A systematic review and dose-response meta-analysis of sleep duration and the occurrence of cognitive disorders

Military Values, Military Virtues, and Vulnerable Narcissism among Cadets of the Swiss Armed Forces-Results of a Cross-Sectional Study

Background: For military leaders, military values and virtues are important psychological prerequisites for successful leadership and for ethical and moral military behavior. However, research on predictors of military values and virtues is scarce. Given this background, we investigated whether Organizational Citizenship Behavior (OCB), resilience, and vulnerable narcissism might be favorably or unfavorably associated with military values and virtues, and whether vulnerable narcissism could moderate the association between the OCB-by-resilience-interaction, and military virtues. Methods: A total of 214 officer cadets (mean age: 20.75 years; 96.8% males) of the Swiss Armed Forces (SAF) volunteered to take part in this cross-sectional study. They completed a booklet of self-rating scales covering dimensions of military values and military virtues, OCB, resilience, and vulnerable narcissism. Results: Higher scores for military virtues were associated with higher scores for military values, OCB, and resilience, and with lower scores for vulnerable narcissism. Multiple regression models showed that higher scores for OCB and resilience were associated with military values and virtues. Vulnerable narcissism moderated the association between military virtues, and the OCB-by-resilience-interaction: the higher the vulnerable narcissism, the more the OCB-by-resilience-interaction was associated with lower scores for military virtues. Conclusions: Among cadets of the SAF, the associations between military values, military virtues, OCB, and resilience were highly intertwined, while vulnerable narcissism appeared to attenuate the association between military virtues, OCB, and resilience.

Charting Alzheimer's Disease and Dementia: Epidemiological Insights, Risk Factors and Prevention Pathways

Alzheimer's disease (AD), the most common cause of dementia, is a complex and multifactorial condition without cure at present. The latest treatments, based on anti-amyloid monoclonal antibodies, have only a modest effect in reducing the progression of cognitive decline in AD, whereas the possibility of preventing AD has become a crucial area of research. In fact, recent studies have observed a decrease in dementia incidence in developed regions such as the US and Europe. However, these trends have not been mirrored in non-Western countries (Japan or China), and the contributing factors of this reduction remain unclear. The Lancet Commission has delineated a constrained classification of 12 risk factors across different life stages. Nevertheless, the scientific literature has pointed to over 200 factors-including sociodemographic, medical, psychological, and sociocultural conditions-related to the development of dementia/AD. This narrative review aims to synthesize the risk/protective factors of dementia/AD. Essentially, we found that risk/protective factors vary between individuals and populations, complicating the creation of a unified prevention strategy. Moreover, dementia/AD explanatory mechanisms involve a diverse array of genetic and environmental factors that interact from the early stages of life. In the future, studies across different population-based cohorts are essential to validate risk/protective factors of dementia. This evidence would help develop public health policies to decrease the incidence of dementia.

Association Between Sleep Duration and Atrial Fibrillation: A Narrative Review

Sleep duration is a substantial risk factor for several cardiovascular diseases, including atrial fibrillation (AF). Despite much research, the precise nature of the relationship between the amount of sleep and AF remains unclear. This narrative review explores the relationship between AF and sleep duration, looking at genetic, mechanistic, and epidemiological data to explain this association. A U-shaped association (nonlinear relationship or curvilinear association) between sleep duration and AF has been seen, where longer and shorter sleep duration, more or less than seven to eight hours, have been associated with increased AF risk. Multiple mechanisms such as autonomic dysfunction, inflammation, and structural atrial remodeling have been proposed linking sleep disturbances to AF. Moreover, confounding factors such as individual lifestyle, comorbidities, and sleep quality could affect this association. Additionally, the interpretation of study results is further impacted by methodological limitations, including self-reported sleep duration and observational study designs. It is imperative to comprehend the complex relationship between sleep duration and AF to develop effective preventive and therapeutic methods. The main goals of future research should focus on prospective cohort studies with objective sleep metrics, exploring the mechanistic pathways, and comprehensive confounder adjustments that link sleep disturbances to AF. In summary, addressing sleep disturbances may represent one of the novel approaches to AF prevention and management, with potential implications for improving cardiovascular health and reducing AF-related morbidity and mortality.

Systemic inflammation, lifestyle behaviours and dementia: A 10-year follow-up investigation

Objectives

Lifestyle behaviours have been linked to dementia incidence, but their cumulative impact on dementia and the underlying mechanisms remain poorly understood. This study investigated the association of co-occurring lifestyle behaviours with dementia incidence and the mediating role of systemic inflammation in this association.

Methods

The sample comprised 3131 participants (55.2% female) from the English Longitudinal Study of Ageing aged 52-92 years at baseline (2008/09). Self-reported baseline lifestyle behaviours (alcohol intake, fruit and vegetable consumption, smoking, physical activity, sleep duration, social engagement, and cognitive activity) were summed to derive an index of lifestyle behaviours, ranging from 0 to 7, with higher scores denoting a higher number of health-risk behaviours. Incident dementia cases (n = 130, 4.2%) were identified through doctor-diagnosed dementia, informant interviews, and health records between 2014/15 and 2018/19. Systemic inflammation was measured through fasting plasma concentrations of C-reactive protein in 2012/13.

Results

Binary logistic regression models indicated that the odds of subsequent dementia increased by 1.19 for each additional health-risk behaviour (95% confidence intervals: 1.04, 1.37, p = 0.014) after adjusting for age, sex, ethnicity, wealth, education, marital status, body mass index, coronary heart disease, hypertension, stroke, and depression. However, this association was not mediated by C-reactive protein.

Conclusions

Co-occurring health-risk behaviours were associated with higher dementia incidence up to 10 years later, underscoring the importance of modifying health-risk behaviours for the prevention of dementia. Systemic inflammation did not explain the association between behaviours and dementia.

Sleep duration, sleep efficiency, and amyloid β among cognitively healthy later-life adults: a systematic review and meta-analysis

BACKGROUND

Abnormal amyloid β (Aβ) deposits in the brain are a hallmark of Alzheimer's disease (AD). Insufficient sleep duration and poor sleep quality are risk factors for developing AD. Sleep may play a role in Aβ regulation, but the magnitude of the relationship between sleep and Aβ deposition remains unclear. This systematic review examines the relationship between sleep (i.e., duration and efficiency) with Aβ deposition in later-life adults.

METHODS

A search of PubMed, CINAHL, Embase, and PsycINFO generated 5,005 published articles. Fifteen studies met the inclusion criteria for qualitative syntheses; thirteen studies for quantitative syntheses related to sleep duration and Aβ; and nine studies for quantitative syntheses related to sleep efficiency and Aβ.

RESULTS

Mean ages of the samples ranged from 63 to 76 years. Studies measured Aβ using cerebrospinal fluid, serum, and positron emission tomography scans with two tracers: Carbone 11-labeled Pittsburgh compound B or fluorine 18-labeled. Sleep duration was measured subjectively using interviews or questionnaires, or objectively using polysomnography or actigraphy. Study analyses accounted for demographic and lifestyle factors. Based on 13 eligible articles, our synthesis demonstrated that the average association between sleep duration and Aβ was not statistically significant (Fisher's Z = -0.055, 95% CI = -0.117 ~ 0.008). We found that longer self-report sleep duration is associated with lower Aβ (Fisher's Z = -0.062, 95% CI = -0.119 ~ -0.005), whereas the objectively measured sleep duration was not associated with Aβ (Fisher's Z = 0.002, 95% CI = -0.108 ~ 0.113). Based on 9 eligible articles for sleep efficiency, our synthesis also demonstrated that the average association between sleep efficiency and Aβ was not statistically significant (Fisher's Z = 0.048, 95% CI = -0.066 ~ 0.161).

CONCLUSION

The findings from this review suggest that shorter self-reported sleep duration is associated with higher Aβ levels. Given the heterogeneous nature of the sleep measures and outcomes, it is still difficult to determine the exact relationship between sleep and Aβ. Future studies with larger sample sizes should focus on comprehensive sleep characteristics and use longitudinal designs to better understand the relationship between sleep and AD.

Umbrella review and Delphi study on modifiable factors for dementia risk reduction

A 2013 systematic review and Delphi consensus study identified 12 modifiable risk and protective factors for dementia, which were subsequently merged into the "LIfestyle for BRAin health" (LIBRA) score. We systematically evaluated whether LIBRA requires revision based on new evidence. To identify modifiable risk and protective factors suitable for dementia risk reduction, we combined an umbrella review of systematic reviews and meta-analyses with a two-round Delphi consensus study. The review of 608 unique primary studies and opinions of 18 experts prioritized six modifiable factors: hearing impairment, social contact, sleep, life course inequalities, atrial fibrillation, and psychological stress. Based on expert ranking, hearing impairment, social contact, and sleep were considered the most suitable candidates for inclusion in updated dementia risk scores. As such, the current study shows that dementia risk scores need systematic updates based on emerging evidence. Future studies will validate the updated LIBRA score in different cohorts. HIGHLIGHTS: An umbrella review was combined with opinions of 18 dementia experts. Various candidate targets for dementia risk reduction were identified. Experts prioritized hearing impairment, social contact, and sleep. Re-assessment of dementia risk scores is encouraged. Future work should evaluate the predictive validity of updated risk scores.

