Correlations between olfactory, gustatory function, and cognitive abilities in different age ranges.

Aging is considered a progressive physiological degeneration associated with a decrease in synaptic plasticity and a decline in different functions such as olfaction, taste, attention, memory, and language. The biological mechanisms of aging are not yet fully understood. The aim of the study was to evaluate correlations between age-related changes in cognitive abilities with olfactory and gustatory functions. In our study, 290 participants with an age range from 18 to 86 years were enrolled. All participants were divided into three age groups: young adults (18-29 years, n=135), middle-aged (30-59 years, n=93), and elderly (≥60 years, n=62). Our results showed that odor threshold (OT), discrimination (OD), and identification (OI) significantly decreased in the elderly group compared to the young adults. Moreover, significant differences were also found for OT, OD, and OI between middle-aged and elderly groups. Instead, gustatory function decreased in relation to age in a different manner, since only sweet and sour taste perceptions decreased in elderly participants compared to the young adults’ group. Similarly, cognitive abilities, memory, language, and global attention significantly declined in the elderly group compared to the young adults and middle-aged groups. The decrease in global attention, memory, and language was significantly correlated to OI performance. Interestingly, significant correlations were observed between sour taste perception versus global cognitive abilities, language, and memory.

In conclusion, olfactory function and cognitive abilities showed a slight decline in relation to age and a dramatic decrease after 60 years, while gustatory function decreased more gradually. The decrease in OI could be considered a predictor for global cognitive function, as well as for specific cognitive subdomains such as global attention, language, and memory. Our study highlighted the importance of using olfactory evaluations in clinical practice for the early diagnosis of cognitive decline and for the development of appropriate personalized risk prevention strategies.