Daytime napping, sleep duration and serum C reactive protein: a population-based cohort study

Negative health outcomes in long sleepers: The societal sleep restriction hypothesis

Society imposes work and school schedules, as well as social expectations, that militate against consistently obtaining more than 7-9 h of sleep every 24 h. For most but not all adults this sleep duration is adequate. But among those who consistently obtain more than 9 h of sleep per day ("long sleepers"), there likely exists a subpopulation of individuals who are nevertheless failing to obtain enough sleep to satisfy their physiological sleep needs - a consequence of "restricting" their daily sleep durations to whatever extent they can tolerate so as to conform as closely as possible to society's norms and expectations. It is hypothesized that the 'long sleep arm' of the seemingly paradoxical U-shaped relationship between sleep duration and negative health outcomes can be explained, at least in part, by the existence of a subpopulation of such 'sleep-restricted long sleepers.'

No evidence linking sleep traits with white blood cell counts: Multivariable-adjusted and Mendelian randomization analyses

BACKGROUND

Disturbances in habitual sleep have been associated with multiple age-associated diseases. However, the biological mechanisms underpinning these associations remain largely unclear. We assessed the possible involvement of the circulating immune system by determining the associations between sleep traits and white blood cell counts using multivariable-adjusted linear regression and Mendelian randomization.

METHODS

Cross-sectional multivariable-adjusted linear regression analyses were done using participants within the normal range of total white blood cell counts (>4.5 × 109 and <11.0 × 109/μL) from UK Biobank. For the sleep traits, we examined (short and long) sleep duration, chronotype, insomnia symptoms and daytime dozing. Two-sample Mendelian randomization analyses were done using instruments for sleep traits derived from European-ancestry participants from UK Biobank (over 410,000 participants) and using SNP-outcome data derived from European-ancestry participants from the Blood Cell Consortium (N = 563,946) to which no data from UK Biobank contributed.

RESULTS

Using data from 357,656 participants (mean [standard deviation] age: 56.5 [8.1] years, and 44.4% men), we did not find evidence that disturbances in any of the studied sleep traits were associated with differences in blood cell counts (total, lymphocytes, neutrophiles, eosinophiles and basophiles). Also, we did not find associations between disturbances in any of the studied sleep traits and white blood cell counts using Mendelian Randomization.

CONCLUSION

Based on the results from two different methodologies, disturbances in habitual sleep are unlikely to cause changes in blood cell counts and thereby differences in blood cell counts are unlikely to be underlying the observed sleep-disease associations.

Associations between sleep duration, sleep disturbance and cardiovascular disease biomarkers among adults in the United States

BACKGROUND

Sleep problems are associated with abnormal cardiovascular biomarkers and an increased risk of cardiovascular diseases (CVDs). However, studies investigating associations between sleep problems and CVD biomarkers have reported conflicting findings. This study examined the associations between sleep problems and CVD biomarkers in the United States.

METHODS

Data were from the National Health and Nutrition Examination Survey (NHANES) (2007-2018) and analyses were restricted to adults ≥ 20 years (n = 23,749). CVD biomarkers [C-reactive Protein (CRP), low-density lipoproteins, high-density lipoproteins (HDL), triglycerides, insulin, glycosylated hemoglobin (HbA1c), and fasting blood glucose] were categorized as abnormal or normal using standardized cut-off points. Sleep problems were assessed by sleep duration (short [≤ 6 h], long [≥ 9 h], and recommended [> 6 to < 9 h) and self-reported sleep disturbance (yes, no). Multivariable logistic regression models explored the associations between sleep duration, sleep disturbance, and CVD biomarkers adjusting for sociodemographic characteristics and lifestyle behaviors.

RESULTS

The mean sleep duration was 7.1 ± 1.5 h and 25.1% of participants reported sleep disturbances. Compared to participants with the recommended sleep duration, those with short sleep duration had higher odds of abnormal levels of HDL (adjusted odds ratio [aOR] = 1.20, 95% confidence interval [CI] = 1.05-1.39), CRP (aOR = 3.08, 95% CI = 1.18-8.05), HbA1c (aOR = 1.25, 95% CI = 1.05-1.49), and insulin (aOR = 1.24, 95% CI = 1.03-1.51). Long sleep duration was associated with increased odds of abnormal CRP (aOR = 6.12, 95% CI = 2.19-17.15), HbA1c (aOR = 1.54, 95% CI = 1.09-2.17), and blood glucose levels (aOR = 1.45, 95% CI = 1.07-1.95). Sleep disturbance predicted abnormal triglyceride (aOR = 1.18, 95% CI = 1.01-1.37) and blood glucose levels (aOR = 1.24, 95% CI = 1.04-1.49).

CONCLUSION

Short and long sleep durations were positively associated with abnormal CRP, HDL, HbA1c, blood glucose, and insulin levels, while sleep disturbance was associated with abnormal triglyceride and blood glucose levels. Since sleep is a modifiable factor, adopting healthy sleeping habits may create a balanced metabolism and reduce the risk of developing a CVD. Our study may provide insights into the relationship between sleep duration, sleep disturbance, and CVD risk.

Associations between sleep-behavioral traits and healthspan: A one-sample Mendelian randomization study based on 388,909 participants of the UK-Biobank

BACKGROUND

Although the association between sleep behavior and morbidity and mortality risk has been reported before, there is still uncertainty whether the observed associations are causal or confounding. Therefore, we investigated the causal relationships between sleep-behavioral traits and terminated healthspan risk using Mendelian randomization (MR).

METHODS

We conducted a one-sample MR analysis to evaluate causality between six sleep-behavioral traits (sleep duration, chronotype/morningness, napping, sleeplessness/insomnia, and getting up from bed) and risk of healthspan termination among 388, 909 UK Biobank (UKB) participants. Instrumental variables for sleep behaviors (N = 590) were obtained from recent genome-wide association studies (GWAS). We defined healthspan based on eight predominant health-terminating events associated with longevity (congestive heart failure, myocardial infarction, chronic obstructive pulmonary disease, stroke, dementia, diabetes, cancer, and death). We further constructed a sleep score and a weighted genetic risk score to increase the predictive ability of the sleep-behavioral traits. Cox regression models and Inverse Probability Treatment Weighting (IPTW) were implemented, followed by MR to assess causation. We used inverse-variance-weighted MR to estimate causal effects, and weighted-median and MR-egger for sensitivity analysis to test the pleiotropic effects.

