Napping in older people ‘at risk’ of dementia: relationships with depression, cognition, medical burden and sleep quality

The associations of daytime napping and motoric cognitive risk syndrome: Findings from the China Health and Retirement Longitudinal Study

INTRODUCTION

Motoric cognitive risk syndrome (MCR), characterized by subjective cognitive complaints and slow gait in older populations, is associated with sleep duration. However, the association between MCR and daytime nap duration has not been thoroughly explored.

METHODS

Baseline data from the China Health and Retirement Longitudinal Study (CHARLS) were used in this study. MCR was defined as the coexistence of subjective cognitive complaints and objective slow gait speed without a history of dementia or mobility disability. Daytime nap duration was categorized into four groups: no napping, short napping (<30 min), moderate napping (30-89 min) and extended napping (≥90 min). Multivariable logistic regression models were used to explore the association of daytime napping duration and MCR.

RESULTS

A total of 4230 individuals aged ≥60 were included in the current analysis, of which 463 were diagnosed with MCR. Moderate napping of 30-89 min per day was found to be significantly associated with lower odds of MCR compared with the reference group of no napping. In subgroup analysis, individuals with sleep durations of <7 h per night had lower odds of MCR in the model that adjusted for all potential confounders with ≥30 min daytime nap duration compared with no napping. Interestingly, for people with a night sleep duration of 7-8 h, only those with a moderate nap of 30-89 min had lower odds of MCR than non-nappers after adjustment for potential confounders.

CONCLUSION

A moderate nap of 30-89 min could lower the odds of MCR, especially for older adults with a night sleep duration of ≤8 h.

Working Memory Precision and Associative Binding in Mild Cognitive Impairment

To better understand working memory (WM) deficits in Mild Cognitive Impairment (MCI), we examined information precision and associative binding in WM in 21 participants with MCI, compared to 16 healthy controls, using an item-location delayed reproduction task. WM, along with other executive functions (i.e. Trail Making Task (TMT) and Stroop task), were measured before and after a 2-h nap. The napping manipulation was intended as an exploratory element to this study exploring potential impacts of napping on executive functions.Compared to healthy participants, participants with MCI exhibited inferior performance not only in identifying encoded WM items but also on item-location associative binding and location precision even when only one item was involved. We also found changes on TMT and Stroop tasks in MCI, reflecting inferior attention and inhibitory control. Post-napping performance improved in most of these WM and other executive measures, both in MCI and their healthy peers.Our study shows that associative binding and WM precision can reliably differentiate MCIs from their healthy peers. Additionally, most measures showed no differential effect of group pre- and post-napping. These findings may contribute to better understanding cognitive deficits in MCI therefore improving the diagnosis of MCI.

Associations between afternoon napping, left amygdala volume and cognitive performance in elderly with normal cognitive function

BACKGROUND

The relationship between afternoon napping and cognitive function in the elderly is very complex and the mechanism is unknown.

METHODS

In the current study, 194 community elders with normal cognitive functions were included. All subjects completed baseline clinical assessment, baseline neuropsychological test as well as baseline structural MRI. Based on their napping status, these 194 participants were divided into the napping group (n = 88) and the non-napping group (n = 106). We then compared the differences in cognitive performance and structural magnetic resonance between the two groups.

RESULTS

In the intergroup analysis, we found that the nappers showed poorer cognitive performance on both overall cognitive function and domain specific cognitive function; while on the whole sample, we found a significant negative association (F = 20.27, p<0.001) between afternoon napping and left amygdala volume. However, we did not find any effect of night sleep length or napping frequency on cognitive performance or left amygdala volume.

CONCLUSIONS

In community elders with normal cognitive functions, afternoon napping is associated with cognitive performance, and left amygdala may play an important role in this process.

Associations of daytime napping and nighttime sleep quality with depressive symptoms in older Chinese: the Guangzhou biobank cohort study

BACKGROUND

Poor sleep quality has been linked to depression in older adults, but results of the association between daytime napping and depression remains limited and conflicting. Moreover, whether the association of daytime napping with depression varies by nighttime sleep quality is unclear. Hence, we examined the associations of daytime napping and nighttime sleep quality with depressive symptoms in older Chinese.

METHODS

A total of 16,786 participants aged ≥50 from the Guangzhou Biobank Cohort Study second-round examination (2008-2012) were included in this cross-sectional study. Geriatric Depression Scale (GDS-15), Pittsburgh Sleep Quality Index (PSQI), napping and demographic data were collected by face-to-face interview using a computerized questionnaire. Logistic regression was used to calculate odds ratio (OR) of depressive symptoms for napping and sleep quality.

RESULTS

The prevalence of depressive symptoms (GDS score > 5) and poor global sleep quality (PSQI score ≥ 6) was 5.3 and 31.9%, respectively. Compared to non-nappers, nappers showed significantly higher odds of depressive symptoms, with OR (95% confidence interval (CI)) being 1.28 (1.11-1.49). The odds of depressive symptoms for daytime napping varied by nighttime sleep quality (P for interaction = 0.04). In good-quality sleepers, compared to non-nappers, nappers had significantly higher odds of depressive symptoms, with OR (95% CI) being 1.57 (1.23-2.01), whereas no association was found in poor-quality sleepers (OR = 1.13, 0.94-1.36).

CONCLUSION

Napping was associated with higher odds of depressive symptoms in older people, and the association was stronger in good-quality sleepers.

Causal relationship between sleep traits and cognitive impairment: A Mendelian randomization study

OBJECTIVE

Observational studies had demonstrated a link between sleep disturbances and cognitive decline. Here, we aimed to investigate the causal association between genetically predicted sleep traits and cognitive impairment using Mendelian randomization (MR).

METHODS

Using strict criteria, we selected genetic variants from European ancestry Genome-wide association studies (GWAS) from the Sleep Disorders Knowledge Portal and UK Biobank as instrumental variables for several sleep traits, including insomnia, sleep duration, daytime sleepiness, daytime napping, and chronotype. Summary statistics related to cognitive impairment were derived from five different GWAS, including the Social Science Genetic Association Consortium. The role of self-reported sleep trait phenotypes in the etiology of cognitive impairment was explored using inverse-variance weighted (IVW) tests, MR-Egger tests, and weighted medians, and sensitivity analyses were conducted to ensure robustness.

RESULTS

In the main IVW analysis, sleep duration (reaction time: β = -0.05, 95% CI -0.07 to -0.04, p = 1.93×10-12 ), daytime sleepiness (average cortical thickness: β = -0.12, 95% CI -0.22 to -0.02, p = 0.023), and daytime napping (fluid intelligence: β = -0.47, 95% CI -0.87 to -0.07, p = 0.021; hippocampal volume in Alzheimer's disease: β = -0.99, 95% CI -1.64 to -0.35, p = 0.002) were significantly negatively correlated with cognitive performance. However, any effects of insomnia and chronotype on cognitive impairment were not determined.

CONCLUSIONS

Our findings highlighted that focusing on sleep behaviors or distinct sleep patterns-particularly sleep duration, daytime sleepiness, and daytime napping, was a promising approach for preventing cognitive impairment. This study also shed light on risk factors for and potential early markers of cognitive impairment risk factors.

Structural validity of nursing diagnosis insomnia in older adults of a community center

PURPOSE

Insomnia is an important sleep disorder in older persons. Conceptual analysis studies on this nursing diagnosis have been developed, but the diagnostic accuracy has not been verified. This study aimed to verify the diagnostic accuracy of the nursing diagnosis of Insomnia (00095) in older adults in a community center in Brazil.

METHODS

A validation study for diagnostic accuracy of the defining characteristics of the nursing diagnosis Insomnia. Data were collected through telephone interviews with 90 participants. Latent class analysis was used to verify the sensitivity and specificity of the defining characteristics. Poisson regression was used to assess the prevalence of the association of factors related to the nursing diagnosis of insomnia.

FINDINGS

A 47.42% prevalence of insomnia in the sample was identified. Defining characteristics such as expresses dissatisfaction with sleep and nonrestorative sleep-wake cycle showed the best accuracy values for insomnia, with a specificity of 0.92 (0.78-1.00) and 0.89 (0.74-1.00), respectively. Related factors such as stressors and frequent naps during the day were more likely to develop insomnia in individuals.

CONCLUSIONS

This study indicates diagnostic accuracy of nursing diagnosis of insomnia in community-dwelling older people from a community center. The findings highlighted the importance of the defining characteristics of nursing diagnosis insomnia and its main related factors contributing to accurate diagnostic identification.

IMPLICATIONS FOR NURSING PRACTICE

This study can contribute to providing objective clinical indicators of insomnia in the older population to guide nurses in early diagnostic confirmation for the selection of health interventions. In addition, it can be a consistent contribution to theoretical and conceptual reviews of this diagnosis.

