Sharper in the morning: Cognitive time of day effects revealed with high-frequency smartphone testing

ABSTRACT

Decades of research has established a shift from an “eveningness” preference to a “morningness” preference with increasing age. Accordingly, older adults typically have better cognition in morning hours compared to evening hours. We present the first known attempt to capture circadian fluctuations in cognition in individuals at risk for Alzheimer disease (AD) using a remotely administered smartphone assessment that samples cognition rapidly and repeatedly over several days. Older adults (N = 169, aged 61–94 years; 93% cognitively normal) completed four brief smartphone-based testing sessions per day for 7 consecutive days at quasi-random time intervals, assessing associate memory, processing speed, and visual working memory. Scores completed during early hours were averaged for comparison with averaged scores completed during later hours. Mixed effects models evaluated time of day effects on cognition. Additional models included clinical status and cerebrospinal fluid (CSF) biomarkers for beta amyloid (Aβ42) and phosphorylated tau181 (pTau). Models with terms for age, gender, education, APOE ε4 status, and clinical status revealed significantly worse performance on associate memory in evening hours compared to morning hours. Contemporaneously reported mood and fatigue levels did not moderate relationships. Using CSF data to classify individuals with and without significant AD pathology, there were no group differences in performance in morning hours, but subtle impairment emerged in associate memory in evening hours in those with CSF-confirmed AD pathology. These findings indicate that memory is worse in evening hours in older adults, that this pattern is consistent across several days, and is independent of measures of mood and fatigue. Further, they provide preliminary evidence of a “cognitive sundowning” in the very earliest stages of AD. Time of day may be an important consideration for assessments in observational studies and clinical trials in AD populations.

KEYWORDS:

• Aging
• Alzheimer’s disease
• smartphone-based cognitive testing
• neuropsychological tests
• circadian rhythms

Acknowledgments

We would like to thank Marisol Tahan, BA, for her contributions as the primary study coordinator for the ARC smartphone study.

Disclosure statement

Neither Dr. Morris nor his family owns stock or has equity interest (outside of mutual funds or other externally directed accounts) in any pharmaceutical or biotechnology company. All authors report no relevant conflicts of interest.

Additional information

Funding

This work was supported by the National Institute on Aging under Grants P01AG03991, P01 AG026276, and P30AG066444.