The interactive effects of nocturnal sleep and daytime naps in relation to serum C-reactive protein

Excessive Daytime Napping Increases the Risk of Non-Alcoholic Fatty Liver Disease: A Meta-Analysis and a Mendelian Randomization Study

Background

Prior research based on observations has furnished evidence that supports a connection between daytime napping and the prevalence of non-alcoholic fatty liver disease (NAFLD). Nevertheless, the question of whether this correlation is indicative of a causal link has not been definitively answered.

Methods

We used meta-analysis and Mendelian randomization (MR) to synthesize genetic and observational data. A two-sample MR analysis was conducted, leveraging 105 single-nucleotide polymorphisms (SNPs) known to be associated with daytime napping patterns. Additionally, summary-level data pertaining to NAFLD outcomes were acquired from the comprehensive UK Biobank study. Network meta-analyses were employed to investigate the relationship between excessive daytime napping and NAFLD, while subgroup was also performed.

Results

Significant associations were observed between daytime napping and NAFLD. The systematic review/meta-analysis uncovered a heightened risk of NAFLD development among individuals who engaged in daytime naps exceeding 30 minutes, when compared to those who did not nap(odds ratio [OR] = 1.32, 95% confidence interval [CI]: 1.05 to 1.66). Furthermore, MR analysis indicated that a genetic propensity towards longer daytime napping was significantly linked to an increased likelihood of NAFLD (OR = 2.26, 95% CI: 1.38 to 3.73).

Conclusion

Daytime napping has been found to be causally related to a higher risk of NAFLD. Furthermore, across all participants, napping for an average duration over 30 minutes was linked to an elevated likelihood of NAFLD.

Association between sleep patterns and galectin-3 in a Chinese community population

BACKGROUND

Irregular sleep patterns have been associated with inflammation. Galectin-3, a novel biomarker, plays an important role in inflammation. We investigated the relationship between sleep patterns and galectin-3 in a Chinese population.

METHODS

A total of 1,058 participants from the Shenzhen-Hong Kong United Network on Cardiovascular Disease study were included in the analysis. Age and sex-adjusted linear regression models were employed to investigate the relationship between galectin-3 level and traditional metabolic biomarkers. Logistic regression models were used to estimate the association among sleep disturbance, nighttime sleep duration, and daytime napping duration and elevated galectin-3, with elevated galectin-3 defined as galectin-3 level > 65.1 ng/ml.

RESULTS

Of study participants, the mean age was 45.3 years and 54.3% were women. Waist circumference, natural logarithm (ln)-transformed triglyceride, and ln-transformed high sensitivity C-reactive protein were positively associated with galectin-3 level (age and sex-adjusted standardized β [95% confidence interval (CI)], 0.12 [0.04, 0.21], 0.11 [0.05, 0.17], and 0.08 [0.02, 0.14], respectively). Sleep disturbance was associated with elevated galectin-3 (odds ratio [95% CI], 1.68 [1.05, 2.68], compared to those without sleep disturbance) after adjusting for traditional metabolic biomarkers. No interaction was observed between galectin-3 and age, sex, obesity, hypertension, and diabetes on sleep disturbance. No association was found between nighttime sleep duration or daytime napping duration and elevated galectin-3.

CONCLUSIONS

Our study provides evidence of a significant association between sleep disturbance and elevated galectin-3 level, independent of traditional metabolic biomarkers. Screening and interventions on galectin-3 could assist in preventing sleep disturbance-induced inflammatory disease.

Association between napping and type 2 diabetes mellitus

As the incidence of type 2 diabetes mellitus (T2DM) is increasing rapidly and its consequences are severe, effective intervention and prevention, including sleep-related interventions, are urgently needed. As a component of sleep architecture, naps, alone or in combination with nocturnal sleep, may influence the onset and progression of T2DM. Overall, napping is associated with an increased risk of T2DM in women, especially in postmenopausal White women. Our study showed that napping >30 minutes (min) increased the risk of T2DM by 8-21%. In addition, non-optimal nighttime sleep increases T2DM risk, and this effect combines with the effect of napping. For nondiabetic patients, napping >30 min could increase the risks of high HbA1c levels and impaired fasting glucose (IFG), which would increase the risk of developing T2DM later on. For diabetic patients, prolonged napping may further impair glycemic control and increase the risk of developing diabetic complications (e.g., diabetic nephropathy) in the distant future. The following three mechanisms are suggested as interpretations for the association between napping and T2DM. First, napping >30 min increases the levels of important inflammatory factors, including interleukin 6 and C-reactive protein, elevating the risks of inflammation, associated adiposity and T2DM. Second, the interaction between postmenopausal hormonal changes and napping further increases insulin resistance. Third, prolonged napping may also affect melatonin secretion by interfering with nighttime sleep, leading to circadian rhythm disruption and further increasing the risk of T2DM. This review summarizes the existing evidence on the effect of napping on T2DM and provides detailed information for future T2DM intervention and prevention strategies that address napping.

Association of daytime napping with incidence of chronic kidney disease and end-stage kidney disease: A prospective observational study

BACKGROUND AND AIMS

Few studies have examined the relationship between daytime napping and risk of kidney diseases. We aimed to investigate the association of daytime napping with the incidence of chronic kidney disease (CKD) and end-stage kidney disease (ESKD). We also examined whether sleep duration modified the association of nap with CKD or ESKD.