An explainable machine learning based prediction model for Alzheimer's disease in China longitudinal aging study

Alzheimer's disease (AD) is the most common cause of dementia. Accurate prediction and diagnosis of AD and its prodromal stage, i.e., mild cognitive impairment (MCI), is essential for the possible delay and early treatment for the disease. In this paper, we adopt the data from the China Longitudinal Aging Study (CLAS), which was launched in 2011, and includes a joint effort of 15 institutions all over the country. Four thousand four hundred and eleven people who are at least 60 years old participated in the project, where 3,514 people completed the baseline survey. The survey collected data including demographic information, daily lifestyle, medical history, and routine physical examination. In particular, we employ ensemble learning and feature selection methods to develop an explainable prediction model for AD and MCI. Five feature selection methods and nine machine learning classifiers are applied for comparison to find the most dominant features on AD/MCI prediction. The resulting model achieves accuracy of 89.2%, sensitivity of 87.7%, and specificity of 90.7% for MCI prediction, and accuracy of 99.2%, sensitivity of 99.7%, and specificity of 98.7% for AD prediction. We further utilize the SHapley Additive exPlanations (SHAP) algorithm to visualize the specific contribution of each feature to AD/MCI prediction at both global and individual levels. Consequently, our model not only provides the prediction outcome, but also helps to understand the relationship between lifestyle/physical disease history and cognitive function, and enables clinicians to make appropriate recommendations for the elderly. Therefore, our approach provides a new perspective for the design of a computer-aided diagnosis system for AD and MCI, and has potential high clinical application value.

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.

Contactless and longitudinal monitoring of nocturnal sleep and daytime naps in older men and women: a digital health technology evaluation study

STUDY OBJECTIVES

To compare the 24-hour sleep assessment capabilities of two contactless sleep technologies (CSTs) to actigraphy in community-dwelling older adults.

METHODS

We collected 7-14 days of data at home from 35 older adults (age: 65-83), some with medical conditions, using Withings Sleep Analyser (WSA, n = 29), Emfit QS (Emfit, n = 17), a standard actigraphy device (Actiwatch Spectrum [AWS, n = 34]), and a sleep diary (n = 35). We compared nocturnal and daytime sleep measures estimated by the CSTs and actigraphy without sleep diary information (AWS-A) against sleep-diary-assisted actigraphy (AWS|SD).

RESULTS

Compared to sleep diary, both CSTs accurately determined the timing of nocturnal sleep (intraclass correlation [ICC]: going to bed, getting out of bed, time in bed >0.75), whereas the accuracy of AWS-A was much lower. Compared to AWS|SD, the CSTs overestimated nocturnal total sleep time (WSA: +92.71 ± 81.16 minutes; Emfit: +101.47 ± 75.95 minutes) as did AWS-A (+46.95 ± 67.26 minutes). The CSTs overestimated sleep efficiency (WSA: +9.19% ± 14.26%; Emfit: +9.41% ± 11.05%), whereas AWS-A estimate (-2.38% ± 10.06%) was accurate. About 65% (n = 23) of participants reported daytime naps either in bed or elsewhere. About 90% in-bed nap periods were accurately determined by WSA while Emfit was less accurate. All three devices estimated 24-hour sleep duration with an error of ≈10% compared to the sleep diary.

CONCLUSIONS

CSTs accurately capture the timing of in-bed nocturnal sleep periods without the need for sleep diary information. However, improvements are needed in assessing parameters such as total sleep time, sleep efficiency, and naps before these CSTs can be fully utilized in field settings.

Daytime Napping and Cognitive Health in Older Adults: A Systematic Review

BACKGROUND

Daytime napping may improve cognitive function in older adults. However, the association can be complicated by specific features of napping and the older adult's health. This systematic review aims to synthesize the current literature on napping and cognition in older adults and provide recommendations for future research and daytime sleep practice in older adults.

METHODS

Systematic searches for relative research published between January 1995 and October 2022 were conducted at PubMed, MEDLINE, PsycINFO, and Google Scholar using keywords individually and in multiple combinations. Manual searches were performed to identify additional studies. All included studies were critically appraised by 2 authors.

RESULTS

Thirty-five studies, including 23 observational and 12 intervention studies, were reviewed. Findings from observational studies suggest a possible inverted U-shaped association between napping duration and cognitive function: short and moderate duration of naps benefited cognitive health in older adults compared with both non-napping and long or extended napping. Findings from intervention studies suggest one session of afternoon napping might improve psychomotor function and working memory, although with some inconsistency. The effect of multiple nap sessions on cognition was inconclusive due to a limited number of studies.

CONCLUSION

More rigorous research studies are needed to investigate what causes different patterns of daytime napping, the associations between these distinct patterns and cognitive function, and to determine whether interventions targeting napping patterns can improve cognition in older adults. In addition, future research needs to comprehensively assess daytime napping using a combination of measures such as sleep diary and actigraphy.

Is there an association between daytime napping, cognitive function, and brain volume? A Mendelian randomization study in the UK Biobank

OBJECTIVES

Daytime napping has been associated with cognitive function and brain health in observational studies. However, it remains elusive whether these associations are causal. Using Mendelian randomization, we studied the relationship between habitual daytime napping and cognition and brain structure.

METHODS

Data were from UK Biobank (maximum n = 378,932 and mean age = 57 years). Our exposure (daytime napping) was instrumented using 92 previously identified genome-wide, independent genetic variants (single-nucleotide polymorphisms, SNPs). Our outcomes were total brain volume, hippocampal volume, reaction time, and visual memory. Inverse-variance weighted was implemented, with sensitivity analyses (Mendelian randomization-Egger and Weighted Median Estimator) for horizontal pleiotropy. We tested different daytime napping instruments to ensure the robustness of our results.

RESULTS

Using Mendelian randomization, we found an association between habitual daytime napping and larger total brain volume (unstandardized ß = 15.80 cm3 and 95% CI = 0.25; 31.34) but not hippocampal volume (ß = -0.03 cm3 and 95% CI = -0.13;0.06), reaction time (expß = 1.01 and 95% CI = 1.00;1.03), or visual memory (expß = 0.99 and 95% CI = 0.94;1.05). Additional analyses with 47 SNPs (adjusted for excessive daytime sleepiness), 86 SNPs (excluding sleep apnea), and 17 SNPs (no sample overlap with UK Biobank) were largely consistent with our main findings. No evidence of horizontal pleiotropy was found.

CONCLUSIONS

Our findings suggest a modest causal association between habitual daytime napping and larger total brain volume. Future studies could focus on the associations between napping and other cognitive or brain outcomes and replication of these findings using other datasets and methods.

Association of sleep behaviors, insulin resistance surrogates, and the risk of hypertension in Chinese adults with type 2 diabetes mellitus

Objective

Our aim was to evaluate the association between midday napping, combined sleep quality, and insulin resistance surrogates and the risk of hypertension in patients with type 2 diabetes mellitus (T2DM).

Methods

Data were collected using a standardized questionnaire. Binary logistic regression was performed to estimate the odds ratio (OR) and 95% confidence interval (CI) for the risk of hypertension. Systolic and diastolic blood pressure were grouped as categorical variables and unpaired two-sided Student's t-test and Spearman correlation analysis were performed to estimate the association between different blood pressure levels and insulin resistance surrogates.

Results

The overall prevalence rate of hypertension was 50%. Age (OR = 1.056, 95% CI:1.044-1.068), poor sleep quality (OR = 1.959, 95% CI:1.393-2.755), hyperlipidemia (OR = 1.821, 95% CI:1.462-2.369), family history of hypertension (OR = 2.811, 95% CI:2.261-3.495), and obesity (OR = 5.515, 95% CI:1.384-21.971) were significantly associated with an increased risk of hypertension. Midday napping for 1-30 min was negatively correlated with the risk of hypertension (OR = 0.534, 95% CI:0.305-0.936, P <0.05).

Conclusion

Poor sleep quality and obesity are independent risk factors for hypertension. Midday napping (1-30 min) is associated with a decreased risk of hypertension in patients with T2DM.

Positive association between weight-adjusted-waist index and dementia in the Chinese population with hypertension: a cross-sectional study

PURPOSE

The links between obesity and dementia remain equivocal. Therefore, this study aimed to explore the association between weight-adjusted waist index (WWI), a new anthropometric indicator reflecting obesity, and dementia in the Chinese population with hypertension.

