Olfactory training in specific anosmia to androstenone and its association with genetic variations of OR7D4

Short-term, repeated exposure to odors, “olfactory training” (OT), improves olfactory function. Clinically, this works not only for trauma- or disease-related olfactory impairment but also in people with specific anosmia. Androstenone is an odorant for which the frequent occurrence of specific anosmia is already known. It is an odorous steroid derived from testosterone. Besides some people who cannot perceive the odor, it is perceived differently by different individuals in terms of odor quality. These differences in the ability to perceive androstenone as well as in the perception of its quality were previously related to single nucleotide polymorphisms of the human olfactory receptor OR7D4. The current study addressed the question of whether changes in the perception of androstenone in relation to a change in sensitivity following specific OT with that odorant are associated with genetic variations of OR7D4. A total of 335 healthy volunteers participated (206 females, 129 males). All participants underwent tests for normal olfactory function; 103 showed specific anosmia for androstenone. Seventy-seven participants initially unable to perceive androstenone performed OT for an average duration of 8 weeks. Detection thresholds as well as subjective evaluation of odor intensity and pleasantness were measured both before and after OT. Buccal swabs were taken to examine the OR7D4 genotype. The study provided the following major results: (1) Detection thresholds were significantly lower after OT. (2) There was no statistically significant impact of the OR7D4 genotype on the ability to perceive androstenone after OT. In conclusion, it appears that the ability to perceive androstenone can be trained in people with specific anosmia, although OR7D4 polymorphisms were not related to a major change in the sensitivity towards androstenone.