Key points What aspects of sleep architecture and breathing-related sleep disorders are associated with cognitive function in middle-aged to older adults? Findings This study of 5946 adults in 5 independent community-based cohorts with an overnight sleep study and neuropsychological assessments found that better sleep consolidation and the absence of sleep apnea were associated with better global cognition , while the percentages sleep stage individuals were not. Meaning These findings suggest that in adults without dementia, sleep consolidation and the absence of sleep apnea may be particularly important for optimizing cognition with aging. |
Sleep of sufficient quality and duration may be associated with a decreased risk of dementia through several mechanisms, including increased glymphatic clearance of Alzheimer’s disease proteins that facilitate memory consolidation and synaptic remodeling, and reducing the risk of cardiometabolic and cerebral vascular diseases, which are known factors associated with the risk of dementia. However, the association between sleep and cognitive decline remains equivocal; Lack of sleep was not among the 12 modifiable risk factors described in the Lancet Commission on Dementia Prevention.
Much of the uncertainty surrounding associations between sleep and dementia arises from a paucity of data with long follow-up durations, objective measures of sleep, or consistent data formats and analysis methods to facilitate combining and sharing data. between studies. 12 To address this gap, we created the Sleep and Dementia Consortium to advance sleep research to inform new strategies for dementia prevention.
This article aimed to investigate the associations of sleep macroarchitecture and obstructive sleep apnea (OSA) with cognition over 5 years of follow-up in participating cohorts of the Sleep and Dementia Consortium. By combining studies, this analysis attempted to address several unanswered questions, including which sleep variables are most strongly associated with cognition, which cognitive domains are most sensitive to differences in sleep, and whether there are systematic differences by key variable. , such as sex and age, APOE genotype. Based on previous work, we hypothesized that a greater percentage of time in rapid eye movement (REM) sleep and greater sleep consolidation would be associated with better cognition.
Importance
Good sleep is essential for health, but associations between sleep and dementia risk remain not fully understood. The Sleep and Dementia Consortium was established to study associations between polysomnography (PSG)-derived sleep and dementia risk and brain and cognitive MRI-related endophenotypes.
Aim
To investigate the association of sleep architecture and obstructive sleep apnea (OSA) with cognitive function in the Sleep and Dementia Consortium .
Design, environment and participants
The Sleep and Dementia Consortium selected data from 5 population-based cohorts in the US with methodologically consistent, overnight, home-based type II neuropsychological and polysomnography (PSG) assessments over 5 years of follow-up: Atherosclerosis Risk in Communities study, Cardiovascular Health Study, Framingham Heart Study (FHS), Osteoporotic Fractures in Men Study, and Osteoporotic Fractures Study.
Sleep metrics were centrally harmonized and then distributed to participating cohorts for cohort-specific analysis using linear regression; study-level estimates were pooled in random-effects meta-analyses.
Results were adjusted for demographic variables, time between PSG and neuropsychological evaluation (0-5 years), body mass index, antidepressant use, and sedative use. 5946 participants without stroke or dementia were included in the pooled analyses. Data was analyzed from March 2020 to June 2023.
Exhibitions
Measures of sleep architecture and OSA derived from PSG at home.
Main results and measures
The main outcomes were global cognitive composite z scores derived from principal components analysis, with cognitive domains investigated as secondary outcomes. Higher scores indicated better performance.
Results
Across all cohorts, 5946 adults were included (1875 women [31.5%]; average age range, 58-89 years). The median (IQR) time to onset of wakefulness after sleep ranged from 44 (27-73) to 101 (66-147) minutes, and the prevalence of moderate to severe Obstructive Sleep Apnea (OSA) ranged from 16 .9% to 28.9%.
Across cohorts, greater sleep maintenance efficiency (pooled β per 1% increase, 0.08; 95% CI, 0.03 to 0.14; P < 0.01) and less wakefulness after sleep onset sleep (pooled β per 1-min increase, −0.07; 95% CI, −0.13 to −0.01 per minute increase, p = 0.02) were associated with better global cognition.
Mild to severe OSA (apnea-hypopnea index [AHI] ≥5) was associated with poorer global cognition (pooled β, −0.06; 95% CI, −0.11 to −0.01; P = .01) vs AHI less than 5; Comparable results were found for moderate-to-severe OSA (pooled β, −0.06; 95% CI, −0.11 to −0.01; P = 0.02) versus AHI less than 5. Differences in sleep stages were not associated with cognition.
Discussion
In this cohort study, we examined associations between sleep and cognition in the Sleep and Dementia Consortium . Results demonstrated that worse sleep consolidation and prevalent OSA were associated with worse global cognition over 5 years.
Sleep stage percentages were not associated with global cognition between cohorts. We found 1 association between sleep metrics and individual cognitive domains: normal sleep duration compared to short sleep duration was associated with better attention and processing speed.
Sleep and cognition are dynamic throughout life. However, it is unclear whether there are sensitive periods in adult life during which good sleep is more critical for preventing cognitive decline in old age or whether it is the duration of exposure to suboptimal sleep that is associated with cognitive outcomes. . Cohorts contributing to the Sleep and Dementia Consortium differed in population characteristics, including age and sex distributions. This allowed us to directly compare and contrast effect sizes between cohorts with these different characteristics. For example, associations between OSA metrics and global cognition often trended against the expected direction of associations in the younger (FHS) and older (SOF) cohorts.
Many factors may underlie differences in results between studies. However, associations of sleep and cognition may be dynamic across the lifespan. Interestingly, we found no consistent patterns of interaction associations by sex, APOE ε4 status, or excessive daytime sleepiness. Therefore, associations between sleep and cognition appear to be relatively consistent across different levels of these variables.
Conclusions
- In this study of Sleep and Dementia Consortium participants , evidence from multiple population-based cohorts indicated that better sleep consolidation and freedom from OSA were associated with higher overall cognitive function.
- No associations were found between sleep stage percentages and cognition. Furthermore, there was little evidence to suggest that sex, APOE ε4, or excessive daytime sleepiness interacted with the associations.
- Regarding individual cognitive domains, only short sleep duration was associated with poorer attention and processing speed.
- Future Sleep and Dementia Consortium analyzes will build on these findings to further investigate whether and how lack of sleep may be associated with cognitive decline and dementia.
Final message This study found that better sleep consolidation and the absence of Obstructive Sleep Apnea (OSA) were associated with better global cognition over 5 years of follow-up. These findings suggest that the role of sleep-enhancing interventions in maintaining cognitive function requires investigation. |