METHODS

We recruited 460,571 European middle- to older-aged adults without prior CKD or ESKD between March 13, 2006, and October 1, 2010, in the UK Biobank. Sleep behavior data were obtained through questionnaires administered during recruitment. The analysis of the relationship between napping and the occurrence of CKD and ESKD utilized Cox proportional hazards regression models. The modification role of sleep duration on the effect of nap on CKD and ESKD was also examined.

RESULTS

After a mean follow-up of 11.1 (standard deviation 2.2) years, we observed 28,330 incident CKD cases and 927 ESKD cases. The daytime napping was associated with incident CKD (P for trend = .004). After fully adjusted, when compared with participants who did not take nap, those in sometimes and usually nap groups had higher risk of CKD. Nevertheless, the available evidence did not support a link between daytime napping and ESKD (P for trend = .06). Simultaneously, there was insufficient evidence suggesting that sleeping duration modified the association of daytime napping with incident CKD or ESKD.

CONCLUSION

Daytime napping was associated with an increased risk of CKD. However, the absence of conclusive evidence did not indicate a connection between daytime napping and ESKD.

Association of daytime napping and nighttime sleep with all-cause mortality: A prospective cohort study of China Health and Retirement Longitudinal Study

STUDY OBJECTIVES

The correlation of daytime napping and nighttime sleep duration on mortality was inconsistent. We aimed to explore their separate links to all-cause/premature mortality, and evaluate their combined impact on all-cause mortality risk.

METHODS

All of 20617 (mean age: 56.90 ± 10.19, 52.18 % females) participants from China Health and Retirement Longitudinal Study were followed for a median of 7 years (interquartile range: 4-7) to detect death status. Baseline self-reported napping and sleep duration was categorized: napping as none, <60 min, 60-90 min, and ≥90 min, sleep as <6 h/night, 6-8 h/night, and ≥8 h/night. Death event was tracked, and premature death was defined using 2015 China's average life expectancy (73.64 years for men, and 79.43 years for women). Cox regression models analyzed the data.

RESULTS

During follow-up, 1621 participants (7.86 %) died, including 985 (4.78 %) premature deaths. Compared to none nappers, napping ≥90 min associated with a higher risk of all-cause mortality (Hazard ratio, [HR] 1.23, 95 % confidence interval [CI] 1.06-1.42) and premature mortality (HR 1.23, 95 % CI 1.02-1.49), while napping <60 min correlated with a lower risk of premature mortality (HR 0.71, 95 % CI 0.54-0.95), after adjustment. Compared to sleep 6-8 h/night, nighttime sleep ≥8 h was associated with an increased risk of all-cause mortality (HR 1.20, 95 % CI 1.04-1.37) and premature mortality (HR 1.28, 95 % CI 1.08-1.52). Participants napping ≥90 min and sleeping ≥8 h had a multi-adjusted HR (95%CI) of 1.50 (95 % CI 1.17-1.92) for all-cause mortality, versus no napping and 6-8 h/night sleep.

CONCLUSIONS

Prolonged napping and extended nighttime sleep linked to increased mortality risk, particularly in combination. Optimizing sleep patterns may have potential implication in mortality prevention.

Physical activity and sleep relate to antibody maintenance following naturalistic infection and/or vaccination in older adults

Health behaviours such as being physically active and having good quality sleep have been associated with decreased susceptibility to infection and stronger antibody responses to vaccination. Less is known about how such factors might influence the maintenance of immunity following naturalistic infection and/or prior vaccination, particularly among older adults who may have formed initial antibodies some time ago. This analysis explored antibody levels against a range of common infectious diseases in 104 older adults (60 women) aged 65+ years, and whether these relate to self-reported physical activity (PA) and sleep. PA and sleep were measured subjectively through standardized questions. Antibody levels to a range of common pathogens, including pneumococcal (Pn) and meningococcal (Men) serotypes, Haemophilus influenza type b, diphtheria, and tetanus were assayed using Multiplex technology. Higher PA at baseline related to higher antibody levels against three Pn serotypes and MenY, and higher PA at one month with higher levels against six Pn serotypes. Longer time in bed related to higher antibody levels against Pn4, and longer sleep related to higher levels against Pn19f. More difficulty staying awake in the day related to lower antibodies against Pn19a, Pn19f, MenA and MenY, and more frequent daytime napping related to lower levels against three Pn serotypes and MenY. Using clinically protective antibody thresholds as an outcome showed similar results for PA, but effects for sleep became non-significant, with the exception of time in bed. This extends beyond existing literature demonstrating associations between PA and sleep and peak antibody response to vaccination to antibody maintenance. Longitudinal research with objective measures of health behaviours is warranted.

Daytime naps and depression risk: A meta-analysis of observational studies

Background

The relationship between daytime napping and depression remains debatable. Thus, a meta-analysis in this study was conducted to evaluate the relationship between daytime napping and depression.

Methods

The PubMed, Embase, Web of Science, and China National Knowledge Infrastructure databases were searched up to February 2022, and the reference lists of the included studies were also retrieved. A random-effects model was used to estimate the combined effect size.

