Explanation
The elderly need sufficient nutrition to maintain their health, but the presence of dysphagia precludes them from eating even when they want to eat. Dysphagia can also take away enjoyment when there already are limited activities for them to enjoy. This section describes dysphagia-related problems among the elderly and age-related changes in eating and swallowing function.
Explanation
We begin with discussing dysphagia-related problems in the elderly. Decreasing appetite is a physiological age-related change. The circadian rhythm of appetite also changes; elderly people tend to have more appetite when eating breakfast and lunch and less appetite when eating dinner. We may need to reconsider dietary patterns focused on dinners for some elderly people.
Explanation
Choking is the leading cause of accidental death among the elderly (followed in order by drowning and falls). Eating appears to be among the daily life activities associated with the highest risk of choking.
Choking is a condition in which aspirated food or other objects block the airway to such an extent that breathing is interrupted. Rice cake and devil's tongue (konjac) jelly are major causes of choking, but other causes include very ordinary, frequently consumed food items, such as rice, bread, confectionery, seafood, meat, and fruit. Elderly people who are not aware of dysphagia in daily life may have reduced functional reserve and can choke when the preparatory and oral stages of swallowing are not properly completed.
Explanation
Pneumonia is the third leading cause of death among Japanese and was responsible for about 120,000 deaths in 2005. It is estimated that aspiration pneumonia accounts for about 70% of all pneumonia-related deaths. The proportion is particularly high among the elderly, highlighting the importance of preventing aspiration pneumonia in this population. Factors significantly associated with aspiration pneumonia in the elderly include age-related decreases in eating and swallowing function, reduced protective responses, and the presence of underlying disease.
Explanation
When assessing age-related changes in eating and swallowing function, it is important to distinguish between age-related physiological changes and pathological changes caused by individual diseases, although this can be difficult in practice. Because there is certain functional reserve in swallowing, it is unlikely that dysphagia results from physiological changes alone. It is likely that dysphagia in the elderly is associated with relatively mild pathological changes in addition to physiological changes. Elderly people are commonly affected by conditions that can cause dysphagia, such as cerebrovascular disorder. In those without known neuromuscular disease, dysphagia can also occur in association with such conditions as vocal cord dysfunction caused by endotracheal intubation under general anesthesia, and disuse of the organs involved in swallowing due to postoperative fasting.
Explanation
First, we need to check whether there are any age-related changes in sensation.
Taste sensation is one of the important factors that determine the palatability of food. It used to be thought that the ability to taste decreases with age, based on the histological changes that occur in the taste buds and taste cells. However, many studies involving healthy elderly individuals have shown that the ability to recognize a single taste does not decrease with age, although a significant age-related change has been observed in their ability to recognize more combined tastes. Taste sensation can also be affected by underlying disease, the occurrence of which tends to increase with age, and the use of drugs to treat them.
Taste stimuli have also been shown to 1) have a positive effect on swallowing function and 2) improve a reduced cough reflex (eg, stimulation with capsaicin), thus providing additional benefits aside from palatability.
The sense of smell adds to the flavor of meals and also promotes appetite-we've all experienced a blunting of the taste and smell of food when we've caught a cold. The age-related change in the sense of smell has been well established. Olfactory acuity peaks around 30 years of age and then declines with age, with the ability to recognize different types of smell more obviously decreased after 50 years of age.
Following a report that the smell of black pepper essential oil stimulated the cough reflex in elderly people requiring care, attempts have been made to use odor stimuli for the prevention of aspiration.
Explanation
This section describes age-related morphological and functional changes in the organs involved in swallowing.
This section describes age-related morphological and functional changes in the organs involved in swallowing.
One study showed that occlusal muscle strength, as measured with the Dental Prescale System, was mostly maintained in individuals up to their 70s compared with younger individuals but was significantly decreased in those aged 80 years or older.
So, an age-related decrease in masticatory function is evident, and it has been shown to result in biased selection of food items, reduced vegetable intake, and increased processed food intake.
Explanation
The tongue also shows age-related histological changes, such as thinning of the muscle layer and an increase in connective tissue. Nevertheless, no age-related decrease in tongue pressure has been documented. It is still possible that the coordinated movement of the tongue and cheeks is affected by aging. This may increase the risks of aspiration and choking due to inadequate bolus formation and poor synchronization of bolus transport and the pharyngeal stage.
