MECHANISMS OF CONSTIPATION IN OLDER PERSONS AND EFFECTS OF FIBER COMPARED WITH PLACEBO

OBJECTIVE: To investigate the mechanisms of constipation and the effec t of fiber supplementation on physiology, mechanisms, stool parameters , and colonic transit times in a group of constipated older patients. DESIGN: Single-blind, randomized, placebo-controlled fiber interventio n with crossover. SETTING: A university-based outpatient center. PATIE NTS: Ten community-living older men and women, healthy except for chro nic constipation. INTERVENTIONS: Patients were given either 24 g psyll ium fiber or placebo fiber daily for 1 month, then crossed over to the other arm for an additional month. Structured testing, including tota l gut transit time and rectal and colonic manometry, was performed at the end of each intervention month. Patients recorded stool frequency, consistency, and weights daily. RESULTS: The predominant mechanism fo r constipation in these patients was outlet delay caused by pelvic dys synergia. Fiber decreased total gut transit time from 53.9 hours (plac ebo condition) to 30.0 hours (P < .05). Stool weights and consistency were not significantly improved by fiber, though there was a trend tow ard an increase in stool frequency (1.3 vs 0.8 bowel movements per day .) Pelvic floor dyssynergia was not remedied by fiber, even when const ipation was clinically improved. CONCLUSIONS: Fiber supplementation ap peared to benefit constipated older patients clinically, and it improv ed colonic transit time, but it did not rectify the most frequent unde rlying abnormality, pelvic floor dyssynergia.