Results

Nine studies with 649,111 participants were included in the final analysis. The pooled odds ratio (OR) was 1.15 (95% confidence interval: 1.01-1.31) with a significant heterogeneity (I ² = 91.3%, P for heterogeneity <0.001), and the results demonstrated an increased risk of depressive symptoms among daytime nappers. Visual inspection of the funnel plot and Egger's and Begg's tests identified no obvious evidence of publication bias.

Conclusion

This meta-analysis indicates that daytime naps are a predictor of depression. The effects of daytime napping on depression may vary depending on the characteristics of people, the pattern of naps, and the individual's sleep experience. The findings may have significant implications for future research on depression.

Sleep duration prior to an enterotoxigenic Escherichia coli challenge predicts diarrhea severity during infection

BACKGROUND

Acute diarrhea is the most frequent diagnosis among ill travelers. Sleep loss may weaken the body's defense against pathogens and increase susceptibility to infection. The relationship between sleep and infectious diarrhea has not been studied and was assessed utilizing data from a controlled human infection model (CHIM) for enterotoxigenic Escherichia coli (ETEC).

METHODS

During a CHIM assessing the efficacy of an immunoprophylactic targeting ETEC against moderate-to-severe diarrhea (MSD) following challenge, we measured sleep via actigraphy over an 8-day inpatient period. We hypothesized better sleep pre-challenge would predict illness symptomatology following challenge.

RESULTS

Among 57 participants (aged 34.4 ± 8.1 years, 64% male), there was no relationship between sleep metrics and incidence of MSD. However, longer total sleep time the night preceding ETEC challenge was associated with lower maximum 24 h diarrhea volume (B = -1.80, p = 0.01) and total diarrhea volume (B = -2.45, p = 0.01).

CONCLUSIONS

This novel study showed that shorter sleep duration predicted diarrhea severity over the course of an ETEC infection. Future work should experimentally manipulate sleep to further clarify its impact on diarrhea-related outcomes for ETEC and other important enteric pathogens.

Daytime napping and cardiovascular risk factors, cardiovascular disease, and mortality: A systematic review

Associations between night sleep duration and cardiovascular risk factors in adults have been well documented. However, the associations for daytime napping remain unclear. In this review, six databases were searched for eligible publications to April 8, 2022. A total of 11 articles were identified for umbrella review on the association of daytime napping with diabetes, metabolic syndrome (MetS), cardiovascular disease (CVD), and mortality in adults, 97 for systematic review on the association with CVD and several CVD risk factors. Our umbrella review showed that the associations of daytime napping with diabetes, MetS, CVD, and mortality in most meta-analyses were mainly supported by weak or suggestive evidence. Our systematic review showed that long daytime napping (≥1 h/d) was associated with higher odds of several CVD risk factors, CVD, and mortality, but no significant association was found between short daytime napping and most of the abovementioned outcomes. Our dose-response meta-analyses showed that daytime napping <30 min/d was not significantly associated with higher odds of most CVD risk factors and CVD among young and middle-aged adults. However, among older adults aged >60 years, we observed significant dose-response associations of daytime napping with higher odds of diabetes, dyslipidemia, MetS, and mortality starting from 0 min/d.

Snoring and napping independently increased the serum uric acid levels and hyperuricemia risk: The Henan Rural Cohort Study

BACKGROUND AND AIMS

Evidence on the association of snoring, daily sleep duration (daytime napping and night sleep duration) with hyperuricemia (HUA) was limited, especially in the resources-poor areas. This study aimed to investigate the independent effect of snoring frequency and daily sleep duration on HUA prevalence in rural Chinese adults.

METHODS AND RESULTS

29,643 participants aged 18-79 years were included in the final cross-sectional analysis from the Henan Rural Cohort Study. Multivariate logistic regression and linear regression models with HUA and serum uric acid (SUA) levels as dependent variables were conducted, respectively. Of the 29,643 included adults, 3498 suffered from HUA. Compared to never snoring, the adjusted odds ratio (OR) and 95% confidence interval (CI) of HUA for rare snoring, occasional snoring, and habitual snoring were 1.35 (1.17, 1.56), 1.30 (1.14, 1.47), and 1.59 (1.47, 1.73), respectively (P for trend <0.001). Compared with no napping, participants who had daytime napping of 61-90 and > 91 min were associated with a 29% and 30% increase in the prevalence of HUA, respectively (P for trend <0.001). But in night sleep duration groups, no significant associations were observed. The positive associations between snoring and HUA were attenuated in people aged ≥65 and people with type 2 diabetes mellitus (both P for interaction <0.05).

CONCLUSION

Habitual snoring or longer daytime napping was independently associated with increased HUA prevalence and SUA levels in rural Chinese adults, which indicates the significance of early intervention and treatment of snoring and longer daytime napping to prevent hyperuricemia.

