Effects of smoking on odour identification in Japanese subjects

Objectives: Effects of smoking on olfaction appear to be well-known. However, there are not many studies that studied these effects on the basis of olfactory testing, and no studies on this topic have been performed so far in an Asian population. Thus, the aim of this study was to investigate the effects of smoking on odour identification. Methods: Five hundred fifty seven Japanese subjects (368 men and 189 women) were given the cross-cultural smell identification test (CC-SIT). Their history was taken with special regard to nasal disease and smoking. Urine nicotine level was assessed in 107 subjects. Results: The CC-SIT scores of current and previous smokers were lower than those of nonsmoking subjects (p < 0.05). The Brinkman index (BI) and CC-SIT score were correlated even when controlling for the subjects' age (r = -0.24, p < 0.001). The time since quitting cigarette smoking did not exhibit a relation with the CC-SIT score (r = -0.04, p = 0.76). In addition, urine levels of nicotine and its metabolites exhibited no significant correlation with the CC-SIT score (r = -0.08, p = 0.40). Conclusion: Smoking reduces olfactory function. Apparently, recovery of olfactory sensitivity after cessation of smoking appears to be exceptional.