RESULTS

In IPTW, we observed a decreased risk of terminated healthspan for healthy sleep behaviors such as 'sleep duration 7-8h/d' (Hazard ratio, HR = 0.93; 95 % confidence interval, CI: 0.92-0.96; P < 0.001); 'morningness' (HR = 0.95; 95%CI: 0.93-0.98; P < 0.01); 'napping' (HR = 0.93; 95%CI: 0.91-0.94; P < 0.001); 'easy getting up from bed' (HR = 0.91; 95%CI: 0.88-0.93; P < 0.001); and, 'never/rarely experience sleeplessness/insomnia' (HR = 0.94; 95%CI: 0.92-0.96; P < 0.001). MR results further indicated causal associations between healthy sleep duration (OR = 0.98; 95%CI: 0.97-1.00; P = 0.036) and insomnia (OR = 1.02; 95%CI: 1.01-1.03; P < 0.001) with terminated healthspan. MR-egger did not suggest any potential pleiotropy.

CONCLUSION

This study supports abnormal sleep duration and insomnia as potential causal risk factors for terminated healthspan. Thus, healthy sleep behavior is valuable for the extension of healthspan, and well-designed and tailored sleep health interventions are warranted.

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.

Relationship between daytime napping and cardiovascular disease: A two-sample mendelian randomization study

OBJECTIVE

Daytime napping has been reported to have a potential association with an increased risk of cardiovascular diseases (CVDs) in several cohort studies, but the causal effects are unclear. In this study, we aimed to investigate the relationship between daytime napping and CVDs, as well as to validate causality in this relationship by Mendelian randomization (MR).

METHODS

A two-sample MR method was used to evaluate the causal effect of daytime napping on CVDs. The exposure of daytime napping was extracted from publicly available genome-wide association studies (GWASs) in the UK Biobank, and the outcomes of 14 CVDs were obtained from the FinnGen consortium. A total of 49 single-nucleotide polymorphisms (SNPs) were used as the instrumental variables. The effect estimates were calculated by using the inverse-variance weighted method.

RESULTS

The MR analyses showed that genetically predicted daytime napping was associated with an increased risk of five CVDs, including heart failure (odds ratio (OR): 1.71, 95% CI: 1.19-2.44, p = 0.003), hypertension (OR: 1.51, 95% CI: 1.05-2.16, p = 0.026), atrial fibrillation (OR: 1.71, 95% CI: 1.02-2.88, p = 0.042), cardiac arrythmias (OR: 1.47, 95% CI: 1.47, 95% CI: 1.01-2.13, p = 0.042) and coronary atherosclerosis (OR: 1.77, 95% CI: 1.17-2.68, p = 0.006). No significant influence was observed for other CVDs.

CONCLUSION

This two-sample MR analysis suggested that daytime napping was causally associated with an increased risk of heart failure, hypertension, atrial fibrillation, cardiac arrythmias and coronary atherosclerosis.

Poor sleep and shift work associate with increased blood pressure and inflammation in UK Biobank participants

Disrupted circadian rhythms have been linked to an increased risk of hypertension and cardiovascular disease. However, many studies show inconsistent findings and are not sufficiently powered for targeted subgroup analyses. Using the UK Biobank cohort, we evaluate the association between circadian rhythm-disrupting behaviours, blood pressure (SBP, DBP) and inflammatory markers in >350,000 adults with European white British ancestry. The independent U-shaped relationship between sleep length and SBP/DBP is most prominent with a low inflammatory status. Poor sleep quality and permanent night shift work are also positively associated with SBP/DBP. Although fully adjusting for BMI in the linear regression model attenuated effect sizes, these associations remain significant. Two-sample Mendelian Randomisation (MR) analyses support a potential causal effect of long sleep, short sleep, chronotype, daytime napping and sleep duration on SBP/DBP. Thus, in the current study, we present a positive association between circadian rhythm-disrupting behaviours and SBP/DBP regulation in males and females that is largely independent of age.

The causal associations of altered inflammatory proteins with sleep duration, insomnia and daytime sleepiness

STUDY OBJECTIVES

Growing evidence linked inflammation with sleep. This study aimed to evaluate the associations and causal effects of sleep traits including insomnia, excessive daytime sleepiness (EDS), and sleep duration (short: <7 h; normal: 7-9 h; long: ≥9 h), with levels of C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), and interleukins.

METHODS

Standard procedures of quantitative analysis were applied to estimate the expression differences for each protein in compared groups. Then, a two-sample Mendelian randomization (MR) analysis was performed to explore their causal relationships with published genome-wide association study summary statistics. The inverse-variance weighted was used as the primary method, followed by several complementary approaches as sensitivity analyses.

RESULTS

A total of 44 publications with 51 879 participants were included in the quantitative analysis. Our results showed that the levels of CRP, interleukin-1β (IL-1β), IL-6, and TNF-α were higher from 0.36 to 0.58 (after standardization) in insomnia compared with controls, while there was no significant difference between participants with EDS and controls. Besides, there was a U/J-shaped expression of CRP and IL-6 with sleep durations. In MR analysis, the primary results demonstrated the causal effects of CRP on sleep duration (estimate: 0.017; 95% confidence intervals [CI], [0.003, 0.031]) and short sleep duration (estimate: -0.006; 95% CI, [-0.011, -0.001]). Also, IL-6 was found to be associated with long sleep duration (estimate: 0.006; 95% CI, [0.000, 0.013]). These results were consistent in sensitivity analyses.

CONCLUSIONS

There are high inflammatory profiles in insomnia and extremes of sleep duration. Meanwhile, elevated CRP and IL-6 have causal effects on longer sleep duration. Further studies can focus on related upstream and downstream mechanisms.

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.