Performance, muscle damage, and inflammatory responses to repeated high-intensity exercise following a 40-min nap

The purpose of this study was to examine the effect of a 40-min nap opportunity (N40) on performance during, markers of muscle damage and inflammation, and the perception of fatigue and recovery, in response to a 5-m shuttle run test (5msrt). Fifteen male amateur athletes performed the 5msrt under two conditions: N40 and no-nap condition (NN). Blood biomarkers were collected at rest and after the 5msrt to measure muscle damage (i.e., creatinine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (ASAT), and alanine aminotransferase (ALAT)) and inflammation (i.e., C-reactive protein (CRP)). RPE was determined immediately after each repetition of the test and PRS and DOMS were determined 5 min, thereafter. Compared to NN, N40 improved the highest distance (p<0.001, Δ=+7.9%) and the total distance (p<0.001, Δ=+7.2%) attained during the 5msrt. Pre and post the 5msrt, participants presented lower muscle damage (i.e., CK, LDH, ASAT and ALAT) and inflammation (i.e., CRP) (p<0.05) values in the N40 compared to NN. Concerning RPE, DOMS, and PRS, there was a positive effect in the N40 vs. NN (p<0.01). N40 represents an effective method for improving repeated high intensity short-term maximal performance, PRS, and associated muscle damage and inflammation, and reducing RPE and DOMS.

Sleep Characteristics and Cognitive Function in Older Adults Without Dementia: The CABLE Study

BACKGROUND

The associations between sleep characteristics and cognition are complicated. Alzheimer's disease (AD) pathologies have been proven to be associated with sleep characteristics.

OBJECTIVE

We aimed to investigate the associations between sleep characteristics and cognitive function and examine the roles of AD pathologies in modulating the association of sleep duration with cognition.

METHODS

A total of 974 participants who had measurements of cerebrospinal fluid (CSF) amyloid-β (Aβ), phosphorylated tau (P-tau), total tau proteins (T-tau), cognitive function, and sleep characteristics were included from the Chinese Alzheimer's Biomarker and Lifestyle (CABLE) study. Linear regression analyses were utilized to explore the associations of sleep characteristics with cognition. Non-linear regression analyses were utilized to explore the associations of sleep habits with cognition. Causal mediation analyses were conducted to explore the mediation effects of AD pathologies on cognition.

RESULTS

The Pittsburgh Sleep Quality Index (PSQI) total score was significantly negatively correlated with Montreal Cognitive Assessment (MoCA) score (p = 0.0176). Long latency (p = 0.0054) and low efficiency (p = 0.0273) were associated with cognitive impairment. Habitual nap behavior was associated with lower MoCA scores (p = 0.0045). U-shaped associations were observed between sleep habits (bedtime and nocturnal sleep duration) and cognition. A causal mediation analysis indicated that P-tau/Aβ42 mediated the association of sleep duration with cognition.

CONCLUSION

These findings showed sleep characteristics were associated with cognitive functions. Sleep habits (duration, bedtime) had U-shaped associations with cognition. AD core pathologies might partially mediate the influence of sleep duration on cognitive impairments.

Association of changes in self-reported sleep duration with mild cognitive impairment in the elderly: a longitudinal study

As a symptomatic predementia stage with progressive cognitive decline, mild cognitive impairment (MCI) is common with aging. How changes in self-reported sleep duration affect MCI risk in the older adults remains unclear. Participants aged ≥ 65 years and enrolled at least two waves in the Chinese Longitudinal Healthy Longevity Survey were included in present longitudinal study. Changes in sleep duration were calculated as the difference between two waves and categorized into five groups: decreased >2 h, decreased 0-2h, stable, increased 0-2 h, and increased >2 h. MCI was measured by the Chinese version of the Mini-Mental State Examination. Generalized estimating equation model and restricted cubic spline function was applied to investigate the association. Among 9,005 participants (mean age, 81.19 years; 4,391 male), 2,877 developed MCI. Comparing with individuals with stable sleep duration, MCI risk [odds ratio (95% confidence intervals)] was: 1.15 (0.99-1.34) for decreased >2 h, 0.99 (0.87-1.13) for decreased 0-2h, 1.09 (0.95-1.24) for increased 0-2 h, and 1.57 (1.36-1.81) for increased >2 h, respectively. Similar patterns were observed among subgroup analyses by sex, age, and sleep quality at baseline. For participants with long sleep duration at baseline (>8h), further increased >2 h was associated with higher MCI risk [2.23 (1.55-3.21)]. Either in the whole or subgroup population, a U-shaped association was observed (P_{non-linearity}<0.05). In conclusion, changes in self-reported sleep duration were associated with MCI risk in a U-shaped pattern. Strategies that shifting sleep duration into normal range and keeping it stable are essential to prevent MCI in clinical practice.

Role of Napping for Learning across the Lifespan

Purpose of review

Napping is a common behavior across age groups. While studies have shown a benefit of overnight sleep on memory consolidation, given differences in nap frequency, composition, and intent, it is important to consider whether naps serve a memory function across development and aging.

Recent findings

We review studies of the role of naps in declarative, emotional, and motor procedural memory consolidation across age groups. Recent findings in both developmental and aging populations find that naps benefit learning of many tasks but may require additional learning or sleep bouts compared to young adult populations. These studies have also identified variations in nap physiology based on the purpose of the nap, timing of the nap, or age.

Summary

These studies lend to our understanding of the function of sleep, and the potential for naps as an intervention for those with reduced nighttime sleep or learning impairments.

