Pronounced Olfactory Habituation with Age

Olfactory habituation is a transient decrease in olfactory sensitivity caused by prolonged odor exposure, aiding in the discernment of new olfactory stimuli against the background. We explored the impact of subclinical olfactory impairment on odor habituation using age as a proxy.

Before the actual experiment, the individual olfactory threshold for the rose-like odorant phenylethyl alcohol (PEA) was assessed separately for the left and right nostril using the "Sniffin' Sticks" test, and ratings for odor intensity and pleasantness were collected. After applying a nasal clip continuously delivering PEA odor to one nostril for 10 min and 2 h, respectively, threshold, intensity, and pleasantness were reassessed immediately after clip removal.

In the group of 80 participants (younger adults-mean age 27.7 ± 4.5 years; older adults-mean age 61.5 ± 4.7 years), olfactory thresholds were already significantly elevated after just 10 min, and this habituation was even more pronounced after 2 h. This effect could be observed bilaterally even though significantly more distinct on the exposed side. Older participants generally exhibited a more pronounced habituation on the exposed side after 2 h compared to the younger participants.

The results indicate that older people experience more notable habituation after extended exposure to odors. This is most likely due to the compromised olfactory function in age. Although older and younger subjects scored in the normosmic range when tested with standardized olfactory tests, the stress on the system after exposure to an odor clearly revealed the lower functionality of the aging sense of smell.

3 Laryngoscope, 134:3765-3768, 2024.