Association of night-time sleep duration and daytime napping with all-cause and cause-specific mortality in older British men: Findings from the British Regional HeartStudy

Short and long night-time sleep and daytime napping in young and middle-aged populations were associated with increased mortality, but it is unclear in very older people. The aim of this prospective study was to assess the associations in people aged >70 years. We examined the data of British Regional Heart Study, which included 1722 men aged 71-92 years and had night-time sleep duration and daytime napping measured at baseline and were followed up for nine years. There were 597 deaths. Compared to night-time sleep at 7-<8 h, age-adjusted hazard ratio of all-cause mortality in participants sleeping <6 h was 1.04 (95% CI 0.80-1.35), 1.07 (0.85-1.34) in 6-<7 h, 1.04 (0.83-1.30) in 8-<9 h and 0.93 (0.65-1.33) in ≥9 h. Further adjustments for other co-variables still showed no association, and neither the association with cardiovascular mortality nor non-cardiovascular mortality. Daytime napping, however, was associated with mortality. After adjustment for age, smoking, physical activity, obesity, cardiovascular diseases, diabetes, frailty, general health, anti-hypertensive medication and C-reactive protein level, hazard ratio of all-cause mortality in participants with daytime napping >1-h versus no napping was 1.62 (1.18-2.22) and hazard ratio of non-cardiovascular mortality was 1.77 (1.22-2.57). The fully adjusted hazard ratio of cardiovascular mortality was not significantly increased 1.26 (0.69-2.28), although age-adjusted hazard ratio was significant 1.94 (1.20-3.16). In the elderly men, daytime napping was independently associated with increased all-cause and non-cardiovascular mortality, while its association with cardiovascular mortality could be explained by cardiovascular risk factors and co-morbidities. Night-time sleep duration was not associated with mortality risk.

Daytime napping and coronary heart disease risk in adults: a systematic review and dose-response meta-analysis

PURPOSE

The present study investigated the association between daytime napping and coronary heart disease (CHD) risk among adults.

METHODS

Articles were detected by using PubMed, ISI Web of Science, and Scopus databases until November 8th, 2021. The relevant data were found among the eight included articles and were pooled for meta-analysis in adult participants via a random-effects model.

RESULTS

Among 167,025 adults, the results revealed that daytime napping was associated with an enhanced risk of CHD (risk ratios [RR] = 1.30; 95% CI: 1.06, 1.60; p < 0.001). Subgroup analysis by daytime napping duration also indicated that daytime napping for at least 1 h had three times higher influence on the enhanced risk of CHD (RR = 1.34; 95% CI: 1.14, 1.58; p < 0.001) than that of daytime napping for less than 1 h (RR = 1.10; 95% CI: 1.02, 1.19; p = 0.014). In addition, subgroup analysis by region illustrated that daytime napping was linked with an enhanced risk of CHD in Chinese (RR = 1.41; 95% CI: 1.19, 1.66; p < 0.001), but not in European or American populations. Furthermore, the subgroup analysis of napping duration and risk of CHD suggested that their relation was significant just in those studies that controlled for depressive symptoms (RR = 1.52; 95% CI: 1.29, 1.80; p < 0.001, n = 3) and night sleep duration (RR = 1.42; 95% CI: 1.21, 1.66; p < 0.001, n = 5). The linear dose-response meta-analysis revealed that each 15-min increase in daytime napping was related with a 5% higher risk of CHD (RR = 1.05; 95% CI: 1.02, 1.08; I2 = 58.7%; p < 0.001). Furthermore, nonlinear dose-response meta-analysis revealed a positive linear relationship between daytime napping and CHD risk in adults (p nonlinearity = 0.484, p dose-response = 0.003).

CONCLUSION

Results showed that daytime napping was related with an increased risk of CHD in adults. The evidence from this study suggests that the public should be made conscious of the adverse outcomes of long daytime napping for CHD, notably among the Chinese population. Additional studies are required to confirm potential links between CHD risk and daytime napping.

The relationship between sleep and salivary and serum inflammatory biomarkers in adolescents

Objectives

Poor sleep behavior can trigger an inflammatory response and contribute to the development of inflammatory diseases. Cytokines can act as indicators of inflammation and may precede the onset of inflammatory diseases. This study aimed to determine the association between sleep timing parameters (bedtime, sleep duration, sleep debt, and social jetlag) and the levels of nine serum and salivary inflammatory and metabolic biomarkers.

Methods

Data were collected from 352 adolescents aged 16-19 years enrolled in Kuwait's public high schools. The levels of C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), adiponectin, leptin, and insulin were measured from saliva and serum samples. We conducted mixed-effect multiple linear regression modeling to account for the school variable as a random effect to assess the relationship between the sleep variables and salivary and serum biomarkers. Mediation analysis was conducted to check if BMI was a mediator between bedtime and the biomarkers.

Results

There was a statistically significant elevation in serum IL-6 level associated with later bedtime (0.05 pg./mL, p = 0.01). Adolescents with severe sleep debt of ≥2 h had an increase in salivary IL-6 biomarker levels (0.38 pg./mL, p = 0.01) compared to those who had sleep debt of <1 h. Adolescents with sleep debt of ≥2 h had significantly higher levels of serum CRP (0.61 μg/mL, p = 0.02) than those without sleep debt. Additionally, we found that the inflammatory biomarkers (CRP, IL-6, IL-8, IL-10, VEGF, and MCP-1) and metabolic biomarkers (adiponectin, leptin, and insulin) had more statistically significant associations with the bedtime variables than with sleep duration variables. CRP, IL-6, and IL-8 were associated with sleep debt, and IL-6, VEGF, adiponectin, and leptin levels were associated with social jetlag. BMIz was a full mediator in the relationship between late bedtime and increased serum levels of CRP, IL-6, and insulin.

Conclusion

Adolescents who go to bed at or later than midnight had dysregulated levels of salivary and serum inflammatory biomarkers, suggesting that disrupted circadian rhythm can trigger higher levels of systemic inflammation and potentially exacerbate chronic inflammation and the risk of metabolic diseases.

The association between daytime napping and risk of type 2 diabetes is modulated by inflammation and adiposity: Evidence from 435 342 UK-Biobank participants

BACKGROUND

Existing evidence concerning the relationship between daytime napping and type 2 diabetes (T2D) is inconsistent, and whether the effects of napping differ by body fat percentage (BFP) and C-reactive protein (CRP) is unclear. We aimed to investigate the association between daytime napping frequency and T2D risk and whether such an association was modified by BFP and CRP.

METHODS

We included 435 342 participants free of diabetes from the UK Biobank. Participants were categorized as nonnappers, occasional nappers, and frequent nappers based on napping frequency, and BFP/CRP was divided into quartiles. Cox proportional hazards models were used.

RESULTS

During a median follow-up of 9.2 years, 17 592 T2D cases occurred. Higher frequency of daytime napping was significantly associated with an increased risk of T2D. Compared with nonnappers, the adjusted hazard ratios (HRs) for occasional nappers and habitual nappers were 1.28 (95% confidence interval [CI]: 1.24-1.32) and 1.49 (95% CI: 1.41-1.57), respectively. There was a significant additive and multiplicative interaction (relative excess risk due to interaction [RERI] = 0.490, 95% CI 0.307-0.673; p for multiplicative interaction <.001) between napping and BFP, whereby a higher hazard of T2D associated with more frequent napping was greatest among participants in the highest BFP quartile (HR = 4.45, 95% CI: 3.92-5.06). The results for CRP were similar (RERI = 0.266, 95% CI: 0.094-0.439; p for multiplicative interaction <.001).