Peripheral white blood cell counts mediated the associations of sleep duration with atherosclerotic cardiovascular disease risk: a cross-sectional study of middle-aged and older Chinese

PURPOSE

To investigate the associations between sleep duration and atherosclerotic cardiovascular disease (ASCVD) risk and the potential mechanism.

METHODS

Overall, 24,471 subjects without ASCVD were included from Dongfeng-Tongji (DFTJ) cohort. Data collection included questionnaires and general medical examinations. We used logistic regression models and generalized linear models to examine the associations between sleep duration, peripheral white blood cell (WBC) counts, and 10-year ASCVD risk. Mediation analyses were further performed to assess the potential role of peripheral WBC counts in the associations between sleep duration and 10-year ASCVD risk.

RESULTS

Increased risk of 10-year ASCVD was observed as sleep duration extended. After adjusting for potential confounders, the odds ratios (ORs) and 95% confidence intervals (CIs) for the risk of 10-year ASCVD were 1.24 (1.11-1.38), 1.12 (1.03-1.22), and 1.21(1.08-1.36) for individuals with nighttime sleeping duration of ≥ 9 h, daytime napping duration of > 30 min, and daily sleep duration of ≥ 9 h, respectively. Peripheral WBC counts mediated 14.1%, 14.5%, and 12.6% in the associations of nighttime sleep duration of ≥ 9 h, daytime napping duration of > 30 min and daily sleep duration of ≥ 9 h with 10-year ASCVD risk, respectively.

CONCLUSIONS

Extended sleep durations are associated with the increased 10-year ASCVD risk, and the associations are partially mediated by peripheral WBC counts.

Relationship between afternoon napping and cognitive function in the ageing Chinese population

BACKGROUND

Several studies have shown that afternoon napping promotes cognitive function in the elderly; on the other hand, some studies have shown opposite results. This current study further examined the relationship between afternoon napping and cognitive function in the ageing Chinese population.

METHODS

A total of 2214 elderly were included (napping group: n=1534; non-napping group: n=680). They all received cognitive evaluations by the Beijing version of the Montreal Cognitive Assessment, the Mini-Mental State Examination, and the Chinese version of the Neuropsychological Test Battery. Among all the subjects, 739 elderly volunteered to take blood lipid tests.

RESULTS

Significant differences in cognitive function and blood lipids were observed between the napping and the non-napping groups. Afternoon napping was associated with better cognitive function including orientation, language, and memory in the present study. Subjects with the habit of afternoon napping also showed a higher level of triglyceride than the non-napping subjects.

CONCLUSION

The results demonstrated that afternoon napping was related to better cognitive function in the Chinese ageing population.

Sleep, Prospective Memory, and Immune Status among People Living with HIV

Background: Persons living with HIV (PLWH) frequently report sleep complaints, but objective measurements are still lacking regarding sleep continuity, total sleep time per 24 h, and the links with both prospective memory performance and HIV infection parameters. Methods: PLWH (n = 96) and control (n = 96) groups (balanced for gender and age) were monitored by 24h-actigraphy for at least seven consecutive days. The prospective memory performance was assessed through a naturalistic, activity-based task performed twice a day on the actigraph. Results: PLWH had greater sleep latency and worse sleep continuity (higher fragmentation index) for night-time sleep and longest daytime nap (mean duration of the longest nap). Comparable results were reported for the prospective memory task; better performance scores were associated with several sleep parameters in controls but not in PLWH. Finally, within the PLWH group, being a long sleeper per 24 h (total sleep time > 8 h including more and long daytime naps) was associated with a greater severity of the disease (lower CD4 nadir and more frequent history of AIDS-defining events). Conclusions: These findings indicate that PLWH have more fragmented sleep and that the severity of HIV infection is associated with increased sleep duration.

Association between weekend catch-up sleep and high-sensitivity C-reactive protein levels in adults: a population-based study

STUDY OBJECTIVES

To investigate the association between weekend catch-up sleep (WCS) and the levels of high-sensitivity C-reactive protein (hsCRP)-a serum inflammatory maker-in adults.

METHODS

Data of 5,506 adults aged 19 years or older were obtained from the nationwide cross-sectional Korea National Health and Nutrition Examination Surveys conducted in 2016. Serum hsCRP level, weekday and weekend sleep durations, and sociodemographic and health-related characteristics were assessed. Participants whose weekend sleep duration was more than 1 h longer than their weekday sleep duration were included in the WCS group. hsCRP level was categorized into quartiles (i.e. highest, middle-high, middle-low, and lowest). Obesity was defined by body mass index ≥ 25.0 kg/m2.

RESULTS

The WCS group included 1,901 participants (34.5%). In the logistic regression analysis controlling for all variables, adults in the WCS group were significantly less likely to show the highest hsCRP level (versus the lowest level) compared with those without WCS in the complete sample (adjusted odds ratio = 0.795, 95% confidence interval [CI] = 0.662 to 0.955). In a subgroup analysis, this association was significant only for those with weekday sleep duration of 6 h or lower. Longer WCS (≥3 h) was not associated with hsCRP levels. Non-obese people with WCS demonstrated a lower risk for high hsCRP levels, while there was no significant difference in obese people with WCS.

CONCLUSIONS

Our findings indicate that WCS may be beneficial for low-grade systemic inflammation in adults, particularly among those with shorter weekday sleep durations. WCS may also interact with obesity.