METHODS

A total of 10,289 participants with hypertension were enrolled in this cross-sectional study, a subset of the China H-type hypertension registry study. WWI was calculated as waist circumference (WC) divided by the square root of bodyweight. Mini-mental state examination (MMSE) scale was performed to evaluate the cognitive function. According to educational background, different MMSE cut-off values were applied to define dementia: < 24 for participants with ≥ 7 years of education, < 20 for those with 1-6 years of education, and < 17 for illiterate participants. Multivariable linear regression and multivariable binary logistic regression analyses were conducted to assess the associations between WWI and MMSE and dementia, respectively.

RESULTS

Overall, the mean age was 63.7 ± 9.7 years, and 49.0% were males. Multivariate linear regression analyses showed that WWI was negatively associated with MMSE (β, -1.09; 95% confidence interval [CI]: -1.24, -0.94). Consistently, multivariable binary logistic regression analyses found a positive association between WWI and the risk of dementia (odds ratio [OR], 1.45; 95% CI: 1.35, 1.56). Compared with individuals in quartile 1 of WWI, the adjusted β and OR values of WWI for MMSE and dementia were -2.28 (95% CI: -2.62, -1.94) and 2.12 (95% CI: 1.81, 2.48), respectively. Results of smoothing curve fitting confirmed the linear association between WWI and MMSE and dementia. Subgroup analysis showed a stronger association between WWI and dementia in participants with hypertension with midday napping.

CONCLUSION

WWI was independently and positively associated with dementia among the population with hypertension, especially in those with midday napping. The data suggests that WWI may serve as a simple and effective tool for the assessment of the risk of dementia in clinical practice.

Hypothetical interventions on risk factors for depression among middle-aged and older community-dwellers in China: An application of the parametric g-formula in a longitudinal study

BACKGROUND

Sleep disturbances, frailty, and body pain are widespread in middle-aged and older adults with depression, and have been identified as depression risk factors. However, there is a scarcity of research on the benefits of sleep improvement, frailty amelioration, and pain management on incident depression.

METHODS

A total of 8895 respondents aged above 45 years were derived from the China Health and Retirement Longitudinal Study (CHARLS) between 2011 and 2018. The parametric g-formula was used to estimate the 7-year risks of depression under independent hypothetical interventions on nighttime sleep duration (NSD), daytime napping duration (DND), perceived sleep quality (PSQ), frailty, and pain, as well as their various combinations.

RESULTS

The observed depression risk was 41.77 %. The independent intervention on frailty was the most effective in lowering incident depression, with a risk ratio (RR) of 0.61 (95 % CI: 0.57-0.64), followed by PSQ (RR: 0.75, 95 % CI: 0.73-0.78), pain (RR: 0.90, 95 % CI: 0.87-0.91), and NSD (RR: 0.96, 95 % CI: 0.93-0.98). In subgroup analysis, intervention on NSD was more effective in men, PSQ was more effective in middle-aged individuals, and frailty and pain were more effective in older persons. The combined intervention of NSD, PSQ, frailty, and pain lowered the risk the greatest (RR: 0.35, 95 % CI: 0.32-0.37).

LIMITATIONS

Generalizing our results to other populations should be possible if they have the same distribution of effect modifiers and interference patterns because of the calculation principle of the parametric g-formula.

CONCLUSIONS

Interventions for sleep disturbances, frailty, and body pain can minimize the risk of depression.

Can afternoon napping protect against the negative effect of short or long sleep duration on cognitive function? A prospective study

OBJECTIVES

Afternoon napping has been found to be able to compensate for the negative health effects of less optimal nighttime sleep duration. Our study aimed to investigate whether napping can protect against the negative effects of short or long sleep duration on cognitive function among middle-aged and older adults.

METHODS

A total of 8107 participants (men, 53.19%) aged 45 and older from the China Health and Retirement Longitudinal Study were followed prospectively for 7 years. The primary outcome was cognitive function (episodic memory and mental status). Afternoon napping was categorized into three groups including non- (0 min), moderate (1-30 min) and long (>30 min) duration. Nighttime sleep was also categorized into three groups including short (<7 h), normal (7-8 h), and long (>8 h) duration. Linear mixed models were used with napping and sleep duration at baseline as predictors. Potential confounders including baseline cognitive function were adjusted.

RESULTS

Shorter sleep duration (B = -0.01, p = 0.048) was independently associated with a faster decline in episodic memory. For participants with shorter sleep duration, either non-napping (B = -0.03, p = 0.017) or longer napping (B = -0.04, p = 0.018) showed a significant decline of episodic memory. For participants with longer sleep duration, non-napping was associated with a significant decline of episodic memory (B = -0.07, p = 0.003).

CONCLUSIONS

This study found that moderate napping could protect against the negative effects of short or long sleep duration on episodic memory, which implied that middle-aged and older adults who have a less optimal sleep duration might benefit from moderate napping for their cognitive function.

Association of sleep with cognitive function during retirement transition: the Whitehall II study

STUDY OBJECTIVES

Sleep duration and difficulties have been shown to associate with cognitive function. This study examined how changes in sleep and in cognitive function are associated during retirement transition.

METHODS

The study population consisted of 2980 Whitehall II study participants, who retired during the follow-up, whose sleep was queried, and cognitive function measured (inductive reasoning and verbal memory) before and after retirement (follow-up 16 years). Using the last information on sleep before and the first after retirement, participants were categorized into constantly without (59%), increasing (13%), decreasing (11%), and constantly with (18%) sleep difficulties; and constantly short (26%), increasing (19%), decreasing (8.5%), and constantly mid-range (47%) sleep duration. Change in cognitive function during retirement transition was examined by sleep change groups using linear regression analyses with generalized estimating equations.

RESULTS

More pronounced decline in inductive reasoning during retirement transition was observed among participants with increasing sleep difficulties (-1.96, 95% CI -2.52 to -1.41) compared to those constantly without sleep difficulties (-1.25, 95% CI -1.52 to -0.98) and constantly with sleep difficulties (-1.26, 95% CI -1.75 to -0.92). Decreasing sleep difficulties (-0.64, 95% CI -0.86 to -0.43) were associated with a more pronounced decline in verbal memory when compared to constantly without sleep difficulties (-0.42, 95% CI -0.52 to -0.32) in post-retirement period. No statistically significant differences across sleep duration groups in cognitive function were observed.

CONCLUSIONS

Increasing and decreasing sleep difficulties may be associated with accelerated decline in cognitive function during retirement transition and post-retirement.

Daytime napping and Alzheimer's dementia: A potential bidirectional relationship

INTRODUCTION

Daytime napping is frequently seen in older adults. The longitudinal relationship between daytime napping and cognitive aging is unknown.

METHODS

Using data from 1401 participants of the Rush Memory and Aging Project, we examined the longitudinal change of daytime napping inferred objectively by actigraphy, and the association with incident Alzheimer's dementia during up to 14-year follow-up.

RESULTS

Older adults tended to nap longer and more frequently with aging, while the progression of Alzheimer's dementia accelerates this change by more than doubling the annual increases in nap duration/frequency. Longer and more frequent daytime naps were associated with higher risk of Alzheimer's dementia. Interestingly, more excessive (longer or more frequent) daytime napping was correlated with worse cognition a year later, and conversely, worse cognition was correlated with more excessive naps a year later.

DISCUSSION

Excessive daytime napping and Alzheimer's dementia may possess a bidirectional relationship or share common pathophysiological mechanisms.

Association of daytime napping frequency and schizophrenia: a bidirectional two-sample Mendelian randomization study

BACKGROUND

The bidirectional causal association between daytime napping frequency and schizophrenia is unclear.

METHODS

A bidirectional two-sample Mendelian randomization (MR) analysis was conducted with summary statistics of top genetic variants associated with daytime napping frequency and schizophrenia from genome-wide association studies (GWAS). The single nucleotide polymorphisms (SNPs) data of daytime napping frequency GWAS came from the UK Biobank (n = 452,633) and 23andMe study cohort (n = 541,333), while the schizophrenia GWAS came from the Psychiatric Genomics Consortium (PGC, 36,989 cases and 113,075 controls). The inverse variance weighted (IVW) analysis was the primary method, with the weighted median, MR-Robust Adjusted Profile Score (RAPS), Radial MR and MR-Pleiotropy Residual Sum Outlier (PRESSO) as sensitivity analysis.

RESULTS

The MR analysis showed a bidirectional causal relationship between more frequent daytime napping and the occurrence of schizophrenia, with the odds ratio (OR) for one-unit increase in napping category (never, sometimes, usually) on schizophrenia was 3.38 (95% confidence interval [CI]: 2.02-5.65, P = 3.58 × 10^-6), and the beta for the occurrence of schizophrenia on daytime napping frequency was 0.0112 (95%CI: 0.0060-0.0163, P = 2.04 × 10^-5). The sensitivity analysis obtained the same conclusions.