CONCLUSIONS

Higher daytime napping frequency is associated with an increased T2D risk, and such relationships are modified by BFP and CRP. These findings underscore the importance of adiposity and inflammation control to mitigate diabetes risk.

Longitudinal associations between daytime napping and cognitive function in Chinese older adults

BACKGROUND

Little was known about the longitudinal associations between daytime napping and cognitive function in China. Thus, the study aimed to explore the cross-sectional and the longitudinal relationship between daytime napping and cognitive performance in the elderly Chinese population.

METHODS

The data was from the China Health and Retirement Longitudinal Study (CHARLS). Daytime napping was self-reported. Cognitive function was assessed via a structured questionnaire in two dimensions: episodic memory and mental status. Linear regression and mixed-effect model were applied to explore the association between daytime napping and cognitive function.

RESULTS

A total of 2,875 and 2,440 participants aged over 65 years were included in the cross-sectional and the longitudinal studies, respectively. In the cross-sectional study, non-nappers and extended nappers had significantly lower global cognition scores (P<0.01), as well as significantly lower scores for episodic memory (P<0.05) and mental status (P<0.01), compared with moderate nappers. In the longitudinal analysis, no napping and extended napping were significantly associated with global cognitive decline (P<0.05) and only extended napping showed the significant association for the decline in episodic memory as well as mental status (P<0.01).

LIMITATIONS

Daytime napping duration was self-reported by participants.

CONCLUSION

The study found a longitudinal association between extended napping duration and worse cognitive function.

Sleep duration and daytime napping in relation to incident inflammatory bowel disease: a prospective cohort study

BACKGROUND

Sleep dysregulation has been linked to gastrointestinal dysfunction and inflammation.

AIMS

To explore the associations between sleep duration, daytime napping and inflammatory bowel disease (IBD), Crohn's disease (CD) and ulcerative colitis (UC).

METHODS

Exposure information was obtained from the baseline questionnaire. Sleep duration was coded as continuous and categorical (≤5, 6, 7, 8, ≥9 h/day) variables. Daytime napping was defined as yes (sometimes/usually) and no (never/rarely). Incident IBD cases were defined from primary care and hospital inpatient records. Polygenic risk scores (PRS) for the outcomes were constructed and categorised into low, intermediate and high risk. Hazard ratio (HR) and confidence interval (CI) were estimated using Cox proportional hazard regression.

RESULTS

The analysis included 2604 incident IBD cases (806 CD and 1798 UC) with a median follow-up of 12.0 years. Comparing sleep duration ≤5 with 7 h/day, the HR of IBD, CD and UC was 1.36 (95% CI, 1.17-1.59), 1.53 (95% CI, 1.17-2.00) and 1.29 (95% CI, 1.07-1.56), respectively. Comparing participants with and without daytime napping, the HR of IBD, CD and UC was 1.13 (95% CI, 1.05-1.23), 1.25 (95% CI, 1.08-1.44) and 1.09 (95% CI, 0.90-1.20), respectively. No interaction of sleep duration and daytime napping with PRS was detected.  However, the associations appeared stronger in individuals with high rather than low PRS.

CONCLUSIONS

This study reveals positive associations between short sleep duration and daytime napping and IBD risk.

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.

Bidirectional Associations between Daytime Napping Duration and Metabolic Syndrome: A Nationally Representative Cohort Study

BACKGROUND

We aimed to examine the bidirectional associations between daytime napping duration and metabolic syndrome (MetS).

METHODS

Using data from the China Health and Retirement Longitudinal Study from 2011 to 2015, modified Poisson regression models were performed to explore the longitudinal associations of baseline napping duration with the occurrence and remission of MetS. Generalized estimating equation was conducted to explore the association between baseline MetS status with subsequent changes in daytime napping duration. Cross-lagged panel analysis was performed to further verify their bidirectional relationships.

RESULTS

During the four-year follow-up, among 5041 participants without MetS at baseline, extended naps were significantly associated with MetS occurrence, compared with non-napping. This association was only significant in individuals with adequate night-time sleep duration or good sleep quality of the 2898 participants with MetS at baseline. Excessive napping duration may be not favorable for MetS remission especially for adequate night-time sleepers. With respect to reverse associations, baseline MetS status significantly increased the napping duration during the subsequent follow-up period. Finally, there were significant bidirectional cross-lagged associations between napping duration and MetS severity score after adjusting for all covariates.

CONCLUSIONS

Our study indicates bidirectional relationships exist between daytime napping duration and MetS. Interestingly, longer napping duration was detrimental to cardiometabolic health only in those with sufficient night-time sleep duration or good sleep quality.

Associations of siesta and total sleep duration with hypertension or cardiovascular diseases in middle-aged and older adults

BACKGROUND

Whether the ratio of siesta duration in the total sleep duration was associated with the occurrence of hypertension or cardiovascular diseases (CVDs) was unclear.

HYPOTHESIS

To explore the associations of siesta, and siesta ratio with hypertension or CVDs in middle-aged and older adults.

METHODS

This cohort study collected the data of 9247 middle-aged and older adults. The associations of siesta, and siesta ratio with hypertension were analyzed in 7619 participants while the associations of siesta, and siesta ratio with CVDs were analyzed in 8685 participants via univariate and multivariate logistic regression analysis.

RESULTS

Total sleep duration < 6 h (odd ratio [OR] = 1.168, 95% confidence interval [CI]: 1.023-1.335) and siesta ratios ≥ 0.4 (OR = 1.712, 95% CI: 1.129-2.594) were associated with increased risk of hypertension in middle-aged and older adults. Siesta ratio ≥ 0.4 was linked with higher risk of hypertension in males aged ≥ 60 years and total sleep duration < 6 h was correlated with elevated risk of hypertension in males < 60 years. The risk of CVDs was elevated in people with siesta duration < 0.5 h (OR = 2.053, 95% CI: 1.323-3.185). In females ≥60 years, the sleep duration at night < 6 h was associated with increased risk of CVDs. In females < 60 years, increased risk was observed in those with siesta duration < 0.5 h and sleep duration at night < 6 h.

CONCLUSION

Short sleep duration or high siesta ratio were associated with higher risk of hypertension. Short siesta duration, sleep duration at night or total sleep duration were correlated with an elevated risk of CVDs.