Mediation effect of platelet indices on the association of daytime nap duration with 10-year ASCVD risk

Daytime nap is associated with the risk of atherosclerotic cardiovascular disease (ASCVD). However, the contribution of platelet to the association of daytime nap with ASCVD remains unclear. We analyzed the mediation effect of abnormal platelet indices on the association between daytime nap and 10-year ASCVD risk. The participants of this study were 2445 adults aged 30 to 74 years without ASCVD from the baseline Wuhan residents (n = 3053) of the Wuhan-Zhuhai (WHZH) Cohort Study. Participants completed the questionnaire and physical examination (including blood pressure, height, weight, and blood biochemical indicators). We assessed the association of daytime nap or nocturnal sleep duration with 10-year ASCVD risk and mediation effects of platelet indices on the associations using generalized linear models (GLM). Individuals with daytime nap duration of 30 or 60 min had a 1.37- (95%CI: 1.05, 1.78) or 1.44- (95%CI: 1.17, 1.78) fold increased risk of 10-year ASCVD compared with non-nappers. As compared with non-nappers, MPV values or MPV/PLT ratio mediated 15.29% or 6.18% of the association of daytime nap duration of 30 min with 10-year ADCVD risk as well as 19.21% or 7.61% of the association of daytime nap duration of 60 min with 10-year ADCVD risk (all p < .05). Platelet might partially contribute to increased 10-year ASCVD risk in individuals with daytime nap duration of 30 or 60 min.

Sleep myths: an expert-led study to identify false beliefs about sleep that impinge upon population sleep health practices

INTRODUCTION

False beliefs about sleep can persist despite contradicting scientific evidence, potentially impairing population health. Identifying commonly held false beliefs lacking an evidence base ("myths") can inform efforts to promote population sleep health.

METHOD

We compiled a list of potential myths using Internet searches of popular press and scientific literature. We used a Delphi process with sleep experts (n = 10) from the fields of sleep medicine and research. Selection and refinement of myths by sleep experts proceeded in 3 phases, including focus groups (Phase 1); email-based feedback to edit, add, or remove myths (Phase 2); and closed-ended questionnaires (Phase 3) where experts rated myths on 2 dimensions, falseness and public health significance, using 5-point Likert scale from 1 ("not at all") to 5 ("extremely false").

RESULTS

The current study identified 20 sleep myths. Mean expert ratings of falseness ranged from 5.00 (SD = 0.00) for the statement "during sleep the brain is not active" to 2.50 (SD = 1.07) for the statement "sleeping in during the weekends is a good way to ensure you get adequate sleep." Mean responses to public health significance ranged from 4.63 (SD = 0.74) for debunking the statement that "many adults need only 5 or less hours of sleep for general health" to 1.71 (SD = 0.49) for the statement that "remembering your dreams is a sign of a good night's sleep."

CONCLUSION

The current study identified commonly held sleep myths that have a limited or questionable evidence base. Ratings provided by experts suggest areas that may benefit from public health education to correct myths and promote healthy sleep.

Impaired sleep quality is associated with concurrent elevations in inflammatory markers: are post-menopausal women at greater risk?

Abstract

Background

Chronic inflammation and impaired sleep increase the risk for cardiovascular disease. Menopausal women may be particularly at risk as a result of impaired sleep. The objective of the current investigation was to assess the relationship between poor sleep and C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and myeloperoxidase (MPO) in healthy non- and postmenopausal women and men.

Methods

A fasting blood draw was obtained from 122 healthy men and women (31 were postmenopausal). Higher scores on the Pittsburgh Sleep Quality Index (PSQI) were used to define poor sleep. Given the sample size and healthy nature of the sample, hierarchical linear regression analyses were performed on a composite inflammatory score involving CRP, IL-6, and TNF-α. Sex/menopausal group and PSQI were entered as predictors, and the interaction of the group by PSQI was entered stepwise. Analyses on MPO were performed separately.

Results

Sleep quality was associated with higher inflammatory activity (β = 0.272, P = 0.003), which remained significant (P = 0.046) after controlling for age, waist circumference, exercise times per week, and depressive symptoms. While in the same direction, sleep quality was not significantly associated with MPO. Dichotomizing sleep quality led to similar results.

Conclusion

Impaired sleep quality is independently associated with greater inflammation in healthy adult men and women. Despite an overall less favorable metabolic and inflammatory profile in postmenopausal women, impaired sleep did not emerge as differentially related to inflammatory activity in this group.

The Sleep-Immune Crosstalk in Health and Disease

Sleep and immunity are bidirectionally linked. Immune system activation alters sleep, and sleep in turn affects the innate and adaptive arm of our body's defense system. Stimulation of the immune system by microbial challenges triggers an inflammatory response, which, depending on its magnitude and time course, can induce an increase in sleep duration and intensity, but also a disruption of sleep. Enhancement of sleep during an infection is assumed to feedback to the immune system to promote host defense. Indeed, sleep affects various immune parameters, is associated with a reduced infection risk, and can improve infection outcome and vaccination responses. The induction of a hormonal constellation that supports immune functions is one likely mechanism underlying the immune-supporting effects of sleep. In the absence of an infectious challenge, sleep appears to promote inflammatory homeostasis through effects on several inflammatory mediators, such as cytokines. This notion is supported by findings that prolonged sleep deficiency (e.g., short sleep duration, sleep disturbance) can lead to chronic, systemic low-grade inflammation and is associated with various diseases that have an inflammatory component, like diabetes, atherosclerosis, and neurodegeneration. Here, we review available data on this regulatory sleep-immune crosstalk, point out methodological challenges, and suggest questions open for future research.