The effects of partial sleep restriction and subsequent caffeine ingestion on neurovascular coupling

Habitual poor sleep is associated with cerebrovascular disease. Acute sleep deprivation alters the ability to match brain blood flow to metabolism (neurovascular coupling [NVC]) but it is not known how partial sleep restriction affects NVC. When rested, caffeine disrupts NVC, but its effects in the sleep-restricted state are unknown. The purpose of this study was therefore to investigate the effects of partial sleep restriction and subsequent caffeine ingestion on NVC. A total of 17 adults (mean [standard deviation] age 27 [5] years, nine females) completed three separate overnight conditions with morning supplementation: habitual sleep plus placebo (Norm_Pl), habitual sleep plus caffeine (Norm_Caf), and partial (50% habitual sleep) restriction plus caffeine (PSR_Caf). NVC responses were quantified as blood velocity through the posterior (PCAv) and middle (MCAv) cerebral arteries using transcranial Doppler ultrasound during a visual search task and cognitive function tests, respectively. NVC was assessed the evening before and twice the morning after each sleep condition-before and 1-h after caffeine ingestion. NVC responses as a percentage increase in PCAv and MCAv from resting baseline were not different at any timepoint, across all conditions (p > 0.053). MCAv at baseline, and PCAv at baseline, peak, and total area under the curve were lower 1-h after caffeine in both Norm_Caf and PSR_Caf as compared to Norm_Pl (p < 0.05), with no difference between Norm_Caf and PSR_Caf (p > 0.14). In conclusion, NVC was unaltered after 50% sleep loss, and caffeine did not modify the magnitude of the response in the rested or sleep-deprived state. Future research should explore how habitual poor sleep affects cerebrovascular function.

Self-Reported Sleep Duration and Bedtime Are Associated with Dementia Risk in Community-Dwelling People Aged 40-74 Years: The Murakami Cohort Study

Background

Sleep is a potentially modifiable factor associated with dementia, including Alzheimer's disease, but current evidence supporting this is insufficient.

Objective

This study aimed to determine whether sleep duration and bedtime patterns are associated with the risk of dementia among middle-aged and older people.

Methods

This cohort study had an eight-year follow-up period. Participants were 13,601 community-dwelling people aged 40-74 years living in Murakami (Niigata, Japan). Data were collected using a self-administered questionnaire. Predictors were self-reported sleep duration and bedtime, and the outcome was newly-diagnosed dementia determined using the long-term care insurance database. Covariates were demographic characteristics, body mass index, smoking, alcohol consumption, total physical activity, insomnia symptoms, disease history, and either bedtime or sleep duration. Cox proportional hazard models were used to calculate hazard ratios (HRs).

Results

The mean age of participants at baseline was 59.2 years. Over a mean follow-up period of 8.0 years, 319 cases of dementia were observed. A long self-reported sleep duration relative to the reference sleep duration (7 hours) was associated with increased dementia risk, with the "8 hours" group (adjusted HR = 1.30, 95% CI:0.99-1.73) and "≥9 hours" group (adjusted HR = 1.46, 95% CI:1.00-2.15) having an increased risk (marginally significant) relative to the reference group. Early bedtime was associated with increased dementia risk (adjusted p for trend = 0.0010), with the "21 : 00 or earlier" group (adjusted HR = 1.61, 95% CI:1.14-2.28) having an increased risk relative to the reference ("23 : 00").

Conclusions

A long self-reported sleep duration and early bedtime are both associated with increased dementia risk in middle-aged and older people.

Artificial intelligence for dementia genetics and omics

Genetics and omics studies of Alzheimer's disease and other dementia subtypes enhance our understanding of underlying mechanisms and pathways that can be targeted. We identified key remaining challenges: First, can we enhance genetic studies to address missing heritability? Can we identify reproducible omics signatures that differentiate between dementia subtypes? Can high-dimensional omics data identify improved biomarkers? How can genetics inform our understanding of causal status of dementia risk factors? And which biological processes are altered by dementia-related genetic variation? Artificial intelligence (AI) and machine learning approaches give us powerful new tools in helping us to tackle these challenges, and we review possible solutions and examples of best practice. However, their limitations also need to be considered, as well as the need for coordinated multidisciplinary research and diverse deeply phenotyped cohorts. Ultimately AI approaches improve our ability to interrogate genetics and omics data for precision dementia medicine. HIGHLIGHTS: We have identified five key challenges in dementia genetics and omics studies. AI can enable detection of undiscovered patterns in dementia genetics and omics data. Enhanced and more diverse genetics and omics datasets are still needed. Multidisciplinary collaborative efforts using AI can boost dementia research.

Association between napping and cognitive impairment: A systematic review and meta-analysis

STUDY OBJECTIVES

Increasing evidence suggests that napping is associated with cognitive impairment and dementia, but the conclusions are inconsistent. Moreover, the extent of the risk is uncertain. We therefore conducted a systematic review and meta-analysis to quantify the connection between napping and cognitive impairment.

METHODS

We performed a systematic search of PubMed, EMBASE, Web of Science, and Cochrane Library for studies that were published up to June 2023, and assessed associations between napping and cognitive impairment. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated as the effect sizes for all studies. Heterogeneity and potential publication biases were assessed.

RESULTS

A total of 4535 papers were retrieved, with 20 reports assessing the relationships between napping and cognitive impairment. Pooled analysis indicated that napping was associated with dementia (OR = 1.14; 95% CI: 1.07-1.21). Importantly, we found that those napping longer than 30, 45, and 60 min/day were 35%, 41%, and 40%, respectively, more likely to have an increased risk of cognitive impairment (30 min: OR = 1.35; 95% CI: 1.24-1.48; 45 min: OR = 1.41; 95% CI: 1.27-1.58; 60 min: OR = 1.40; 95% CI: 1.26-1.56). North America and Europe showed that associations existed between napping and cognitive impairment (North America: OR = 1.15; 95% CI: 1.04-1.27; Europe: OR = 1.13; 95% CI: 1.08-1.18).

CONCLUSIONS

This meta-analysis indicated associations between long napping durations and cognitive impairment or dementia, suggesting that longer napping might be a potential risk factor of adverse cognitive outcomes.

Dietary amino acid intake and sleep duration are additively involved in future cognitive decline in Japanese adults aged 60 years or over: a community-based longitudinal study

BACKGROUND

Sleep duration and amino acid intake are independently associated with cognitive decline. This study aimed to determine the longitudinal association between sleep duration and cognitive impairment incidence and to examine the involvement of diet, particularly amino acid intake, in these associations in community dwellers.

METHODS

In this longitudinal study in a community-based setting, we analyzed data from 623 adults aged 60-83 years without cognitive impairment at baseline. Sleep duration was assessed using a self-report questionnaire. Amino acid intake was assessed using 3-day dietary records. Cognitive impairment was defined as a Mini-Mental State Examination score ≤ 27. Participants were classified into short-, moderate-, and long-sleep groups according to baseline sleep duration (≤ 6, 7-8, and > 8 h, respectively). Using moderate sleep as a reference, odds ratios (ORs) and 95% confidence intervals (CIs) of short- and long-sleep for cognitive-impairment incidence were estimated using the generalized estimating equation. Participants were classified according to sex-stratified quartiles (Q) of 19 amino acid intake: Q1 and Q2-Q4 were low- and middle to high-intake groups, respectively. Using middle- to high-intake as a reference, ORs and 95% CIs of low intake for cognitive impairment incidence were estimated using the generalized estimating equation in each sleep-duration group. Follow-up period, sex, age, body mass index, depressive symptoms, education, smoking status, employment status, sleep aids use, physical activity, medical history, and Mini-Mental State Examination score at baseline were covariates.

RESULTS

Mean follow-up period was 6.9 ± 2.1 years. Adjusted ORs (95% CIs) for cognitive impairment in short- and long-sleep groups were 0.81 (0.49-1.35, P = 0.423) and 1.41 (1.05-1.87, P = 0.020), respectively. Particularly in long sleepers (i.e., > 8 h), cognitive impairment was significantly associated with low cystine, proline, and serine intake [adjusted ORs (95% CIs) for cognitive impairment were 2.17 (1.15-4.11, P = 0.017), 1.86 (1.07-3.23, P = 0.027), and 2.21 (1.14-4.29, P = 0.019), respectively].

CONCLUSIONS

Community-dwelling adults aged ≥ 60 years who sleep longer are more likely to have cognitive decline, and attention should be paid to the low cystine, proline, and serine intake.

Serum Vitamin D3 Concentration, Sleep, and Cognitive Impairment among Older Adults in China

BACKGROUND

Cognitive decline in older adults has become one of the critical challenges to global health. This study aims to examine both cross-sectional and longitudinal associations of levels of serum 25-hydroxyvitamin D3 (25(OH)D3) (briefed as VD3) concentration and sleep quality/duration, especially their interactions, with risk of cognitive impairment among older adults in China.

