Associations between self-reported sleep quality and cerebrospinal fluid biomarkers in mild cognitive impairment and Alzheimer's disease

Sleep Fragmentation and Sleep-Wake Cycle Dysregulation Are Associated with Cerebral Tau Burden in Patients with Mild Cognitive Impairment due to Alzheimer's Disease: A Case Series

Background

Although disturbed sleep is frequent in patients with mild cognitive impairment (MCI) and dementia due to Alzheimer's disease (AD), the association between sleep and tau pathology is unclear.

Objective

This case series focused on measuring the sleep-wake rhythm over 7 days through actigraphy in patients diagnosed with MCI due to AD. Further, the association between sleep-wake cycle and tau deposition measured through positron emission tomography (PET) was explored.

Methods

This case series included 6 MCI due to AD patients (2 women and 4 men, mean age 73.17±5.53 years), who completed neuropsychological testing, 7-day actigraphy, and tau PET imaging with radiolabeled compounds aimed to estimate the density and distribution of aggregated tau neurofibrillary tangles in the brain.

Results

The case series indicated that patients with MCI due to AD who exhibited greater tau deposition in the frontal, parietal, and limbic regions, as well as in the precuneus and olfactory regions, also showed increased sleep fragmentation, as measured through actigraphy.

Conclusion

The findings from this case series suggest a potential link between tau deposition in key brain regions associated with AD and both sleep fragmentation and sleep-wake cycle dysregulation in a small sample of patients with MCI due to AD. These preliminary results warrant further investigation in larger, more comprehensive studies to confirm and expand upon these findings.

Prevalence of sleep disturbances in people with mild cognitive impairment: A systematic review and meta-analysis

This review was performed to determine sleep disturbance prevalence in individuals with mild cognitive impairment (MCI). The MEDLINE, Embase, Cochrane Library, CINAHL, PsycINFO, and Web of Science databases were systematically searched from inception to January 20, 2024. Fifty-two studies fulfilling the eligibility criteria were included. However, six of these studies were excluded from data synthesis due to poor methodological quality. The subjective sleep disturbance prevalence among all individuals with MCI was 35.8 % (95 % CI: 31.9-39.7) across 44 studies, and the objective sleep disturbance prevalence was 46.3 % (95 % CI: 36.3-56.3) across 6 studies. Five studies examined TST and WASO, while three assessed SE. Among all potential objective assessments of sleep disturbance prevalence, only TST, WASO, and SE could be meta-analyzed in MCI because of the limited number of studies available. The estimated sleep disturbance prevalence differed significantly according to measurement method, geographical region, and research design. However, the data source did not significantly influence prevalence estimates. In meta-regression analysis, publication year, participant age, percentage of females, and study quality did not predict prevalence. As subjective and objective sleep disturbances are common in people with MCI, effective intervention strategies should be developed to alleviate them.

Recent advances in understanding of sleep disorders and disturbances for dementia risk and prevention

PURPOSE OF REVIEW

To synthesise the recent work examining the relationship between sleep disturbances and dementia, emphasising studies involving individuals with mild cognitive impairment (MCI) or Alzheimer's disease (AD) and/or those investigating AD biomarkers. Additionally, we provide an update on recent interventions targeting sleep-related issues in older adults with MCI or AD.

RECENT FINDINGS

Various studies have examined obstructive sleep apnoea, sleep duration, and circadian alterations in relation to Alzheimer's pathology and dementia risk, with an emerging body of evidence suggesting that cardiovascular disease, hypertension, glymphatic function, and inflammation might serve as plausible pathophysiological mechanisms contributing to dementia during critical brain periods. Conversely, recent studies investigating insomnia have produced disparate results. Regarding intervention studies, the scarcity of prospective randomised control trials poses a challenge in establishing the benefits of addressing sleep disorders and disturbances.

SUMMARY

Recent work examining the pathophysiological links between sleep and dementia is strongest for obstructive sleep apnoea and sleep duration, while findings in insomnia studies exhibit inconsistency, possibly due to varied associations with dementia among different insomnia subtypes. It is apparent that more longitudinal studies examining the underlying pathophysiological mechanisms are necessary, alongside more rigorous clinical trials. Although some trials are underway in this field, there is still scarcity in trials examining interventions for circadian disturbances.

Tailored lighting intervention (TLI) for improving sleep-wake cycles in older adults living with dementia

Introduction: Sleep disturbance is a hallmark of Alzheimer's disease and related dementias, and caregiver stress caused by patients' nighttime wandering, injuries, and agitation are frequently at the root of decisions to move them to assisted living facilities, where typically dim institutional lighting can further exacerbate their sleep problems. This study explored the effects of a circadian-effective lighting intervention on actigraphic sleep measures and subjective assessments of sleep disturbance, depression, and sleep-disturbed behaviors. Methods: Fourteen older adult (≥60 years) participants (11 females, mean age = 84.1 [SD 8.9]), all diagnosed with moderate to severe dementia and sleep disturbance, were recruited from 3 assisted living and memory care facilities. Following a crossover, placebo-controlled design, 3 different lighting modes were used to deliver high levels of circadian stimulus to the participants' eyes for two 8-week intervention periods in a counter balanced order with a 4-week washout between the study's 2 conditions (dim light control vs. active intervention). Actigraphy and questionnaire data were collected over 7-day assessment periods that preceded (baseline weeks 1 and 9) and concluded (post-intervention week 9 and 22) the intervention periods. Actigraphic outcomes included sleep duration, sleep time, sleep efficiency, sleep start time, and sleep end time. Subjective assessments included the Cornell Scale for Depression in Dementia (CSDD), Pittsburgh Sleep Quality Index (PSQI), and Sleep Disorders Inventory (SDI) instruments. Results: Under the active condition, sleep duration significantly (p = 0.018) increased and sleep start time significantly (p = 0.012) advanced after the intervention compared to baseline. Also under the active condition, PSQI (p = 0.012), CSDD (p = 0.007), Sleep Disorders Inventory frequency (p = 0.015), and SDI severity (p = 0.015) scores were significantly lower after the intervention compared to baseline. Discussion: This study demonstrates that a circadian-effective lighting intervention delivering bright days and dark nights improves measures of sleep and mood in dementia patients living in controlled environments.