Total Sleep Time Interacts With Age to Predict Cognitive Performance Among Adults

STUDY OBJECTIVES

To investigate interactions between high and low amounts of sleep and other predictors of cognitive performance.

METHODS

We used four cognitive tests to determine whether sleep time interacted with age, personal history of a memory problem, parental history of a memory problem, or personal concerns about memory and were associated with cognitive performance. Data were collected from an internet-based cohort study. We used an ordinary least squares regression with restricted cubic splines, controlling for demographic variables and comorbidities.

RESULTS

We found significant nonlinear interactions between (1) total sleep time and age and (2) total sleep time and personal history of a memory problem and cognitive performance. Short and long sleep durations and self-reported memory complaints were associated with poorer performance on a test of attention and this was true to a greater degree in younger and older adults. A repeat analysis excluding subjects reporting dementia was significant only for the test of attention.

CONCLUSIONS

These results extend existing data on sleep duration and cognition across the lifespan by combining in a single study the results from four specific cognitive tests, both younger and older adults, and four self-reported risk factors for cognitive impairment. Longitudinal studies with biomarkers should be undertaken to determine whether causal mechanisms, such as inflammation or amyloid buildup, account for these associations.

Sleep Disturbance and Total Sleep Time in Persons Living with HIV: A Cross-Sectional Study

Short and long sleep durations have been associated with inflammation and chronic diseases. To study the association between sleep duration/quality and HIV disease severity, a cross-sectional study was conducted in patients living with HIV (PLWHs) using self-administered questionnaires assessing total sleep time, insomnia (ICSD-3 criteria), and poor sleep quality (PSQI > 5). Multivariable logistic regression identified the factors associated with sleep disorders and with HIV features. 640 Parisian ambulatory PLWHs were included. The prevalence of insomnia was 50 and 68% of patients had a PSQI > 5. Patients with CD4 count < 500 cells/mm³ were more likely to be long sleepers (> 8 h/day) (OR 1.49; 95% CI [1.10-1.99]: p < 0.01), and less likely to be short sleepers (< 6 h/day) (OR 0.69; 95% CI[0.50-0.96]; p = 0.04) or to experience insomnia (OR 0.59; 95% CI[0.40-0.86]; p < 0.01). HIV features were not associated with a PSQI > 5. Thus, insomnia and impaired sleep quality were highly prevalent in well-controlled PLWHs and the severity of HIV infection was associated with long sleep times.

The Association between Daytime Napping Characteristics and Bone Mineral Density in Elderly Thai Women without Osteoporosis

Low bone mass is more prevalent with increasing age. Studies have found associations between sleep duration, sleep quality and obstructive sleep apnea and bone mineral density (BMD). However, less is known about the relationship between daytime napping and BMD. We aimed to investigate the association between daytime napping and BMD in elderly Thai women. Demographic data, lifestyle information and sleep characteristics were obtained by interviewing 387 elderly women. Weight and height were measured. Serum 25-hydroxyvitamin D [25(OH)D] was measured by radioimmunoassay. BMD was measured by dual-energy X-ray absorptiometry (DXA). Higher BMI and having type 2 diabetes (T2DM) were correlated with higher lumbar spine 2–4 (L2-4) BMD, while younger age, higher BMI and higher serum 25(OH)D level were correlated with higher femoral neck (FN) and total hip (TH) BMD. After adjusting for age, age at menopause, BMI, 25(OH)D level and T2DM, a higher frequency of weekly daytime napping was associated with lower FN and TH BMD but not at L2-4 BMD. Additionally, longer daytime napping duration was negatively associated with BMD at TH. In summary higher frequency and longer duration of daytime napping are associated with lower femoral BMD in elderly women. Mechanisms underlying these associations should be further explored.

Sleep Duration Trajectories and Systemic Inflammation in Young Adults: Results From the National Longitudinal Study of Adolescent to Adult Health (Add Health)

Study Objectives

This study examines the effects of short and long sleep duration patterns in young adults on the levels of C-reactive protein (CRP), as well as the potential effect modification by sex.

Methods

Using data from waves III (age 18-26) and IV (age 24-32) of the National Longitudinal study of adolescent to adult health, we examined the association between sleep trajectories in young adults, and the risk of elevated high sensitivity-CRP (hs-CRP), a marker of systemic inflammation.