METHODS

We utilized a special subsample of adults aged 65-105 years (individuals = 3412, observations = 4816) from eight provinces in China derived from the 2011/2012 and 2014 waves of the Chinese Longitudinal Healthy Longevity Survey. Cognitive impairment was measured by the Mini-Mental State Examination scale. Sleep quality was classified as good versus fair/poor, and sleep duration was classified into short (<7 h), normal (≥7 but <9 h), and long (≥9 h). The VD3 concentration was divided into three levels: deficiency (VD3 < 25 nmol/L), insufficiency (25 nmol/L ≤ VD3 < 50 nmol/L), and sufficiency (VD3 ≥ 50 nmol/L). A wide set of covariates that include demographics, socioeconomic status, family support, health practice, and health conditions was adjusted for robust findings. Multilevel random intercept logit regression models were used to examine the cross-sectional associations between VD3, sleep, and cognitive impairment, whereas logit regression models were applied to investigate the longitudinal associations.

RESULTS

In the cross-sectional analyses, when all covariates were adjusted, VD3 sufficiency was significantly associated with a 33% lower risk of cognitive impairment compared with VD3 deficiency; good sleep quality was associated with 34% lower odds of cognitive impairment compared with fair/poor sleep quality; sleep hours were not associated with cognitive impairment, although a long sleep duration (≥9 h) was associated with 30% higher odds of being cognitively impaired when baseline health was not controlled. Interaction analyses reveal that VD3 sufficiency could help to additionally reduce the risk of cognitive impairment for good sleep quality and normal sleep hours. In the longitudinal analyses, the association of VD3 sufficiency remains significant, whereas sleep quality and sleep duration were not significant associates.

CONCLUSIONS

Good sleep quality, normal sleep hours, and VD3 sufficiency are positively associated with good cognitive function. VD3 sufficiency could enhance the associations between sleep and cognitive impairment.

A health behaviour pandemic: The COVID-19 pandemic has impacted the physical activity, sleep, and sedentary behaviour of already-struggling Canadians

Objectives

The Canadian 24-Hour Movement Guidelines (24HMG) provide evidence-based recommendations for health behaviours, including light physical activity, moderate-to-vigorous physical activity (MVPA), sedentary behaviour (SB), sleep, and muscle strengthening activities. These behaviours likely changed as a result of public health measures implemented throughout the COVID-19 pandemic. We aimed to understand how Canadians' health behaviours changed during the pandemic.

Methods

We conducted a nationwide survey asking Canadians aged 18-64 to report their health behaviours according to the 24HMG at three timepoints: 1) immediately prior to the pandemic, 2) the most restricted timepoint of the pandemic, and 3) more recently, in March 2022.

Results

We received 494 eligible responses from across Canada. Prior to the pandemic, only 7.7% of respondents were able to meet all 24HMG, which reduced to 3.8% during the most restricted phase of the pandemic (p < 0.01). During this timepoint, self-reported MVPA decreased by -21.9 ± 55.6 weekly minutes, muscle strengthening decreased by -0.34 ± 0.94 weekly sessions, and SB increased by 0.88 ± 2.04 daily hours (p < 0.00001 for all), with nonsignificant increases in nightly sleep. At the more recent March 2022 timepoint, mild recoveries were observed in all health behaviours, however remained significantly lower than baseline levels, with the exception of sleep, which decreased significantly (-0.18 ± 1.42 nightly hours, p = 0.005).

Conclusions

Unfavourable health behaviour changes among Canadians were observed throughout the COVID-19 pandemic, which increases the risk for acute and long-term health conditions. Improved education, infrastructure, and support from public and private sectors can reverse the negative risk factors that arise from these health behaviour changes, and can improve the culture of proactive health behaviours in Canada.

Secular Trends in Sleep Conditions in Chinese Elderly Individuals: A National Population-Based Study

Purpose

As one of the most rapidly aging countries in the world, the elderly population is expected to reach over 400 million in China by 2032. Many studies have suggested a positive association between sleep duration and adverse health events among elderly individuals. This study aimed to investigate the sleep conditions of Chinese elderly individuals between 2005 and 2018.

Patients and methods

Data for 53,013 elderly individuals were taken from five cycles of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) during 2005-2018. Sex- and age-specific means and 95% confidence intervals (95% CIs) were used to estimate sleep duration trends. Changes in sleep patterns were explored during this period. The prevalence of short and long sleep durations was assessed and age-standardized by the 2010 census. Finally, self-reported sleep quality was used to determine sleep conditions from another perspective among elderly individuals.

Results

The mean sleep duration decreased from 7.87 (95% CI: 7.83-7.91) to 7.29 (95% CI: 7.25-7.33) hours between 2005 and 2018. Changes in sleep duration patterns were found during the study period. The proportion of the elderly population who slept ≤6 hours increased and that of those who slept ≥9 hours decreased noticeably over the past 13 years. The age-standardized prevalence of short sleep duration increased from 32.7% (95% CI: 32.7-32.9%) to 38.4% (95% CI: 38.3-38.5%). A significant decrease was observed in the prevalence of long sleep duration.

Conclusion

Sleep conditions are gradually shifting toward a shorter sleep duration and poorer sleep quality among Chinese elderly individuals.

Examining the Canadian 24-Hour Movement Guidelines among Adults with Intellectual Disability: A Pilot Study

The purpose of this pilot study was to investigate the extent to which adults with intellectual disability (ID) met the 2020 Canadian 24-Hour Movement Guidelines. Fifteen adults (six females and nine males) participated in this nine-day observational study (age = 20-64 years) in 2021-2022, during the COVID-19 pandemic. Moderate-to-vigorous physical activity (MVPA), sedentary time, and total sleep time were measured with a smartwatch to compare to the guidelines. A diary subjectively tracked physical activity. Of the 15 participants, 11 met the MVPA guidelines (73%), 4 met the sedentary behaviour guidelines (27%), 7 met the sleep guidelines (47%), and only 1 participant met all 3 of the guidelines (7%). There were no differences in physical activity or sleep between weekends and weekdays, or between males and females. Walking, cleaning dishes, and swimming were the most common types of physical activity performed by the participants. The findings of this pilot study indicate the need to improve sleep and reduce sedentary time in adults with ID. As most participants met the MVPA guidelines, few met the sedentary behaviour guidelines, and nearly half met the sleep guidelines, these data also demonstrate how important it is to assess all three aspects of the movement guidelines. All these behaviours have independent health benefits and risks, which interact to influence overall health.

Association between objective sleep measures and cognitive performance: a cross-sectional analysis in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) study

Sleep disturbances often co-exist, which challenges our understanding of their potential impact on cognition. We explored the cross-sectional associations of insomnia and objective measures of sleep with cognitive performance in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) study stratified by middle-aged and older adults. Participants aged ≥55 years underwent cognitive evaluations, polygraphy for 1 night, and actigraphy for 7 days. Insomnia was evaluated using the Clinical Interview Scheduled Revised. Obstructive sleep apnea (OSA) and short sleep duration (SSD) were defined by an apnea-hypopnea index (AHI) of ≥15 events/h and <6 h/ night, respectively. In 703 participants (mean [SD] age 62 [6] years, 44% men), cognition was evaluated using a 10-word list, verbal fluency, and trail-making tests. The frequencies of insomnia, SSD, and OSA were 11%, 24%, and 33%, respectively. In all, 4% had comorbid OSA and insomnia, and 11% had both OSA and SSD. Higher wake after sleep onset (β = -0.004, 95% confidence interval [CI] -0.008, -0.001) and the number of awakenings (β = -0.006, 95% CI -0.012, -0.001) were associated with worse verbal fluency performance. Compared to those without insomnia, older participants with insomnia had worse global performance (β = -0.354, 95% CI -0.671, -0.038). Insomnia was an effect modifier in the associations between AHI and executive function performance (p for the interaction between insomnia and AHI = 0.004) and between oxygen saturation <90% and memory performance (p for the interaction between insomnia and oxygen saturation = 0.02). Although some associations between sleep measures and cognition were significant, they should be considered with caution due to the large sample size and multiple testing performed in this study.

Sleep disorders affect cognitive function in adults: an overview of systematic reviews and meta-analyses

Sleep disorders frequently result in poor memory, attention deficits, as well as a worse prognosis for neurodegenerative changes, such as Alzheimer's disease. The purpose of this study is to investigate the impact of sleep disorders on cognition. We screened four databases for all meta-analyses and systematic reviews from the establishment through March 2022. We have carried out quality evaluation and review the eligible systematic reviews. Evidence grading and quality assessment were performed on 22 eligible articles. Sleep deprivation primarily affects simple attention, complex attention, and working memory in cognition and alertness. The moderate-to-high-quality evidence proves optimal sleep time as 7-8 h. Sleep time outside this range increases the risk of impaired executive function, non-verbal memory, and working memory. Sleep-related breathing disorders is more likely to cause mild cognitive impairment and affects several cognitive domains. In older adults, insomnia primarily affects working memory, episodic memory, inhibitory control, cognitive flexibility, problem-solving, operational ability, perceptual function, alertness, and complex attention, and maintaining sensitivity. Sleep disturbances significantly impair cognitive function, and early detection and intervention may be critical steps in reducing poor prognosis. A simple neuropsychological memory test could be used to screen people with sleep disorders for cognitive impairment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41105-022-00439-9.