CONCLUSION

Our findings support the bidirectional causal association between more daytime napping frequency and schizophrenia, implying that daytime napping frequency is a potential intervention for the progression and treatment of schizophrenia.

Age differences in the association between sleep and Alzheimer's disease biomarkers in the EPAD cohort

Introduction

We aimed to determine the independent association between sleep quality and Alzheimer's disease (AD) biomarkers, and whether the associations differ with age.

Methods

We included 1240 individuals aged ≥50, without dementia from the European Prevention of Alzheimer's Disease v1500.0 dataset. Linear regression was used to examine Pittsburgh Sleep Quality Index (PSQI) scores against cerebrospinal fluid (CSF) phosphorylated tau/β-amyloid ratio (p-tau/Aβ42) for the entire sample and via age tertiles. Models controlled for demographic, clinical, genetic, vascular, and neuroimaging variables.

Results

For the youngest age tertile, shorter sleep duration and higher sleep efficiency were associated with greater p-tau/Aβ42 ratio. For the oldest tertile, longer sleep latency was associated with greater p-tau/Aβ42.

Discussion

Differential relationships between sleep and AD pathology depend on age. Short sleep duration and sleep efficiency are relevant in middle age whereas time taken to fall asleep is more closely linked to AD biomarkers in later life.

Highlights

This study shows age differences in the link between sleep and AD biomarkers.Shorter sleep was associated with greater p-tau/Aβ42 ratio in middle age.The association was independent of genetic, vascular, and neuroimaging markers of AD.

Napping and cognitive decline: a systematic review and meta-analysis of observational studies

BACKGROUND

No clear evidence is available for the influence of napping on cognitive function in older adults. This systematic review and meta-analysis aimed to elucidate the cross-sectional and longitudinal relationships between napping and cognitive function (global cognition and memory) and to explore whether some individual characteristics and sleep characteristics can modify this relationship.

METHODS

We systematically searched Medline (via PubMed), Web of Science, and Scopus. DerSimonian and Lair and Hartung-Knapp-Sidik-Jonkman random effects methods were used to compute pooled estimates of odds ratios (ORs) and their respective 95% confidence intervals (95% CIs) for the association of global cognition and memory with napping. The mean age, the night sleep time (hours), and the percentage of women, no nappers, and people in the less night-time sleep duration category were used for meta-regressions.

RESULTS

Twenty-five studies were included in this systematic review and meta-analysis, 18 cross-sectional and seven longitudinal studies, including 95,719 participants older than 60 years. The pooled ORs from the cross-sectional analyses were 1.03 (95% CI: 1.01 to 1.06) for global cognition and 1.06 (95%: 0.90 to 1.26) for memory. The pooled ORs from the longitudinal analyses were 1.00 (95% 0.85 to 1.18) for global cognition and 1.08 (95% 0.98 to 1.19) for memory. These associations were not modified by individual or sleep characteristics.

CONCLUSION

Our data confirm the absence of association between napping and global cognition and memory regardless of the characteristics of the population. This information might be considered when providing lifestyle recommendations to adults with and without cognitive complaints.

Afternoon Napping Durations in Chinese Population Over 60 Years Old: Longitudinal Associations With Cognitive Performance

Introduction

Previous studies indicated inconsistent associations between daytime napping and cognitive decline. This study aimed to examine the associations between self-reported changes in napping and longitudinal cognitive performance.

Methods

A national representative sample of 4,024 participants over 60 was obtained from the China Health and Retirement Longitudinal Study from 2011 to 2018. Afternoon napping and potential factors were collected by a questionnaire. Cognitive performance was assessed on three aspects. The generalized additive models and generalized estimating equations were used to examine relationships between daytime napping and longitudinal global cognition, and generalized linear models were used to examine the longitudinal associations between change in napping at four waves and cognition in wave 4.

Results

After controlling the potential confounders, participants with afternoon napping were significantly related to better global cognition than no nappers at baseline. A change from short napping to no/long napping was associated with worse cognitive performance (β = −2.593, P < 0.001). A move from no napping to short/long napping was also associated with lower cognition scores (β = −0.694, P < 0.001). For participants with moderate napping, a >30 min increase (β = −1.558, P < 0.001) in afternoon napping was associated with worse cognitive function in wave 4.

Conclusion

We observed that adults over 60 years old with napping <30 min per day may be at lower risk of cognitive decline. Change in napping, especially a move to extreme napping would be a risk marker underlying health conditions that impact cognition or go along with cognitive decline.

Association of daily sleep duration with the incident dementia by serum soluble TREM2 in a community

BACKGROUND

Little is known about the influence of serum level of soluble triggering receptor expressed on myeloid cells 2 (sTREM2), which is a soluble type of an innate immune receptor expressed on the microglia, on the association of the daily sleep duration with the risk of dementia.

METHODS

A total of 1230 Japanese community-residents aged 60 and older without dementia were followed prospectively for 10 years (2002-2012). Serum sTREM2 levels were divided into two groups using the median value (334.8 pg/ml). Self-reported daily sleep duration was grouped into three categories of <5.0, 5.0-7.9, and ≥8.0 h. A Cox proportional hazards model was used to estimate the hazard ratios (HRs) and their 95% confidence intervals (CIs) of daily sleep duration on the risk of dementia according to serum sTREM2 levels.

RESULTS

During the follow-up, 262 subjects developed dementia. In subjects with low serum sTREM2 levels, subjects with ≥8.0 h of daily sleep had a significantly greater risk of dementia (multivariable-adjusted HR 2.05 [95% CI 1.32-3.19]) than those with 5.0-7.9 h of daily sleep, but those with <5.0 h did not. In contrast, the risk of dementia increased significantly in subjects with both <5.0 (1.95 [1.03-3.68]) and ≥8.0 h of daily sleep (1.48 [1.06-2.07]) in the subjects with high serum sTREM2 levels.

CONCLUSIONS

The influence of daily sleep duration on risk of dementia differed according to serum sTREM2 levels in the older Japanese population. Short daily sleep may be associated with greater risk of dementia only in subjects with a high serum sTREM2 level.

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.

Memory-relevant nap sleep physiology in healthy and pathological aging

STUDY OBJECTIVES

Aging is associated with detrimental changes in sleep physiology, a process accelerated in Alzheimer's disease. Fine-tuned temporal interactions of non-rapid eye movement slow oscillations and spindles were shown to be particularly important for memory consolidation, and to deteriorate in healthy older adults. Whether this oscillatory interaction further decline in early stages of Alzheimer's disease such as mild cognitive impairment has not been investigated to date, but may have important therapeutic implications.

METHODS

Here, we assessed differences in sleep architecture and memory-relevant slow oscillation, sleep spindles and their functional coupling during a 90-min nap between healthy young and older adults, and in older patients with mild cognitive impairment. Furthermore, associations of nap-sleep characteristics with sleep-dependent memory performance change were evaluated.

RESULTS

We found significant differences between young and older healthy adults, and between young adults and patients with mild cognitive impairment, but not between healthy older adults and patients for several sleep metrics, including slow oscillation-spindle coupling. Moreover, sleep-dependent retention of verbal memories was significantly higher in young healthy adults versus older adults with and without mild cognitive impairment, but no difference between the two older groups was observed. Associations with sleep metrics were only found for pre-nap memory performances.

CONCLUSIONS

In conclusion, our results indicate changes in nap sleep physiology and sleep-related memory consolidation in older adults with and without mild cognitive impairment. Thus, interventions targeted at improving sleep physiology may help to reduce memory decline in both groups, but our study does not indicate additional benefits for patients with mild cognitive impairment.

CLINICAL TRAIL REGISTRATION

Effects of Brain Stimulation During Daytime Nap on Memory Consolidation in Younger, Healthy Subjects: https://clinicaltrials.gov/ct2/show/NCT01840865; NCT01840865. Effects of Brain Stimulation During a Daytime Nap on Memory Consolidation in Older Adults; https://clinicaltrials.gov/ct2/show/study/NCT01840839?term=01840839&draw=2&rank=1; NCT01840839. Effects of Brain Stimulation During a Daytime Nap on Memory Consolidation in Patients With Mild Cognitive Impairment; https://clinicaltrials.gov/ct2/show/NCT01782365?term=01782365&draw=2&rank=1; NCT01782365.

Is disrupted sleep a risk factor for Alzheimer's disease? Evidence from a two-sample Mendelian randomization analysis

Background

It is established that Alzheimer’s disease (AD) patients experience sleep disruption. However, it remains unknown whether disruption in the quantity, quality or timing of sleep is a risk factor for the onset of AD.

