Midday naps and the risk of coronary artery disease: results of the Heinz Nixdorf Recall Study

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Association of 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.

Association of modifiable risk factors with obstructive sleep apnea: a Mendelian randomization study

BACKGROUND

The risk factors involved in obstructive sleep apnea (OSA) have not been clearly identified yet. We attempted to systematically investigate genetically predicted modifiable risk factors and lifestyle behaviors associated with OSA.

METHODS

The association between 34 risk factors and OSA was evaluated using the two-sample Mendelian randomization (MR). Genetic variants for risk factors were acquired from European-descent genome-wide studies. Data sources for OSA were extracted from FinnGen study with 16,761 cases and 201,194 controls. The primary analysis chosen was the inverse-variance weighted method.

RESULTS

MR analyses provide evidence of genetically predicted poor overall health rating (odds ratio (OR), 2.82; 95% confidence interval (CI), 1.95-4.08), nap during day (OR, 2.01; 95% CI, 1.37-2.93), high body mass index (BMI) (OR, 1.14; 95% CI, 1.09-1.19), increased body fat mass (OR, 1.83; 95% CI, 1.83-2.05), elevated body water mass (OR, 1.50; 95% CI, 1.31-1.70) and hypertension (OR, 1.81; 95% CI, 1.34-2.45) were associated with higher OSA risk, while high education level (OR, 0.55; 95% CI, 0.40-0.75) correlated with reduced OSA risk. Suggestive evidence was obtained for smoking and waist-to-hip ratio (WHR) with higher OSA odds, and vigorous physical activity, and HDL cholesterol with lower OSA odds. After adjusting for BMI using multivariable MR analysis, the effects of smoking, WHR, vigorous physical activity, and HDL-cholesterol were fully attenuated.

CONCLUSIONS

This MR study indicates that overall health rating, nap during day, BMI, body fat mass, body water mass, hypertension, and education are causally associated with the risk of OSA, which means that these modifiable risk factors are key targets for OSA prevention.

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.

Characterization of global research trends and prospects on sudden coronary death: A literature visualization analysis

Background

Sudden coronary death is a major global public health issue that has a significant impact on both individuals and society. Nowadays, scholars are active in sudden coronary death all over the world. However, no relevant bibliometric studies have been published. Here, we aim to gain a better understanding the current state of research and to explore potential new research directions through bibliometric analysis.

Methods

Articles and reviews on sudden coronary death from 2012 to 2023 were retrieved from the Web of Science Core Collection (WoSCC). The topic search was conducted using the following keywords: ((("sudden cardiac death" OR "sudden death") AND (coronary OR "myocardial infarction")) OR "sudden coronary death"). Knowledge maps of authors, countries, institutions, journals, keywords, and citations were conducted by CiteSpace. Publication dynamics, hotspots, and frontiers were analyzed independently by authors.

Results

A total of 2914 articles were identified from January 1, 2012 to June 20, 2023. The USA (n = 972) contributed the greatest absolute productivity and UK (centrality = 0.13) built a robust global collaboration. Harvard University was the institution with the highest number of publications (n = 143). Huikuri HV and Junttila MJ were the most published authors who devoted to searching for biomarkers of sudden coronary death. American Journal of Cardiology was the journal with the most publications, and Circulation was the most cited journal. Left ventricular ejection fraction, society, inflammation, and fractional flow reserve became novel burst words that lasted until 2023. Research on etiology and pathology, role of early risk factors in risk stratification, potential predictive biomarkers and novel measurement methods for the prevention and management of sudden coronary death were identified as the research hotspots and frontiers.

Conclusion

Our knowledge and understanding of sudden coronary death have significantly improved. Ongoing efforts should focus on the various etiologies and pathologies of sudden coronary death. Furthermore, a novel sudden coronary death risk model, large-scale population studies, and the rational use of multiple indicators to individualize the assessment of sudden coronary death and other risk factors are other emerging research trends.

Lifestyle mediators of associations among siestas, obesity, and metabolic health

OBJECTIVE

The aim of this study was to determine the association between siestas/no siestas and obesity, considering siesta duration (long: >30 minutes, short: ≤30 minutes), and test whether siesta traits and/or lifestyle factors mediate the association of siestas with obesity and metabolic syndrome (MetS).

METHODS

This was a cross-sectional study of 3275 adults from a Mediterranean population (the Obesity, Nutrigenetics, TIming, and MEditerranean [ONTIME] study) who had the opportunity of taking siestas because it is culturally embedded.

RESULTS

Thirty-five percent of participants usually took siestas (16% long siestas). Compared with the no-siesta group, long siestas were associated with higher values of BMI, waist circumference, fasting glucose, systolic blood pressure, and diastolic blood pressure, as well as with a higher prevalence of MetS (41%; p = 0.015). In contrast, the probability of having elevated SBP was lower in the short-siesta group (21%; p = 0.044) than in the no-siesta group. Smoking a higher number of cigarettes per day mediated the association of long siestas with higher BMI (by 12%, percentage of association mediated by smoking; p < 0.05). Similarly, delays in nighttime sleep and eating schedules and higher energy intake at lunch (the meal preceding siestas) mediated the association between higher BMI and long siestas by 8%, 4%, and 5% (all p < 0.05). Napping in bed (vs. sofa/armchair) showed a trend to mediate the association between long siestas and higher SBP (by 6%; p = 0.055).

