Objective: Maintaining attention underlies many aspects of cognition and becomes compromised early in neurodegenerative diseases like Alzheimer’s disease (AD). The consistency of maintaining attention can be measured with reaction time (RT) variability. Previous work has focused on measuring such fluctuations during in-clinic testing, but recent developments in remote, smartphone-based cognitive assessments can allow one to test if these fluctuations in attention are evident in naturalistic settings and if they are sensitive to traditional clinical and cognitive markers of AD. Method: Three hundred and seventy older adults (aged 75.8 +/− 5.8 years) completed a week of remote daily testing on the Ambulatory Research in Cognition (ARC) smartphone platform and also completed clinical, genetic, and conventional in-clinic cognitive assessments. RT variability was assessed in a brief (20-40 seconds) processing speed task using two different measures of variability, the Coefficient of Variation (CoV) and the Root Mean Squared Successive Difference (RMSSD) of RTs on correct trials. Results: Symptomatic participants showed greater variability compared to cognitively normal participants. When restricted to cognitively normal participants, APOE ε4 carriers exhibited greater variability than noncarriers. Both CoV and RMSSD showed significant, and similar, correlations with several in-clinic cognitive composites. Finally, both RT variability measures significantly mediated the relationship between APOE ε4 status and several in-clinic cognition composites. Conclusions: Attentional fluctuations over 20–40 seconds assessed in daily life, are sensitive to clinical status and genetic risk for AD. RT variability appears to be an important predictor of cognitive deficits during the preclinical disease stage.

中文翻译：

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对有阿尔茨海默病风险的老年人反应时间变异性的自然评估

目的：保持注意力是认知的许多方面的基础，并且在阿尔茨海默病 (AD) 等神经退行性疾病的早期就会受到损害。保持注意力的一致性可以通过反应时间（RT）的变化来衡量。以前的工作主要集中在测量临床测试期间的这种波动，但基于智能手机的远程认知评估的最新发展可以让人们测试这些注意力波动在自然环境中是否明显，以及它们是否对传统的临床和认知敏感。 AD 的标记。方法：三百七十名老年人（年龄 75.8 +/- 5.8 岁）在认知动态研究 (ARC) 智能手机平台上完成了为期一周的远程每日测试，并完成了临床、遗传和传统的临床认知评估。 RT 变异性通过简短（20-40 秒）的处理速度任务进行评估，使用两种不同的变异性度量，即正确试验中 RT 的变异系数 (CoV) 和均方根连续差值 (RMSSD)。结果：与认知正常的参与者相比，有症状的参与者表现出更大的变异性。当仅限于认知正常的参与者时，APOE ε4 携带者比非携带者表现出更大的变异性。 CoV 和 RMSSD 均与几种临床认知复合材料显示出显着且相似的相关性。最后，两种 RT 变异性测量均显着调节 APOE ε4 状态与几种临床认知复合之间的关系。结论：日常生活中评估的 20-40 秒注意力波动对 AD 的临床状态和遗传风险很敏感。 RT 变异性似乎是临床前疾病阶段认知缺陷的重要预测因子。