Odor Threshold Differs for Some But Not All Odorants Between Older and Younger Adults.

Abstract

Olfactory function deteriorates with age, and definitive mechanisms by which this decline occurs are likely multifactorial. The present study, conducted on a large cohort of healthy participants, aimed to investigate whether odor thresholds would differ for variable odors with different physicochemical (e.g., heavy- vs lightweight molecules) and perceptual characteristics. In 81 participants (51%, ≥50 years old), we assessed odor threshold in 2 sessions. Linear mixed-model analyses revealed that odor thresholds in younger and older adults changed with different odor conditions, presumably due to the common exposition to some of the odors, their trigeminality, and lipophilicity. This effect was observed for piperine, eucalyptol, 2-nonanone, gamma-valerolactone, and pinene-alpha, but not for the other 15 odorants studied. Furthermore, suprathreshold perception, that is, intensity and, to some extent, irritation, contributed independently to sensorial odor threshold, the latter ones particularly in older adults. We also found that the molecular weight of the odorants did not add to their threshold by, respectively, younger and older adults. To conclude, the present findings are in line with previous studies showing that the age-related change of chemosensory abilities is a multifaceted phenomenon, which does not affect all odorants.