CONCLUSIONS

Siesta duration is relevant in obesity/MetS. Timing of nighttime sleep and eating, energy intake at lunch, cigarette smoking, and siesta location mediated this association.

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.

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.

Risk of Developing Metabolic Syndrome Is Affected by Length of Daily Siesta: Results from a Prospective Cohort Study

Background: Siesta has been associated with increased incidence of cardiovascular disease but the mechanism remains unclear. New studies into the relationship between siesta and metabolic syndrome have identified siesta length as a crucial differential, suggesting that siesta less than 40 min is associated with decreased risk of metabolic syndrome, while longer siesta is associated with increased risk. We aimed to investigate the effect of siesta duration on development of metabolic syndrome in a Mediterranean population using a prospective cohort study design. Methods: Our sample consisted of 9161 participants of the SUN cohort without components of metabolic syndrome at baseline. Siesta exposure was assessed at baseline and the development of metabolic syndrome components was assessed after an average 6.8 years of follow-up. We estimated odds ratios and fitted logistic regression models to adjust for potential cofounders including night-time sleep duration and quality, as well as other diet, health, and lifestyle factors. Results: We observed a positive association between average daily siesta >30 min and development of metabolic syndrome (aOR = 1.39 CI: 1.03–1.88). We found no significant difference in risk of developing metabolic syndrome between the group averaging ≤30 min of daily siesta and the group not taking siesta (aOR = 1.07 CI: 0.83–1.37). Further analysis suggested that average daily siesta <15 min may reduce risk of metabolic syndrome. Conclusions: Our study supports the J-curve model of the association between siesta and risk of metabolic syndrome, but suggests the protective effect is limited to a shorter range of siesta length than previously proposed.

Effects of sleep habits on acute myocardial infarction risk and severity of coronary artery disease in Chinese population

Background

Growing evidence indicates that poor sleep harms health. Early to bed and early to rise is considered as a healthy lifestyle in Chinese population. The current study aimed to examine the effects of sleep habits on acute myocardial infarction (AMI) risk and severity of coronary artery disease (CAD) in Chinese population from two centers.

Methods

A total of 873 patients including 314 AMI cases and 559 controls were recruited from the inpatient cardiology department of the Affiliated Jiangning Hospital and the First Affiliated Hospital of Nanjing Medical University. 559 controls included 395 CAD cases and 164 non-CAD cases. We used a 17-item sleep factors questionnaire (SFQ) to evaluate sleep habits comprehensively by face-to-face interview. The severity of CAD was assessed by Gensini score in AMI and CAD groups. The effects of sleep factors on AMI risk and Gensini score were examined by unconditional logistic regression.

Results

After mutually adjustment for other sleep factors and demographic characteristics, the timing of sleep (24:00 and after) and morning waking (after 7:00) and sleep duration (< 6 h) were associated with increased risk of AMI (OR = 4.005, P < 0.001, OR = 2.544, P = 0.011 and OR = 2.968, P < 0.001, respectively). Lower level of light exposure at night was correlated with reduced risk of AMI (OR = 0.243, P = 0.009). In subgroup analysis by age, both late sleep timing and short sleep duration were associated with increased risk of AMI regardless of age. In subjects with age ≤ 65 years, daytime napping was related to reduced risk of AMI (OR = 0.645, P = 0.046). In subjects with age > 65 years, the frequency of night-time waking (3 times) was associated with increased risk of AMI (OR = 3.467, P = 0.035). Short sleep duration was correlated with increased risk of high Gensini score (OR = 2.374, P < 0.001).

Conclusion

Sleep insufficiency is an important risk factor both for AMI risk and CAD severity. Late sleeping is also associated with increased risk of AMI. In young and middle-aged people, regular naps may have a protective effect.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02251-8.

Objective Assessment of Daytime Napping and Incident Heart Failure in 1140 Community-Dwelling Older Adults: A Prospective, Observational Cohort Study

Background

Disrupted nighttime sleep has been associated with heart failure (HF). However, the relationship between daytime napping, an important aspect of sleep behavior commonly seen in older adults, and HF remains unclear. We sought to investigate the association of objectively assessed daytime napping and risk of incident HF during follow‐up.

