Associations Between Olfactory Impairment and Cognitive Functions in Patients with Parkinson Disease.

Introduction: Olfactory impairment and cognitive impairment are common non-motor symptoms in Parkinson's disease (PD). Olfactory impairment may be present even many years before the main symptoms of the disease develop. The associations between olfactory loss and cognition in PD are evaluated in this study.

Methods: 31 patients with PD and 31 healthy subjects were included in this study. The Unified Parkinson's Disease Rating Scale (UPDRS) and Hoehn and Yahr Scale (H&Y Scale) were administered to all subjects. Butanol threshold test and Sniffin'Sticks test were used to assess olfaction. The Mini Mental State Examination (MMSE) and Clock Drawing Test (CDT) and Stroop Color Word Test (SCWT) were used to assess cognition.

Results: The Sniffin'Sticks test scores were significantly lower in the Parkinson group in comparison to the control group (p<0.001). The rate of anosmia was 90% in the PD group while this rate was found to be 54.8% in control group (p=0.005). A significant correlation was found between butanol test scores and stoop 5 and 5 errors. Significant correlations were found between the Sniffin'Sticks scores and MMSE scores (p=0.047) and orientation (p=0.041) and language (p=0.003) functions of the MMSE test. Worse olfaction was associated with worse memory.

Conclusions: In PD, olfactory impairment correlates with cognitive impairment and olfactory tests may be used to predict the likelihood of developing dementia in this patient population.