The effect of smoking on the olfactory function

Although smoking is a widely spread habit, its effect on olfaction has not been clearly established. The aim of this study was to investigate the effect of cigarette smoking on the olfactory function, using the "Sniffin' Sticks" test. Sixty-five smokers were studied, with a median period of smoking of 10 years (range: 1-45 years) and a median number of 15 cigarettes smoked per day (range: 5-20). Forty-nine non-smokers were used as controls. Olfactory function was evaluated using the "Sniffin' Sticks" test, which consists of odour threshold (OT), odour discrimination (OD) and odour identification (OI) and its overall results may be presented as a composite threshold-discrimination-identification (TDI) score. Multivariate linear and logistic regression analyses were performed. All OT, OD, OI and TDI scores were statistically significantly lower in smokers compared to non-smokers, even when controlled for gender and age. Low OT, OD, OI and TDI scores were more prevalent among smokers than non-smokers. Multivariate logistic regression analysis, adjusted for gender and age, revealed that smoking remained a strong independent risk factor for low OT, OD, OI and TDI scores. Among smokers, statistically significant negative relationships were found between pack-years and OT, OD, OI and TDI, controlling for age. In conclusion, smoking was found to be adversely associated with the olfactory ability in a dose-related manner. Smokers were found to be nearly six times as likely to evidence an olfactory deficit as non smokers, depending on the duration and the amount of cigarettes smoked.