Methods and Results

We studied 1140 older adults (age, 80.7±7.4 [SD] years; female sex, 867 [76.1%]) in the Rush Memory and Aging Project who had no HF at baseline and were followed annually for up to 14 years. Motor activity (ie, actigraphy) was recorded for ≈10 days at baseline. We assessed daytime napping episodes between 9 am and 7 pm objectively from actigraphy using a previously published algorithm for sleep detection. Cox proportional hazards models examined associations of daily napping duration and frequency with incident HF. Eighty‐six participants developed incident HF, and the mean onset time was 5.7 years (SD, 3.4; range, 1–14). Participants who napped longer than 44.4 minutes (ie, the median daily napping duration) showed a 1.73‐fold higher risk of developing incident HF than participants who napped <44.4 minutes. Consistently, participants who napped >1.7 times/day (ie, the median daily napping frequency) showed a 2.20‐fold increase compared with participants who napped <1.7 times/day. These associations persisted after adjustment for covariates, including nighttime sleep, comorbidities, and cardiovascular disease/risk factors.

Conclusions

Longer and more frequent objective napping predicted elevated future risk of developing incident HF. Future studies are needed to establish underlying mechanisms.

The effect of Mid-Day Sleep on blood pressure levels in patients with arterial hypertension

STUDY OBJECTIVES

Lifestyle changes decrease blood pressure (BP) levels by 3-5 mmHg in hypertensive patients. We assessed the effect of mid-day sleep on BP levels in hypertensive patients.

METHODS

We prospectively studied two hundred and twelve hypertensive patients. Mid-day sleep duration, lifestyle habits, anthropometric characteristics, office BP, ambulatory BP monitoring, pulse wave velocity (PWV), augmentation index (AI) were recorded. A standard echocardiographic evaluation was performed.

RESULTS

53.8% were females, mean age was 62.5±11.0 years and mean body mass index was 28.9±5.4kg/m². Mean average 24h systolic and diastolic BP (SBP & DBP) was 129.9±13.2/76.7±7.9 mmHg respectively. The majority was non-smokers (70.3%) and did not have diabetes (74.7%). The mean midday sleep duration was 48.7±54.3 min. Average 24h SBP (127.6±12.9 mmHg vs 132.9±13.1 mmHg), average daytime SBP & DBP were lower in patients who sleep at midday, compared to those who do not (128.7±13/76.2±11.5 vs 134.5±13.4/79.5±10.4 mmHg) (p<0.005). The effect was not correlated to the dipping status. Midday sleep duration was negatively correlated with average 24h SBP & daytime SBP. In a linear regression model, for every 60 min of midday sleep, 24h average SBP decreases by 3 mmHg (p<0.001). There were no differences in the number of antihypertensive medications, PWV, AI or echocardiographic indices between study groups.

CONCLUSIONS

Mid-day sleep significantly decreases average 24h and daytime SBP/DBP in hypertensives. Its effect seems to be as potent as other well-established lifestyle changes and is independent of dipping status.

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.

One-year changes in self-reported napping behaviors across the retirement transition

OBJECTIVE

To estimate associations of retirement with self-reported frequency and duration of naps.

DESIGN

Prospective cohort study.

SETTING

Population-based.

PARTICIPANTS

1359 current and former Wisconsin state employees, aged 54-69.

MEASUREMENTS

Four annual surveys mailed between 2010 and 2014 elicited employment status and nap characteristics. Changes in employment status and nap characteristics were identified from survey pairs measured 1 year apart (up to 3 survey pairs per subject). General linear mixed models with repeated measures were used to estimate changes in minutes napped per week (MNPW), weekly nap frequency, and individual nap duration as predicted by retirement transitions vs stable employment status. All models were adjusted for demographic characteristics, self-rated health, medical diagnoses, sleep problems, circadian preference, and change in nocturnal sleep duration.

RESULTS

There were 3101 survey pairs in the analytic sample. Full retirement (transition from working ≥35 h/wk to not working for pay) over a 1-year period predicted a statistically significantly larger mean change in MNPW than stable employment status: mean (95% confidence interval) = +48 (+16, +80) MNPW. Associations between staged retirement transitions (from full-time to part-time work, or from part-time work to full retirement) and 1-year changes in MNPW were not statistically significant. The MNPW changes associated with full retirement were attributable to nap frequency increase of +0.4 (+0.1, +0.8) d/wk; nap duration did not change significantly.

CONCLUSIONS

Compared with stable employment status, full retirement is associated with an average 1-year increase of +48 MNPW. This change is attributable to a frequency gain of 0.4 d/wk napped. Changes in nap duration were negligible.

Association of napping with incident cardiovascular events in a prospective cohort study

Objective

There is controversy regarding the effect of napping on cardiovascular disease (CVD), with most studies failing to consider napping frequency. We aimed to assess the relationship of napping frequency and average nap duration with fatal and non-fatal CVD events.

Methods

3462 subjects of a Swiss population based cohort with no previous history of CVD reported their nap frequency and daily nap duration over a week, and were followed over 5.3 years. Fatal and non-fatal CVD events were adjudicated. Cox regressions were performed to obtain HRs adjusted for major cardiovascular risk factors and excessive daytime sleepiness or obstructive sleep apnoea.

