Survey of the frequency of olfactory dysfunction in Taiwan

Olfactory function is related to the scrutiny of environmental dangers and the tasting of food. However, olfactory dysfunction is not as distinctive as visual loss and may go unnoticed, especially when olfactory function deteriorates slowly. Most studies have used either questionnaires or relatively insensitive tests to assess olfactory dysfunction. Therefore, the objective of this study was to evaluate the frequency of olfactory dysfunction in Taiwan.

A total of 211 participants were recruited randomly from the community, factories or offices in Taichung City, Taiwan from April 2005 to March 2006. Age ranged from 19 to 89 years (mean age, 43.3 +/- 12.7 years). All participants filled in questionnaires about sociodemographic data, self-rated olfactory function and impact on quality of life. The olfactory test was performed with identification task of the "Sniffin' Sticks" olfactory function test.

The frequency of olfactory dysfunction in our series was 12.3%. There was a statistically significant difference in the ages of the normal and olfactory dysfunction groups (t test, p < 0.0001). The incidences of parosmia and phantosmia in the 211 participants were 10% and 30.8%, respectively. Most subjects did not rate their olfactory function well. There was no correlation between olfactory function and self-ratings of impact of olfactory function on quality of life.

Our present results provide preliminary data and clinical experience regarding the frequency of olfactory dysfunction in Taiwan. Future modifications and suggestions for the study of the prevalence of olfactory dysfunction are also mentioned.