Methods

We used the largest published genome-wide association studies of self-reported and accelerometer-measured sleep traits (chronotype, duration, fragmentation, insomnia, daytime napping and daytime sleepiness), and AD. Mendelian randomization (MR) was used to estimate the causal effect of self-reported and accelerometer-measured sleep parameters on AD risk.

Results

Overall, there was little evidence to support a causal effect of sleep traits on AD risk. There was some suggestive evidence that self-reported daytime napping was associated with lower AD risk [odds ratio (OR): 0.70, 95% confidence interval (CI): 0.50–0.99). Some other sleep traits (accelerometer-measured ‘eveningness’ and sleep duration, and self-reported daytime sleepiness) had ORs of a similar magnitude to daytime napping, but were less precisely estimated.

Conclusions

Overall, we found very limited evidence to support a causal effect of sleep traits on AD risk. Our findings provide tentative evidence that daytime napping may reduce AD risk. Given that this is the first MR study of multiple self-report and objective sleep traits on AD risk, findings should be replicated using independent samples when such data become available.

Age-related losses in cardiac autonomic activity during a daytime nap

In healthy, young individuals, a reduction in cardiovascular output and a shift from sympathetic to parasympathetic (vagal) dominance is observed from wake into stages of nocturnal and daytime sleep. This cardiac autonomic profile, measured by heart rate variability (HRV), has been associated with significant benefits for cardiovascular health. Aging is associated with decreased nighttime sleep quality and lower parasympathetic activity during both sleep and resting. However, it is not known whether age-related dampening of HRV extends to daytime sleep, diminishing the cardiovascular benefits of naps in the elderly. Here, we investigated this question by comparing the autonomic activity profile between young and older healthy adults during a daytime nap and a similar period of wakefulness (quiet wake; QW). For each condition, from the electrocardiogram (ECG), we obtained beat-to-beat HRV intervals (RR), root mean square of successive differences between adjacent heart-beat-intervals (RMSSD), high-frequency (HF), low-frequency (LF) power, and total power (TP), HF normalized units (HFnu ), and the LF/HF ratio. As previously reported, young subjects showed a parasympathetic dominance during NREM, compared with REM, prenap rest, and WASO. Moreover, older, compared to younger, adults showed significantly lower vagally mediated HRV (measured by RMSSD, HF, HFnu ) during NREM. Interestingly, however, no age-related differences were detected during prenap rest or QW. Altogether, our findings suggest a sleep-specific reduction in parasympathetic modulation that is unique to NREM sleep in older adults.

Effects of nighttime sleep duration and sex on the association between siesta and hypertension

OBJECTIVE

To examine the association between siesta and hypertension by sex and nighttime sleep duration among Chinese adults aged ≥35 years in Yinzhou, Ningbo City.

METHODS

All data were obtained from physical examinations and structured questionnaires. A total of 44, 652 participants were included. Logistic regression models were applied to calculate odds ratios and 95% confidence intervals for the association between siesta and hypertension.

RESULTS

When compared with no siesta, siesta durations of 60∼89 min (OR = 1.10, 95% CI:1.04-1.17) and ≥90 min (OR = 1.21, 95% CI:1.08-1.36) were associated with higher risk of hypertension in women. But no significant association was observed in men. Siesta durations of 30∼59 min (OR = 1.09, 95% CI:1.00-1.19) and 60-89 min (OR = 1.10, 95% CI:1.05-1.16) were associated with hypertension in people with 6∼8 h sleep, and this association appeared seemingly stronger with ≥90 min siesta either in short (<6 h) sleepers (OR = 1.20, 95% CI: 0.99-1.47) or in long (>8 h) sleepers (OR = 1.29, 95% CI: 1.00-1.68). However, in short sleepers, 60∼89 min siesta seemed to be associated with decreased risk of hypertension (OR = 0.95, 95% CI: 0.85-1.06); while in long sleepers, the same range of siesta seemed to be associated with increased risk of hypertension (OR = 1.11, 95% CI: 0.93-1.34).

CONCLUSION

Long siesta was associated with increased risk of hypertension in women but not in men. Not too long siesta may be related to decreased risk of hypertension in short sleepers but not in people with adequate or even long sleep. These findings warrant further examination with prospective studies and laboratory investigations.

Daytime sleepiness and napping in nursing-home eligible community dwelling older adults: A mixed methods study

Objectives

To describe perceptions and beliefs about daytime sleepiness and napping along with subjective and objective daytime sleep characteristics in nursing-home eligible community dwelling older adults.

Methods

A mixed methods study; we conducted semi-structured interviews and measured sleep variables via Actigraphy, sleep diary, and Epworth Sleepiness Scale (ESS). Napping was defined as >10 minutes; anything less was considered dozing.

Results

Final sample (n = 40) was primarily female (85%), Black (100%), with a mean age of 72 ± 9.5 years. Few (25%) reported daytime sleepiness (ESS >10). However, average duration of napping per day was 33.1 ± 11.5 minutes with a nap frequency of 2.5 ± 1.5 naps.

Conclusion

Our sample napped frequently throughout the day, yet the majority reported no daytime sleepiness. These older adults did not always recognize napping or how much they napped.

Combined effect of three common lifestyle factors on cognitive impairment among older Chinese adults: a community-based, cross-sectional survey

AIM

Lifestyle factors may influence cognitive function. Therefore, we compared the risk of cognitive impairment (COI) of all possible combinations of three lifestyle factors-tea consumption, physical activity, and siesta (afternoon nap or rest)-to the absence of any of these lifestyle factors.

METHODS

This cross-sectional study consisted of 4579 community-dwelling Chinese individuals aged 60 years or older living in Suzhou. Among the subjects were 3634 participants with normal cognition and 945 who had been diagnosed with COI according to the Abbreviated Mental Test. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated with a multivariate-adjusted model by logistic regression.

RESULTS

Individually, tea consumption and physical activity significantly lowered the risk of COI to 0.66 (95%CI: 0.48-0.90) and 0.79 (95%CI: 0.65-0.96), respectively. In combination, physical activity and siesta reduced the risk of COI to the greatest extent (OR = 0.44, 95%CI: 0.31-0.64). Based on multivariate adjustment, almost all combinations of factors had a significant negative association with COI, but the combination of tea consumption and siesta had an irrelevant correlation with COI. All combinations of lifestyle factors had a lower OR than any single lifestyle factor among the correlations that were significant.

CONCLUSION

Based on our findings, engaging in physical activity in combination with either or both of the other lifestyle factors was associated with a lower OR of having COI than adhering on a single factor in elderly Chinese people.

Association between daytime napping duration and depression in middle-aged and elderly Chinese: evidence from the China Health and Retirement Longitudinal Study (CHARLS): A cross-sectional study in China

The effect of the afternoon napping duration on the risk of depression has not been well established, particularly with regard to sex and age differences. The present study examines the association between afternoon napping duration and depression stratified by sex and age among Chinese adults aged 45 years or older.The 2011 to 2012 survey of the China Health and Retirement Longitudinal Study was utilized, including 5746 participants. We conducted logistic regression with the overall sample and subjects stratified by sex and age.Elderly men with short napping (<30 minutes) had lower odds of having depression symptoms compared with those with no napping group (OR = 0.66, 95% CI = 0.44-0.97). In addition, the finding indicated that middle-aged women with long napping (≥90 min) had a marginally significant difference than those in reference, which showed a negative effect on depression (OR = 0.72, 95% CI = 0.51-1.01).Our findings revealed that extended daytime napping duration can decrease the risk of depression status among middle and elderly people. Moreover, relevant promotion measures should be adopted, such as a suitable rest environment and regular napping habits. The potential mechanism should be clarified by a longitudinal survey to examine the specific causality.

Napping in Older Adults: A Review of Current Literature

Purpose of Review

Daytime napping-frequently reported among older populations-has attracted increasing attention in geriatric research due to its association with multiple health conditions. This review aims to integrate the latest knowledge about napping in older adults to provide implications for future research.

Recent Findings

The prevalence of napping in older adults ranges from 20% to 60% in different studies, but has been consistently reported to be higher than in other age groups. Age-related changes in circadian rhythm and sleep patterns, cultural beliefs, chronic conditions, medications, and lifestyle changes contribute to the high prevalence of napping in older adults. Daytime napping has been associated with multiple health conditions in older adults. Naps of short duration (e.g., 30 minutes) are reported in adults with better health; naps with longer durations (e.g., >90 minutes) have been linked to adverse cardiovascular and diabetes outcomes, declining cognitive function, and increased mortality. Current evidence in the literature, however, is not enough for us to determine the exact role of napping in the health of older adults.

Summary

Longitudinal and interventional studies are needed to investigate the influence of napping and the critical parameters such as duration, timing, and frequency on health in older adults and the underlying mechanisms. A combination of objective and self-reported measurements of napping are recommended instead of self-reported data only.

