A broad series of changes occur in gastroenterologic tissues, but the redundancy of overall gastrointestinal function usually prevents clinical symptoms. Age-related changes in the mouth include slower production of dentine, shrinkage of the root pulp, and decreasing bone density of the jaw. Taste and smell decline progressively with advancing age, with rising thresholds for salt, sweet, and certain proteins. The overall net effect is that food may taste more bitter, and more sugar is required before something tastes sweet. Salivary gland function normally does not change with age. The loss of bone and tongue musculature makes the tongue appear to be enlarged.

The esophagus seems to function relatively normally. The strength of muscular contraction declines, however, and peristaltic waves slow with advancing age. There is also a tendency for the lower esophageal sphincter to become lax with advancing age.

The gastric mucosa secretes less acid with advancing age. Although these changes do not seem to affect digestion in most individuals, associated conditions, such as atrophic gastritis, may decrease the absorption of nutrients. Most studies suggest delayed gastric emptying is a feature of aging, leading to a sense of false or early satiety, which can impair subsequent food ingestion.

Liver weight declines by one third between ages 30 and 90 years owing primarily to the loss of hepatocytes. The result is a decreased ability to process medications, such as benzodiazepines, and dietary components, such as alcohol and vitamin K-blocking agents. Doses of drugs often must be adjusted, and their blood levels should be monitored when possible.

Aging is associated with a significant reduction in small intestinal surface area with the consequence of reduced absorption of some dietary components, such as calcium. Colonic function seems to decline with advancing age. Motility up to the rectosigmoid area, measured by passage of markers, does not seem to decline with advancing age. Distal to this point, however, evacuation is characteristically slower with advancing age. Stool frequency tends to decline, and hardness of stools seems to increase with advancing age. Diverticuli are present in approximately 50% of people older than age 80 and likely are related to reduced dietary fiber and the resulting greater pressure on colonic tissues.

AGE-RELATED GASTROENTEROLOGIC SYNDROMES.

The most important age-related symptom is constipation, which may affect 60% of individuals in late life. Obstipation can present atypically with confusion, nausea, and vomiting or as obscure fevers resulting from stercoral ulcerations. Perhaps the most common abnormality related to declining hepatic function is increased sensitivity to medications that require hepatic metabolism.