Mediating role of depressive symptoms on the relationship between sleep duration and cognitive function

Although some studies have shown the association between sleep duration and cognitive impairment is positive, the mechanism explaining how sleep duration is linked to cognition remains poor understood. The current study aims to explore it among Chinese population. A cross-sectional study of 12,589 participants aged 45 or over was conducted, cognition was assessed by three measures to capture mental intactness, episodic memory, and visuospatial abilities. The Center for Epidemiologic Studies Depression Scale 10 (CES-D₁₀) was administered during the face-to-face survey to assess depressive status. Sleep duration was reported by the participants themselves. Partial correlation and linear regression were used to explore the association between sleep duration, cognition, and depression. The Bootstrap methods PROCESS program was used to detect the mediation effect of depression. Sleep duration was positively correlated with cognition and negatively with depression (p < 0.01). The CES-D₁₀ score (r = - 0.13, p < 0.01) was negatively correlated with cognitive function. Linear regression analysis showed sleep duration was positively associated with cognition (p = 0.001). When depressive symptoms were considered, the association between sleep duration and cognition lost significance (p = 0.468). Depressive symptoms have mediated the relationship between sleep duration and cognitive function. The findings revealed that the relationship between sleep duration and cognition is mainly explained by depressive symptoms and may provide new ideas for interventions for cognitive dysfunction.

Sleep disturbance predicts worse cognitive performance in subsequent years: A longitudinal population-based cohort study

BACKGROUND

Poor sleep is a potential modifiable risk factor for later life development cognitive impairment. The aim of this study is to examine if subjective measures of sleep duration and sleep disturbance predict future cognitive decline in a population-based cohort of 60, 66, 72 and 78-year-olds with a maximal follow up time of 18 years.

METHODS

This study included participants from the Swedish National Study on Ageing and Care - Blekinge, with assessments 2001-2021. A cohort of 60 (n = 478), 66 (n = 623), 72 (n = 662) and 78 (n = 548) year-olds, were assessed at baseline and every 6 years until 78 years of age. Longitudinal associations between sleep disturbance (sleep scale), self-reported sleep duration and cognitive tests (Mini Mental State Examination and the Clock drawing test) were examined together with typical confounders (sex, education level, hypertension, hyperlipidemia, smoking status, physical inactivity and depression).

RESULTS

There was an association between sleep disturbance at age 60 and worse cognitive function at ages 60, 66 and 72 years in fully adjusted models. The association was attenuated after bootstrap-analysis for the 72-year-olds. The items of the sleep scale most predictive of later life cognition regarded nightly awakenings, pain and itching and daytime naps. Long sleep was predictive of future worse cognitive function.

CONCLUSION

Sleep disturbance was associated with worse future cognitive performance for the 60-year-olds, which suggests poor sleep being a risk factor for later life cognitive decline. Questions regarding long sleep, waking during the night, pain and itching and daytime naps should be further explored in future research and may be targets for intervention.

Sex differences in the effects of sleep disorders on cognitive dysfunction

Sleep is an essential physiological function that sustains human life. Sleep disorders involve problems with the quality, duration, and abnormal behaviour of sleep. Insomnia is the most common sleep disorder, followed by sleep-disordered breathing (SDB). Sleep disorders often occur along with medical conditions or other mental health conditions. Of particular interest to researchers is the role of sleep disorders in cognitive dysfunction. Sleep disorder is a risk factor for cognitive dysfunction, yet the exact pathogenesis is still far from agreement. Little is known about how sex differences influence the changes in cognitive functions caused by sleep disorders. This narrative review examines how sleep disorders might affect cognitive impairment, and then explores the sex-specific consequences of sleep disorders as a risk factor for dementia and the potential underlying mechanisms. Some insights on the direction of further research are also presented.

Cretan Aging Cohort-Phase III: Methodology and Descriptive Characteristics of a Long-Term Longitudinal Study on Predictors of Cognitive Decline in Non-Demented Elderly from Crete, Greece

Identifying modifiable factors that may predict long-term cognitive decline in the elderly with adequate daily functionality is critical. Such factors may include poor sleep quality and quantity, sleep-related breathing disorders, inflammatory cytokines and stress hormones, as well as mental health problems. This work reports the methodology and descriptive characteristics of a long-term, multidisciplinary study on modifiable risk factors for cognitive status progression, focusing on the 7-year follow-up. Participants were recruited from a large community-dwelling cohort residing in Crete, Greece (CAC; Cretan Aging Cohort). Baseline assessments were conducted in 2013-2014 (Phase I and II, circa 6-month time interval) and follow-up in 2020-2022 (Phase III). In total, 151 individuals completed the Phase III evaluation. Of those, 71 were cognitively non-impaired (CNI group) in Phase II and 80 had been diagnosed with mild cognitive impairment (MCI). In addition to sociodemographic, lifestyle, medical, neuropsychological, and neuropsychiatric data, objective sleep was assessed based on actigraphy (Phase II and III) and home polysomnography (Phase III), while inflammation markers and stress hormones were measured in both phases. Despite the homogeneity of the sample in most sociodemographic indices, MCI persons were significantly older (mean age = 75.03 years, SD = 6.34) and genetically predisposed for cognitive deterioration (APOE ε4 allele carriership). Also, at follow-up, we detected a significant increase in self-reported anxiety symptoms along with a substantial rise in psychotropic medication use and incidence of major medical morbidities. The longitudinal design of the CAC study may provide significant data on possible modifiable factors in the course of cognitive progression in the community-dwelling elderly.

Multidimensional Sleep Health and Long-Term Cognitive Decline in Community-Dwelling Older Men

Specific sleep characteristics have been associated with cognitive decline, Alzheimer's disease, and related dementias; however, studies examining the association between multidimensional sleep (a more comprehensive integration of sleep parameters) and cognitive decline are lacking. Among 2,811 older men without dementia, those with none, 1-2, and 3-5 "poor" self-reported sleep health dimensions had an adjusted 10-year change score of global cognition (3MS) of 2.9, 4.0 and 3.5 points (p-trend = 0.05), and in executive function (Trails B) completion time of 36.7, 42.7, and 46.7 seconds (p-trend < 0.01), respectively. In conclusion, a multidimensional measure of sleep health was associated with greater cognitive decline.

Lighter sleep is associated with higher enlarged perivascular spaces burden in middle-aged and elderly individuals

BACKGROUND

While healthy sleep is suggested to promote glymphatic clearance in the brain, poorer sleep may be associated with higher enlarged perivascular spaces (ePVS) burden, potentially representing impaired perivascular drainage. This study aims to evaluate the association between ePVS burden and polysomnographic sleep characteristics in a large community-based sample.

METHODS

552 dementia and stroke-free Framingham Heart Study participants (age: 58.6 ± 8.9 years; 50.4% men) underwent a full-night in-home polysomnography. Three years later on average, participants underwent a brain MRI. ePVS were rated in the basal ganglia and centrum semiovale, and dichotomized as low burden (<20 counts, grades 1 and 2) or high burden (>20 counts, grades 3 and 4). Logistic regression analyses relating sleep variables to subsequent ePVS burden were used, adjusted for age, sex, time interval between polysomnography and MRI, ApoE ε4 allele carrier status, hypertension, and smoking.

RESULTS

Longer N1 sleep and shorter N3 sleep duration were associated with higher ePVS burden in the centrum semiovale. When stratifying these associations by subpopulations, longer N1 sleep duration with ePVS burden was observed especially in older individuals and hypertensive participants. Associations between ePVS burden and other sleep characteristics such as total sleep time and REM sleep duration varied according to ApoE ε4 allele carrier status.

CONCLUSIONS

Lighter sleep, as characterized by longer N1 sleep and shorter slow-wave sleep, is associated with higher ePVS burden. These findings suggest that sleep architecture may be involved in glymphatic clearance and cerebral small vessel disease, which could be an important biological link between sleep and dementia risk.

Prospective association between sleep duration and cognitive impairment: Findings from the China Health and Retirement Longitudinal Study (CHARLS)

Objective

The association between sleep duration and cognition are inconclusive. Our study aimed to comprehensively investigate the effects of sleep duration on the risk of cognitive impairment in the middle-aged and older Chinese population.

Methods

We used the longitudinal cohort data from waves 1–4 (2011–2018) of the China Health and Retirement Longitudinal Study (CHARLS). Self-reported exposures included total sleep duration, nocturnal sleep duration, post-lunch napping, and changes in sleep duration over time according to face-to-face interviews. Cognitive function was assessed by a Chinese version of the Modified Mini-Mental State Examination (MMSE).

Results

A total of 7,342 eligible participants were included. The mean age was 61.5 ± 6.5 years, and 48.9% (3,588/7,342) were male. We identified a U-shaped association of total sleep duration as well as nocturnal sleep duration with the risk of cognitive impairment. People with 7–8 h of total sleep duration and 6–7 h of nocturnal sleep had the lowest risk of cognitive impairment. Further results showed that post-lunch napping within 2 h was beneficial to cognition and 60 min was optimal. Moreover, analyses of changes in sleep duration further supported that sleeping less or more was harmful to cognition. Notably, those “excessive-change” sleepers (from ≤6 to ≥9 h, or from ≥9 to ≤6 h) had more risks.