Is Sleep Disruption a Cause or Consequence of Alzheimer's Disease? Reviewing Its Possible Role as a Biomarker

In recent years, the idea that sleep is critical for cognitive processing has gained strength. Alzheimer's disease (AD) is the most common form of dementia worldwide and presents a high prevalence of sleep disturbances. However, it is difficult to establish causal relations, since a vicious circle emerges between different aspects of the disease. Nowadays, we know that sleep is crucial to consolidate memory and to remove the excess of beta-amyloid and hyperphosphorilated tau accumulated in AD patients' brains. In this review, we discuss how sleep disturbances often precede in years some pathological traits, as well as cognitive decline, in AD. We describe the relevance of sleep to memory consolidation, focusing on changes in sleep patterns in AD in contrast to normal aging. We also analyze whether sleep alterations could be useful biomarkers to predict the risk of developing AD and we compile some sleep-related proposed biomarkers. The relevance of the analysis of the sleep microstructure is highlighted to detect specific oscillatory patterns that could be useful as AD biomarkers.

Longitudinal Association Between Sleep Duration and Depressive Symptoms in Chinese Elderly

AIM

This study aimed to evaluate the longitudinal association between sleep duration and depressive symptoms among the elderly in China.

METHODS

A data set from China Health and Retirement Longitudinal Study (CHARLS) in 2011, 2013 and 2015 was adopted with a total of 22,847 respondents aged ≥60-years-old. A linear regression analysis with generalized estimating equations was employed to examine the longitudinal associations between duration of total sleep, nighttime sleep and daytime nap, and depressive symptoms.

RESULTS

An extra hour of total sleep including nighttime sleep and daytime nap was associated with lower incidence of depressive symptoms among the elderly after adjusting all confounders (OR=0.83, 95% CI: 0.82-0.84). In addition, an extra hour of nighttime sleep (OR=0.82, 95% CI: 0.80-0.83) or daytime nap (OR=0.93, 95% CI: 0.89-0.97) was also negatively associated with depressive symptoms among the elderly. After controlling the total sleep time, an extra hour of nighttime sleep was negatively associated with depressive symptoms (OR=0.88, 95% CI: 0.84 to 0.92), while an extra hour of daytime nap displayed a positive association with depressive symptoms (OR=0.88, 95% CI: 0.84 to 0.92). Compared with the moderate nappers, only extended nappers had significantly higher incidence of depressive symptoms (OR=1.32, 95% CI: 1.19 to 1.45).

CONCLUSION

For the elderly in China, increasing their total sleep, nighttime sleep, and/or daytime nap duration would reduce the incidence of depressive symptoms. Moreover, after fixing the total sleep time, increasing nighttime sleep was more beneficial to the decrease of the incidence of depressive symptoms than daytime nap.

Sleep quality and cognitive impairment in older Chinese: Guangzhou Biobank Cohort Study

BACKGROUND

evidence concerning the relationship between sleep quality and cognitive impairment is limited and inconsistent.

OBJECTIVE

to examine the association of sleep quality with memory impairment and poor cognitive function in a large sample of older Chinese.

METHODS

15,246 participants aged 50+ years of the Guangzhou Biobank Cohort Study who attended the second physical examination from 2008 to 2012 were included. Sleep quality was assessed using Pittsburgh Sleep Quality Index (PSQI), and cognitive performance was assessed using both Delayed Word Recall Test (DWRT) and Mini-Mental State Examination (MMSE). Memory impairment was defined by DWRT score < 4 and poor cognitive function by MMSE score < 25.

RESULTS

after adjusting for potential confounders, lower habitual sleep efficiency was associated with a higher risk of memory impairment and poor cognitive function with a dose-response pattern (both P for trend <0.001). The adjusted odds ratio (OR, 95% confidence interval (CI)) for poor cognitive function in those with the sleep efficiency of 75-85%, 65-75% and <65%, versus ≥85%, was 1.31 (1.12-1.53), 1.41 (1.16-1.73) and 1.33 (1.09-1.63), respectively. No association of the global PSQI score with memory impairment or poor cognitive function was found.

CONCLUSIONS

in older Chinese people, lower habitual sleep efficiency was associated with a higher risk of memory impairment and poorer cognitive function.

Excessive daytime sleepiness and napping in cognitively normal adults: associations with subsequent amyloid deposition measured by PiB PET

Study Objectives

To determine the association of excessive daytime sleepiness (EDS) and napping with subsequent brain β-amyloid (Aβ) deposition in cognitively normal persons.

Methods

We studied 124 community-dwelling participants in the Baltimore Longitudinal Study of Aging Neuroimaging Substudy who completed self-report measures of EDS and napping at our study baseline and underwent [11C] Pittsburgh compound B positron emission tomography (PiB PET) scans of the brain, an average ±standard deviation of 15.7 ± 3.4 years later (range 6.9 to 24.6). Scans with a cortical distribution volume ratio of >1.06 were considered Aβ-positive.

Results

Participants were aged 60.1 ± 9.8 years (range 36.2 to 82.7) at study baseline; 24.4% had EDS and 28.5% napped. In unadjusted analyses, compared with participants without EDS, those with EDS had more than 3 times the odds of being Aβ+ at follow-up (odds ratio [OR] = 3.37, 95% confidence interval [CI]: 1.44, 7.90, p = 0.005), and 2.75 times the odds after adjustment for age, age2, sex, education, and body mass index (OR = 2.75, 95% CI: 1.09, 6.95, p = 0.033). There was a trend-level unadjusted association between napping and Aβ status (OR = 2.01, 95% CI: 0.90, 4.50, p = 0.091) that became nonsignificant after adjustment (OR = 1.86, 95% CI: 0.73, 4.75, p = 0.194).

Conclusions

EDS is associated with more than 2.5 times the odds of Aβ deposition an average of 15.7 years later. If common EDS causes (e.g., sleep-disordered breathing, insufficient sleep) are associated with temporally distal AD biomarkers, this could have important implications for AD prevention.

Prospective association between sleep-related factors and the trajectories of cognitive performance in the elderly Chinese population across a 5-year period cohort study

The integral role of sleep in cognition, such as night-time sleep and napping duration, has yielded mixed findings, especially in healthy elderly adults. This study aimed to identify the heterogeneous classes of the cognitive trajectories and investigated the associations between sleep parameters and the trajectories of cognition in different elderly subpopulations. The study was based on a large, national representative sample aged 60 years or older. Two cognitive measures were assessed, including executive function and episodic memory. Sleep parameters were evaluated, including post-lunch napping, night-time sleep duration, and sleep disturbances. Latent growth mixture model (LGMM) was used to describe the trajectories of cognition and investigate the effects of sleep factors on cognition. Three heterogeneous trajectories were identified for executive cognition and four for episodic memory. Inverted U-shape associations of cognition with night-time sleep and napping duration were found. In LGMM, night-time sleep duration was negatively associated with the baseline episodic memory in elderly adults. Post-lunch napping was positively associated with the baseline executive function (β = 0.078, P<0.05) and episodic memory (β = 0.084, P<0.05) in men, whereas it was only associated with impaired episodic memory (β = -0.152, P<0.05) in women. Frequent sleep disturbances were only associated with the impaired executive function at baseline (β = -0.088, 95%CI -0.162, -0.013) among older men. Overall, sleep parameters played different roles in heterogeneous trajectories of cognition by sex difference. Sleep factors may not be related to the rate of cognition decline, but these factors, independent of time-variant depressive symptoms, were associated with the initial status of cognition at baseline.

Sleep and β-Amyloid Deposition in Alzheimer Disease: Insights on Mechanisms and Possible Innovative Treatments

The growing interest in the preclinical stage of Alzheimer's disease (AD) led investigators to identify modifiable risk and predictive factors useful to design early intervention strategies. The preclinical stage of AD is characterized by β-amyloid (Aβ) aggregation into amyloid plaques and tau phosphorylation and aggregation into neurofibrillary tangles. There is a consensus on the importance of sleep within this context: the bidirectional relationship between sleep and AD pathology is supported by growing evidence that proved that the occurrence of sleep changes starting from the preclinical stage of AD, many years before the onset of cognitive decline. Hence, we review the most recent studies on sleep disturbances related to Aβ and the effects of sleep deprivation on Aβ accumulation in animal and human models. We also discuss evidence on the role of sleep in clearing the brain of toxic metabolic by-products, with original findings of the clearance activity of the glymphatic system stimulated by sleep. Furthermore, starting from new recent advances about the relationship between slow-wave sleep (SWS) and Aβ burden, we review the results of recent electroencephalographic (EEG) studies in order to clarify the possible role of SWS component disruption as a novel mechanistic pathway through which Aβ pathology may contribute to cognitive decline and, conversely, the eventual useful role of SWS in facilitating Aβ clearance. Finally, we discuss some promising innovative, effective, low-risk, non-invasive interventions, although empirical evidence on the efficacy of sleep interventions in improving the course of AD is at the very beginning.