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.

Obesity indicators as mediators of association between daytime napping and type 2 diabetes mellitus: the Guangzhou Biobank Cohort Study

OBJECTIVE

To examine the mediating effect of obesity indicators on the association between daytime napping and type 2 diabetes mellitus (T2DM) qualitatively and quantitatively using baseline data from the Guangzhou Biobank Cohort Study.

METHODS

Twenty-nine thousand three hundred fifty-five participants aged 50+ years were included in this cross-sectional study. Mediation analysis was used to assess the mediating effect of body mass index (BMI), waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR) on the association between daytime napping and T2DM after adjustment for sex, age, education, occupation, smoking status, alcohol use and physical activity.

RESULTS

The mean (standard deviation) age of participants was 61.5 ( 7.1) years. The prevalence of T2DM and daytime napping was 12.5% and 65.2%, respectively. After adjustment for potential confounders, WC, WHR and WHtR showed partial mediating effects on the association between daytime napping and T2DM, with the proportion (95% confidence interval) of mediation effect being 10.17% (8.14-14.43%), 14.91% (11.95-21.24%) and 9.36% (7.49-13.29%), respectively. No mediating effect of BMI or HC on the association between daytime napping and T2DM was found.

CONCLUSIONS

Our results showed significant mediating effects of WC, WHR and WHtR on the association between daytime napping and T2DM, suggesting that waist circumference management could be important in daytime nappers.

Both increased and decreased sleep duration over time are associated with subsequent cancer development

PURPOSE

Changes in sleep duration have been reported to correlate with lifestyle-related diseases in humans. However, equivalent studies regarding the effects of sleep on cancer progression are lacking. This study aimed to determine whether or not increase or decrease in sleep duration over time is associated with subsequent cancer development.

METHODS

A large-scale, retrospective cohort study was conducted at a preventive medicine health center at a general community hospital in Tokyo, Japan. All participants who underwent health checkups at the hospital between January 2005 and December 2018 were included. The primary study outcome was development of any type of cancer according to the slope of sleep duration over the study period. The Cox proportional hazard model was used to adjust the outcomes based on potential covariates.

RESULTS

Of 15,025 participants, 7,692 (51.2%) were men. The mean age (standard deviation) was 66.0 (7.5) years. During a median follow-up of 2,588 (interquartile range: 1,583-3,695) days, 1,396 (9.3%) participants developed cancer of any type. Compared to hazard ratio in the stable sleep duration group (- 0.1 to + 0.1 h/day in 1 year), both greatly decreased (less than - 0.2 h/day in 1 year; hazard ratio (HR), 2.13; 95% confidence interval (CI), 1.72-2.62) and increased (more than + 0.2 h/day in 1 year; HR, 2.55; 95% CI 2.14-3.04) groups showed significantly higher hazard ratio for the development of any type of cancer.

CONCLUSION

Both increased and decreased sleep duration over time are associated with subsequent cancer development.

Blood biomarker levels by total sleep duration: cross-sectional analyses in UK Biobank

BACKGROUND

Short or long sleep duration has been associated with some major chronic diseases, but whether disease-related blood biomarkers vary according to habitual sleep duration is unclear. This cross-sectional study aimed to assess blood biomarker levels in relation to total sleep duration.

METHODS

The analysis includes 459,796 white British adults aged 40-69 during 2006-2010 in UK Biobank. At recruitment, blood samples and self-reported information on total sleep duration were collected from participants. A panel of blood biomarkers were measured. Using linear regression, we estimated geometric mean concentrations of blood biomarkers and mean ratio of ApoB/ApoA1 by sleep duration adjusted for sex, age at data collection, time of blood collection, and lifestyle covariates.

RESULTS

Percentage differences in the concentrations of most biomarkers by sleep duration were modest. The largest differences were for C-reactive protein (CRP, an inflammatory biomarker) and gamma glutamyltransferase (GGT, a liver function biomarker), and the differences were markedly attenuated after multivariable-adjustment. The multivariable-adjusted geometric means of CRP and of GGT were 14% and 14% higher in <6 h vs 7-8 h of sleep; and 22% and 12% higher in >9 h vs 7-8 h of sleep, respectively.

CONCLUSION

In white British adults, most blood biomarker levels varied only modestly with sleep duration and the remaining associations may be due to residual confounding.

Role of sleep deprivation in immune-related disease risk and outcomes

Modern societies are experiencing an increasing trend of reduced sleep duration, with nocturnal sleeping time below the recommended ranges for health. Epidemiological and laboratory studies have demonstrated detrimental effects of sleep deprivation on health. Sleep exerts an immune-supportive function, promoting host defense against infection and inflammatory insults. Sleep deprivation has been associated with alterations of innate and adaptive immune parameters, leading to a chronic inflammatory state and an increased risk for infectious/inflammatory pathologies, including cardiometabolic, neoplastic, autoimmune and neurodegenerative diseases. Here, we review recent advancements on the immune responses to sleep deprivation as evidenced by experimental and epidemiological studies, the pathophysiology, and the role for the sleep deprivation-induced immune changes in increasing the risk for chronic diseases. Gaps in knowledge and methodological pitfalls still remain. Further understanding of the causal relationship between sleep deprivation and immune deregulation would help to identify individuals at risk for disease and to prevent adverse health outcomes.

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.

Modest Gains After an 8-Week Exercise Program Correlate With Reductions in Non-traditional Markers of Cardiovascular Risk

