Association of napping and all-cause mortality and incident cardiovascular diseases: a dose–response meta analysis of cohort studies

Changes in sleep score and leisure-time physical activity, their combination, and all-cause mortality in middle-aged and older Chinese adults: The Dongfeng-Tongji cohort study

OBJECTIVES

To prospectively investigate the associations of longitudinal changes in sleep score and LTPA and their combination with all-cause mortality.

METHODS

Among 12,543 participants (mean age: 66.1 years) from the Dongfeng-Tongji cohort, we calculated sleep score (range, 0-4, integrating bedtime, sleep duration, sleep quality, and midday napping, higher score indicating healthier sleep) and LTPA at baseline (2008-2010) and the first follow-up (2013) surveys and their 5-year changes (defining stable sleep score as no change and stable LTPA as change within 150 min/week). We prospectively documented deaths from the first follow-up survey (2013) through December 31, 2018.

RESULTS

During a mean 5.5-year follow-up, 792 deaths occurred. The 5-year changes in sleep score and LTPA were inversely associated with all-cause mortality risk, regardless of their initial values. When assessing 5-year changes in sleep score and LTPA jointly, compared with the stable sleep score-stable LTPA group, the decreased sleep score-decreased LTPA group had a 40 % (5-85 %) higher all-cause mortality risk, whereas the increased sleep score-increased LTPA group had a 34 % (9-52 %) lower risk. The direction of the joint association was mainly driven by sleep score change. Participants maintaining sleep scores ≥ 3 and LTPA ≥ 150 min/week over 5 years had a 44 % (28-56 %) lower all-cause mortality risk.

CONCLUSIONS

Promoting sleep hygiene and LTPA together may benefit efforts in reducing mortality risk, with particular attention to monitoring long-term sleep health.

Association of a Mediterranean Lifestyle With All-Cause and Cause-Specific Mortality: A Prospective Study from the UK Biobank

OBJECTIVE

To examine the association between the Mediterranean lifestyle and all-cause, cancer, and cardiovascular disease (CVD) mortality in a British population.

PATIENTS AND METHODS

We studied 110,799 individuals 40 to 75 years of age from the UK Biobank cohort, free of CVD or cancer between 2009 and 2012 who were followed-up to 2021. The Mediterranean lifestyle was assessed at baseline through the Mediterranean Lifestyle (MEDLIFE) index, derived from the lifestyle questionnaire and diet assessments and comprising three blocks: (1) "Mediterranean food consumption," (2) "Mediterranean dietary habits," and (3) "physical activity, rest, social habits, and conviviality." Death information was retrieved from death register records. Cox regression models were used to analyze the study associations.

RESULTS

During a median 9.4-year follow-up, 4247 total deaths, 2401 cancer deaths, and 731 CVD deaths were identified. Compared with the first quartile of the MEDLIFE index, increasing quartiles had HRs of 0.89 (95% CI, 0.81 to 0.97), 0.81 (95% CI, 0.74 to 0.89), and 0.71 (95% CI, 0.65 to 0.78) (P-trend<.001 for all-cause mortality). For cancer mortality, the quartiles had HRs of 0.90 (95% CI, 0.80 to 1.01), 0.83 (95% CI, 0.74 to 0.93), and 0.72 (95% CI, 0.64 to 0.82) (P-trend<.001). All MEDLIFE index blocks were independently associated with lower risk of all-cause and cancer death, and block 3 was associated with lower CVD mortality.

CONCLUSION

Higher adherence to the Mediterranean lifestyle was associated with lower all-cause and cancer mortality in British middle-aged and older adults in a dose-response manner. Adopting a Mediterranean lifestyle adapted to the local characteristics of non-Mediterranean populations may be possible and part of a healthy lifestyle.

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.

Association of insomnia and daytime napping with metabolic syndrome and its components in a Korean population: an analysis of data from the Korean Genome and Epidemiology Study

OBJECTIVES

We investigated the association between metabolic syndrome (MetS) and the coexistence of insomnia and daytime napping, because limited data have been reported regarding this association.

METHODS

The study population was 8,440 participants aged 40-65 years, who were from the Korean Genome and Epidemiology Study. Self-reported information on insomnia symptoms and nap duration was used to define exposure variables. Data on waist circumference (WC), blood pressure (BP), and fasting blood glucose (FBG), triglyceride (TG), and high-density lipoprotein cholesterol levels in blood were used to define MetS. Multivariate logistic regression analysis was performed to obtain odds ratio (OR) and 95% confidence interval (CI).

