Is the Age-Related Loss in Olfactory Sensitivity Similar for Light and Heavy Molecules?

The process of aging affects olfaction quite early and can lead to a major handicap. One may ask whether olfactory loss is general or if it affects some odors more specifically? We investigated whether an age-related increase in olfactory threshold could be more or less specific to heavy or light molecules, based on the idea that these odors would bind differently to olfactory receptors. One group of 30 older subjects (50-70 years) and one group of 30 young adults (18-30 years) were tested for their threshold to 4 odors. Two odorants were light molecules (<150 g/mol) and the 2 others were heavy molecules (>150 g/mol). Both sets contained a single molecule and a binary mixture. Older subjects performed worse than young adults in an odor identification task, confirming a decline in the olfactory function. As a major result, young adults were as sensitive to light and heavy molecules; on the contrary, older subjects were less sensitive to heavy molecules (single molecule and binary mixture). The results suggest that older people present a heterogeneous olfactory loss more specific to heavier molecules.