Conclusions

Keeping 7–8 h per day was related to the lowest risk of cognitive impairment in midlife and late life, and an optimal post-lunch napping was 60 min for these stable sleepers. Especially, excessive changes in sleep duration over time led to poorer cognition. Our work highlights the importance of optimal sleep habits to cognitive function. The self-reported sleep measures limited our findings, and further studies are needed for verification.

Excessive sleep increased the risk of incidence of cognitive impairment among older Chinese adults: a cohort study based on the Chinese Longitudinal Healthy Longevity Survey (CLHLS)

STUDY OBJECTIVES

Based on a cohort from the Chinese Longitudinal Healthy Longevity Survey (CLHLS), we aimed to evaluate the relationship between sleep duration and the incidence of cognitive impairment among older Chinese adults.

METHODS

We conducted a prospective analysis based on 3692 participants from the CLHLS at baseline (in 2011), and as a 3-year follow-up (till 2014), 531 participants (14.4%) had cognitive impairment, which was defined as a Mini-Mental State Examination score <24. Sleep duration was classified into three groups: short (≤5 hours/day), normal (>5 but <10 hours), and long (≥10 hours/day). A logistic regression model was used to examine the association between baseline sleep duration and cognitive impairment after adjusting for sociodemographic data, living habits, and health conditions.

RESULTS

Five hundred sixty-two participants (15.2%) were in the short-duration group, and 608 participants (16.5%) were in the long-duration group. After adjusting for multiple potential confounders, compared with normal sleep duration, long sleep duration was associated with the incidence of cognitive impairment (OR = 1.309, 95% CI: 1.019-1.683), especially among men (OR = 1.527, 95% CI: 1.041-2.240) and those having a primary and above education level (OR = 1.559, 95% CI: 1.029-2.361). No significant association was observed between short sleep duration and cognitive impairment (OR = 0.860, 95% CI: 0.646-1.145).

CONCLUSIONS

Excessive sleep may increase the risk of cognitive impairment in older individuals. It may be a suggestive sign of early neurodegeneration and may be a useful clinical tool to identify those at a higher risk of progressing to cognitive impairment.

Gait Speed and Sleep Duration Is Associated with Increased Risk of MCI in Older Community-Dwelling Adults

This study aimed to examine the linear and nonlinear associations between sleep duration and gait speed and the risk of developing mild cognitive impairment (MCI) in community-dwelling older adults. Participants were 233 older adults who met the study inclusion criteria. The MCI diagnosis was based on medical evaluations through a clinical interview conducted by a dementia specialist. Self-reported sleep duration was evaluated using the Pittsburgh Sleep Quality Index. The usual gait speed was calculated from the time taken to walk along a 4 m walkway. Multivariate logistic regression analysis was used to calculate the odds ratio (OR) and the 95% confidence interval (95% CI) of developing MCI in relation to sleep duration and gait speed. Generalized additive models were used to examine the dose−response relationships between sleep duration, gait speed, and the risk of developing MCI. Slower gait speed (OR: 1.84, 95%; CI: 1.00−3.13) and poor sleep duration (OR: 1.76, 95%; CI: 1.00−3.35) were associated with the risk of developing MCI, compared with their optimal status. In addition, the combination of poor sleep and slower gait was associated with a higher risk of developing MCI than optimal sleep duration and gait speed (OR: 3.13, 95%; CI: 1.93−5.14). Furthermore, gait speed and sleep duration were non-linearly associated with the risk of developing MCI. These results highlight the complex interplay and synergism between sleep duration and gait abilities on the risk of developing MCI in older adults. In addition, our results suggest that slower gait speed (<1.0 m/s) and short (<330 min) and long (>480 min) sleep duration may be linked to MCI risks through underlying pathways.

Are clinical trials randomising households to lifestyle interventions to delay cognitive decline feasible? A pilot study to determine the beliefs, preferences, and deterrents for households impacted by dementia based on semi-structured interviews

Introduction

While lifestyle risk factors are implicated in the development and progression of cognitive impairment, interventional trials of individual participants have yielded unconvincing evidence. We sought to explore the development of lifestyle interventions targeting the household-unit.

Methods

Semi-structured interviews were carried out among eight households affected by cognitive impairment (i.e. member of the household had cognitive impairment). Interviews took place online using a secure, web-based video platform recommended for patient clinician interaction. Interview content was analysed, and important themes identified.

Results

Eighteen participants were interviewed within households, of which eight (one per household) had cognitive impairment and others were spouses or first-degree relatives living in the same home. Several themes emerged; 1) household members without cognitive impairment were more likely to report poor sleep habits, and sleep was perceived to be the hardest behaviour to change; 2) diet generated most interest as a potential lifestyle intervention target as most participants believed there is a strong link with nutrition and cognition; 3) physical activity is challenging to adapt due to lack of motivation and focus when individuals are cognitively impaired. Barriers to study participation, including risk of harm, complexity of intervention and deviation from routine emerged during discussions.

Conclusions

This study identified beliefs and preferences of households towards lifestyle intervention trials. Findings from this study may be used to inform future clinical trial protocols and future qualitative studies should explore acceptability and feasibility of digital intervention applications.

Sleep Duration/Quality With Health Outcomes: An Umbrella Review of Meta-Analyses of Prospective Studies

Background

To quantitatively evaluate the evidence of duration and quality of sleep as measured by multiple health outcomes.

Methods

This review is registered with PROSPERO, number CRD42021235587. We systematically searched three databases from inception until November 15, 2020. For each meta-analysis, the summary effect size using fixed and random effects models, the 95% confidence interval, and the 95% prediction interval were assessed; heterogeneity, evidence of small-study effects, and excess significance bias were also estimated. According to the above metrics, we evaluated the credibility of each association.

Results

A total of 85 meta-analyses with 36 health outcomes were included in the study. We observed highly suggestive evidence for an association between long sleep and an increased risk of all-cause mortality. Moreover, suggestive evidence supported the associations between long sleep and 5 increased risk of health outcomes (stroke, dyslipidaemia, mortality of coronary heart disease, stroke mortality, and the development or death of stroke); short sleep and increased risk of overweight and/or obesity; poor sleep quality and increased risk of diabetes mellitus and gestational diabetes mellitus.

Conclusions

Only the evidence of the association of long sleep with an increased risk of all-cause mortality was graded as highly suggestive. Additional studies are needed to be conducted.

Systematic Review Registration:https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42021235587

Sleep and longitudinal cognitive performance in preclinical and early symptomatic Alzheimer's disease

Sleep monitoring may provide markers for future Alzheimer's disease; however, the relationship between sleep and cognitive function in preclinical and early symptomatic Alzheimer's disease is not well understood. Multiple studies have associated short and long sleep times with future cognitive impairment. Since sleep and the risk of Alzheimer's disease change with age, a greater understanding of how the relationship between sleep and cognition changes over time is needed. In this study, we hypothesized that longitudinal changes in cognitive function will have a non-linear relationship with total sleep time, time spent in non-REM and REM sleep, sleep efficiency and non-REM slow wave activity. To test this hypothesis, we monitored sleep-wake activity over 4-6 nights in 100 participants who underwent standardized cognitive testing longitudinally, APOE genotyping, and measurement of Alzheimer's disease biomarkers, total tau and amyloid-β42 in the CSF. To assess cognitive function, individuals completed a neuropsychological testing battery at each clinical visit that included the Free and Cued Selective Reminding test, the Logical Memory Delayed Recall assessment, the Digit Symbol Substitution test and the Mini-Mental State Examination. Performance on each of these four tests was Z-scored within the cohort and averaged to calculate a preclinical Alzheimer cognitive composite score. We estimated the effect of cross-sectional sleep parameters on longitudinal cognitive performance using generalized additive mixed effects models. Generalized additive models allow for non-parametric and non-linear model fitting and are simply generalized linear mixed effects models; however, the linear predictors are not constant values but rather a sum of spline fits. We found that longitudinal changes in cognitive function measured by the cognitive composite decreased at low and high values of total sleep time (P < 0.001), time in non-REM (P < 0.001) and REM sleep (P < 0.001), sleep efficiency (P < 0.01) and <1 Hz and 1-4.5 Hz non-REM slow wave activity (P < 0.001) even after adjusting for age, CSF total tau/amyloid-β42 ratio, APOE ε4 carrier status, years of education and sex. Cognitive function was stable over time within a middle range of total sleep time, time in non-REM and REM sleep and <1 Hz slow wave activity, suggesting that certain levels of sleep are important for maintaining cognitive function. Although longitudinal and interventional studies are needed, diagnosing and treating sleep disturbances to optimize sleep time and slow wave activity may have a stabilizing effect on cognition in preclinical or early symptomatic Alzheimer's disease.

Short daytime napping reduces the risk of cognitive decline in community-dwelling older adults: a 5-year longitudinal study

BACKGROUND

Beneficial effects of napping on cognition have been suggested in cross-sectional studies. This study aimed to clarify longitudinal associations between cognitive decline and sleep characteristics, particularly daytime napping, over a 5-year period in older adults.

METHODS

Study participants were 389 community-dwelling individuals aged ≥65 years living in Ojiya City, Niigata, Japan. Baseline and follow-up examinations were conducted in 2011-2013 and 2016-2018, respectively. Trained nurses visited and interviewed participants to collect the following information at baseline and follow-up: demographic characteristics, disease history, lifestyle habits including bedtime, sleeping hours, and daytime nap duration, and cognitive function. The assessment of cognitive function was performed using the revised Hasegawa's dementia scale (HDS-R), with cognitive decline defined as a change in the HDS-R of ≤ - 3 over 5 years. Odds ratios (ORs) for cognitive decline were calculated using multiple logistic regression analysis.