Results

155 fatal and non-fatal events occurred. We observed a significantly lower risk for subjects napping 1–2 times weekly for developing a CVD event (HR 0.52, 95% CI 0.28 to 0.95) compared with non-napping subjects, in unadjusted as well as adjusted models. The increased HR (1.67, 95% CI 1.10 to 2.55) for subjects napping 6–7 times weekly disappeared in adjusted models (HR 0.89, 95% CI 0.58 to 1.38). Neither obstructive sleep apnoea nor excessive daytime sleepiness modified this lower risk. No association was found between nap duration and CVD events.

Conclusion

Subjects who nap once or twice per week have a lower risk of incident CVD events, while no association was found for more frequent napping or napping duration. Nap frequency may help explain the discrepant findings regarding the association between napping and CVD events.

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.

Association of daytime napping with incident cardiovascular disease in a community-based population

OBJECTIVE

To investigate the association between self-reported daytime napping habits and cardiovascular disease (CVD) in a large community-based study population.

METHODS

Of the 4170 participants, 55.5% were women and the mean age was 63.1 years (SD, 11.0 years). CVD included cardiovascular death, congestive heart failure, myocardial infarction, stroke, angina, and revascularization and was defined as the first confirmed incidence of CVD during an average 11-year follow-up. Self-reported daytime napping habits were recorded using baseline questionnaires. Backward stepwise Cox regression analysis was used to explore the relationship between CVD and napping habits.

RESULTS

In this study, 914 participants with CVD (21.9%) were observed. Participants who took regular long naps had a higher prevalence of incident CVD than did those who took regular short naps, irregular naps, or no naps (34.5% vs. 28.4%, 22.4%, 16.6%, respectively; P < 0.001). In the final backward stepwise Cox regression model, regular long naps were found to be associated with CVD (HR: 1.403, 95% CI: 1.079-1.825, P = 0.012).

CONCLUSIONS

Regular long daytime napping was an independent risk factor for CVD. Healthy sleep habits may promote human health and prevent CVD.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00005275.

The association between physical and mental chronic conditions and napping

The objectives of this study were to assess the associations among various physical and mental chronic conditions and napping. A cross-sectional epidemiological survey was proposed within the NutriNet-Santé population-based e-cohort launched in France in 2009. Participants were 43,060 French volunteers aged 18 y and over with Internet access. A self-report questionnaire assessing sleep characteristics was administered in 2014. The main outcome (dependent) variable was weekday or weekend napping (yes/no). The main exposure (independent) variables were overweight/obesity, hypertension, diabetes, anxiety and depressive disorders, incident major cardiovascular diseases (myocardial infarction, stroke, unstable angina), and incident cancer (breast and prostate). The associations of interest were investigated with multivariable logistic regression analysis. No significant associations were found between major cardiovascular diseases or breast or prostate cancer and napping. Instead, we found that napping was more common among males (46.1%) than among females 36.9% (p < 0.0001). Individuals who were overweight or obese or had hypertension, diabetes, depression or anxiety disorders had an increased likelihood of napping compared with their healthy peers. The adjusted ORs ranged from 1.14 to 1.28″. In conclusion, most chronic conditions were independently associated with napping. Future longitudinal analyses are needed to elucidate causality.

Napping Improves HRV in Older Patients With Cardiovascular Risk Factors

Heart rate variability (HRV), especially increased high frequency (HF), has been reported to provide clinically useful prognostic information regarding cardiovascular disease. Napping is an excellent sleep management strategy in older adults. This study was conducted to clarify the effect of napping on HRV in older adult patients with cardiovascular risk factors. The patients were divided into two groups: one group of 32 patients who reported napping (nap group) and another group of 45 patients who did not report napping (nonnap group). The HRV was calculated in terms of the HF component over 24 hr during wakefulness, sleep, and 1 hr after sleep onset. The HF in the nap group was significantly higher than that in the nonnap group during all times measured. In addition, napping was a significant predictor of increased HF. This study shows the effectiveness of napping in the daily lives of patients with cardiovascular risk factors.

Daytime napping and diabetes-associated kidney disease

BACKGROUND

Diabetes-associated Kidney Disease (DKD) is a common comorbidity in patients with type 2 diabetes. The present study investigates whether daytime sleeping duration in patients, ill with type 2 diabetes, is associated with DKD.

METHODS

A total of 733 outpatients of the cross-sectional baseline survey of the DIACORE study were analyzed with respect to their self-reported daytime sleeping duration, assessed by a standardized questionnaire. DKD was defined as eGFR <60 ml/min/1.73 m² and/or urinary albumin-to-creatinine-ratio (UACR) > 30 mg/g.

