JAMA Neurol. Published online January 29, 2018. doi:10.1001/jamaneurol.2017.4719
Question Is preclinical Alzheimer disease associated with circadian rest-activity rhythm disturbances?
Findings In this cross-sectional study, preclinical Alzheimer disease, as assessed by Pittsburgh Compound B imaging or increased cerebrospinal fluid phosphorylated tau to amyloid β 42 ratio in cognitively normal participants, was associated with increased rest-activity rhythm fragmentation. Older age and male sex were also associated with increased fragmentation and decreased amplitude of rest-activity rhythm, independent of Alzheimer disease pathology.
Meaning Disturbances of the rest-activity rhythm are present in preclinical Alzheimer disease, even after accounting for effects of aging and sex, demonstrating that circadian dysfunction occurs very early in the course of Alzheimer disease and precedes cognitive symptom onset.
Importance Circadian rhythm disturbances occur in symptomatic Alzheimer disease (AD) and have been hypothesized to contribute to disease pathogenesis. However, it is unknown whether circadian changes occur during the presymptomatic phase of the disease.
Objective To examine the associations between circadian function, aging, and preclinical AD pathology in cognitively normal adults.
Design, Setting, and Participants This cross-sectional study was conducted using community volunteers from the Knight Alzheimer’s Disease Research Center at Washington University in St Louis. Cognitively normal participants (n = 205) underwent 7 to 14 days of actigraphy in their home environment between 2010 and 2012, in addition to clinical assessment, amyloid imaging with Pittsburgh Compound B (PiB), and cerebrospinal fluid biomarker collection. Data collected from 3 years before to 6 months after actigraphy were included. Sixteen participants were excluded owing to incomplete data collection.
Main Outcomes and Measures Circadian rhythm analysis was performed on actigraphy data using 3 methods: cosinor, nonparametric, and empirical mode decomposition. Preclinical AD was assessed by longitudinal clinical assessment, amyloid imaging with PiB, and cerebrospinal fluid biomarker collection.
Results Data from 189 participants were included in the analyses. The mean (SD) age was 66.6 (8.3) years, and 121 participants (64%) were women. Older age (β = .247; P = .003) and male sex (β = .170; P = .04), in the absence of amyloid pathology, were associated with a significant increase in intradaily variability, a nonparametric measure of rest-activity rhythm fragmentation, as well as decreased amplitude by several measures. After correction for age and sex, the presence of preclinical amyloid plaque pathology, assessed by positive PiB imaging (mean [SD], 0.804 [0.187] for PiB negative vs 0.875 [0.178] for PiB positive; P = .05) or increasing cerebrospinal fluid phosphorylated-tau to amyloid β 42 ratio (β = .231; P = .008), was associated with increased intradaily variability, indicating rest-activity rhythm fragmentation.
Conclusions and Relevance Preclinical AD is associated with rest-activity rhythm fragmentation, independent of age or sex. Aging was also associated with circadian dysfunction independently of preclinical AD pathology, particularly in men. The presence of circadian rhythm abnormalities in the preclinical phase of AD suggests that circadian dysfunction could contribute to early disease pathogenesis or serve as a biomarker of preclinical disease