Older and Young Adults Experience Similar Long-Term Olfactory Habituation

Olfactory habituation corresponds to a decreased behavioral or perceptual response to an odor after a prolonged exposure to this odor. Our aim was to investigate whether long-term olfactory habituation and its recovery are similar in young (<35 years old) and older adults (>50). Fifty-seven participants were recruited for a 5-week longitudinal study. They were exposed to one of the two odors (manzanate alpha [MA], irone alpha [IA]) for 2 weeks at home. Olfactory detection thresholds for both odors were measured before and after exposure. Results showed that the two age groups behaved similarly. The long-term exposure to an odor led to a temporary increase of its detection threshold (lower sensitivity to the odor). IA thresholds were more sensitive to the duration of exposure with the odor than MA thresholds. One week after termination of exposure, participants fully recovered and even became more sensitive to both odors. No cross-habituation was found between the two odors. Our findings highlight that long-term habituation is specific to the odor exposed, behaves the same in young and older adults, and is fully reversible in both age groups after 1 week.