RESULTS

Mean daytime sleeping duration was 17 ± 27 min. With increasing daytime sleeping duration a statistically significant decrease in eGFR (p = 0.002) and increase in UACR (p < 0.001) were found, respectively. Prevalence of DKD was significantly higher in patients with longer daytime sleeping duration (31% in patients not napping, 40% in patients napping less than 30 min, 47% in patients napping 30-60 min, 56% in patients napping 60 min or more; p = 0.001). After accounting for known modulators (Age, sex, BMI, waist-hip-ratio, systolic and diastolic blood pressure, physical activity, diabetes duration, HbA1c, homeostasis model assessment (HOMA-Index), nighttime sleeping duration, apnea-hypopnea-index (AHI), Epworth Sleepiness Scale (ESS)), longer daytime sleeping duration was significantly associated with impaired eGFR [B (95% CI) = -0.05 (-0.09; 0.00), p = 0.044] and increased UACR [B (95% CI) = 0.01 (0.01; 0.02), p < 0.001], respectively.

CONCLUSION

Increased daytime sleeping duration is significantly associated with reduced eGFR and higher UACR, independent of known modulators of DKD. The direction of this relationship remains unclear.

Limited contribution of health behaviours to expanding income-related chronic disease disparities based on a nationwide cross-sectional study in China

This study estimated the association of income and prevalence of cardiovascular diseases (CVD) and hypertension, and then quantified the contribution of health behaviors to the association in China. Using the 2013 survey of the China Health and Retirement Longitudinal Study (CHARLS), a logit model was applied to examine income-related health disparities in relation to CVD and hypertension. A four-step regression method was then constructed to measure the role of health behaviors in income-related health disparities. Using indirect effects, mediation by health behaviors was examined. Income-related health disparities in chronic diseases were found to exist in China. Specifically, individuals in the high-income group had a 14% (OR = 0.86; 95% CI 0.73-1.02) and 14% (OR = 0.86; 95% CI 0.76-0.97) lower odds of suffering from CVD and hypertension than those in the low-income group. However, limited evidence shows this association was mediated by health behaviors. The Heaviness of Smoking Index (HSI), heavy drinking, irregular eating, and nap time did not significantly mediate the association of income and prevalence of CVD and hypertension. To curb the rising prevalence of CVD and hypertension in China, policies should focus on the low-income subpopulation. However, healthy behaviors interventions targeting smoking, heavy drinking, unhealthy napping and irregular eating habits among low-income people may be ineffective in reduction of income-related disparities in prevalence of CVD and hypertension.

Sleep and Cardio-Metabolic Disease

PURPOSE OF REVIEW

This review summarises and discusses the epidemiological evidence suggesting a causal relationship between sleep duration and cardio-metabolic risk and outcomes in population.

RECENT FINDINGS

Sleep duration is affected by a variety of cultural, social, psychological, behavioural, pathophysiological and environmental influences. Changes in modern society-like longer working hours, more shift-work, 24/7 availability of commodities and 24-h global connectivity-have been associated with a gradual reduction in sleep duration and sleeping patterns across westernised populations. We review the evidence of an association between sleep disturbances and the development of cardio-metabolic risk and disease and discuss the implications for causality of these associations. Prolonged curtailment of sleep duration is a risk factor for the development of obesity, diabetes, hypertension, heart disease and stroke and may contribute, in the long-term, to premature death.

J-curve relation between daytime nap duration and type 2 diabetes or metabolic syndrome: A dose-response meta-analysis

Adequate sleep is important for good health, but it is not always easy to achieve because of social factors. Daytime napping is widely prevalent around the world. We performed a meta-analysis to investigate the association between napping (or excessive daytime sleepiness: EDS) and the risk of type 2 diabetes or metabolic syndrome, and to quantify the potential dose-response relation using cubic spline models. Electronic databases were searched for articles published up to 2016, with 288,883 Asian and Western subjects. Pooled analysis revealed that a long nap (≥60 min/day) and EDS were each significantly associated with an increased risk of type 2 diabetes versus no nap or no EDS (odds ratio 1.46 (95% CI 1.23-1.74, p < 0.01) for a long nap and 2.00 (1.58-2.53) for EDS). In contrast, a short nap (<60 min/day) was not associated with diabetes (p = 0.75). Dose-response meta-analysis showed a J-curve relation between nap time and the risk of diabetes or metabolic syndrome, with no effect of napping up to about 40 minutes/day, followed by a sharp increase in risk at longer nap times. In summary, longer napping is associated with an increased risk of metabolic disease. Further studies are needed to confirm the benefit of a short nap.

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

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

Self-Reported Napping Behavior Change After Continuous Positive Airway Pressure Treatment in Older Adults with Obstructive Sleep Apnea

OBJECTIVES

To assess the effect of continuous positive airway pressure (CPAP) on napping behavior in adults aged 60 and older with obstructive sleep apnea-hypopnea syndrome (OSAHS).

DESIGN

Retrospective cohort study using questionnaires.

SETTING

Sleep center.

PARTICIPANTS

Individuals starting CPAP treatment between April 2010 and March 2012 (mean age 65.2 ± 4.7; M:F = 3.9:1; N = 107).

MEASUREMENTS

All subjects underwent sleep studies, clinical reviews, and CPAP adherence checks and completed a questionnaire regarding CPAP adherence, current employment status, sleep patterns before and after CPAP, and factors affecting their current sleep patterns.

