Evaluation of Olfactory Function by Iranian Smell Diagnostic Test in Patients with Parkinson's disease in North of Iran

Parkinson's disease is a neurodegenerative and multisystem disorder affecting systems more than the motor system. The olfactory disorder is an early non-motor symptom of Parkinson's disease. The present study was conducted on 110 patients aged 50-95 years with a diagnosis of Parkinson's disease referred to the Neurology Clinic of Babol University of Medical Sciences between  2018-2019. The control group consisted of 50-95-year-old non-neurological patients who were matched for age and gender with patients with Parkinson's disease. Data were collected by examination, demographic and clinical information questionnaire (duration of disease, the severity of disease, symptom index), as well as Iranian smell diagnostic test. A p-value less than 0.05 was considered statistically significant. The mean age scores of Parkinson's disease and control groups were obtained at 69±9 and 66±9 years, respectively. The mean duration of the disease was 5 years. Patients with Parkinson's disease scored lower on the Iranian smell test, and olfactory function was significantly reduced in the case group (p <0.001). Based on the results, olfactory function in patients with Parkinson's disease was not significantly correlated with gender, marital status, education, place of residence, and occupation(p <0.05). Only olfactory dysfunction was increased with age (P=0.01). In addition, olfactory dysfunction showed no significant relationship with severity of disease, duration of disease, and clinical index sign. Rapid Iranian smell test with a cut-off of 3.5% had a sensitivity of 87.3% and a specificity of 66.4%. According to the obtained results,olfactory dysfunction is an important non-motor and a primary symptom in patients with Parkinson's disease and is not related to the duration and severity of motor symptoms and symptom index.