RESULTS

Mean age of participants was 74.6 years (SD 6.4), and the cumulative incidence of cognitive decline was 106/389 (27.3%). The adjusted OR for 1-29 min daytime napping was significantly lower compared to that for no napping (OR = 0.47, 95%CI: 0.23-0.96). Earlier bedtime was associated with cognitive decline (adjusted P for trend = 0.0480).

CONCLUSION

Short daytime napping (< 30 min) reduces the risk of cognitive decline over 5 years for community-dwelling older people. A future study will be necessary to confirm the effect of short napping on the reduction of risk for clinically diagnosed dementia.

Sleep duration and health outcomes: an umbrella review

PURPOSE

To collect existing evidence on the relationship between sleep duration and health outcomes.

METHODS

A thorough search was conducted in PubMed, Web of Science, Embase, and the Cochrane Database of Systematic Reviews from inception to January, 2021. Meta-analyses of observational and interventional studies were eligible if they examined the associations between sleep duration and human health.

RESULTS

In total, this umbrella review identified 69 meta-analyses with 11 outcomes for cancers and 30 outcomes for non-cancer conditions. Inappropriate sleep durations may significantly elevate the risk for cardiovascular disease (CVD), cognitive decline, coronary heart disease (CHD), depression, falls, frailty, lung cancer, metabolic syndrome (MS), and stroke. Dose-response analysis revealed that a 1-h reduction per 24 hours is associated with an increased risk by 3-11% of all-cause mortality, CHD, osteoporosis, stroke, and T2DM among short sleepers. Conversely, a 1-h increment in long sleepers is associated with a 7-17% higher risk of stroke mortality, CHD, stroke, and T2DM in adults.

CONCLUSION

Inappropriate sleep duration is a risk factor for developing non-cancer conditions. Decreasing and increasing sleep hours towards extreme sleep durations are associated with poor health outcomes.

Social capital and cognitive decline: Does sleep duration mediate the association?

Background

Studies have found that social capital (SC) is associated with the risk of cognitive decline; however, the mechanism explaining how SC leads to cognitive decline is unclear. The current study examines the mediation effect of sleep duration on the relationship between SC and cognitive decline in Chinese older adults.

Methods

A cross-sectional study of 955 community-dwelling aged 60 or over was conducted. The mini-mental state examination (MMSE), self-report sleep duration questionnaire, and social capital scales were administered during the face-to-face survey. The Bootstrap methods PROCESS program is employed to test the mediation model.

Results

After controlling for covariates, both social cohesion and social interaction were positively correlated with the MMSE score (p<0.001), and social cohesion was negatively correlated with sleep duration (p = 0.009); On the contrary, sleep duration was negatively correlated with MMSE score (p<0.001). Linear regression analysis showed social cohesion was positively associated with the MMSE score (β = 0.16, p = 0.005), while sleep duration was associated with an increased risk of cognitive decline (β = -0.72, p<0.001). Sleep duration has mediated the relationship between social cohesion and cognitive decline (explaining 21.7% of the total variance).

Conclusions

Social capital negatively associated with the risk of cognitive decline in this Chinese population, and sleep duration may partly explain this relationship. It may be a suggestive clue to identify those at a higher risk of progressing to cognitive impairment. Further prospective study in need to confirm this finding due to the cross-sectional design.

Prospective associations between change in sleep duration and cognitive impairment: Findings from the Singapore Chinese Health Study

BACKGROUND

The relation of changes in sleep duration with risk of cognitive impairment are inconclusive. This study evaluated the prospective relationships of changes in sleep duration with risk of cognitive impairment in Singapore Chinese.

METHODS

We used data from 16,948 Chinese men and women who were aged 45-74 years at baseline (1993-1998) during recruitment into the Singapore Chinese Health Study cohort. Daily sleep duration was assessed at baseline, follow-up 2 (2006 to 2010) and follow-up 3 interviews (2014-2016). Cognitive function was evaluated with a Singapore-Modified Mini-Mental State Examination at follow-up 3 interviews when participants were 61-96 years old. Multivariable logistic regression models were used to calculate odd ratios (ORs) and 95% confidence intervals (95% CIs) for cognitive impairment.

RESULTS

Of the 16,948 participants, 14.4% were defined to have cognitive impairment. Compared with 7 h/day sleep at both baseline and follow-up 2, the OR (95% CI) for cognitive impairment was 1.50 (1.04-2.16) for those who maintained long sleep duration (≥9 h/day), 2.18 (1.37-3.45) for those who prolonged sleep from short duration (≤5 h/day) to long duration (≥9 h/day), and 1.55 (1.20-2.02) for those who prolonged sleep from recommended duration (7 h/day) to long duration. The highest risk was observed in those who shortened sleep from long to short duration (2.93, 1.35-6.34).

LIMITATIONS

Measures of sleep were self-reported.

CONCLUSIONS

Substantial changes in sleep duration over time were associated with higher risks of cognitive impairment. The findings underscore the importance of maintaining optimal sleep duration for the prevention of cognitive impairment.

Systemic inflammation as a moderator between sleep and incident dementia

STUDY OBJECTIVES

To determine whether C-reactive protein (CRP), a marker of systemic inflammation, moderates the association between sleep and incident dementia.

METHODS

We studied Framingham Heart Study participants who completed at baseline a serum CRP assessment and in-home polysomnography to measure sleep duration, sleep efficiency, sleep latency, wake after sleep onset (WASO), number of awakenings, arousal index, and apnea-hypopnea index. Participants were divided into groups according to their CRP level: low (<1 mg/L), average (1-3 mg/L), and high inflammation (>3 mg/L). Surveillance for outcomes (incident all-cause and Alzheimer's disease [AD] dementia) commenced at baseline and continued up to 22.5 years.

RESULTS

In 291 participants (mean age 67.5 ± 4.9 years, 51.6% men) followed for 13.4 ± 5.4 years, we observed 43 cases of all-cause dementia, 33 of which were clinically consistent with AD. Whereas no direct association between CRP or sleep exposures was observed with incident dementia, CRP levels interacted with nighttime wakefulness when predicting both incident all-cause and AD dementia. In the high CRP group, longer WASO (hazard ratio [HR], 2.89; 95% CI, 1.31-6.34) and more nighttime awakenings (HR, 4.55; 95% CI, 1.19-17.38) were associated with higher risk of incident dementia. In the low CRP group, fewer nighttime awakenings were associated with a higher risk of incident dementia (HR, 0.07; 95% CI, 0.01-0.68).

CONCLUSIONS

Our findings suggest that inflammation moderates the association between sleep, particularly nighttime wakefulness, and dementia risk. The presence of inflammation may be an important determinant in evaluating how sleep disturbances relate to neurodegeneration.

Association between sleep disturbance with motoric cognitive risk syndrome in Chinese older adults

BACKGROUND AND PURPOSE

Sleep disturbance and cognitive impairment are common and related in the elderly population worldwide. The aim of the present study was to explore the association between sleep disturbance and motoric cognitive risk (MCR) syndrome, which is characterized by subjective cognitive complaints and objective slow gait in older individuals without dementia or any mobility disability in the community-dwelling elderly Chinese population.

METHODS

We recruited 940 participants aged ≥65 years from November 2016 to March 2017 in the Ningbo Community Study on Aging (NCSA). Self-reported sleep duration and sleep-quality variables, comprehensive geriatric evaluation, as well as indicators for diagnosing MCR syndrome were evaluated in this cross-sectional study.

RESULTS

Multiple logistic regression analysis showed that a 1-SD increase in night (1.1 h) and 24-h sleep duration (1.3 h) was associated, respectively, with a 21% (95% confidence interval [CI], 1%-47%; p = 0.04) and 30% (95% CI, 3%-64%; p = 0.03) higher odds of having MCR syndrome. Considering sleep duration as a categorical variable, longer night-sleep duration (>8.5 h) was associated with MCR syndrome (OR, 2.03; p = 0.02) compared to shorter night-sleep duration (<8 h). For sleep-quality factors, increasing frequency of trouble falling asleep, waking early or easily, nightmares, and taking sleep drugs were significantly associated with MCR syndrome after adjusting for potential covariables (all p for trend < 0.05), but not for self-perceived sleep quality (p for trend = 0.10).

CONCLUSIONS

Long sleep duration, poor sleep quality, and taking sleep drugs were associated with higher odds of having MCR syndrome in the community-dwelling elderly Chinese population. Further research is needed to explore the underlying mechanisms.

Effect of Interaction Between Slow Wave Sleep and Obstructive Sleep Apnea on Insulin Resistance: A Large-Scale Study

OBJECTIVE

Slow-wave sleep (SWS) and obstructive sleep apnea (OSA) have attracted recent research attention. However, their joint effects on insulin resistance (IR) remain unclear. This study explored whether SWS influences the relationship between OSA and IR.

