Objective but not subjective sleep predicts memory in community‐dwelling older adults

Abstract

SUMMARYResearch on the relationship between habitual sleep patterns and memory performance in older adults is limited. No previous study has used objective and subjective memory measures in a large, older-aged sample to examine the association between sleep and various domains of memory. The aim of this study was to examine the association between objective and subjective measures of sleep with memory performance in older adults, controlling for the effects of potential confounds. Onehundred and seventy-three community-dwelling older adults aged 65-89 years in Victoria, Australia completed the study. Objective sleep quality and length were ascertained using the Actiwatch 2 Mini-Mitter, while subjective sleep was measured using the Pittsburgh Sleep Quality Index. Memory was indexed by tests of retrospective memory (Hopkins Verbal Learning Test -Revised), working memory (n-back, 2-back accuracy) and prospective memory (a habitual button pressing task). Compared with normative data, overall performance on retrospective memory function was within the average range. Hierarchical regression was used to determine whether objective or subjective measures of sleep predicted memory performances after controlling for demographics, health and mood. After controlling for confounds, actigraphic sleep indices (greater wake after sleep onset, longer sleep-onset latency and longer total sleep time) predicted poorer retrospective (ΔR 2 = 0.05, P = 0.016) and working memory (ΔR 2 = 0.05, P = 0.047). In contrast, subjective sleep indices did not significantly predict memory performances. In community-based older adults, objectively-measured, habitual sleep indices predict poorer memory performances. It will be important to follow the sample longitudinally to determine trajectories of change over time. IN TROD UCTI ONReductions in the length and quality of sleep are common in normal ageing (Ohayon et al., 2004), and while recent research has evaluated the importance of sleep for general cognition (Yaffe et al., 2007) and memory consolidation postlearning (see Scullin and Bliwise, 2015 for comprehensive review), the relationship between habitual sleep patterns and memory in older adults has not been sufficiently studied (Cochrane et al., 2012;Naismith et al., 2011;Seelye et al., 2015;Wilckens et al., 2014). Deterioration in various domains of memory is common with age, and evaluating the relationship between habitual sleep patterns and domains of memory (such as retrospective memory, working memory and prospective memory) will contribute to strategies for improving cognitive health in ageing populations.In studies using polysomnography, which examines cerebral sleep-wake states in addition to other physiological changes that occur with sleep, and is the gold standard of objective sleep measurement, indices of good sleep quality have been associated with better subsequent memory performance (Lafortune et al

Actigraphic, but not subjective, sleep measures are associated with cognitive impairment in memory clinic patients

“…Nevertheless, our finding of a relationship between actigraph‐measured sleep disturbances (lower sleep efficiency, increased total wake time, and wake after sleep onset) and cognitive impairment is corroborated by previous studies that separately investigated homogenous patient groups, such as those with MCI or geriatric depression, and cognitively intact elderly (i.e. without MCI and dementia) . We did not find significant differences in sleep continuity parameters between patients classified as having a dementia syndrome and those categorized as having SCI or MCI, probably because of the clinical and aetiological heterogeneity within both subgroups.…”

“…without MCI and dementia). 30 We did not find significant differences in sleep continuity parameters between patients classified as having a dementia syndrome and those categorized as having SCI or MCI, probably because of the clinical and aetiological heterogeneity within both subgroups. Interestingly, increased nocturnal activity in the demented subgroup was found; in addition to the binary sleep-wake differentiation, this could be of importance for the clinical assessment of patients with progressed disease stages.…”

“…According to previous reports, no subjective sleep measures were related to cognitive performance, irrespective of their differences in time frame . This could be explained by the limited appropriateness of self‐reports in this patient population, potentially due to poor symptom awareness or cognitive deficits contributing to a disagreement between subjective and actigraphic sleep measures …”

“…31 One could speculate that this finding reflects a phase advance of sleep-wake rhythm in patients with cognitive impairment (MCI or dementia) due to Alzheimer's disease, which involves neurodegenerative processes that can affect the suprachiasmatic nucleus pacemaker 2 According to previous reports, no subjective sleep measures were related to cognitive performance, irrespective of their differences in time frame. 3,30 This could be explained by the limited appropriateness of self-reports in this patient population, 32 potentially due to poor symptom awareness or cognitive deficits contributing to a disagreement between subjective and actigraphic sleep measures. 10,33 With regard to pathophysiological considerations, there is evidence for an association-probably a bidirectional association-between disturbed sleep and both amyloid deposition and tau pathology.…”

Sleep and Human Aging

“…The degree of actigraphy-measured sleep disturbance in older adults predicts increasingly worse scores on standardized neuropsychological tests, including memory subcomponents that depend upon the hippocampus. Moreover, these associations remain significant when controlling for cardiovascular conditions, history of medication use, indices of depression, anxiety, and stress (Cavuoto et al, 2016), suggesting sleep-specific associations with impaired memory encoding, beyond age-related cofactors.…”