Association between Olfactory Deficit and Motor and Cognitive Function in Parkinson’s Disease
Han Soo Yoo, Seok Jong Chung, Yang Hyun Lee, Byoung Seok Ye, Young H. Sohn, Phil Hyu Lee
Abstract
OBJECTIVE: To investigate whether baseline olfactory dysfunction in Parkinson's disease (PD) patients is associated with baseline and longitudinal motor and cognitive function. METHODS: F]fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl) nortropane positron emission tomography within 6 months of the baseline evaluation. Olfactory dysfunction was categorized as normosmia (CCSIT score ≥ 9), hyposmia (CCSIT score 5-8), and anosmia (CCSIT score ≤ 4). During the follow-up period, we investigated changes in the levodopa-equivalent dose (LED) and the occurrence of wearing-off, levodopa-induced dyskinesia, and dementia. RESULTS: Among the PD patients, 80.7% were hyposmic at the time of diagnosis, and 26.1% were anosmic. Baseline olfactory dysfunction was not associated with either initial parkinsonian motor symptoms or with the longitudinal LED increment and motor complications. Meanwhile, the anosmic group had lower baseline scores on the Korea version of the Boston Naming Test and Stroop color reading test than the normosmic and hyposmic groups. The anosmic group exhibited a higher rate of conversion to dementia than the normosmic [adjusted hazard ratio (HR) 3.99, 95% confidence interval (CI) 1.08-14.72] and hyposmic (adjusted HR 2.48, 95% CI 1.15-5.32) PD groups, regardless of baseline motor deficits and cognitive status. CONCLUSION: Baseline olfactory dysfunction was not associated with motor deficits and complications, but it was associated with cognitive dysfunction and prognosis, suggesting that severe olfactory impairment may reflect early cortical involvement, probably in the frontotemporal region, and rapid spreading of Lewy body pathology.