METHODS

We enrolled potential participants in our sleep center from 2007 to 2019. We collected demographic and clinical characteristics and determined IR status. SWS was derived from polysomnography data. Logistic regression analysis was used to reveal the associations between SWS and IR.

RESULTS

In all, 6966 participants (5709 OSA and 1257 primary snoring [PS] subjects) were enrolled. Less SWS increased the risk of IR in OSA patients but not in PS patients. OSA patients with SWS <6.5% were more likely to have IR than were those with SWS >21.3%. OSA was an independent risk factor for IR after adjusting for potential confounding factors. In stratified analyses according to the percentage of SWS, OSA patients with SWS <6.5% had an odds ratio for IR of 2.461 (95% CI, 2.018-3.002) compared to the PS group after adjusting for potential confounders.

CONCLUSION

Less SWS is associated with higher odds for IR in OSA patients but not in PS patients. OSA is independently associated with IR. In addition, OSA combined with an extreme lack of SWS has a more harmful effect on the status of IR than OSA itself.

The Potential Contribution of Chronic Pain and Common Chronic Pain Conditions to Subsequent Cognitive Decline, New Onset Cognitive Impairment, and Incident Dementia: A Systematic Review and Conceptual Model for Future Research

BACKGROUND

Growing evidence suggests that chronic pain and certain chronic pain conditions may increase risk for cognitive decline and dementia.

OBJECTIVE

In this systematic review, we critically evaluate available evidence regarding the association of chronic pain and specific common chronic pain conditions to subsequent decline in cognitive function, new onset cognitive impairment (CI), and incident Alzheimer's disease and related dementias (ADRD); outline major gaps in the literature; and provide a preliminary conceptual model illustrating potential pathways linking pain to cognitive change.

METHODS

To identify qualifying studies, we searched seven scientific databases and scanned bibliographies of identified articles and relevant review papers. Sixteen studies met our inclusion criteria (2 matched case-control, 10 retrospective cohort, 2 prospective cohort), including 11 regarding the association of osteoarthritis (N = 4), fibromyalgia (N = 1), or headache/migraine (N = 6) to incident ADRD (N = 10) and/or its subtypes (N = 6), and 5 investigating the relation of chronic pain symptoms to subsequent cognitive decline (N = 2), CI (N = 1), and/or ADRD (N = 3).

RESULTS

Studies yielded consistent evidence for a positive association of osteoarthritis and migraines/headaches to incident ADRD; however, findings regarding dementia subtypes were mixed. Emerging evidence also suggests chronic pain symptoms may accelerate cognitive decline and increase risk for memory impairment and ADRD, although findings and measures varied considerably across studies.

CONCLUSION

While existing studies support a link between chronic pain and ADRD risk, conclusions are limited by substantial study heterogeneity, limited investigation of certain pain conditions, and methodological and other concerns characterizing most investigations to date. Additional rigorous, long-term prospective studies are needed to elucidate the effects of chronic pain and specific chronic pain conditions on cognitive decline and conversion to ADRD, and to clarify the influence of potential confounding and mediating factors.

Effects of treatment of sleep disorders on sleep, psychological and cognitive functioning and biomarkers in individuals with HIV/AIDS and under methadone maintenance therapy

BACKGROUND

Poor sleep is a major complaint of people with human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) and undergoing methadone maintenance therapy (MMT). We tested the impact of three different sleep-improving interventions (trazodone; sleep hygiene training; sleep hygiene training + trazodone) on sleep, psychological functioning and biomarkers in males with HIV and undergoing MMT.

METHODS

A total of 75 male outpatients (mean age: 39.6 years) participated in a 12 week intervention. Participants were randomly assigned to one of the following conditions: trazodone 50 mg/d (TRAZ); sleep hygiene training (SHT); sleep hygiene training and trazodone (SHT + TRAZ). At baseline, and six and 12 weeks later, participants completed questionnaires covering subjective sleep and daytime sleepiness, and symptoms of depression and anxiety. In parallel, their cognitive performance (working memory; sustained attention) was assessed. Biomarkers (cortisol, BNDF, CD4⁺) were assessed at baseline and at the end of the study.

RESULTS

Over time, sleep disturbances decreased and daytime functioning and overall sleep quality improved. More specifically, both sleep disturbances and daytime functioning improved in the two SHT conditions from baseline to week 6. Daytime functioning remained stable from week 6 to week 12. Over time, in all conditions symptoms of depression and anxiety declined from baseline to week 6 and remained lower from week 6 to week 12. Daytime sleepiness, symptoms of insomnia and sleep-disordered breathing remained unchanged. Sustained attention performance improved over time from baseline to week 6 and remained high through to week 12. Biomarkers remained unchanged.

CONCLUSIONS

In males with HIV and undergoing MMT, treating sleep disturbances over a period of six to 12 weeks had a positive impact on aspects of sleep disturbance, symptoms of depression and anxiety, and cognitive performance. The results indicate that sleep hygiene training, either as stand-alone or in combination with trazodone, can produce positive results.

Short sleep duration and high exposure to quick returns are associated with impaired everyday memory in shift workers

PURPOSE

To investigate the relationship between self-reported everyday memory problems the last month, and: (a) shift work schedule, (b) night shifts and quick returns worked the last year, and (c) sleep duration the last month.

METHODS

In all, 1,275 nurses completed the Everyday Memory Questionnaire - revised, and answered questions about shift work exposure and sleep duration. We performed multiple linear regression analyses with memory score as dependent variable, and the shift work exposure variables as well as sleep duration as predictors, while adjusting for potential confounders.

FINDINGS

High exposure to quick returns (β = .10, p < .05) and short sleep duration (β = .10, p < .05) were both positively associated with memory problems, whereas shift work schedule, long sleep duration, night shift exposure, and low and moderate exposure to quick returns were not.

DISCUSSION

Frequent insufficient time for rest between shifts as well as short sleep was associated with poorer everyday memory.

Sleep, major depressive disorder, and Alzheimer disease: A Mendelian randomization study

OBJECTIVE

To explore the causal relationships between sleep, major depressive disorder (MDD), and Alzheimer disease (AD).

METHODS

We conducted bidirectional 2-sample Mendelian randomization analyses. Genetic associations were obtained from the largest genome-wide association studies currently available in UK Biobank (n = 446,118), Psychiatric Genomics Consortium (n = 18,759), and International Genomics of Alzheimer's Project (n = 63,926). We used the inverse variance-weighted Mendelian randomization method to estimate causal effects and weighted median and Mendelian randomization-Egger for sensitivity analyses to test for pleiotropic effects.

RESULTS

We found that higher risk of AD was significantly associated with being a "morning person" (odds ratio [OR] 1.01, p = 0.001), shorter sleep duration (self-reported: β = -0.006, p = 1.9 × 10^-4; accelerometer based: β = -0.015, p = 6.9 × 10^-5), less likely to report long sleep (β = -0.003, p = 7.3 × 10^-7), earlier timing of the least active 5 hours (β = -0.024, p = 1.7 × 10^-13), and a smaller number of sleep episodes (β = -0.025, p = 5.7 × 10^-14) after adjustment for multiple comparisons. We also found that higher risk of AD was associated with lower risk of insomnia (OR 0.99, p = 7 × 10^-13). However, we did not find evidence that these abnormal sleep patterns were causally related to AD or for a significant causal relationship between MDD and risk of AD.

CONCLUSION

We found that AD may causally influence sleep patterns. However, we did not find evidence supporting a causal role of disturbed sleep patterns for AD or evidence for a causal relationship between MDD and AD.

Sleep duration and health in adults: an overview of systematic reviews

The objective of this overview of systematic reviews was to examine the associations between sleep duration and health outcomes in adults. Four electronic databases were searched in December 2018 for systematic reviews published in the previous 10 years. Included reviews met the a priori determined population (community-dwelling adults aged 18 years and older), intervention/exposure/comparator (various levels of sleep duration), and outcome criteria (14 outcomes examined). To avoid overlap in primary studies, we used a priority list to choose a single review per outcome; reviews that examined the effect of age and those that looked at dose–response were prioritized. A total of 36 systematic reviews were eligible and 11 were included. Reviews included comprised 4 437 101 unique participants from 30 countries. Sleep duration was assessed subjectively in 96% of studies and 78% of studies in the reviews were prospective cohort studies. The dose–response curves showed that the sleep duration that was most favourably associated with health was 7–8 h per day. Modification of the effect by age was not apparent. The quality of the evidence ranged from low to high across health outcomes. In conclusion, the available evidence suggests that a sleep duration of 7–8 h per day is the one most favourably associated with health among adults and older adults. (PROSPERO registration no.: CRD42019119529.)

Novelty This is the first overview of reviews that examines the influence of sleep duration on a wide range of health outcomes in adults. Seven to 8 h of sleep per day was most favourably associated with health. Effect modification by age was not evident.

Interaction between obstructive sleep apnea and short sleep duration on insulin resistance: a large-scale study : OSA, short sleep duration and insulin resistance

Objectives

Both short sleep duration and obstructive sleep apnea (OSA) seem to be associated with insulin resistance. We aimed to explore whether short sleep duration modifies the relationship between OSA and insulin resistance.

