Abstract
Background: Dementia causes severe functional impairment and contributes to significant burden and disability among older adults. Alzheimer’s Disease is a neurodegenerative disease of old age that contributes to 60-80% of dementia. Sleep disturbances are common in dementia, which may occur early in the disease process. Emerging literature also suggests sleep disturbance may act as a modifiable risk factor for dementia prevention. However, current research regarding sleep across early stages of dementia development is limited and mixed.
Aims: To systematically assess the current literature regarding sleep in subjective cognitive decline (SCD); to assess feasibility of remote sleep assessment in older adults with cognitive concerns; to assess sleep in older adults with cognitive concerns, including SCD, mild cognitive impairment (MCI), and mild dementia; and to investigate whether sleep parameters are associated with cognitive dysfunction in this population.
Methods: A systematic literature review was conducted to assess current findings regarding sleep in SCD, regarding both objectively and subjectively determined parameters. Studies 1 and 2 included assessment of 7 SCD, 7 MCI, and 7 mild Alzheimer’s Disease (AD) dementia participants over age 55. Study 1 randomly allocated participants (older adults with SCD, MCI, and mild AD) for remote or in-person sleep assessment to investigate feasibility, data quality and participant acceptability of remote monitoring. Participants submitted feedback concerning comfort, comprehension, and comments regarding the study procedures for quantitative and qualitative assessment. Study 2 measured sleep using actigraphy, the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and sleep diaries. Sleep parameters were compared across SCD, MCI and AD, and regression analyses were completed to assess whether derived sleep parameters are associated with neuropsychological test outc omes.
Results: The systematic review found reduced sleep efficiency (SE), percentage of rapid eye movement sleep (REM%), and subjective sleep quality in SCD compared to age- matched controls. Wake after sleep onset (WASO) and daytime somnolence were also greater in those with SCD. WASO also lengthened with greater SCD severity. Though, literature generally varied with limited concordance in sleep assessment methodology and SCD criterion, limiting comparability.
Study 1 had good recruitment rates (75%), low missing data rates, high comprehension ratings and high comfort ratings between study groups and across cognitive stage groups. Study groups and cognitive stage groups generally did not differ, although the MCI group reported lower comprehension for actigraphy (p=0.008) and the PSQI (p=0.032) than SCD.
In Study 2, the MCI group had reduced SE (p=0.022) and greater WASO (0.046) compared to SCD, and AD participants spent more time in bed (p=0.046; TIB) and had greater total sleep time (p=0.046; TST) than MCI participants. WASO and number of night-time awakenings were associated with matrix reasoning scores following adjustment for age, sex, depression, diabetes, and body mass index (WASO, ß=-0.06, 95%CI=-0.09,-0.01; number of awakenings, ß=-0.26, 95%CI=-0.35,-0.03; BMI).
Conclusions: Remote assessment of sleep is feasible in older adults with cognitive concerns. Furthermore, sleep alterations are present in the earliest stages of cognitive decline. Sleep duration, continuity and daytime wakefulness appear to be particularly disrupted in early stages of cognitive decline. This sleep disruption may indicate early stages of AD pathology, meaning they may be able to identify those at increased risk for dementia. Sleep continuity disruption also associated with poorer problem-solving ability. Future studies should investigate whether sleep disturbance evident in preclinical AD are able to predict dementia development.