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Moderate Physical Activity Tied to Reduced Risk of Fecal Incontinence in Women

Key findings

  • In the Nurses' Health Study, higher levels of physical activity were associated with a modest reduction in the risk of fecal incontinence (FI)
  • This relationship persisted even after adjustment for suspected mediators between physical activity and FI, including BMI, diabetes and hypertension
  • The risk of FI was 25% lower among women who engaged in =27 MET-hours/week of physical activity versus <3 MET-hours/week
  • Moderate, low-impact physical activity was more protective against FI than high-impact activity

Fecal incontinence (FI) affects 7% to 15% of women and has substantial negative effects on quality of life, but little is known about its risk factors. Potentially modifiable factors, such as body weight and physical activity, are of particular interest, but cross-sectional studies have produced conflicting results about whether they influence the risk of FI.

Therefore, Kyle Staller, MD, MPH, gastroenterologist at Massachusetts General Hospital, Mary K. Townsend, ScD, associate epidemiologist at Brigham and Women's Hospital, and colleagues prospectively examined the associations between FI, body mass index (BMI) and physical activity in the Nurses' Health Study. According to their report in Clinical and Translational Gastroenterology, higher levels of low-impact physical activity are associated with a modest reduction in the risk of FI.

Study Design

The Nurses' Health Study, a large, ongoing study of older U.S. women, began in 1976 when 121,701 female registered nurses, then 30 to 55 years of age, completed a mailed questionnaire about their health and lifestyle. Participants have provided updated information every two years since. Questions about the frequency of FI were included beginning in 2008.

The current study analyzed 51,708 women who returned the 2008 questionnaire, did not have FI already in 2008, had BMI ≥18.5 kg/m2 and supplied complete data about physical activity during the period of 2008 to 2012. The researchers confirmed 5,954 incident cases of FI during this period (175,447 person-years of follow-up).

Fecal Incontinence and Physical Activity

On the 2008 questionnaire, participants were asked about their average time per week during the preceding year spent walking or hiking outdoors; jogging; running; bicycling; swimming laps; playing tennis; doing calisthenics, aerobics or aerobic dance; using a rowing machine; playing squash or racquetball; or doing other vigorous activities (e.g., mowing the lawn). Each activity was assigned a value for the metabolic equivalent task (MET) according to established criteria, and total physical activity was the sum of MET-hours/week.

The risk of FI decreased with increasing physical activity, even after adjustment for suspected mediators between physical activity and FI, including BMI, diabetes and hypertension. Compared with women in the lowest category of physical activity (≤3 MET-hours/week), adjusted hazard ratios for FI were (P < .0001 for the trend):

  • 0.86 (95% CI, 0.80–0.93) for 3–8 MET-hours/week
  • 0.78 (95% CI, 0.72–0.84) for 9–17 MET-hours/week
  • 0.76 (95% CI, 0.69–0.83) for 18–26 MET-hours/week
  • 0.75 (95% CI, 0.70–0.81) for =27 MET-hours/week

FI and BMI

After adjustment for potential mediating variables of the relationship between BMI and FI (physical activity, hypertension and diabetes), there was no association between BMI and risk of FI.

FI and Type of Physical Activity

Data from multiple studies suggest that strenuous, high-impact activity may cause pelvic floor muscle fatigue and increase the risk of FI. To explore this, the researchers categorized participants according to whether their participation in high-impact activity (jogging, running, tennis and aerobics) was above or below the group median. They created similar categories for the other physical activities listed on the 2008 questionnaire, which they designated low impact.

For high-impact activity, the risk of developing FI was similar among women above and below the median. However, higher levels of low-impact activity were associated with a lower risk of FI (multivariable-adjusted HR, 0.84; 95% CI, 0.79–0.88).

Biologic Plausibility

Several studies have linked pelvic floor activation and concomitant activity of the abdominal musculature with pelvic floor activity known to be associated with lifting tasks, spinal stabilization and functional tasks such as head and shoulder raising. Thus, it seems that the pelvic floor musculature and the muscles of the rest of the body function as an integrated unit.

Aging is associated with significant changes in the female pelvic floor, including decreased sphincter strength, perineal laxity, reduced rectal sensation and reduced rectal compliance. To the extent that overall physical activity benefits the pelvic floor, it is plausible that regular physical activity mitigates the risk of FI in older women.

Points for Patient Counseling

When it comes to patient care, it's important to stress the fact that not all exercises protect equally against FI. Patients should not feel the need to push themselves too hard: Moderate, low-impact physical activity may be enough to reduce the risk of FI in older women. In fact, the risk of FI was similar in women participating in higher amounts of high-impact physical activity and those with less high-impact physical activity. The high-impact activity might stress the pelvic floor and increase the likelihood of FI among women already at risk.

It is unclear from this study whether the physical activity would benefit women with existing FI. Further research aims to shed light on lifestyle changes that may modify the risk of FI or limit its progression.

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