Title : Mild cognitive impairment (MCI) in Parkinson’s disease: Prevalence given MDS criteria
Abstract:
The prevalence of mild cognitive impairment (MCI) in Parkinson’s Disease (PD) has been wide ranging, from 15-90% across reports, likely due to a number of key variables, including age at evaluation, and time since symptom onset (Jellinger, 2024). Additionally, the criteria used for identifying cognitive impairment is important, with some studies applying more rigorous Movement Disorder Society (MDS) Level II criteria, report a higher incidence of MCI, than Level I (40-60+% vs 20-30%, respectively; Yu & Wu, 2022; Geursten et al., 2014; Szeto, 2015). The Level I criteria utilizes a brief global cognitive screening, such as the Montreal Cognitive Assessment (MoCA), while the Level II criteria calls for a more formal neuropsychological evaluation, including two tests in each of five cognitive domains: attention/working memory, executive function, episodic memory, visuospatial function, and language. The threshold for MCI requires at least two impaired test scores (<-1.5 SD below the normative cut-off), wherein either two tests fall within a single cognitive domain, or one test is impaired within each of two separate cognitive domains. Additionally, change in cognitive functions from pre-morbid intelligence is to be considered, per MDS Level II criteria, and such relative change has been found to further increase identification of MCI (to 79%, Geurtsen et al., 2014). Through careful application of the MDS Level II criteria and comparison with more lenient Level I criteria, a high prevalence of MCI was identified at baseline among initial enrolees (n=15) in an on-going pedal-n-play clinical trial investigating interactive physical and cognitive exercise (iPACES), such that 90% were classified as MCI with Level II criteria vs. 40% with Level I. This preliminary finding is consistent with some prior reports of very high initial prevalence of MCI (e.g., approximately 92% in McDermott et al., 2018), and suggests that MDS Level II criteria, when also considering pre-morbid intelligence, appears significantly more powerful for detecting cognitive challenges. Given the apparently high prevalence of MCI when using a thorough approach, care should be taken to methodically examine neuropsychological functions among those with PD.
