The senses of smell and taste are termed chemical senses because they detect chemical stimuli and encode chemosensory information into neural signals. A variety of diagnostic terms have been used to describe smell and taste disorders. Standard classification terms for olfactory disorders are anosmia (absence of smell), hyposmia (diminished sensitivity of smell), and dysosmia (distortion of normal smell). Phantosmia, a type of dysosmia, refers to perception odor in absence of an odor stimulus, and parosmia refers to distortion of odor perception when an odor is present. For taste, diagnostic terms include ageusia (absence of taste), hypogeusia (diminished sensitivity of taste), and dysgeusia (distortion of normal taste). Dysosmia and dysgeusia are not necessarily correlated with decreased ability to perceive chemo-sensory stimuli.
While disorders of taste and smell can occur throughout the life span, they are far more prevalent in an chronic diseases elderly population. The terms presbyosmia and presbygeusia are occasionally used to describe olfactory or taste losses with age. Typically, olfactory perception is more likely to be disrupted during the aging process than the sense of taste.
The decrements in smell and taste perception that occur with advancing age can have profound effects on integral activities in the daily lives of elderly persons. These chemical senses provide critical information about potential dangers in the environment. For this reason, smell and taste losses are not merely an inconvenience; rather, they leave elderly persons vulnerable to hazards such as spoiled foods, smoke, hazardous chemicals, natural gas leaks, and dangerous fumes.
Smell and taste losses can impair the ability to perform routine activities such as food shopping and meal preparation, personal hygiene, and proper handling of household chemicals such as bleach, cleaning products, and pesticides. Loss of the senses of smell and/or taste can also affect elderly who are still working in professions that are best performed by persons with intact chemosensation, such as gourmet chefs, bakers, beauticians, perfumers, wine specialists, chemists, nurses, gardeners, florists, plumbers, or caregivers of infants or small children in diapers.
As chemosensory losses progress, alterations in food selection and intake can exacerbate disease states, produce weight loss, and impair nutritional status and immunity. Conversely, nutritional deficits may induce smell or taste losses. Importantly, deficits in the chemical senses can severely impact quality of life because they reduce pleasure and comfort obtained from food, beverages (such as coffee), flowers, fragrances, and natural settings such as forests.