Background: Although engaging in physical exercise has been shown to reduce the incidence of cardiovascular events, the molecular mechanisms by which exercise mediates these benefits remain unclear. Based on epidemiological evidence, reductions in traditional risk factors only accounts for 50% of the protective effects of exercise, leaving the remaining mechanisms unexplained. The objective of this study was to determine whether engaging in a regular exercise program in a real world clinical setting mediates cardiovascular protection via modulation of non-traditional risk factors, such as those involved in coagulation, inflammation and metabolic regulation. Methods and Results: We performed a prospective, cohort study in 52 sedentary patients with cardiovascular disease or cardiovascular risk factors at two tertiary medical centers between January 1, 2016 and December 31, 2019. Prior to and at the completion of an 8-week exercise program, we collected information on traditional cardiovascular risk factors, exercise capacity, and physical activity and performed plasma analysis to measure levels of fibrinolytic, inflammatory and metabolic biomarkers to assess changes in non-traditional cardiovascular risk factors. The median weight change, improvement in physical fitness, and change in physical activity for the entire cohort were: -4.6 pounds (IQR: +2 pounds, -11.8 pounds), 0.37 METs (IQR: -0.076 METs, 1.06 METs), and 252.7 kcals/week (IQR: -119, 921.2 kcals/week). In addition to improvement in blood pressure and cholesterol, patients who lost at least 5 pounds, expended at least 1,000 additional kcals/week, and/or achieved ≥0.5 MET increase in fitness had a significant reduction in plasminogen activator inhibitor-1 [9.07 ng/mL (95% CI: 2.78-15.35 ng/mL); P = 0.026], platelet derived growth factor beta [376.077 pg/mL (95% CI: 44.69-707.46 pg/mL); P = 0.026); and angiopoietin-1 [(1104.11 pg/mL (95% CI: 2.92-2205.30 pg/mL); P = 0.049)]. Conclusion: Modest improvements in physical fitness, physical activity, and/or weight loss through a short-term exercise program was associated with decreased plasma levels of plasminogen activator inhibitor, platelet derived growth factor beta, and angiopoietin, which have been associated with impaired fibrinolysis and inflammation.

Daytime Napping and Nighttime Sleep Duration with Incident Diabetes Mellitus: A Cohort Study in Chinese Older Adults

Background: We aimed to examine the longitudinal associations between daytime napping and nighttime sleep duration with the risk of diabetes mellitus (DM) among Chinese elderly using data from the China Health and Retirement Longitudinal Study (CHARLS). Methods: A cohort study was conducted among 2620 participants aged 60 years or above. Information on daytime napping and nighttime sleep duration was self-reported during the 2011 baseline survey. DM status during the 2015 follow-up survey was confirmed according to the American Diabetes Association criteria. Results: Individuals with long daytime napping (>1 h/day) had increased risk of developing DM than non-nappers (adjusted RR = 1.52, 95%CI: 1.10, 2.10). In addition, we observed a U-shaped association between nighttime sleep duration and incident DM risk. We further found that nappers with <4 h of nighttime sleep, and those with >1 h of daytime napping and >6 h nighttime sleep had approximately two-fold elevated risk of DM, compared to non-nappers with 6–8 h of nighttime sleep. Conclusion: Long daytime napping and extreme nighttime sleep duration were associated with increased DM risk among Chinese elderly. There was a joint effect of long daytime napping and nighttime sleep duration on the risk of DM.

Investigation of the relationships between sleep behaviors and risk of healthspan termination: a prospective cohort study based on 323,373 UK-Biobank participants

OBJECTIVES

To examine the associations between four sleep behaviors and the risk of healthspan termination.

METHODS

This study included 323,373 participants, free of terminated healthspan at baseline, from the UK-Biobank (UKB). We applied multivariable-adjusted Cox regression models to estimate the risk of terminated healthspan based on four sleep behaviors (insomnia/sleeplessness, napping, daytime sleepiness, and difficulty getting up from bed), which were self-reported and measured on Likert scales from "usually" to "never/rarely" experiences. In this study, healthspan was defined based on eight events that are strongly associated with longevity (congestive heart failure, myocardial infarction, chronic obstructive pulmonary disease, stroke, dementia, diabetes, cancer, and death).

RESULTS

Participants who reported the following unhealthy sleep behaviors had a significantly higher risk of terminated healthspan: "usually experience sleeplessness/insomnia" (HR = 1.05, 95% CI: 1.03-1.07; P < 0.001); "usually nap" (HR = 1.22, 95% CI: 1.18-1.26; P < 0.01); "excessive daytime sleepiness" (HR = 1.25, 95% CI: 1.19-1.32; P < 0.001); and "difficult getting up from bed" (HR = 1.08, 95% CI: 1.05-1.10; P < 0.001). The corresponding population attributable risk percentage (PAR%) indicated that about 7% of healthspan termination in this cohort would have been eliminated if all participants had healthy sleep behaviors.

CONCLUSION

Participants who reported "usually experience sleeplessness/insomnia," "usually nap," "excessive daytime sleepiness," and "difficult getting up from bed" had increased risk of shortened healthspan. Therefore, adherence to healthy sleep behavior is significant for the extension of healthspan.

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.

Midday Nap Duration and Hypertension among Middle-Aged and Older Chinese Adults: A Nationwide Retrospective Cohort Study

The goal of this study was to investigate the associations of midday nap duration and change in midday nap duration with hypertension in a retrospective cohort using a nationwide representative sample of middle-aged and older Chinese adults. Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS) database during 2011–2015. Information on midday nap duration was collected via a self-reported questionnaire and blood pressure was objectively measured. Hazard ratios (HR) with 95% confidence interval (CI) were estimated using Cox proportional hazards regression models to quantify the associations. A sample of 5729 Chinese adults (≥45 years old) were included in the longitudinal analysis. Relative to non-nappers, participants who napping for ≥90 min/day was associated with significantly larger HR for hypertension at four-year follow-up (HR = 1.18, 95% CI = 1.01–1.40, p = 0.048). Compared with people who napped ≥90 min/day both at baseline (2011) and follow-up (2013), hypertension risk at four-year follow-up declined in individuals whose midday nap durations decreased in the 2-year study period from ≥ 90 min/day to 1–59 min/day (HR = 0.59, 95% CI = 0.36–0.97, p = 0.037) and 60–89 min/day (HR = 0.68, 95% CI = 0.47–0.99, p = 0.044). Among middle-aged and older Chinese adults, relative to non-nappers, people who had longer midday nap duration (≥90 min/day) were associated with significantly larger HR for hypertension and decreased napping duration may confer benefit for hypertension prevention.

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.

Association of daytime napping in relation to risk of diabetes: evidence from a prospective study in Zhejiang, China

BACKGROUND

Diabetes was a major risk factor for numerous chronic diseases. However, the associations between daytime napping and diabetes in the existing literature is still inconsistent.

METHODS

The analysis included 53,916 participants aged 30-79 years of the China Kadoorie Biobank prospective study from Tongxiang. Incident diabetes were identified through linkage with incident diabetes surveillance systems, health insurance system, and death registries. Cox regressions were used to estimate the associations of daytime napping with diabetes.

RESULTS

5.11% of participants reported habitual daytime napping. During 488,233 person-years (median 9.4 years) of follow-up, 3333 incident diabetes, including 1249 males and 2084 females, were documented. After adjusting for socio-demographic status, behavioral lifestyle, BMI, waist circumference and snoring, as comparison with those without daytime napping, the hazard ratios for risk of diabetes were 1.39 (95% CI 1.21-1.59). The corresponding figures for males and females were 1.45 (95% CI 1.20-1.74) and 1.30 (95% CI 1.05-1.59), respectively. The corresponding figures for postmenopausal and premenopausal females were 1.41 (95% CI 1.08-1.80) and 1.13 (95% CI 0.78-1.59), respectively.

