Relation of colonic transit to functional bowel disease in older people: a population-based study.
OBJECTIVE: The pathophysiology underlying chronic constipation in older people is poorly understood. Our objective was to determine if functional bowel disease (particularly constipation) in this population is associated with risk factors (age, immobility, low dietary fiber intake, and medication use) or directly with slow colonic transit. METHODS: A previously validated questionnaire was administered to a random sample of older residents (age range 65-104 years, n = 1609) of Olmsted County, MN. A random subset who met standard diagnostic criteria for functional constipation (n = 52) or irritable bowel syndrome (IBS) (n = 55) and a group without gastrointestinal symptoms (n = 93) were selected for further study. Each subject underwent structured interview and physical examination. Total caloric and fiber intake were assessed by dietitian interview, a food frequency questionnaire, and a food diary. Physical activity was assessed using a previously validated instrument. Medication use was determined by self-report, physician interview, and review of medical records. Total and segmental colonic transit was assessed radiographically using radioopaque markers. RESULTS: Total colonic transit times were prolonged in subjects with functional constipation (median 50.4 hours) but not in subjects with IBS (median 34.2 hours) or in healthy controls (median 28.8 hours); however, only rectosigmoid transit was delayed significantly. Age, gender, physical activity, and dietary fiber intake were not associated with total transit times, nor could they discriminate among the three patient groups. Laxative use was associated with prolonged total transit times independent of patient group. CONCLUSIONS: Older subjects can be classified by abdominal pain and bowel symptoms, which reflect colonic transit times. Older subjects with constipation symptoms generally have prolonged rectosigmoid transit. Other potential risk factors do not distinguish symptom subgroups, nor are they associated with altered colonic transit although older people who use laxatives regularly have prolonged colonic transit.