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 i rritable bowel syndrome (IBS), constipation, and diverticulosis, for the pu rpose of addressing these three common conditions in older adults (>65 year s of age). DESIGN: Using a MEDLINE search, we identified original English language jou rnal articles and reviews from 1965 to December 1998. We also selected arti cles published before 1965 or after 1998 that were cross-referenced or pert inent to the topics researched. RESULTS: The prevalence of constipation and diverticulosis is higher in old er than in younger adults. Significant risk factors for constipation in old er women are failure of the anorectal angle to open or excessive perineal d escent, which represent disturbances of pelvic floor function and rectal ev acuation. In contrast, the prevalence of IBS is no greater than in younger adults. Nevertheless, these syndromes impact on the patient's functional st atus and quality of life. The mechanisms resulting in these gastrointestina l syndromes are unclear. Uncoordinated colonic activity and colonic segment ation may lead to IBS and diverticulosis, respectively, and these pathophys iological 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 hum ans. 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 sim ilar mechanisms underlie human disease. Currently, treatment is aimed at re lief of symptoms of IBS or constipation or dealing with the complications o f diverticulosis. CONCLUSIONS: Constipation, IBS, and diverticulosis are common problems of a ging. There is a need for further systematic research of the basic mechanis ms in neuromuscular dysfunction with aging, including the studies of physic al characteristics of the colonic wall, pelvic floor function (particularly in women with excessive perineal descent), and neurohormonal control of mo tility and sensation. Insights on the pathophysiology and mechanisms of neu ral injury may lead to more specific treatments in the future, e.g., seroto nergic agents and neurotrophins. Meanwhile, collaborations between primary care physicians, geriatricians, and gastroenterologists can optimize manage ment of these three common conditions that significantly impact the quality of life of older adults.