CONCLUSIONS

Habitual daytime napping is positively associated with risk of diabetes in adults, except premenopausal females.

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.

Rest-activity rhythms in emerging adults: implications for cardiometabolic health

Emerging adulthood (18-25 years) represents a window of opportunity to modify the trajectory of cardiometabolic disease risk into older adulthood. Not known is the extent to which rest-activity rhythms (RAR) may be related to biomarkers of cardiometabolic health in this population. In this cross-sectional, observational study, 52 healthy emerging adults wore wrist accelerometers (14 consecutive days; 24 h/day) for assessment of nonparametric RAR metrics, including interdaily stability (IS; day-to-day RAR consistency), intradaily variability (IV; within-day RAR fragmentation), and relative amplitude (RA; robustness of RAR), as well as autocorrelation (correlation of rest/activity levels at 24-h lag-times). Cardiometabolic biomarkers, including body mass index (BMI), body fat percentage, blood pressure (BP), fasting lipids, glucose, and C-reactive protein (CRP) were assessed. Additional measures including physical activity, sleep duration, and habitual caffeine and alcohol consumption were also evaluated. A series of multivariable regression models of cardiometabolic biomarkers were used to quantify associations with RAR metrics. On average, participants were 20 ± 1 years of age (21 males, 31 females), non-obese, and non-hypertensive. All were nonsmokers and free of major diseases or conditions. In separate models, which adjusted for sex, BMI, moderate-vigorous physical activity, sleep duration, caffeine, and alcohol consumption, IS was inversely associated with total cholesterol (p ≤ 0.01) and non-HDL cholesterol (p < .05), IV was positively associated with CRP (p < .05), and autocorrelation was inversely associated with total cholesterol (p < .05) and CRP (p < .05). Conversely, associations between RA and cardiometabolic biomarkers were nonsignificant after adjustment for BMI, alcohol, and caffeine consumption. In conclusion, RAR metrics, namely, a higher IS, lower IV, and higher autocorrelation, emerged as novel biomarkers associated with more favorable indices of cardiometabolic health in this sample of apparently healthy emerging adults.

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.

The interactive effect of habitual midday napping and nighttime sleep duration on impaired fasting glucose risk in healthy adolescents

OBJECTIVES

To investigate the association between habitual midday napping and impaired fasting glucose (IFG), and the interactive effect of napping and time in bed (TIB) at night on IFG among healthy adolescents.

METHODS

The sample comprised 625 early adolescents (12.26 ± 0.63 years old) who self-reported good health status from Jintan, China. Midday napping and nighttime sleep were measured using the Youth Self-report Sleep Questionnaire. Fasting plasma glucose was dichotomized into normal (<5.6 mmol/L) and impaired (≥5.6 mmol/L) levels. The multivariate random-effect logistic regression examined the nap-glucose relationship and the interaction between nap and TIB. Marginal effects of napping were calculated when TIB was held constant at different values.

RESULTS

Of the participants, 83.20% (n = 520) took naps and 62.28% reported average nap durations ≥31 min in the past month. Moreover, 16% (n = 101) of participants had IFG. After adjusting for covariates, early adolescents who napped 3-4 days/week (OR = 1.72, p < 0.001), 5-7 days/week (OR = 1.34, p = 0.02) or ≥31 min/nap (OR = 1.52, 1.56, p's < 0.05) were associated with increased likelihoods of IFG compared to non-nappers. There was an inverse relationship between TIB and IFG among non-nappers (OR = 0.45, p = 0.03). Interaction analyses also showed significantly increased likelihoods of IFG only among nappers with TIB ≥9 hours.

CONCLUSION

The relationship between midday napping and IFG is dependent on TIB. Midday naps may increase the risk for IFG among early adolescents who have sufficient nighttime sleep. However, further research is needed to confirm our preliminary findings.

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.

Long Daytime Napping Is Associated with Increased Adiposity and Type 2 Diabetes in an Elderly Population with Metabolic Syndrome

Research examining associations between objectively-measured napping time and type 2 diabetes (T2D) is lacking. This study aimed to evaluate daytime napping in relation to T2D and adiposity measures in elderly individuals from the Mediterranean region. A cross-sectional analysis of baseline data from 2190 elderly participants with overweight/obesity and metabolic syndrome, in the PREDIMED-Plus trial, was carried out. Accelerometer-derived napping was measured. Prevalence ratios (PR) and 95% confidence intervals (CI) for T2D were obtained using multivariable-adjusted Cox regression with constant time. Linear regression models were fitted to examine associations of napping with body mass index (BMI) and waist circumference (WC). Participants napping ≥90 min had a higher prevalence of T2D (PR 1.37 (1.06, 1.78)) compared with those napping 5 to <30 min per day. Significant positive associations with BMI and WC were found in those participants napping ≥30 min as compared to those napping 5 to <30 min per day. The findings of this study suggest that longer daytime napping is associated with higher T2D prevalence and greater adiposity measures in an elderly Spanish population at high cardiovascular risk.

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.

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.

Prevalence and risk factors of excessive daytime sleepiness in major depression: A study with 703 individuals referred for polysomnography

BACKGROUND

To date, few studies have investigated the prevalence and risk factors of excessive daytime sleepiness (EDS) in major depression. Thus, the aim of the present study was to examine the prevalence and risk factors of EDS in a large sample of individuals with major depression.

METHODS

Data from 703 individuals with major depression were retrospectively collected from the sleep laboratory research database of Erasme Hospital for analysis. A score of > 10 on the Epworth Sleepiness Scale was used as the cut-off for EDS. Logistic regression analyses were conducted to examine the clinical and demographic risk factors of EDS in major depression.

RESULTS

The prevalence of EDS in our sample was 50.8%. Multivariate logistic regression analysis revealed that the following were significant risk factors of EDS in major depression: non-use of short to intermediate half-life benzodiazepine receptor agonists, BMI ≥ 25 kg/m², age < 60 years, C-reactive protein > 7 mg/L, Beck Depression Inventory score ≥ 16, atypical depression, apnea-hypopnea index ≥ 15/h, and use of selective serotonin reuptake inhibitors or serotonin-norepinephrine reuptake inhibitors.

