Global study of variability in olfactory sensitivity

Variability in human olfactory sensitivity has been attributed to individual-level factors such as genetics, age, sex, medical history of infections and trauma, neurogenerative diseases, and emotional disorders. Scarce evidence exists on the cross-cultural variation in olfactory sensitivity. Hence, we performed 2 studies to estimate the variability in olfactory threshold as a function of location and environment. Study 1 involved 11 laboratories from 4 continents (N = 802). In each location, in a designated laboratory, approximately 80 subjects underwent olfactory sensitivity testing with custom-made tests with eucalyptol and phenylethanol (PEA) odors. Tests were based on the Threshold subtest of the Sniffin' Sticks battery. In Study 2, we compared olfactory sensitivity and suprathreshold perception of PEA and eucalyptol in 2 Chinese (N = 160) and 2 Indian (N = 92) populations-one based in their native country and the other in Germany. Both studies present large-scale evidence that olfactory sensitivity varies as a function of geographical location and suggest that environmental factors play an important role in shaping olfactory sensitivity and suprathreshold olfactory perception. We delineate further steps necessary to identify specific factors underlying uncovered variability and the relationship between olfactory sensitivity and suprathreshold odor perception.