RESULTS

In multivariate logistic regression analysis, the coexistence of insomnia and napping was not significantly associated with MetS. However, the insomnia and non-napping group showed higher ORs of high TG (OR, 1.19; 95% CI, 1.02 to 1.39) and high BP (OR, 1.28; 95% CI, 1.10 to 1.49) than the non-insomnia and non-napping group. The combination of non-insomnia and napping and that of insomnia and napping showed higher ORs of high TG (OR, 1.13; 95% CI, 1.00 to 1.29) and high FBG (OR, 1.59; 95% CI, 1.14 to 2.21), respectively. In analyses of insomnia symptoms, only the combination of difficulty in maintaining sleep (DMS) and non-napping showed a higher OR for MetS (OR, 1.25; 95% CI, 1.03 to 1.52) than the non-DMS and non-napping group.

CONCLUSIONS

Individuals with insomnia, particularly those who do not take naps, were disproportionately likely to have MetS components, especially TG or BP. Information on these variables may help predict individuals' vulnerability to specific MetS components.

Causal associations between leisure sedentary behaviors and sleep status with frailty: insight from Mendelian randomization study

BACKGROUND

Observational studies have suggested that sedentary behaviors and sleep status are associated with frailty. However, it remains unclear whether these associations are causal.

METHODS

Using summary statistics from genome-wide association studies, we evaluated the causal effect of modifiable risk factors, including leisure sedentary behaviors and sleep status on the frailty index (FI) using two-sample univariable and multivariable Mendelian randomization (MR) analyses. Genetic correlations were tested between the correlated traits.

RESULTS

We identified potential causal associations between the time spent watching television (β = 0.26, 95% confidence interval [CI]: 0.21-0.31, P = 3.98e-25), sleep duration (β = -0.18, 95%CI: -0.26, -0.10; P = 6.04e-06), and daytime napping (β = 0.29, 95%CI: 0.18-0.41, P = 2.68e-07) and the FI based on the inverse-variance-weighted method. The estimates were consistent across robust and multivariate MR analyses. Linkage disequilibrium score regression detected a genetic correlation between the time spent watching television (Rg = 0.43, P = 6.46e-48), sleep duration (Rg = -0.20, P = 5.29e-10), and daytime napping (Rg = 0.25, P = 3.34e-21) and the FI.

CONCLUSIONS

Genetic predispositions to time spent watching television and daytime napping were positively associated with the FI, while sleep duration was negatively associated with the FI. Our findings offer key insights into factors influencing biological aging and suggest areas for interventions to promote healthy aging and slow down the aging process.

Sleep Duration and Daytime Napping and Risk of Type 2 Diabetes Among Japanese Men and Women: The Japan Collaborative Cohort Study for Evaluation of Cancer Risk

BACKGROUND

Little is known about the impacts of sleep duration and daytime napping on the risk of type 2 diabetes mellitus (T2DM).

METHODS

In this study, 20,318 participants (7,597 men, 12,721 women) aged 40-79 years without a history of T2DM, stroke, coronary heart disease, or cancer at baseline (1988-1990), completed the baseline survey and the 5-year follow-up questionnaires, which included average sleep duration, napping habits, and self-reports of physician-diagnosed diabetes. The multivariable odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using a logistic regression model.

RESULTS

During the 5-year follow-up, 531 new cases of T2DM (266 men and 265 women) were documented. Sleep duration ≥10 hours was associated with higher risk of T2DM compared to sleep duration of 7 hours (OR 1.99; 95% CI, 1.28-3.08). The excess risk was observed for both sexes and primarily found among the non-overweight; the multivariable ORs of sleeping ≥10 hours compared to 7 hours were 2.05 (95% CI, 1.26-3.35) for the non-overweight (BMI <25 kg/m2) and 1.38 (95% CI, 0.49-3.83) for the overweight (BMI ≥25 kg/m2). The respective ORs of nappers versus non-nappers were 1.30 (95% CI, 1.03-1.63) and 0.92 (95% CI, 0.65-1.29). Among the non-overweight, nappers who slept ≥10 hours had the highest risk of T2DM (OR 2.84; 95% CI, 1.57-5.14), non-nappers who slept ≥10 hours (OR 2.27; 95% CI, 1.27-4.06), and nappers who slept <10 hours (OR 1.30; 95% CI, 1.03-1.64), compared with non-nappers who slept <10 hours.