LIMITATIONS

To evaluate EDS, we used the Epworth Sleepiness Scale, which only allows for a subjective measure of daytime sleepiness.

CONCLUSION

EDS is a common symptom in individuals with major depression. In this subpopulation, interventions are possible for most risk factors of EDS, which justifies improved management of this symptom to avoid its negative consequences.

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.

The relationship between depression, daytime napping, daytime dysfunction, and snoring in 0.5 million Chinese populations: exploring the effects of socio-economic status and age

BACKGROUND

Daytime napping has been postulated as both a protective and a risk factor for depression in previous studies. In addition to these conflicting results, research gaps also exist with regard to controlling confounding bias between daytime napping and depression and examining the potential association within the Chinese population. To facilitate the prevention and diagnosis of depression, this study aims to provide insight into the association of daytime napping and depression in 0.5 million Chinese adults by fully controlling confounders, and further examine the modifying effects of socio-economic status (SES) and age.

METHODS

Data were drawn from the baseline of a Chinese cohort study of 0.5 million adults. Depressive status was measured by the Composite International Diagnostic Inventory (CIDI). Logistic regression models were used to examine the association between depression and daytime napping adjusted for SES, sleep-related factors, lifestyle factors and related diseases. Further stratified analyses were conducted to identify the modifying effects of socio-economic status and age.

RESULTS

The odds ratio of depression by daytime napping was 1.15 (95% CI: 1.01-1.31) in females and 1.42 (95% CI: 1.18-1.71) in males. Factors including living in a rural area (OR = 1.31, 95% CI: 1.13-1.52), receiving less education (OR = 1.42, 95% CI: 1.22-1.66), getting married (OR = 1.24, 95% CI: 1.10-1.40) and being 45-65 years old (OR = 1.29, 95% CI: 1.12-1.49) had a modifying effect on daytime napping and depression that could strengthen the association.

CONCLUSIONS

A significantly positive association was found between depression and daytime napping, as well as daytime dysfunction, snoring and both shorter and longer sleep duration. Lower SES and age could possibly modify the association. Further clinical or epidemiological studies are needed to investigate the mechanism and facilitate the prevention of depression.

Association of daytime napping with prediabetes and diabetes in a Chinese population: Results from the baseline survey of the China Health and Retirement Longitudinal Study

BACKGROUND

Only a few studies have investigated the effects of daytime napping on diabetes, and these studies have reported conflicting results. The aim of the present study was to examine whether daytime napping is associated with a higher risk of prediabetes and diabetes.

METHODS

The present cross-sectional study of napping duration in relation to prediabetes and diabetes was conducted in 12 277 participants. Data from the first wave (2011) of the China Health and Retirement Longitudinal Study were used. Daytime napping was divided into four groups: no napping (reference) and napping for 1-30, 31-90, and >90 min. Multinomial logistic regression was used to obtain odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Individuals who reported taking daily afternoon naps accounted for 53.39% of all participants. Nappers had a higher prevalence of prediabetes and diabetes than non-nappers. Compared with the reference group, the weighted fully adjusted ORs (95% CI) were 1.36 (1.10-1.68) and 1.61 (1.22-2.13) for napping >90 min in prediabetic and diabetic patients, respectively.

CONCLUSIONS

Long daytime napping duration was positively associated with prediabetes and diabetes. Further physiological and cohort studies are needed to confirm these results and elucidate potential mechanisms.

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.

Self-reported sleep duration and napping, cardiac risk factors and markers of subclinical vascular disease: cross-sectional study in older men

STUDYOBJECTIVES

Daytime sleep has been associated with increased risk of cardiovascular disease and heart failure (HF), but the mechanisms remain unclear. We have investigated the association between daytime and night-time sleep patterns and cardiovascular risk markers in older adults including cardiac markers and subclinical markers of atherosclerosis (arterial stiffness and carotid intima-media thickness (CIMT)).

METHODS

Cross-sectional study of 1722 surviving men aged 71-92 examined in 2010-2012 across 24 British towns from a prospective study initiated in 1978-1980. Participants completed a questionnaire and were invited for a physical examination. Men with a history of heart attack or HF (n=251) were excluded from the analysis.

RESULTS

Self-reported daytime sleep duration was associated with higher fasting glucose and insulin levels (p=0.02 and p=0.01, respectively) even after adjustment for age, body mass index, physical activity and social class. Compared with those with no daytime sleep, men with daytime sleep >1 hour, defined as excessive daytime sleepiness (EDS), had a higher risk of raised N-terminal pro-brain natriuretic peptide of ≥400 pg/mL, the diagnostic threshold for HF (OR (95% CI)=1.88 (1.15 to 3.1)), higher mean troponin, reduced lung function (forced expiratory volume in 1 s) and elevated von Willebrand factor, a marker of endothelial dysfunction. However, EDS was unrelated to CIMT and arterial stiffness. By contrast, night-time sleep was only associated with HbA1c (short or long sleep) and arterial stiffness (short sleep).

CONCLUSIONS

Daytime sleep duration of >1 hour may be an early indicator of HF.

The association between daytime napping and risk of diabetes: a systematic review and meta-analysis of observational studies

OBJECTIVE

To investigate the association between daytime napping and prevalent/incident diabetes mellitus (DM) based on systematic review and meta-analytic data.

METHODS

The electronic databases of Embase, Medline, Pubmed and Web of Science were searched. Relevant studies were extracted by two reviewers independently. The associations between daytime napping (irrespective of duration), long nap (≥1 h/day) and short nap (<1 h/day), and risk of DM were assessed according to study types. Overall estimates were pooled using either fixed- or random-effect with inverse variance meta-analysis. Heterogeneity of included studies was assessed using the I² test and possible cause of the heterogeneity was examined by meta-regression analyses.

RESULTS

Ten studies (four cross-sectional and six longitudinal cohort) comprising a total of 304,885 individuals and 20,857 cases of DM were included in the systematic review, with an average napping prevalence of 47%. Nappers were found to have increased risk of DM in both cross-sectional and cohort studies. However, significant heterogeneity was present. Long nap (≥1 h/day) was associated with both prevalent and incident DM; in particular, those with a daily nap over 1 h had a 31% increased risk of developing DM during follow-up (95% confidence interval: 2-67%). Conversely, no such association was found in individuals with short naps (<1 h/day) in cohort studies.

CONCLUSIONS

Long daytime napping over 1 h per day was associated with increased risk of both prevalent and incident DM. Further studies are needed to confirm the findings.