Supplementary Material for: Is Reaction Time Slowing an Early Sign of Alzheimer’s Disease? A Meta-Analysis

Background: Although simple reaction time (SRT) slowing is associated with dementia in Alzheimer’s disease (AD), its presence in individuals with mild cognitive impairment (MCI) is subject to debate. Objective: The aim of this study was to perform a systematic review and meta-analysis of the literature data on SRT slowing in MCI. Methods: Publications with data on SRT, age, and educational level in participants with MCI were included. After calculating the log SRT and its variance for each study, we took interstudy heterogeneity into account by conducting a random effects (restricted maximum likelihood estimation) meta-analysis. Results: The 7 selected studies featured a total of 327 participants with MCI and 468 healthy controls (HCs). The mean age was 68.2 years for participants with MCI and 72.3 years for HCs. The weighted mean Mini-Mental State Examination score was 26.4 in the MCI group, and 28.4 in the HC group. The mean SRT was significantly (p = 0.0217) longer in the MCI group (by 11%) than in the HC group. Conclusion: This meta-analysis showed that SRTs are longer in individuals with MCI. Further studies are needed to determine the mechanism of SRT slowing, its anatomical correlates, and a threshold value for diagnosing prodromal AD.