factor for subsequent diverticulitis in both men and women and called for additional studies to examine the potential mechanisms that might underlie this association. Explanations may include body position during defecation, changes in the gut microbiota, or low-grade inflammation, the authors said. “Further understanding of these mechanisms could inform new targets for prevention and treatment of diverticulitis,” they wrote.