Assessment tools for cognitive performance in Parkinson's disease and its genetic contributors.

Background: We have shown that genetic factors associating with motor progression of Parkinson's disease (PD), but their roles in cognitive function is poorly understood. One reason is that while cognitive performance in PD can be evaluated by various cognitive scales, there is no definitive guide indicating which tool performs better. Methods: Data were obtained from the Parkinson's Progression Markers Initiative, where cognitive performance was assessed using five cognitive screening tools, including Symbol Digit Modalities Test (SDMT), Montreal Cognitive Assessment, Benton Judgment of Line Orientation, Modified Semantic Fluency Test, and Letter Number Sequencing Test, at baseline and subsequent annual follow-up visit for 5 years. Genetic data including ApoE and other PD risk genetic information were also obtained. We used SPSS-receiver operating characteristic and ANOVA repeated measures to evaluate which cognitive assessment is the best reflecting cognitive performance in PD at early stage and over time. Logistic regression analyses were used to determine the genetic associations with the rapidity of cognitive decline in PD. Results: SDMT performed better in detecting mild cognitive impairment at baseline (AUC = 0.763), and SDMT was the only tool showing a steady cognitive decline during longitudinal observation. Multigenetic factors significantly associated with cognitive impairment at early stage of the disease (AUC = 0.950) with IP6K2 rs12497850 more evident, and a significantly faster decline (AUC = 0.831) within 5 years after motor onset, particularly in those carrying FGF20 rs591323. Conclusion: SDMT is a preferable cognitive assessment tool for PD and genetic factors synergistically contribute to the cognitive dysfunction in PD.

Constipation and sleep behaviour disorder associate with processing speed and attention in males with Parkinson's disease over five years follow-up.

Constipation and REM sleep behaviour disorder (RBD) are the earliest non-motor manifestations of Parkinson's disease (PD). Among non-motor symptoms of PD, it is unclear whether constipation and RBD at early stages of PD are related to cognitive outcomes at later stages. Herein, this study aims to investigate whether the presence of constipation and RBD have an impact on future cognitive outcomes in PD. Access to Parkinson's Progression Markers Initiative (PPMI) database of 360 PD patients with longitudinal observation was requested. Constipation, probable RBD (pRBD) and neuropsychological task scores of PD patients were assessed at baseline and after 5 years. Linear mixed-effects modelling, controlling for gender, age, years of education and LEDD was used to evaluate the association between baseline constipation, pRBD and cognitive performance on follow-up. Gender differences in neuropsychological test performances were found, with men having worse global cognition, speed-attention processing, verbal learning and memory than women at early stages of the disease. We found constipation and pRBD are strongly associated with future decline in some cognitive measures among PD patients, more prominently in men. Our data suggest that early assessment of pRBD and constipation may allow better understanding of the progression of cognitive changes in later phases of PD.