RESULTS

CPAP treatment duration was 82.7 ± 30.0 weeks, and objective adherence was 5.4 ± 2.0 hours per night overall. Daytime nap frequency before CPAP treatment was higher in those with a history of stroke or cardiovascular disease. Both sexes had a significant reduction in daytime napping (men, P < .001; women, P = .008), evening napping (men, P < .001; women, P = .02), and daily nap duration (men, P < .001; women, P = .02). Logistic regression analysis showed that the reduction in self-reported daily nap duration was associated with younger age (odds ratio (OR) = 0.86, P = .04), a decrease in ESS score (OR = 1.20, P = .03), and longer self-reported daily nap duration at baseline (OR = 31.52, P < .001).

CONCLUSION

Long-term CPAP treatment in older adults with OSAHS can play a significant role in reducing nap frequency and daily nap duration. Aging or shorter baseline daily nap duration may attenuate this effect.

Self-Reported Sleep Duration, Napping, and Incident Heart Failure: Prospective Associations in the British Regional Heart Study

Objectives

To examine the associations between self‐reported nighttime sleep duration and daytime sleep and incident heart failure (HF) in men with and without preexisting cardiovascular disease (CVD).

Design

Population‐based prospective study.

Setting

General practices in 24 British towns.

Participants

Men aged 60–79 without prevalent HF followed for 9 years (N = 3,723).

Measurements

Information on incident HF cases was obtained from primary care records. Assessment of sleep was based on self‐reported sleep duration at night and daytime napping.

Results

Self‐reported short nighttime sleep duration and daytime sleep of longer than 1 hour were associated with preexisting CVD, breathlessness, depression, poor health, physical inactivity, and manual social class. In all men, self‐reported daytime sleep of longer than 1 hour duration was associated with significantly greater risk of HF after adjustment for potential confounders (adjusted hazard ratio (aHR) = 1.69, 95% CI = 1.06–2.71) than in those who reported no daytime napping. Self‐reported nighttime sleep duration was not associated with HF risk except in men with preexisting CVD (<6 hours: aHR = 2.91, 95% CI = 1.31–6.45; 6 hours: aHR = 1.89, 95% CI = 0.89–4.03; 8 hours: aHR = 1.29, 95% CI = 0.61–2.71; ≥9 hours: aHR = 1.80, 905% CI = 0.71–4.61 vs nighttime sleep of 7 hours). Snoring was not associated with HF risk.

Conclusion

Self‐reported daytime napping of longer than 1 hour is associated with greater risk of HF in older men. Self‐reported short sleep (<6 hours) in men with CVD is associated with particularly high risk of developing HF.

Is daytime napping associated with inflammation in adolescents?

OBJECTIVE

Daytime napping has been associated with poor health outcomes in adults. It is not known whether daytime napping is similarly linked to adverse health in adolescents, although many report napping. The present study evaluated associations between daytime napping and 2 markers of increased inflammation, high-sensitivity C-reactive protein and interleukin-6 (IL-6), in healthy high school students.

METHODS

Two hundred thirty-four Black and White high school students completed a week of actigraph and diary measures of sleep and napping and provided a fasting blood sample. Napping measures were the proportion of days napped and the average minutes napped across 1 week during the school year.

RESULTS

Linear regressions adjusted for age, sex, race, average nocturnal sleep duration, time between sleep protocol and blood draw, and body mass index percentile demonstrated that proportion of days napped measured by actigraphy, B(SE) = .41(.19), p < .05, across the full week was positively associated with IL-6. Higher proportions of school days napped between 2 p.m. and 6 p.m., B(SE) = .40(.20), p < .05, and between 6 p.m. and 10 p.m., B(SE) = .57(.28), p < .05, were associated with increased IL-6. No associations emerged between average actigraphy-assessed nap duration and either study outcome. Diary-reported napping was unrelated to either study outcome.

CONCLUSIONS

Actigraphy-assessed napping and IL-6 are associated but the direction of the relationship remains to be determined. Overall, napping is an important factor to consider to better understand the relationship between short sleep and cardiovascular health in adolescents. (PsycINFO Database Record

The effects of midday nap duration on the risk of hypertension in a middle-aged and older Chinese population: a preliminary evidence from the Tongji-Dongfeng Cohort Study, China

OBJECTIVE

Evidence from epidemiological studies suggested that shorter and longer duration of nocturnal sleeping may increase the risk of hypertension for older adults. Little is known about the duration of midday nap on the variability of blood pressure among older adults. In this study, we examined whether duration of habitual midday nap is associated with level of blood pressure or the risk of hypertension in a middle-aged and older Chinese population.

METHODS

A total of 27 009 participants (mean age 63.6 years) from Dongfeng-Tongji Cohort Study received baseline examination including physical examination and laboratory tests, and a face-to-face-interview including demographic information, disease history, and lifestyle. Participants were categorized into five groups according to nap duration, such as no napping, less than 30 min, 30∼60 min, 60∼90 min, and at least 90 min. A series of categorical logistic regression models was used to examine the odd ratios of nap duration with hypertension.