CONCLUSION

Long sleep duration was associated with the risk of T2DM in both sexes, which was confined to the non-overweight.

Association of healthy sleep pattern with risk of recurrent cardiovascular events among patients with coronary heart disease

AIMS

To examine the association of a healthy sleep pattern with the risk of recurrent cardiovascular events among patients with coronary heart disease (CHD).

METHODS AND RESULTS

This prospective cohort study included 21 193 individuals with CHD from the UK Biobank. A healthy sleep score was generated based on a combination of chronotype, sleep duration, insomnia, and excessive daytime sleepiness. Cox proportional hazards regression models were applied to estimate the associations between healthy sleep score and recurrent cardiovascular events. During a median of 11.1 years of follow up, we documented 3771 recurrent cardiovascular events, including 1634 heart failure cases and 704 stroke cases. After multivariable adjustment, including lifestyle factors, medical history, and CHD duration, sleep 7-8 h/day, never/rarely insomnia, and no frequent daytime sleepiness were each significantly associated with a 12-22% lower risk of heart failure. In addition, compared with participants who had a healthy sleep score of 0-1, the multivariable-adjusted HR (95% CI) for participants with a healthy sleep score of 4 was 0.86 (0.75, 0.99) for recurrent cardiovascular events, 0.71 (0.57, 0.89) for heart failure, and 0.72 (0.51, 1.03) for stroke.

CONCLUSIONS

Adherence to a healthy sleep pattern was significantly associated with a lower risk of recurrent cardiovascular events among patients with CHD, especially for heart failure. These findings indicate that healthy sleep behaviours could be beneficial in the prevention of cardiovascular event recurrence.

Association of Midday Napping with All-Cause Mortality in Chinese Adults: A 8-Year Nationwide Cohort Study

This study aimed to investigate the longitudinal association of estimated daytime nap duration with all-cause mortality in Chinese adults. We conceived a prospective cohort design using adult survey data of the baseline and four follow-up waves (2010-2019) from China Family Panel Studies. Cox frailty models with random intercepts for surveyed provinces were used to estimate risks of all-cause mortality associated with midday napping. Trend and subgroup analyses were also performed stratified by demographic, regional and behavioral factors. Compared with non-nappers, those who reported a long napping duration (≥60 min/day) had an increased risk of all-cause mortality, while shorter napping (<60 min) showed no association with mortality. We observed significant trends for greater risks of mortality associated with longer nap duration. Long nap-associated higher risk of all-cause mortality was seen in a group of nocturnal sleep duration ≥9 h. We identified stronger associations of long nap with mortality among adults aged over 50 years, those with lower BMI (<24 kg/m2), residents in rural regions and unregular exercisers. Long midday napping is independently associated with higher risks of all-cause mortality in Chinese adults.

Association of longitudinal patterns of nighttime sleep duration and daytime napping duration with risk of multimorbidity

OBJECTIVES

To determine whether longitudinal trajectories of nighttime sleep duration and daytime napping duration are related to subsequent multimorbidity risk. To explore whether daytime napping can compensate for negative effects of short nighttime sleep.

METHODS

The current study included 5262 participants from China Health and Retirement Longitudinal Study. Self-reported nighttime sleep duration and daytime napping duration were collected from 2011 to 2015. The 4-year sleep duration trajectories were conducted by group-based trajectory modeling. The 14 medical conditions were defined by self-reported physician diagnoses. Multimorbidity was diagnosed as participants with 2 or more of the 14 chronic diseases after 2015. Associations between sleep trajectories and multimorbidity were assessed by Cox regression models.

RESULTS

During 6.69 years of follow-up, we observed multimorbidity in 785 participants. Three nighttime sleep duration trajectories and three daytime napping duration trajectories were identified. Participants with persistent short nighttime sleep duration trajectory had the higher risk of multimorbidity (hazard ratio = 1.37, 95% confidence interval: 1.06-1.77), compared with those with persistent recommended nighttime sleep duration trajectory. Participants with persistent short nighttime sleep duration and persistent seldom daytime napping duration had the highest risk of multimorbidity (hazard ratio = 1.69, 95% confidence interval: 1.16-2.46).

CONCLUSIONS

In this study, persistent short nighttime sleep duration trajectory was associated with subsequent multimorbidity risk. Daytime napping could compensate for the risk of insufficient night sleep.