Saliva secretion plays an important role in bolus formation, with reduced secretion leading to difficulty in swallowing. While purely age-related, minor acinar atrophy has been reported; however, no age-related decrease in salivary function has been documented. Nevertheless, suppressed saliva secretion is often observed in elderly people affected by disease or taking medications. Moreover, elderly people have reduced bodily water content and so they are likely to have reduced salivary reserve, making them prone to dehydration. This is why many elderly people suffer from oral dryness (xerostomia).
Explanation
One of the well-known age-related changes is lowered laryngeal position at rest, which becomes apparent after 70 years of age. The larynx, which is at around the height of the 5th cervical vertebra in younger people, descends to around the height of the 7th cervical vertebra. This results in an larger pharyngeal cavity, making bolus residue (pooling) in the pharynx likely to occur. To swallow this residue, another attempt to swallow may be needed. Also, the time needed for laryngeal elevation and repositioning lengthens the pharyngeal stage. The incidence of laryngeal penetration also increases in elderly people with lowered laryngeal position due to the longer time needed for laryngeal closure.
Explanation
Investigators' opinions about age-related changes in the pharyngeal stage vary depending on the method for investigating induction of the swallowing reflex. While many videofluoroscopy (VF) studies have shown a prolonged interval from the bolus entering the pharynx to onset of the swallowing reflex, other studies assessing the frequency of swallowing reflex induction by incrementally dripping small amounts of liquid into the pharynx have shown no age-related change in the frequency but a decreased frequency of the swallowing reflex in patients with a history of aspiration pneumonia and those with basal ganglia lesion. These results may appear to be discrepant. Because VF results are affected by the aforementioned coordinated movements of the oral structures, it is possible that bolus movement proceeds ahead of the onset of the pharyngeal stage, even with no change in the threshold for swallowing reflex induction. If this is the case, the incidence of laryngeal penetration would increase with age. Although it is generally believed that aspiration does not occur without pathological change, this appears not to apply to the oldest elderly.
In any case, regular elderly people, who could have age-related lowered laryngeal position and subclinical cerebral infarction, are likely to have impaired function of the pharyngeal stage.
Explanation
Investigators' opinions about age-related changes in the pharyngeal stage vary depending on the method for investigating induction of the swallowing reflex. While many videofluoroscopy (VF) studies have shown a prolonged interval from the bolus entering the pharynx to onset of the swallowing reflex, other studies assessing the frequency of swallowing reflex induction by incrementally dripping small amounts of liquid into the pharynx have shown no age-related change in the frequency but a decreased frequency of the swallowing reflex in patients with a history of aspiration pneumonia and those with basal ganglia lesion. These results may appear to be discrepant. Because VF results are affected by the aforementioned coordinated movements of the oral structures, it is possible that bolus movement proceeds ahead of the onset of the pharyngeal stage, even with no change in the threshold for swallowing reflex induction. If this is the case, the incidence of laryngeal penetration would increase with age. Although it is generally believed that aspiration does not occur without pathological change, this appears not to apply to the oldest elderly.
Moreover, impaired esophageal peristalsis and organic changes of the esophagus are likely to increase with age, resulting in increased risks of bolus retention in the esophagus and gastroesophageal reflux.
Explanation
In terms of the breathing pattern during swallowing, the airway opens and breathing occurs during the preparatory, oral, and esophageal stages and the larynx closes and breathing stops during the pharyngeal stage. Age-related extension of the apneic period during swallowing has been reported. This reflects lengthening of the pharyngeal stage.
Normally, swallowing is followed by expiration. This helps push out any small amounts of residue remaining at the entrance to the airway after swallowing. In the elderly, swallowing is more likely to be followed by inspiration.
It also appears that clearing cough is less likely to occur due to a higher cough threshold.
Consequently, aging is associated with reduced airway protection and increased risk of aspiration.
References
- Mukai Y: H19 Report of Health and Labor Sciences Research Grant (in Japanese), 2007
- Yamawaki M:Epidemiology of aspiration pneumonia (in Japanese),General Rehabilitation 37,105-109, 2009
- Miwa T. Dysosmia in elderly (in Japanese), Geriatric Medicine 44 (6): 813-817, 2006
- Ebihara T et al: Effect of black pepper on swallowing reflex in residents of nursing home (in Japanese), Rinsho Eiyo 112 (7) 802-803, 2008
- Matsuo K: Swallowing function in elderly people (in Japanese), Modern Physician 26, 11-14, 2006.
- Logemann JA: Evaluation and Treatment of Swallowing Disorders (translated into Japanese), 29-43, 2000, Ishiyaku publisher (Michi K, Michiwaki Y supervisor of translation)
