ABSTRACT
This chapter provides an up-to-date overview of the nature and causes of chemosensory disturbances in older age, tools for their evaluation, and approaches useful for counselling patients and treating the underlying dysfunction. In addition to the sensory innervation of the olfactory nerve, free nerve endings of the trigeminal nerve are distributed throughout the nasal mucosa. Threshold tests establish the lowest concentration of an odorant that can be perceived or recognised as a quality. Odour identification tests determine the degree of a person's olfactory function. The loss of smell can be quite severe in patients with nasal sinus disease, with most being anosmic or profoundly hyposmic. Severe acute respiratory syndrome coronavirus 2, which causes coronavirus disease 2019, affects chemosensory functions. During the last decade, more extensive research in the area of central nervous diseases has accumulated evidence on neurodegenerative processes and impaired olfaction. Taste function, like olfactory function, declines over the lifespan. © 2022 John Wiley & Sons Ltd. All rights reserved.