Insights into the pathophysiology and mechanisms of constipation, irritable bowel syndrome, and diverticulosis in older people.

OBJECTIVES: To review the epidemiology, pathophysiology and mechanisms of irritable bowel syndrome (IBS), constipation, and diverticulosis, for the purpose of addressing these three common conditions in older adults (>65 years of age).
DESIGN: Using a MEDLINE search, we identified original English language journal articles and reviews from 1965 to December 1998. We also selected articles published before 1965 or after 1998 that were cross-referenced or pertinent to the topics researched.
RESULTS: The prevalence of constipation and diverticulosis is higher in older than in younger adults. Significant risk factors for constipation in older women are failure of the anorectal angle to open or excessive perineal descent, which represent disturbances of pelvic floor function and rectal evacuation. In contrast, the prevalence of IBS is no greater than in younger adults. Nevertheless, these syndromes impact on the patient's functional status and quality of life. The mechanisms resulting in these gastrointestinal syndromes are unclear. Uncoordinated colonic activity and colonic segmentation may lead to IBS and diverticulosis, respectively, and these pathophysiological findings suggest disorders of inhibitory control of neuromuscular function. The total number of neurons in the myenteric plexus is decreased, and collagen deposited in the distal colon is increased with aging in humans. Animal studies suggest that senescent colonic muscle responds less to excitatory factors in vitro, and neural injury in older animals may result from apoptosis, defects of mitochondrial metabolism, and inadequate levels or response to neurotrophins. Future investigations will reveal whether similar mechanisms underlie human disease. Currently, treatment is aimed at relief of symptoms of IBS or constipation or dealing with the complications of diverticulosis.
CONCLUSIONS: Constipation, IBS, and diverticulosis are common problems of aging. There is a need for further systematic research of the basic mechanisms in neuromuscular dysfunction with aging, including the studies of physical characteristics of the colonic wall, pelvic floor function (particularly in women with excessive perineal descent), and neurohormonal control of motility and sensation. Insights on the pathophysiology and mechanisms of neural injury may lead to more specific treatments in the future, e.g., serotonergic agents and neurotrophins. Meanwhile, collaborations between primary care physicians, geriatricians, and gastroenterologists can optimize management of these three common conditions that significantly impact the quality of life of older adults.