Circadian activity rhythm patterns in nondemented older women and cognitive function 5 years later

Abstract

Patients with dementia often have impaired sleep wake cycles and circadian rhythms but the direction of this association is less clear. Weaker circadian activity rhythm (CAR) patterns are associated with health declines and could predict cognitive impairment. The object of this study was to determine whether CAR patterns were associated with cognitive tasks 5 years later. We studied 1,298 community dwelling older women (age = 82.8 ± 3 years), as part of an ongoing prospective study. Women with dementia at initial assessment were excluded. CAR measures were obtained from actigraphy and analyzed as phase of peak activity (acrophase) and quartile of amplitude (peak-to-nadir difference), mesor and robustness of rhythm. Cognitive performance was assessed using Modified Mini Mental Status Exam (3MS), California Verbal Learning Task (CVLT-II) 10-minute delayed recall, backward digit span, Trails B, categorical fluency and verbal fluency 5 years later. We used ANCOVA to determine differences in cognitive performance between the highest and lowest category of each predictor. Analyses were adjusted for age, education, body mass index, caffeine use, physical activity, depression, antidepressant or benzodiazepine use, and comorbidities. Overall, weaker CAR patterns were associated with poorer performance on measures of executive function (Trails B and categorical fluency) but not on other cognitive domains. Specifically, women with lower amplitude performed worse on both Trails B and categorical fluency (p<0.05); those with lower mesor or weaker robustness had worse categorical fluency (p≤0.05) and participants with delayed acrophase had worse performance on Trails B (p<0.05) and a trend towards worse scores on categorical fluency and 3MS (p=0.06 for both). In summary, circadian measures were related to executive function tasks involving processing speed, along with either task switching or the lexical axis. CAR patterns in older non-demented women are associated with worse executive function (but not performance on other cognitive tasks) 5 years later. Etiology of this requires further study and may involve underlying vascular disease.