A comparison of neuropsychological performance between US and Russia: Preparing for a global clinical trial

Background Understanding regional differences in cognitive performance is important for interpretation of data from large multinational clinical trials. Methods Data from Durham and Cabarrus Counties in North Carolina, USA and Tomsk, Russia (n = 2972) were evaluated. The Montreal Cognitive Assessment (MoCA), Trail Making Test Part B (Trails B), Consortium to Establish a Registry for Alzheimer's Disease Word List Memory Test (WLM) delayed recall, and self-report Alzheimer's Disease Cooperative Studies Mail-In Cognitive Function Screening Instrument (MCFSI) were administered at each site. Multilevel modeling measured the variance explained by site and predictors of cognitive performance. Results Site differences accounted for 11% of the variation in the MoCA, 1.6% in Trails B, 1.7% in WLM, and 0.8% in MCFSI scores. Prior memory testing was significantly associated with WLM. Diabetes and stroke were significantly associated with Trails B and MCFSI. Conclusions Sources of variation include cultural differences, health conditions, and exposure to test stimuli. Findings highlight the importance of local norms to interpret test performance.