Results

Short sleep trajectories were associated with significantly elevated log-transformed hs-CRP (coefficient = 0.11, p-value .03) and with significantly higher odds of having hs-CRP levels > 3 mg/L (OR = 1.86, 95% CI 1.29, 2.67). The association was modified by sex, with the association between short sleep duration and hs-CRP limited to males. Both the continuous (coefficient 0.117, p-value = .0362) and the categorized hs-CRP (OR = 2.21, 95% CI 1.48, 3.30) were significantly elevated with short sleep durations in males, whereas no significant associations were seen in females with short sleep durations. By contrast, log hs-CRP was significantly elevated in females with long sleep durations (coefficient = 0.232, p-value = .0296), with a nonsignificant increase in the odds of having hs-CRP levels greater than 3 mg/L (OR = 1.48, 95% CI 0.75, 2.93), whereas there were no associations with long sleep duration in males.

Conclusions

Systemic inflammation, measured by an elevated level of hs-CRP, is seen with persistent short sleep duration in young adult men and persistent long sleep duration in young adult women.

Poor sleep moderates the relationship between daytime napping and inflammation in Black and White men

OBJECTIVES

To test whether napping was associated with 2 inflammatory markers with known relationships to cardiovascular disease: high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6). Because IL-6 is known to impact central inflammatory processes that relate to sleep regulation, including subjective fatigue, we tested whether this relationship was moderated by sleep duration, sleep efficiency, and self-reported sleep quality.

DESIGN

Cross-sectional.

PARTICIPANTS

A community sample of Black and White men (N=253) completed a week of actigraphy and diary measures of sleep and napping and provided a fasting blood sample.

MEASUREMENTS/ANALYSIS

Napping was measured as the proportion of days with at least 30 minutes napped and the average minutes napped per day. Linear regressions adjusted for race, socioeconomic status, employment, body mass index, smoking, medications that affect sleep or inflammation, working the nightshift, and day-sleeping status, followed by interaction terms between napping and sleep duration, efficiency, and quality, respectively.

RESULTS

There were no significant main effects of actigraphy- or diary-measured napping on IL-6 or hsCRP. Moderation analyses indicated elevated IL-6 values among men who napped more days (by actigraphy) and demonstrated short sleep duration (P=.03). Moderation analyses also indicated elevated IL-6 among men who demonstrated greater average minutes napped (by actigraphy) and short sleep duration (P<.001), low efficiency (P=.03), and poor quality (P=.03). Moderation analyses involving diary napping or hsCRP were not significant.

CONCLUSIONS

Actigraphy-assessed daytime napping is related to higher IL-6 in men who demonstrate worse sleep characteristics. Daytime napping may pose additional risk for inflammation beyond the known risk conferred by short sleep.

Exploring the nap paradox: are mid-day sleep bouts a friend or foe?

The mid-day nap, sometimes called a siesta, is a ubiquitous occurrence across the lifespan. It is well established that in addition to reducing sleepiness, mid-day naps offer a variety of benefits: memory consolidation, preparation for subsequent learning, executive functioning enhancement, and a boost in emotional stability. These benefits are present even if a sufficient amount of sleep is obtained during the night prior. However, we present a paradox: in spite of these reported benefits of naps, frequent napping has also been associated with numerous negative outcomes (eg, cognitive decline, hypertension, diabetes), particularly in older populations. This association exists even when statistically controlling for relevant health- and sleep-affecting determinants. An emerging hypothesis suggests inflammation is a mediator between mid-day naps and poor health outcomes, yet further research is necessary. Given this, it may be premature to 'prescribe' naps as a health enhancer. Herein, we aggregate findings from several branches of sleep research (eg, developmental neuroscience, cognitive neuroscience, sleep medicine) to critically examine the paradoxical role of naps in cognitive and somatic health. This review uncovers gaps in the literature to guide research opportunities in the field.

Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences, and Countermeasures

Circadian (∼24-hour) timing systems pervade all kingdoms of life and temporally optimize behavior and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to the level of synchronization between our daily cycles of behavior and the solar day. Sleep/wake cycles are intertwined with the circadian system, and global trends indicate that these, too, are increasingly subject to disruption. A large proportion of the world's population is at increased risk of environmentally driven circadian rhythm and sleep disruption, and a minority of individuals are also genetically predisposed to circadian misalignment and sleep disorders. The consequences of disruption to the circadian system and sleep are profound and include myriad metabolic ramifications, some of which may be compounded by adverse effects on dietary choices. If not addressed, the deleterious effects of such disruption will continue to cause widespread health problems; therefore, implementation of the numerous behavioral and pharmaceutical interventions that can help restore circadian system alignment and enhance sleep will be important.

Napping: A public health issue. From epidemiological to laboratory studies

Sleep specialists have proposed measures to counteract the negative short- and long-term consequences of sleep debt, and some have suggested the nap as a potential and powerful "public health tool". Here, we address this countermeasure aspect of napping viewed as an action against sleep deprivation rather than an action associated with poor health. We review the physiological functions that have been associated positively with napping in both public health and clinical settings (sleep-related accidents, work and school, and cardiovascular risk) and in laboratory-based studies with potential public health issues (cognitive performance, stress, immune function and pain sensitivity). We also discuss the circumstances in which napping-depending on several factors, including nap duration, frequency, and age-could be a potential public health tool and a countermeasure for sleep loss in terms of reducing accidents and cardiovascular events and improving sleep-restriction-sensitive working performance. However, the impact of napping and the nature of the sleep stage(s) involved still need to be evaluated, especially from the perspective of coping strategies in populations with chronic sleep debt, such as night and shift workers.