The influences of age on olfaction: a review

Abstract

Decreased olfactory function is very common in the older population, being present in over half of those between the ages of 65 and 80 years and in over three quarters of those over the age of 80 years. Such dysfunction significantly influences physical well-being and quality of life, nutrition, the enjoyment of food, as well as everyday safety. Indeed a disproportionate number of the elderly die in accident gas poisonings each year. As described in this review, multiple factors contribute to such age-related loss, including altered nasal engorgement, increased propensity for nasal disease, cumulative damage to the olfactory epithelium from viral and other environmental insults, decrements in mucosal metabolizing enzymes, ossification of cribriform plate foramina, loss of selectivity of receptor cells to odorants, changes in neurotransmitter and neuromodulator systems, and neuronal expression of aberrant proteins associated with neurodegenerative disease. It is now well established that decreased smell loss can be an early sign of such neurodegenerative diseases as Alzheimer's disease and sporadic Parkinson's disease. In this review we provide an overview of the anatomy and physiology of the aging olfactory system, how this system is clinically evaluated, and the multiple pathophysiological factors that are associated with its dysfunction.

Olfactory function evaluation in a 1102 community-dwelling 20-90-year old Japanese population in relation with age, sex and mental decline

“…The loss of smell has been reported in a number of studies and is associated with aging [1,2], gender [3] and various health ailments including neurodegenerative diseases such as Alzheimer's disease (AD) [2,[4][5][6]. It has been reported that olfactory dysfunction is one of the earliest sign of neurodegeneration in AD [7].…”

The olfactory dysfunctions occurring in the course of Alzheimer’s disease

“…Szacunki dotyczące częstości występowania zaburzeń funkcji olfaktorycznej wskazują na jej powszechność. Według różnych badaczy odsetek obiektywnie potwierdzonych zaburzeń węchu wzrasta z 11-24% w wieku średnim do 37-80% w wieku starczym [1,8,11,[15][16][17][18]. Około połowa populacji USA w wieku 65-80 lat cierpi na różnego stopnia utratę sprawności węchu.…”

“…Estimates concerning the occurrence of olfactory dysfunction suggest its common prevalence. According to various researchers, a percentage of the objectively confirmed smell dysfunctions increases from 11-24% in the middle age to 37-80% in old age [1,8,11,[15][16][17][18]. Approximately half of the US population between the age of 65-80 suffers from various degrees of olfactory loss.…”

The Hitchhiker’s guide to the rhinencephalon

“…The thickness, extent and integrity of the olfactory mucosa decreases significantly with age, and neuroepithelial degeneration seems to be an inevitable feature of human aging with significant reduction in olfaction 29,30,31 .…”