English summary

Taste and smell are senses reacting upon solutes from food and breathing air conveyed by the cranial nerves. Normal aging includes cellulary and extracellulary biochemical mechanisms detrimental to neurons in the central nervous system, including those processing taste and smell signals. Aging also means reduction of the number of taste buds in the oral cavity and of the number of odor receptors in the nasal mucosa. hysiological age related taste and smell dysfunction is difficult to distinguish from similar effects related to oral and general diseases and ultidrug use, characteristic of institutionalized elderly.
In general, clinical trials show impaired taste and smell with increasing age, smell more so than taste. The most evident age impact on taste is on acid, salt and umami, whereas sweet and bitter taste seems to be less affected. Otherwise self-managing older people are often unaware of dysfunction of this kind, risking loss of appetite and weight loss or other malnutrition such as increased consumption of salt. Olfactory dysfunction also may have social implications such as undetected poor indoor air and substandard personal hygiene. In addition, the age related neurodegenerative process of olfactory dysfunction is part of the pathology of dementia. Loss of smell could therefore be a warning of cognitive malfunction in progress.

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Reference
Aldring, smak og lukt
Jacobsen N.
Nor Tannlegeforen Tid. 2017; 127: 954–7