Olfactory dysfunction in passive vs active smoking

Background The aim of this study is to assess the olfactory functions of passive smokers compared to active smokers and nonsmokers. Methods This prospective case‐control study included 30 nonsmokers, 30 passive smokers, and 30 active smoker participants. All groups were matched for gender and age. The Sino‐Nasal Outcome Test 22 (SNOT‐22) and Sniffin' Sticks test battery were administered to all subjects. Threshold (T), discrimination (D), and identification (I) scores were noted. Olfactory function was subjectively assessed as 0: severe dysfunction and 5: no problem. Results Overall, TDI scores of active smokers (24.78 ± 3.02) and passive smokers (24.90 ± 2.45) were significantly lower than nonsmokers (34.23 ± 3.46). There was no statistically significant difference between passive smokers and smokers ( F (2,87)  = 13.47, P  < .001)). All subscores are negatively affected by active or passive smoking. The greatest impact of smoking was on threshold scores ( η 2 T  = 0.719), followed by identification ( η 2 I  = 0.353) and discrimination ( η 2 D  = 0.282) scores. SNOT‐22 and TDI scores were weakly ( r  = −.352) correlated as subjective assessment, and TDI scores were moderately correlated ( r : .539) ( P values < .001). Age and pack‐years cigarette dosage had a negative effect on the TDI score (TDI = 26.386 − (0.084 × age) − (0.072 × Pack.Year)) according to stepwise linear regression model ( F  = 10.187; P  = .001). Conclusions Passive smoking has nearly the same adverse effect on olfactory function as active smoking. The threshold scores are the most negatively affected. The olfactory effect of cigarette smoke may not be directly related to nasal inflammation. Olfactory neuronal pathways should be investigated to elucidate the exact pathophysiology. Level of Evidence 3b.