Predictors of Olfactory Impairment among Northern Iranian Population

Abstract

Introduction: The performance in most smell identification tests is subjected to cultural variations. This study aimed to evaluate age, gender, and smoking-related effects on the test performance in the North of Iran.

Materials and methods: The olfactory function of 1470 eligible subjects was assessed in this study. Moreover, this study evaluated the influence of age, gender, and education on the test scores.

Results: According to the results, females obtained higher mean test scores, compared to males (18.4 vs. 17.6). In general, the elderly obtained lower scores, and about 30% of the subjects who were ≥65 years of age had severe hyposmia or anosmia. Furthermore, the olfactory impairment frequency in smoker subjects was significantly more than non-smokers (P<0.001). Test scores were generally higher in subjects with higher education levels. Logistic regression analysis revealed that the total number of cigarette doses in smokers and age had a significant association with olfactory dysfunction (P value <0.001 and 0.004, respectively). Cronbach's α of Iran-SIT was obtained at 0.78 which was more than an acceptable value of 0.7.

Conclusion: The findings of this study revealed that a low score in the Iran-SIT correlated with smoking, older age, low education level, and gender (male).

Keywords: Iran; Olfactory disorders; Olfactory perception; Smell; Smell identification test.

Fig 1

Mean and 95% confidence interval of the Iran-SIT score as a function of age

Fig 2

Clinical classification of olfactory deficit in different age groups.

Fig 3

Comparison of Iran-SIT scores among male and female subjects with different levels of education (Q1=lowest level of education, Q4= highest level of education).