Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 66

The GI tract starts with the mouth. Mouth health is essential for digestion. Dental problems tend to occur more often in the elderly and can result in tooth loss. The salivary glands produce less saliva, and mucosal erosions due to physical trauma heal more slowly. All of these factors contribute to chewing problems and can cause an elderly person to eat less. This situation may result in inadequate nutritional intake or dyspeptic symptoms because of impaired mechanical digestion with chewing. A decreased ability to taste or smell causes loss of appetite as well.^45‐46

Swallowing is essential for transferring a bolus from the mouth to the oesophagus. The swallowing function requires oropharyngeal muscle integrity and coordination. Swallowing is under the control of cranial nerves V, VII, IX, X, and XI, which coordinate the tongue and pharyngeal muscles. The oropharyngeal muscles tend to get weak, and muscle coordination tends to become impaired with age. Comorbidities such as cerebrovascular disease and dementia may contribute to impaired swallowing function and dysphagia. Impaired swallowing may result in another frequent complication: food aspiration into the trachea.⁴⁷

Once the bolus is transferred into the oesophagus, smooth muscle contractions of the oesophageal wall cause peristalsis toward the stomach. Peristalsis of the oesophagus slows with advanced age. Until age 80, oesophagus motility remains intact. After 80, the transfer time of the bolus from the mouth to the stomach becomes longer. Thus the risk of esophagitis increases if the bolus includes irritating component such as pills. In addition, hiatal hernia prevalence increases by age 60, which causes reflux symptoms.⁴⁸

A feeling of early satiety occurs with age because gastric compliance and the emptying rate decrease with age. Gastric acid secretion decreases, and atrophic gastritis occurs more frequently after 60, which is responsible for reduced produced of gastric acid. Acidic pH is required for protein digestion and vitamin B12 absorption. Dyspeptic complaints such as heartburn and fullness may increase with age. Accompanying comorbidities such as dementia, chronic obstructive pulmonary disease, and heart failure may also contribute to loss of appetite.^49‐50

Slower peristalsis and slightly decreased enzymatic activity occur in the small intestine with age. Although enzymes linked to the brush border of the mucosa decrease, carbohydrate, fat, and protein digestion and absorption remain normal. Absorption of fat‐soluble vitamins A and D changes with age, with an increase in vitamin A absorption and a decrease in vitamin D absorption. Water‐soluble vitamin absorption remains intact unless hypochlorhydria is present, leading to decreased absorption of B12. Folate absorption slightly decreases with age. These changes rarely cause malabsorption unless a pathological condition coexists.^51‐52

Slower peristalsis occurs with age in the colon, and anal sphincter tone decreases, contributing to constipation. The rectoanal angle and perineal descent can be impaired in older women following labour traumas, and thus elderly women tend to have more rectal evacuation problems than elderly men.⁵³ The colonic microbiota also changes with age. While the Bacteroides spp. population increases, the Firmicutes spp. population decreases in the colon mucosa. These changes are components of the inflammageing process,⁵⁴ which is discussed separately in the immune system section. Bacterial population changes were found to be correlated with obesity, carcinogenesis, and metabolic age in previous studies. Maintaining the microbiota from a younger age remains a key factor for preventing multiple geriatric syndromes, such as frailty and dementia.