**3. Changes associated with normal aging, which might influence swallowing**

A holistic approach is required while studying swallowing in the elderly. Swallowing cannot be regarded as an isolated action; one has to take into account the age-related functional decline occurring in several body-functions and its repercussions on swallowing (figure 1).

First of all there is an age-related decrease of sense of smell and taste, which are important for the pleasure we enjoy while eating [35-37].

Also, some anatomical differences arise in the older person such as a smaller cross-sectional area of masticatory muscles (masseter and medial pterygoid) and an increased lingual atrophy [38]. Next to the anatomical changes also, functional alterations occur in the muscle activity of the masseter, orbicularis oris, the supra- and infra-hyoidal muscles [39], and the thyroaryte‐ noid muscle [39].

The respiratory system undergoes some changes as well; there is a decreased cough reflex, a diminished ciliary clearing, and a weakening of the respiratory muscles. These changes in combination with a deterioration of the immune system make the elderly more prone to developing an aspiration pneumonia.

As far as the digestive system is concerned, a delayed gastric emptying may lead to an earlier feeling of fullness at mealtime. Recent studies have shown a decreased sensibility and an increased stiffness of the esophagus in old age [40].

Another important issue is fatigue [41]. Fatigue, being a very common complaint in the elderly, is often associated with functional decline and may, as well as sleeping disturbances and depression, lead to a reduced food intake [42-44]. The elderly also often experience a declined perception of thirst and subsequently they have a low fluid intake. Tongue strength and endurance decline during a meal and this in combination with a diminished reserve may negatively influence deglutition especially in already weakened elderly [45].

As people get older, the slower swallowing act may actually also be a benefit as it can allow greater time to recruit the necessary number of muscle fibers to generate the necessary pressures for adequate bolus propulsion through the oropharynx. Hence, speeding up an elderly patient's swallow may induce contradictory results, as it may lead to insufficient swallow pressures and therefore may be contraindicated as a therapy technique.

Cognitive changes are also considered to be part of the normal aging process and cognitive processes such as concentration, attention, and double-tasking are influenced by age. A decline in concentration and attention together with a reduced reserve may lead to aspiration. Moreover as eating is a social event, people tend to talk during mealtime further increasing the risk of penetration and aspiration.

Staying physically active is associated with healthy aging, therefore elderly who are bedridden are additionally exposed to a number of important risk factors due to the sedative life style such as a diminished lung capacity and a weaker cough, a greater risk to develop a pneumonia, muscle weakness, and a loss of appetite [46].

Finally, medication may also negatively influence deglutition [47]. Drugs with an anticholi‐ nergic effect may cause xerostomia while some may lead to a diminished (e.g., allopurinol, carbamazepine, and penicillamine) or an altered (e.g., captopril lithium) taste perception. Sedatives can reduce the level of alertness and neuroleptics may mimic the swallowing problems encountered in Parkinson's disease. Nitrates are relatively contraindicated in gastroesophageal, reflux disease as they lower the pressure in the lower gastro-esophageal sphincter and steroids can not only induce a Candida infection orally but they can also provoke a steroid myopathy. Moreover, 40% of already weakened elderly take at least one medication that is completely superfluous [48].

**Figure 1.** The relationship between presbyphagia and dysphagia