Objective napping, cognitive decline, and risk of cognitive impairment in older men

INTRODUCTION

Little is known about the longitudinal association between napping and cognitive impairment in older adults.

METHODS

We used wrist actigraphy to measure naps in 2751 community-dwelling older men. Cognition was assessed repeatedly over 12 years, and clinically significant cognitive impairment was determined by physician diagnosis, Alzheimer's medication use or a significant cognitive decline.

RESULTS

After adjustment for all covariates, men with longer napping duration had greater cognitive decline and higher risk of cognitive impairment. Men who napped for ≥120 min/day (vs. <30 min/day) were 66% more likely to develop cognitive impairment (odds ratio = 1.66, 95% CI: 1.09-2.54) in 12 years. Further adjustment for nighttime sleep quality did not appreciably alter the results. The association between napping and cognitive impairment was more pronounced among those with higher sleep efficiency and average sleep duration.

DISCUSSION

Napping might be useful as an early marker of cognitive impairment in the elderly, and its cognitive effects may differ by nighttime sleep.

Modifiable Lifestyle Factors and Cognitive Function in Older People: A Cross-Sectional Observational Study

Background: The development of evidence-based interventions for delaying or preventing cognitive impairment is an important challenge. Most previous studies using self-report questionnaires face problems with reliability and consistency due to recall bias or misclassification among older people. Therefore, objective measurement of lifestyle components is needed to confirm the relationships between lifestyle factors and cognitive function. Aims: The current study examined the relationship between lifestyle factors collected with wearable sensors and cognitive function among community-dwelling older people using machine learning. Methods: In total, 855 participants (mean age: 73.8 years) wore a wristband sensor for 7.8 days on average every 3 months. Various lifestyle parameters were measured, including walking steps, conversation time, total sleep time (TST), sleep efficiency, time awake after sleep onset, awakening count, napping time, and heart rate. Random forest (RF) regression analysis was used to examine the relationships between total daily sensing data and Mini-Mental State Examination (MMSE) scores. Confounding factor analysis was conducted with models that were adjusted and unadjusted for demographic and vascular risk factors, and selected variables were assessed as risk and protective factors using partial dependence plots (PDPs). Results: Lifestyle data were collected for 31.3 ± 7.1 days per year using wristband sensors. RF regression analysis adjusted for age, gender, and education levels selected four variables, including number of walking steps, conversation time, TST, and heart rate. Moreover, walking steps, conversation time, and heart rate remained after RF regression analysis adjusted for demographic and vascular risk factors. Number of walking steps, conversation time, and heart rate were categorized as protective factors, whereas TST was categorized as a risk factor for cognitive function. Although PDPs of number of walking steps and heart rate revealed continuously increased MMSE scores, those of conversation time and TST and revealed that the tendency in the graph was reversed at the boundary of a particular threshold (321.1 min for conversation time, 434.1 min for TST). Conclusions: Lifestyle factors, such as physical activity, sleep, and social activity appear to be associated with cognitive function among older people. Physical activity and appropriate durations of sleep and conversation are important for cognitive function.

Who Take Naps? Self-Reported and Objectively Measured Napping in Very Old Women

Background

Despite the widespread belief that napping is common among older adults, little is known about the correlates of napping. We examined the prevalence and correlates of self-reported and objectively measured napping among very old women.

Methods

We studied 2,675 community-dwelling women (mean age 84.5 ± 3.7 years; range 79-96). Self-reported napping was defined as a report of regular napping for ≥1 hour per day. Individual objective naps were defined as ≥5 consecutive minutes of inactivity as measured by actigraphy and women were characterized as "objective nappers" if they had at least 60 minutes of naps per day.

Results

Seven percent of the women only had self-reported napping, 29% only had objective napping, and 14% met the criteria for both. Multinomial logistic regression showed that the independent correlates of "both subjective and objective napping" were age (per 5 year odds ratio [OR] = 1.59; 95% CI: 1.31-1.93), depressive symptoms (per SD of score, OR = 1.53; 1.32-1.77), obesity (OR =1.93; 1.42-2.61), current smoking (OR = 3.37; 1.56-7.30), heavier alcohol drinking (OR = 0.49; 0.34-0.71), history of stroke (OR = 1.56; 1.08-2.26), diabetes (OR = 2.40; 1.61-3.57), dementia (OR = 3.31; 1.27-8.62), and Parkinson's disease (OR = 7.43; 1.87-29.50). Besides, having objective napping alone was associated with age and diabetes, whereas subjective napping was associated with stroke and myocardial infarction. These associations were independent of nighttime sleep duration and fragmentation.

Conclusions

Daytime napping is very common in women living in their ninth decade and both subjective and objective napping were significantly related to age and comorbidities. Future studies are needed to better understand napping and its health implications.

Napping characteristics and cognitive performance in older adults

OBJECTIVES

To determine the association of napping intention, frequency, and duration with cognition in a nationally-representative sample of US older adults.

METHODS

We performed a cross-sectional analysis of community-dwelling Medicare beneficiaries aged ≥65 years from Rounds 3 or 4 (2013-2014) of the National Health and Aging Trends Study (N = 2549). Participants reported past-month napping intention (intentional/unintentional), napping frequency (rarely/never [non-nappers], some days [infrequent nappers], most days/every day [frequent nappers]), and average nap duration (we categorized as ≤30 minutes [short]; 31-60 minutes [moderate]; and > 60 minutes [long]). Cognitive outcomes were performance on immediate and delayed word recall tests (IWR and DWR, respectively), the Clock Drawing Test (CDT), and self-rated memory (score: 1[excellent]-5[very poor]).

RESULTS

After adjustment for potential confounders, unintentional nappers had poorer immediate word recall test performance than non-nappers (B = -0.23, P < 0.01) and intentional nappers (B = -0.26, P < 0.01). After further adjustment for daytime sleepiness, frequent nappers reported poorer self-rated memory than non-nappers (B = 0.14, P < 0.05). Compared with short nappers, long nappers had poorer IWR (B = -0.26, P < 0.05) and CDT scores (B = -0.17, P < 0.05). Except for the association of nap duration with IWR and CDT, these associations remained after excluding participants with dementia and/or proxy respondents. Among participants undiagnosed with dementia or proxies, moderate-duration naps were associated with better DWR than short naps (B = 0.24, P < 0.05). Neither napping intentionality nor frequency was associated with CDT performance.

CONCLUSIONS

Among older adults, distinct aspects of napping are associated with cognitive performance. Prospective research, with objective measures of napping, is needed to elucidate the link between napping and cognitive trajectories.

Sleep Physiology, Circadian Rhythms, Waking Performance and the Development of Sleep-Wake Therapeutics

Disturbances of the sleep-wake cycle are highly prevalent and diverse. The aetiology of some sleep disorders, such as circadian rhythm sleep-wake disorders, is understood at the conceptual level of the circadian and homeostatic regulation of sleep and in part at a mechanistic level. Other disorders such as insomnia are more difficult to relate to sleep regulatory mechanisms or sleep physiology. To further our understanding of sleep-wake disorders and the potential of novel therapeutics, we discuss recent findings on the neurobiology of sleep regulation and circadian rhythmicity and its relation with the subjective experience of sleep and the quality of wakefulness. Sleep continuity and to some extent REM sleep emerge as determinants of subjective sleep quality and waking performance. The effects of insufficient sleep primarily concern subjective and objective sleepiness as well as vigilant attention, whereas performance on higher cognitive functions appears to be better preserved albeit at the cost of increased effort. We discuss age-related, sex and other trait-like differences in sleep physiology and sleep need and compare the effects of existing pharmacological and non-pharmacological sleep- and wake-promoting treatments. Successful non-pharmacological approaches such as sleep restriction for insomnia and light and melatonin treatment for circadian rhythm sleep disorders target processes such as sleep homeostasis or circadian rhythmicity. Most pharmacological treatments of sleep disorders target specific signalling pathways with no well-established role in either sleep homeostasis or circadian rhythmicity. Pharmacological sleep therapeutics induce changes in sleep structure and the sleep EEG which are specific to the mechanism of action of the drug. Sleep- and wake-promoting therapeutics often induce residual effects on waking performance and sleep, respectively. The need for novel therapeutic approaches continues not at least because of the societal demand to sleep and be awake out of synchrony with the natural light-dark cycle, the high prevalence of sleep-wake disturbances in mental health disorders and in neurodegeneration. Novel approaches, which will provide a more comprehensive description of sleep and allow for large-scale sleep and circadian physiology studies in the home environment, hold promise for continued improvement of therapeutics for disturbances of sleep, circadian rhythms and waking performance.

