Hyposalivation strongly influences hypogeusia in the elderly

Aging is sometimes associated with decreased sensitivity to tastants, i.e., hypogeusia. The loss of taste sense induces not only the decreased quality of life (QOL), but also weight loss or health problems in the elderly. In our recent study, whole saliva secretion including minor salivary secretion, was found to be significantly decreased in the elderly with gustatory impairment, while it was normal in all of the elderly with normal taste thresholds, indicating that hyposalivation is closely related to hypogeusia. Moreover, clinical studies have shown that treatment for hyposalivation alleviates hypogeusia, even that due to the side effects of prescribed drugs or the effects of disease, e.g., nervous disorders or endocrine disorders. Thus, salivation is essential for maintenance of the normal taste function. Many medications for relief of dry mouth, primarily parasympathomimetic drugs, have serious adverse effects such as palpitation, sweating, nausea, diarrhea or dizziness, particularly in the elderly. To circumvent this problem, we use glutamate (umami taste) in an attempt to increase salivary secretion and to alleviate hypogeusia. An umami stimulus might be an effective method for the alleviation of hypogeusia through improvement of hyposalivation or dry mouth without side effects in aged patients. Consequently, attempts should be made to remedy hypogeusia by alleviation of hyposalivation so as to maintain and promote the health of the elderly.