Methods

Participants were consecutively enrolled from our sleep center during the period from 2007 to 2017. The index of homeostasis model assessment insulin resistance (HOMA-IR) was calculated from insulin and glucose. Sleep duration was determined by standard polysomnography. The associations between sleep duration and insulin resistance were estimated by logistic regression analyses.

Results

A total of 5447 participants (4507 OSA and 940 primary snorers) were included in the study. OSA was independently correlated with insulin resistance after adjusting for all potential confounders (OR, 1.319; 95% CI, 1.088–1.599), but not short sleep duration. In stratified analysis by sleep duration, compared with primary snorers, in the OSA group only extremely short sleep duration (< 5 h) was significantly associated with insulin resistance after adjusting for all covariates (OR, 2.229; 95% CI, 1.283–3.874). Rapid eye movement predominant OSA was significantly associated with insulin resistance (OR = 1.355, 95% CI: 1.019–1.802) after adjustment for confounding factors including age, sex and body mass index.

Conclusions

OSA, but not short sleep duration, was independently associated with insulin resistance. It is worth noting that OSA combined with extremely short sleep duration showed a greater detrimental effect than OSA itself with regard to insulin resistance.

Toward Using Wearables to Remotely Monitor Cognitive Frailty in Community-Living Older Adults: An Observational Study

Physical frailty together with cognitive impairment (Cog), known as cognitive frailty, is emerging as a strong and independent predictor of cognitive decline over time. We examined whether remote physical activity (PA) monitoring could be used to identify those with cognitive frailty. A validated algorithm was used to quantify PA behaviors, PA patterns, and nocturnal sleep using accelerometer data collected by a chest-worn sensor for 48-h. Participants (N = 163, 75 ± 10 years, 79% female) were classified into four groups based on presence or absence of physical frailty and Cog: PR-Cog-, PR+Cog-, PR-Cog+, and PR+Cog+. Presence of physical frailty (PR-) was defined as underperformance in any of the five frailty phenotype criteria based on Fried criteria. Presence of Cog (Cog-) was defined as a Mini-Mental State Examination (MMSE) score of less than 27. A decision tree classifier was used to identify the PR-Cog- individuals. In a univariate model, sleep (time-in-bed, total sleep time, percentage of sleeping on prone, supine, or sides), PA behavior (sedentary and light activities), and PA pattern (percentage of walk and step counts) were significant metrics for identifying PR-Cog- (p < 0.050). The decision tree classifier reached an area under the curve of 0.75 to identify PR-Cog-. Results support remote patient monitoring using wearables to determine cognitive frailty.

Sleep Duration and the Risk of Dementia: A Systematic Review and Meta-analysis of Prospective Cohort Studies

OBJECTIVE

Epidemiologic studies have reported inconsistent findings about the association between sleep duration and the risk of dementia. We aimed to clarify this association by method of meta-analysis.

DESIGN

Systematic review and meta-analysis of prospective cohort studies.

SETTING AND PARTICIPANTS

Community or clinical settings. Participants included patients with dementia or Alzheimer's disease and the general population.

MEASURES

We systematically searched the PubMed, EMBASE, and Web of Science for prospective cohort studies investigating the association between sleep duration and all-cause dementia or Alzheimer's disease (AD). Generic inverse-variance method was used to combine the outcomes with a random effects model for the association between sleep duration (short or long vs normal) and all-cause dementia or AD.

RESULTS

We identified 7 studies for all-cause dementia and 6 studies for AD. Pooled analyses showed that long sleep duration was associated with a 77% increased risk of all-cause dementia [hazard ratio (HR) = 1.77, 95% confidence interval (CI) = 1.32-2.37] and a 63% increased risk of AD (HR = 1.63, 95% CI = 1.24-2.13). Short sleep duration was not statistically associated with an increased risk of all-cause dementia (HR = 1.20, 95% CI = 0.91-1.59) or AD (HR = 1.18, 95% CI = 0.91-1.54).

CONCLUSIONS AND IMPLICATIONS

Only long sleep duration is significantly associated with an increased risk of all-dementia and AD. Future studies are needed to better understand the mechanisms underlying this association.

Associations between sleep duration and cognitive impairment in mild cognitive impairment

The prevalence of mild cognitive impairment (MCI) increases among elderly people and is associated with a high risk of dementia. Identifying factors that may contribute to the progress of MCI to dementia is critical. The objective of this study was to examine the association of objective sleep with cognitive performance in MCI patients. A subsample of 271 participants with a diagnosis of probable Alzheimer's disease (AD; N = 50) or mild cognitive impairment (MCI; N = 121) and 100 persons who were not cognitively impaired (NI) were recruited from a large population-based cohort in the island of Crete, Greece (3140 older adults aged >60 years). All participants underwent extensive neuropsychiatric/neuropsychological evaluation and a 3-day 24-hr actigraphy. Objective sleep variables and their association with neuropsychological performance were examined across the three groups, controlling for demographics, body mass index, depression, sleep apnea symptoms and psychotropic medications. Patients with AD had significantly longer 24-hr total sleep time (TST) compared to the MCI and NI groups. Long 24-hr TST was associated with reduced performance on tasks that placed significant demands on attention and processing speed in the MCI group and the AD group. Elderly patients with MCI have similar objective sleep duration to normal controls, whereas AD patients sleep longer. Long sleep duration in patients with multidomain subtypes of MCI is associated with critical non-memory cognitive domains. It appears that within the MCI group those that sleep longer have more severe cognitive impairment.

US acculturation and poor sleep among an intergenerational cohort of adult Latinos in Sacramento, California

Acculturation may shape the disproportionate burden of poor sleep among Latinos in the United States. Existing studies are limited by unidimensional acculturation proxies that are incapable of capturing cultural complexities across generations. Understanding how acculturation relates to sleep may lead to the identification of modifiable intervention targets. We used multivariable regression and latent class methods to examine cross-sectional associations between a validated multidimensional scale of US acculturation and self-reported poor sleep measures. We analyzed an intergenerational cohort: first-generation (GEN1) older Latinos (Sacramento Area Latino Study on Aging; N = 1,716; median age: 69.5) and second-generation (GEN2) middle-aged offspring and relatives of GEN1 (Niños Lifestyle and Diabetes Study; N = 670; median age: 54.0) in Sacramento, California. GEN1 with high US acculturation, compared with high acculturation towards another origin/ancestral country, had less restless sleep (prevalence ratio [PR] [95% confidence interval (CI)]: 0.67 [0.54, 0.84]) and a higher likelihood of being in the best sleep class than the worst (OR [95% CI]: 1.62 [1.09, 2.40]), but among nonmanual occupations, high intergenerational US acculturation was associated with more general fatigue (PR [95% CI: 1.86 [1.11, 3.10]). GEN2 with high intergenerational US acculturation reported shorter sleep (PR [95% CI]: 2.86 [1.02, 7.99]). High US acculturation shaped sleep differentially by generation, socioeconomic context, and intergenerational acculturative status. High US acculturation was associated with better sleep among older, lower socioeconomic Latinos, but with shorter sleep duration among middle-aged, higher socioeconomic Latinos; results also differed by parental acculturation status. Upon replication, future studies should incorporate prospective and intergenerational designs to uncover sociobehavioral pathways by which acculturation may shape sleep to ultimately inform intervention efforts.

Multi-angles of smoking and mild cognitive impairment: is the association mediated by sleep duration?

Although the association between cigarette smoking and risk of mild cognitive impairment (MCI) is controversial, most recent studies have shown that this influence is negative. However, it is unknown how multiple factors of smoking affect MCI, and the mechanisms of different smoking factors are not yet clarified. This study will examine the impact of various angles of smoking on MCI and the potential mediating effects of sleep duration on smoking MCI association in the elderly. In the case group, 109 elderly people who met the inclusion criteria were selected, and 123 were selected in the control group. Participant characteristics include sleep duration and a detailed lifetime history of smoking. After adjusting the relevant covariates, higher odds of MCI occurrence were found in ex-smokers/current smokers; moderate/heavy smokers; smokers for 30-44, 45-59 and more than 60 years; smokers with cumulative smoking duration of 30-44 or more than 60 years and smokers with cumulative dose smoking intensity of 200-399 or 400-599 cigarettes monthly. Elderly subjects who had quit smoking for 21 years or longer were found to have lower odds of MCI occurrence. The indirect effects of smoking on MCI via sleep duration were statistically significant, as the ratio of indirect effect to total effect ranged from 0.14 to 0.29. Smoking affects cognitive function through multi-angles of smoking and influences the cognitive function partly via the duration of sleep.

Disturbed sleep and diabetes: A potential nexus of dementia risk

Type 2 diabetes (T2D) and sleep disturbance (e.g., insomnia, sleep-disordered breathing) are prevalent conditions among older adults that are associated with cognitive decline and dementia, including Alzheimer's disease (AD). Importantly, disturbed sleep is associated with alterations in insulin sensitivity and glucose metabolism, and may increase the risk of T2D, and T2D-related complications (e.g., pain, nocturia) can negatively affect sleep. Despite these associations, little is known about how interactions between T2D and sleep disturbance might alter cognitive trajectories or the pathological changes that underlie dementia. Here, we review links among T2D, sleep disturbance, cognitive decline and dementia-including preclinical and clinical AD-and identify gaps in the literature, that if addressed, could have significant implications for the prevention of poor cognitive outcomes.