Predictors of total mortality and their differential association on premature or late mortality in the SUN cohort

Several studies have tried to analyse the association between all-cause mortality and different risk factors, (especially those which are modifiable, such as smoking, diet or exercise), to develop public health preventive strategies. However, a specific analysis of predictors of premature and late mortality is needed to give more precise recommendations. Considering that there are risk factors which exert an influence on some diseases and not on others, we expect that, similarly, they may have a different impact depending on the timing of mortality, separating premature (≤65 years) from late mortality (>65 years). Thus, we prospectively followed-up during a median of 12 years a cohort of 20,272 university graduates comprising an ample range of ages at inception. Time-dependent, covariate-adjusted Cox models were used to estimate adjusted hazard ratios (HR) and their 95 % confidence intervals (CI) for each predictor. The strongest independent predictor of mortality at any age was physical activity which was associated with reduced risk of total, premature and late mortality (range of HRs when comparing the highest vs. the lowest level: 0.24 to 0.48). Specific strong predictors for premature mortality were smoking, HR: 4.22 (95 % CI: 2.42-7.38), and the concurrence of ≥2 metabolic conditions at baseline, HR: 1.97 (1.10-3.51). The habit of sleeping a long nap (≥30 min/d), with HR: 2.53 (1.30-4.91), and poor adherence to the Mediterranean Diet (≤3 points in a 0 to 8 score vs. ≥6 points), with HR: 2.27 (1.08-4.76), were the strongest specific predictors for late mortality. Smoking, diet quality or lifestyles, probably should be differentially assessed as specific predictors for early and late mortality. In the era of precision medicine, this approach will allow tailored recommendations appropriate to each person's age and baseline condition.

Goldilocks at work: Just the right amount of job demands may be needed for your sleep health

OBJECTIVES

It has been reported that job demands affect sleep, but how different levels of job demands affect sleep remains unclear. We examined whether curvilinear relationships exist between job demands and multiple sleep health outcomes.

DESIGN

Cross-sectional analyses with linear and quadratic effects, using self-administered survey data.

SETTING

A national sample of US adults.

PARTICIPANTS

Workers from Midlife in the United States Study (MIDUS2; n = 2927).

MEASUREMENTS

The Job Content Questionnaire assessed overall and 5 specific aspects of job demands (intensity, role conflict, work overload, time pressure, and interruptions). Habitual sleep health patterns across 5 dimensions (regularity, satisfaction/quality, daytime alertness, efficiency, and duration) were assessed. Age, sex, race/ethnicity, marital/partnered status, education, job tenure, work hours, body mass index, smoking status, and study sample were covariates.

RESULTS

There were significant linear and quadratic relationships between job demands and sleep outcomes. Specifically, the linear effects indicated that participants with higher job demands had worse sleep health, such as shorter duration, greater irregularity, greater inefficiency, and more sleep dissatisfaction. The quadratic effects, however, indicated that sleep regularity and efficiency outcomes were the best when participants' job demands were moderate rather than too low or too high. These effects were found for overall job demands as well as for specific aspects of job demands. Stratified analyses further revealed that these curvilinear associations were mainly driven by participants with low job control.

CONCLUSIONS

Moderate levels of job demands, especially if combined with adequate job control, are related to optimal sleep health.

Causal relationships of excessive daytime napping with atherosclerosis and cardiovascular diseases: a Mendelian randomization study

STUDY OBJECTIVES

Previous observational studies have found conflicting evidence on the relationship between daytime napping and incident cardiovascular diseases (CVDs), but it remains unclear whether these associations present causality. This study aims to verify whether and why there is a causal relationship between these parameters, and whether there is an etiological basis.

METHODS

A two-sample Mendelian randomization analysis was performed using 79 single nucleotide polymorphisms associated with daytime napping. Summary-level data for coronary atherosclerosis, peripheral atherosclerosis, total CVD, and five CVD outcomes were obtained from the FinnGen study. Meta-analyses were aimed at investigating the relationships of excessive daytime napping with total CVD, coronary heart disease, myocardial infarction (MI), and stroke incidence. Subgroup, network meta-analysis (NMA) and trial sequential analysis (TSA) were also performed in this study.