RESULTS

The level of SBP and DBP increased significantly with longer duration of habitual midday napping. Nappers with longer nap duration had considerably higher rate of hypertension. The longer duration of napping was related to higher blood pressure level and was associated with a higher risk of hypertension. After adjusting for possible confounders, the longer duration (>60 min) of napping was still associated with hypertension

CONCLUSION

: Our findings showed that the practice of longer afternoon nap is associated with a higher increased risk of hypertension, independent of several covariates. Further prospective researches are needed to examine the midday nap duration for development of hypertension.

Longer Sleep Duration and Midday Napping Are Associated with a Higher Risk of CHD Incidence in Middle-Aged and Older Chinese: the Dongfeng-Tongji Cohort Study

STUDY OBJECTIVES

To analyze the independent and combined relations of sleep duration and midday napping with coronary heart diseases (CHD) incidence along with the underlying changes of cardiovascular disease (CVD) risk factors among Chinese adults.

METHODS

We included 19,370 individuals aged 62.8 years at baseline from September 2008 to June 2010, and they were followed until October 2013. Cox proportional hazards models and general linear models were used for multivariate longitudinal analyses.

RESULTS

Compared with sleeping 7- < 8 h/night, the hazard ratio (HR) of CHD incidence was 1.33 (95% CI = 1.10 to 1.62) for sleeping ≥ 10 h/night. The association was particularly evident among individuals who were normal weight and without diabetes. Similarly, the HR of incident CHD was 1.25 (95% CI = 1.05 to 1.49) for midday napping > 90 min compared with 1-30 min. When sleep duration and midday napping were combined, individuals having sleep duration ≥ 10 h and midday napping > 90 min were at a greater risk of CHD than those with sleeping 7- < 8 h and napping 1-30 min: the HR was 1.67 (95% CI = 1.04 to 2.66; P for trend = 0.017). In addition, longer sleep duration ≥ 10 h was significantly associated with increases in triglycerides and waist circumference, and a reduction in HDL-cholesterol; while longer midday napping > 90 min was related to increased waist circumference.

CONCLUSIONS

Both longer sleep duration and midday napping were independently and jointly associated with a higher risk of CHD incidence, and altered lipid profile and waist circumference may partially explain the relationships.

Daytime Napping and the Risk of Cardiovascular Disease and All-Cause Mortality: A Prospective Study and Dose-Response Meta-Analysis

STUDY OBJECTIVES

To summarize evidence about the association between daytime napping and the risk of cardiovascular disease and all-cause mortality, and to quantify the potential dose-response relation.

DESIGN

Meta-analysis of prospective cohort studies.

METHODS AND RESULTS

Electronic databases were searched for articles published up to December 2014 using the terms nap, cardiovascular disease, and all-cause mortality. We selected well-adjusted prospective cohort studies reporting risk estimates for cardiovascular disease and all-cause mortality related to napping. Eleven prospective cohort studies were identified with 151,588 participants (1,625,012 person-years) and a mean follow-up period of 11 years (60% women, 5,276 cardiovascular events, and 18,966 all-cause deaths). Pooled analysis showed that a long daytime nap (≥ 60 min/day) was associated with a higher risk of cardiovascular disease (rate ratio [RR]: 1.82 [1.22-2.71], P = 0.003, I(2) = 37%) compared with not napping. All-cause mortality was associated with napping for ≥ 60 min/day (RR: 1.27 [1.11-1.45], P < 0.001, I(2) = 0%) compared with not napping. In contrast, napping for < 60 min/day was not associated with cardiovascular disease (P = 0.98) or all-cause mortality (P = 0.08). Meta-analysis demonstrated a significant J-curve dose-response relation between nap time and cardiovascular disease (P for nonlinearity = 0.01). The RR initially decreased from 0 to 30 min/day. Then it increased slightly until about 45 min/day, followed by a sharp increase at longer nap times. There was also a positive linear relation between nap time and all-cause mortality (P for non-linearity = 0.97).

CONCLUSIONS

Nap time and cardiovascular disease may be associated via a J-curve relation. Further studies are needed to confirm the efficacy of a short nap.

Sleep Disturbances in the Elderly

Sleep disturbances are a common presenting symptom of older-age adults to their physicians. This article explores normal changes in sleep pattern with aging and primary sleep disorders in the elderly. Behavioral factors and primary psychiatric disorders affecting sleep in this population are reviewed. Further discussion examines sleep changes associated with 2 common forms of neurocognitive disorder: Alzheimer disease and Lewy Body Dementia. Common medical illnesses in the elderly are discussed in relation to sleep symptoms. Nonpharmacological and pharmacologic treatment strategies are summarized, with emphasis placed on risk of side effects in older adults. Future targets are considered.

Is There an Association between Sleeping Patterns and Other Environmental Factors with Obesity and Blood Pressure in an Urban African Population?