Napping, functional capacity and satisfaction with life in older adults: A population-based study

AIM AND OBJECTIVE

To analyse the association between napping, functional capacity and satisfaction with life in older adult residing in the community.

METHOD

A cross-sectional population-based study using data from a health survey conducted in a city of the state of São Paulo. Information on sociodemographic and clinical variables was collected through a questionnaire, as well as the occurrence or not of napping and satisfaction with life. Functional capacity was assessed using the Katz Index and Lawton-Brody Scale. Statistical analysis was performed using the Rao-Scott chi-square test and a hierarchical analysis using stepwise backward multiple Poisson regression. p-Values <0.05 were considered significant. In this paper, we adhere to STrengthening the Reporting of OBservational studies in Epidemiology guidelines.

RESULTS

There was predominance of the 60-69 years age group (51.3%) and of females (60.8%). The majority of the older adults (57.5%), of both sexes, reported napping. A higher prevalence of napping was found in the older subjects, the male sex, the subjects without children, those with health problems and those that were partially dependent in instrumental activities of daily living.

CONCLUSIONS

The study showed that naps are prevalent in older adults. The need to identify the issues that permeate napping is emphasised, in order to promote health in individuals of this age group, before classifying the practice as beneficial or harmful.

RELEVANCE TO CLINICAL PRACTICE

It is essential that health professionals, in their practices, consider the complaints and reports of naps in the elderly, in an attempt to detect and reduce possible consequences in activities of daily living.

Psychological Interventions for Late-life Insomnia: Current and Emerging Science

Purpose of Review

Late-life insomnia is a serious medical condition associated with many untoward consequences. The high prevalence of late-life insomnia, along with the concomitant risks inherent in the use of hypnotic medications in older adults necessitates non-pharmacological (i.e., psychological) treatment options. We aim to summarize and evaluate the state-of-the-science of psychological treatment options for late-life insomnia.

Recent Findings

Cumulative scientific evidence suggests the efficacy of psychological treatment of late-life insomnia. During the previous decade, trials of psychological treatments for insomnia have begun to test various modifications to treatments that have the potential to improve access for older adults, along with expanding their focus to include individuals with comorbid conditions that are common to older adults. While these modifications represent positive advances in the science of treatment for late-life insomnia, the evidence is still largely explanatory/efficacious in nature.

Summary

Psychological strategies represent the best approaches for the treatment of late-life insomnia. Future investigations would be wise to progressively move towards increasingly pragmatic/effectiveness investigations, adding to the literature base regarding the treatment of late-life insomnia under usual/real-world conditions as opposed to ideal/artificial conditions.

Sleep quality as predictor of BMI in non-depressed caregivers of people with dementia

PURPOSE

Although most cross-sectional and longitudinal studies of children and adolescents have found a link between short duration of sleep and obesity, the literature related to adults provides a non-consensual framework. The aim of the present study was to examine the association between sleep quality and BMI in a population of caregivers looking after people suffering from dementia, with a view to identifying the moderating role of depressive symptoms in the relationship between sleep problems and BMI.

METHODS

A total of 117 subjects took part in the study, filling in a Sociodemographic Questionnaire, the Pittsburgh Sleep Quality Index, the Eating behavior Questionnaire and The Center for Epidemiologic Studies-Depression.

RESULTS

Depressive symptoms were greater in females than in males. The sample was divided into two subgroups based on depressive-symptom scores. Only within the subsample with low depressive symptoms, higher sleep disturbances influenced BMI positively. Within this subsample of participants with low depressive symptoms, the variables that seem to play a pivotal role in explaining a high BMI are: female gender, sleep problems, and diet quality, while within the subsample with high depressive symptoms only the female gender factor was found to influence BMI.

CONCLUSIONS

Depressive symptoms seem to act as moderators in the relationship between sleep and BMI. They should be evaluated to identify the risk of high BMI, and to differentiate clinical intervention, at least in this population, which experiences the stress of caregiving chronically, though not suffering from clinical eating disorders.

LEVEL OF EVIDENCE

Level II, cross-sectional study.

Advancing Research on Care Needs and Supportive Approaches for Persons With Dementia: Recommendations and Rationale

The first National Research Summit on Care, Services, and Supports for Persons with Dementia and Their Caregivers was held on October 16-17, 2017, at the National Institutes of Health. In this paper, participants from the Summit Session on Research on Care Needs and Supportive Approaches for Persons with Dementia summarize the state of the science, identify gaps in knowledge, and offer recommendations to improve science and practice in long-term care. Recommendations cover 4 areas focused on persons living with dementia: (1) symptoms (behavioral and psychological symptoms of dementia, function, cognition, and sleep); (2) dementia care settings (physical and social environments, home, and residential care); (3) living with dementia (living well with dementia, living alone with dementia, and living with dementia and intellectual and developmental disabilities); and (4) technology as a cross-cutting theme. The participants identify 10 of the most pressing research issues based on the findings from their collective papers. Final Summit recommendations included those presented by session participants and will be used to advise federal agencies and other organizations that fund research.

Napping Characteristics and Restricted Participation in Valued Activities Among Older Adults

Background

Napping is associated with both positive and negative health outcomes among older adults. However, the association between particular napping characteristics (eg, frequency, duration, and whether naps were intentional) and daytime function is unclear.

Methods

Participants were 2,739 community-dwelling Medicare beneficiaries aged ≥65 years from the nationally representative National Health and Aging Trends Study. Participants reported napping frequency, duration, and whether naps were intentional versus unintentional. Restricted participation in valued activities was measured by self-report.

Results

After adjusting for potential confounders and nighttime sleep duration, those who took intentional and unintentional naps had a greater odds of any valued activity restriction (ie, ≥1 valued activity restriction), compared to those who rarely/never napped (unintentional odds ratio [OR] = 1.34, 95% confidence interval [CI] 1.01, 1.79, intentional OR = 1.49, 95% CI 1.09, 2.04). There was no difference between unintentional napping and intentional napping with respect to any valued activity restriction after adjustment for demographics. Compared to participants napping "some days," those napping most days/every day had a greater odds of any valued activity restriction (OR = 1.68, 95% CI 1.30, 2.16). Moreover, each 30-minute increase in average nap duration was associated with a 25% greater odds of any valued activity restriction (OR = 1.25, 95% CI 1.10, 1.43).

Conclusion

Older adults who took more frequent or longer naps were more likely to report activity restrictions, as were those who took intentional or unintentional naps. Additional longitudinal studies with objective measures of sleep are needed to further our understanding of associations between napping characteristics and daytime dysfunction.

Caregiver-Reported Sleep Disturbances Are Associated With Behavioral and Psychological Symptoms in an Asian Elderly Cohort With Cognitive Impairment-No Dementia

OBJECTIVE

Sleep disturbances were found to be associated with more behavioral and psychological symptoms (BPS) in early patients with Alzheimer's disease (AD). However, data on preclinical stages of dementia are lacking. Hence, the present study sought to investigate the association between sleep disturbances and BPS in dementia-free elderly with varying severity of cognitive impairment in an Asian sample.

METHODS

Community-living elderly were recruited and administered a comprehensive cognitive battery (vascular dementia battery [VDB]) and the Neuropsychiatric Inventory to assess symptoms of sleep disturbances and BPS. Severity of cognitive impairment was diagnosed and classified as no cognitive impairment (NCI), cognitive impairment-no dementia (CIND) -mild (1-2 impaired domains on the VDB), and CIND-moderate (≥3 impaired domains on the VDB). Analysis of variance was conducted to assess the associations between the presence of sleep disturbances and BPS scores in each diagnostic group. Logistic regression was used to examine whether the coexistence of sleep disturbances and other BPS was associated with CIND-moderate, which is known to carry a higher risk of progression to AD.

RESULTS

Among 839 elderly, 79 (9.4%) reported sleep disturbances. Participants with sleep disturbances had higher total BPS burden than those without among CIND participants but not in NCIs. Furthermore, CIND-moderate participants with sleep disturbances had more delusions, hallucinations, anxiety, depression, irritability, aberrant motor behavior, and appetite change ( P < .05). The presence of both sleep disturbances and other BPS was associated with CIND-moderate (odds ratio: 2.5, 95% confidence interval: 1.1-5.5).

CONCLUSIONS

Sleep disturbances are associated with higher total BPS burden and specific BPS among elderly patients with cognitive impairment, particularly those with CIND moderate, which carries higher risk of developing dementia.