RESULTS

The inverse-variance weighted method demonstrated that a genetic predisposition to more frequent daytime napping was significantly associated with higher odds of coronary atherosclerosis (odds ratio [OR] = 1.55, 95% confidence interval [CI]: 1.11 to 2.17), MI (OR = 1.63, 95% CI: 1.06 to 2.50), and heart failure (OR = 1.80, 95%CI: 1.28 to 2.52). In NMA, an increased risk of developing CVD in people who napped for more than 60 min a day than those who did not nap was demonstrated and then supported by TSA results (summary relative risk = 1.98, 95% CI: 1.39 to 2.82).

CONCLUSION

Habitual daytime napping is causally associated with an increased risk of incident CVD primarily via the development of coronary atherosclerosis. An average napping duration of more than 60 min is associated with an elevated risk of CVD in all participants.

Association between napping and 24-hour blood pressure variability among university students: A pilot study

Background

Blood pressure variability (BPV) has been reported to be a predictor of cardiovascular and some cognitive diseases. However, the association between napping and BPV remains unknown. This study aimed to explore the association between napping and BPV.

Materials and methods

A cross-sectional study including 105 university students was conducted. Participants' 24 h ambulatory blood pressure monitoring (24 h ABPM) were measured, and napping behaviors were investigated. BPV were measured by the 24 h ABPM, included standard deviation (SD), coefficient of variation (CV), and average real variability (ARV).

Results

Among the participants, 61.9% reported daytime napping. We found that nap duration was significantly associated with daytime CV of diastolic blood pressure (DBP) (r = 0.250, P = 0.010), nighttime CV of systolic blood pressure (SBP) (r = 0.217, P = 0.026), 24 h WCV of DBP (r = 0.238, P = 0.014), 24 h ARV of SBP (r = 0.246, P = 0.011) and 24 h ARV of DBP (r = 0.291, P = 0.003). Compared with the no napping group, 24 h WCV of DBP, daytime CV of DBP, and daytime SD of DBP were significantly higher in participants with napping duration >60 min. With multiple regression analysis we found that nap duration was an independent predictor for 24 h ARV of SBP (β = 0.859, 95% CI, 0.101-1.616, P = 0.027) and 24 h ARV of DBP (β = 0.674, 95% CI, 0.173-1.175, P = 0.009).

Conclusions

Napping durations are associated with BPV among university students. Especially those with napping durations >60 min had a significantly higher BPV than those non-nappers.

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.

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.

Association of Sleep Duration, Midday Napping with Atrial Fibrillation in Patients with Hypertension

Objective

This study aimed to assess the associations of sleep duration, midday napping and the risk of atrial fibrillation (AF) in patients with hypertension.

Methods

We conducted a cross-sectional study enrolling 11,524 hypertensive participates from the Chinese Hypertension Registry Study. Information on sleep duration and midday napping were obtained by a self-administered questionnaire. Multivariate logistic regression analyses were performed to estimate odds ratio (OR) and 95% confidence intervals (CIs) for the risk of AF.

Results

Compared with sleeping 6 to ≤8 hours/night, those reporting shorter sleep duration (≤5 hours/night) had a greater risk of AF (OR 1.95; 95% CI 1.28–2.95) in the fully adjusted model, while longer sleep (≥9 hours/night) was not significantly associated with the risk of AF. Compared with nonhabitual nappers, nappers had a higher risk of AF (OR 1.28; 95% CI 1.03–1.60) in the fully adjusted model. Moreover, we observed significant joint effects of sleeping ≤5 hours/night and nap (OR 2.13; 95% CI 1.09–4.14) on the risk of AF after adjusting for confounding factors.

Conclusion

Short sleep duration and midday napping were independently and jointly associated with higher risks of AF in patients with hypertension.

Cardiovascular risks and sociodemographic correlates of multidimensional sleep phenotypes in two samples of US adults

Study Objectives

Sleep is a modifiable risk factor for cardiovascular conditions. Holistic examination of within-person, multidimensional sleep patterns may offer more detailed information about the sleep-cardiovascular condition link, including who is more vulnerable to both. This study aimed to identify common sleep phenotypes in adulthood, establish the validity of the phenotypes in relation to cardiovascular conditions, and explore sociodemographic and background characteristics of the phenotypes.

Methods

Across two independent samples of adults (N ₁ = 4600; N ₂ = 2598) from the Midlife in the United States Study, latent class analysis (LCA) extracted sleep phenotypes using five key self-reported sleep dimensions. Log-binomial regression was used to determine whether sleep phenotypes differentially predicted cardiovascular conditions, adjusting for known risk factors. LCA with covariates was used to compare sociodemographic characteristics of the identified sleep phenotypes.