Beyond changing dietary patterns, there is a paucity of data to fully explain the high prevalence of obesity and hypertension in urban African populations. The aim of this study was to determine whether other environmental factors (including sleep duration, smoking and physical activity) are related to body anthropometry and blood pressure (BP). Data were collected on 1311 subjects, attending two primary health care clinics in Soweto, South Africa. Questionnaires were used to obtain data on education, employment, exercise, smoking and sleep duration. Anthropometric and BP measurements were taken. Subjects comprised 862 women (mean age 41 ± 16 years and mean BMI 29.9 ± 9.2 kg/m²) and 449 men (38 ± 14 years and 24.8 ± 8.3 kg/m²). In females, ANOVA showed that former smokers had a higher BMI (p<0.001) than current smokers, while exposure to second hand smoking was associated with a lower BMI (p<0.001) in both genders. Regression analyses demonstrated that longer sleep duration was associated with a lower BMI (p<0.05) in older females only, and not in males, whilst in males napping during the day for > 30 minutes was related to a lower BMI (β = -0.04, p<0.01) and waist circumference (β = -0.03, p<0.001). Within males, napping for >30 minutes/day was related to lower systolic (β = -0.02, p<0.05) and lower diastolic BP (β = -0.02, p = 0.05). Longer night time sleep duration was associated with higher diastolic (β = 0.005, p<0.01) and systolic BP (β = 0.003, p<0.05) in females. No health benefits were noted for physical activity. These data suggest that environmental factors rarely collected in African populations are related, in gender-specific ways, to body anthropometry and blood pressure. Further research is required to fully elucidate these associations and how they might be translated into public health programs to combat high levels of obesity and hypertension.

Meta-analysis of self-reported daytime napping and risk of cardiovascular or all-cause mortality

Background

Whether self-reported daytime napping is an independent predictor of cardiovascular or all-cause mortality remains unclear. The aim of this study was to investigate self-reported daytime napping and risk of cardiovascular or all-cause mortality by conducting a meta-analysis.

Material/Methods

A computerized literature search of PubMed, Embase, and Cochrane Library was conducted up to May 2014. Only prospective studies reporting risk ratio (RR) and corresponding 95% confidence intervals (CI) of cardiovascular or all-cause mortality with respect to baseline self-reported daytime napping were included.

Results

Seven studies with 98,163 subjects were included. Self-reported daytime napping was associated with a greater risk of all-cause mortality (RR 1.15; 95% CI 1.07–1.24) compared with non-nappers. Risk of all-cause mortality appeared to be more pronounced among persons with nap duration >60 min (RR 1.15; 95% CI 1.04–1.27) than persons with nap duration <60 min (RR 1.10; 95% CI 0.92–1.32). The pooled RR of cardiovascular mortality was 1.19 (95% CI 0.97–1.48) comparing daytime nappers to non-nappers.

Conclusions

Self-reported daytime napping is a mild but statistically significant predictor for all-cause mortality, but not for cardiovascular mortality. However, whether the risk is attributable to excessive sleep duration or napping alone remains controversial. More prospective studies stratified by sleep duration, napping periods, or age are needed.

Daytime napping and mortality from all causes, cardiovascular disease, and cancer: a meta-analysis of prospective cohort studies

OBJECTIVES

The association between daytime napping and mortality remains controversial. We conducted a meta-analysis to examine the associations between daytime napping and the risks of death from all causes, cardiovascular disease (CVD), and cancer.

METHODS

PubMed and Embase databases were searched through 19 September 2014. Prospective cohort studies that provided risk estimates of daytime napping and mortality were eligible for our meta-analysis. Two investigators independently performed study screening and data extraction. A random-effects model was used to estimate the combined effect size. Subgroup analyses were conducted to identify potential effect modifiers.

RESULTS

Twelve studies, involving 130,068 subjects, 49,791 nappers, and 19,059 deaths, were included. Our meta-analysis showed that daytime napping was associated with an increased risk of death from all causes [n = 9 studies; hazard ratio (HR), 1.22; 95% confidence interval (CI), 1.14-1.31; I(2) = 42.5%]. No significant associations between daytime napping and the risks of death from CVD (n = 6 studies; HR, 1.20; 95% CI, 0.96-1.50; I(2) = 75.0%) and cancer (n = 4 studies; HR, 1.07; 95% CI, 0.99-1.15; I(2) = 8.9%) were found. There were no significant differences in risks of all-cause and CVD mortality between subgroups stratified by the prevalence of napping, follow-up duration, outcome assessment, age, and sex.

CONCLUSIONS

Daytime napping is a predictor of increased all-cause mortality but not of CVD and cancer mortality. However, our findings should be treated with caution because of limited numbers of included studies and potential biases.

Sudden cardiac death and diabetes mellitus

Sudden cardiac death (SCD) affects a significant percentage of diabetic patients. SCD in these patients can be due to several factors, such as diastolic dysfunction, heart failure, altered platelet function, inflammation, sympathetic nervous stimulation and other factors. In the present review, we discuss the association between diabetes mellitus and SCD.