Results

Four sleep phenotypes were identified consistently across the two samples: good sleepers, nappers, dissatisfied/inefficient sleepers, and irregular sleepers. Compared to good sleepers (reference), dissatisfied/inefficient sleepers exhibited a higher risk of cardiovascular conditions in both samples (RR _Sample1: 29%, RR _Sample2: 53%) and consisted of relatively more racial/ethnic minorities. Nappers exhibited a higher risk of cardiovascular conditions in one sample (RR _Sample1: 38%) and consisted of more women and older adults. Irregular sleepers exhibited no significantly different cardiovascular risk and were relatively younger.

Conclusions

Common sleep phenotypes in adulthood exhibit differential risks for cardiovascular conditions. Cooccurring sleep dissatisfaction and inefficiency, in particular, may relate to increased risk of cardiovascular conditions. Certain sociodemographic groups (racial minorities, women, older adults) disproportionately fit within high-risk sleep phenotypes.

Nighttime sleep duration, daytime napping, and metabolic syndrome: findings from the China Health and Retirement Longitudinal Study

PURPOSE

This study aimed to assess the association between nighttime sleep, daytime napping, and metabolic syndrome (MetS) in an elderly Chinese population.

METHODS

A cross-sectional study was conducted using data from the 2011 China Health and Retirement Longitudinal Study (CHARLS) to examine the association between nighttime sleep, daytime napping, and MetS (defined according to the Chinese Diabetes Society criteria). Sleep duration was assessed by a self-reported questionnaire. Binary logistic regression models were used to estimate odds ratios and 95% confidence intervals of the associations adjusting for covariates.

RESULTS

Among 4785 elderly Chinese aged over 65 years old, there was no association between short-time sleep duration (< 7 h/day) and MetS. However, long-time sleep duration (> 8 h/day) decreased the odds of MetS by 53% (aOR= 0.47; 95% CI 0.23-0.96) compared to normal sleep duration (7-8 h/day). Compared to no daytime napping, short-time napping (≤ 30 min/day) was associated with increased odds of MetS (aOR = 1.55, 95% CI 1.02-2.36) and long-time napping (> 30 min/day) was associated with even higher odds of MetS (aOR = 1.77, 95%CI 1.24-2.53). Individuals who were over 75 years old, with elementary school education, and good health status had lower odds of MetS, while women, individuals living in rural areas, and those who reported poor health status had higher odds of MetS.

CONCLUSION

Long-time sleep duration decreased and daytime napping increased the risk of MetS among the elderly Chinese population. We speculate that increasing nighttime sleep duration and decreasing daytime napping may help reduce the risk of MetS.

Sleep and Cardiovascular Risk

Sleep is essential for healthy being and healthy functioning of human body as a whole, as well as each organ and system. Sleep disorders, such as sleep-disordered breathing, insomnia, sleep fragmentation, and sleep deprivation are associated with the deterioration in human body functioning and increased cardiovascular risks. However, owing to the complex regulation and heterogeneous state sleep per se can be associated with cardiovascular dysfunction in susceptible subjects. The understanding of sleep as a multidimensional concept is important for better prevention and treatment of cardiovascular diseases.

Association between daytime napping and stroke: A dose-response meta-analysis

Daytime napping is common in many regions around the world and has been an important part of people's daily life. Daytime napping has attracted increasing attention in recent years. Thus, we conducted a meta-analysis to evaluate the relationship between daytime napping and stroke, and help reduce the risk of stroke by improving living habits. The Embase, PubMed, Web of Science and PsycINFO databases were searched for cohort studies published before October 2020 and eight eligible studies with 524,408 participants and 5,875 stroke cases were included in the final analysis. The pooled relative risk (RR) of stroke was 1.47 (95% confidence interval [CI]: 1.24-1.74; p < .001) with significant heterogeneity (I²  = 58%, p for heterogeneity = 0.02). However, the heterogeneity decreased when the study in which adjusting for sleep duration and stratifying the results based on sleep duration was not performed was excluded (RR: 1.38; 95% CI: 1.19-1.60, I²  = 44%, p for heterogeneity = 0.10). In dose-response analysis, the linear trend indicated that for every 10-min increase in daytime napping, the risk of stroke increased by 3%. Further well-designed large studies are needed to explore the effects of daytime napping on stroke and the underlying biological mechanisms.