Changes in sleep duration and risk of metabolic syndrome: the Kailuan prospective study

The Global Prevalence of Metabolic Syndrome in Connection with Sleep Duration: A Systematic Review and Meta-Analysis

The duration and quality of sleep are believed to significantly influence the onset of metabolic syndrome (MetS), but existing data lack consistency. The meta-analysis aims to evaluate the prevalence of the MetS in association with sleep duration. We conducted a systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses 2020 guidelines. A comprehensive search of PubMed, Google Scholar, and Research Gate databases was performed to identify cohort and cross-sectional studies published in English between 2013 and 2023. We included studies that examined the association between sleep duration/quality and MetS, and two independent reviewers assessed study quality and bias using the Newcastle-Ottawa scale. The systematic review included 11 studies with a total of 343,669 participants, including 4 cohort studies and 7 cross-sectional studies. Sample sizes varied widely, ranging from 293 to 162,121 individuals. The studies had different follow-up periods, participant ages ranging from 10 to 80 years, and predominantly male populations. The prevalence of MetS was higher in average sleepers [52%, 95% confidence interval (CI): 40%-64%] compared with short sleepers (13%, 95% CI: 8%-18%) and long sleepers (15%, 95% CI: 9%-24%). Globally, North American countries exhibit the highest prevalence of MetS across short- (25.3%, 95% CI: 4.2%-72.4%) and long-sleeper (22.4%, 95% CI: 2.8%-74.1%) categories, whereas Asian countries experience the highest prevalence among the average sleeper category (58.7%, 95% CI: 44.1%-71.9%). Our meta-analysis indicates an elevated prevalence of MetS in average sleepers. Future research endeavors address delve into the underlying mechanisms and incorporate objective measures to understand the multifaceted connection between sleep patterns and MetS, guiding more effective preventive and management strategies.

Heatwave exposure in relation to decreased sleep duration in older adults

Few studies have delved into the effects of heatwaves on sleep duration loss among older adults. Our study examined correlations between heatwave exposure and sleep duration reductions in this demographic. Utilizing data of 7,240 older adults drawn from the China Health and Retirement Longitudinal Study (CHARLS) from 2015 to 2018, we assessed sleep duration differences between the baseline year (2015) and follow-up year (2018). Absolute reductions in sleep duration were defined as differences of ≥ 1, 1.5, or 2 h. Changes in sleep duration were categorized based on cut-offs of 5 and 8 h, including excessive decrease, moderate to short and persistent short sleep duration types. 12 heatwave definitions combining four thresholds (90th, 92.5th, 95th, and 97.5th percentiles of daily minimum temperature) and three durations (≥2, ≥3 and ≥ 4 days) were used. Heatwave exposure was determined by the difference in the number of 12 preceding months' heatwave days or events in 2015 and the number of 12 preceding months' heatwave days or events in 2018. The results showed that increased heatwave events (defined as ≥ P90th percentile & lasting three days) were associated with a higher likelihood of ≥ 1-hour sleep reduction and persistent short sleep duration. An increase in heatwave event (defined as ≥ P95th percentile & lasting three days) was linked to shifts from moderate to short sleep duration. For the association between an absolute reduction in sleep duration and heatwave exposure, while higher thresholds signified greater sleep reduction risks, the effect estimates of longer durations were not uniformly consistent. We observed that air pollution and green space modified the relationship between heatwaves and sleep duration. Females, urban residents, and individuals with chronic diseases were identified as vulnerable populations. This study found that increased heatwave exposure was associated with a higher risk of sleep duration loss in older adults.

Association of sleep duration and insomnia with metabolic syndrome and its components in the Women's Health Initiative

BACKGROUND

Epidemiological evidence suggests that inadequate sleep duration and insomnia may be associated with increased risk of metabolic syndrome (MetS). However, longitudinal data with repeated measures of sleep duration and insomnia and of MetS are limited. We examined the association of sleep duration and insomnia with MetS and its components using longitudinal data from the Women's Health Initiative (WHI).

METHODS

The study included postmenopausal women (ages 50-79 years) diabetes-free at enrollment in the WHI, with baseline data on sleep duration (n = 5,159), insomnia (n = 5,063), MetS, and its components. Repeated measures of self-reported sleep duration and insomnia were available from years 1 or 3 of follow-up and of the MetS components from years 3, 6 and 9. Associations were assessed using logistic regression and generalized estimating equations models, and odds ratios and 95% confidence intervals (CI) adjusted for major risk factors were calculated.

RESULTS

In cross-sectional analysis, baseline sleep duration ≥ 9 h was positively associated with MetS (OR = 1.51; 95%CI 1.12-2.04), while sleep duration of 8- < 9 h was associated with waist circumference > 88 cm and triglycerides ≥ 150 mg/dL (OR = 1.18; 95%CI 1.01-1.40 and OR = 1.23; 95%CI 1.05-1.46, respectively). Insomnia had a borderline positive association with MetS (OR = 1.14; 95%CI 0.99-1.31), and significant positive associations with waist circumference > 88 cm and glucose ≥ 100 mg/dL (OR = 1.18; 95%CI 1.03-1.34 and OR = 1.17; 95%CI 1.02-1.35, respectively). In the longitudinal analysis, change from restful sleep to insomnia over time was associated with increased odds of developing MetS (OR = 1.40; 95%CI 1.01-1.94), and of a triglyceride level ≥ 150 mg/dL (OR = 1.48; 95%CI 1.08-2.03).

CONCLUSIONS

Among postmenopausal women in the WHI, sleep duration and insomnia were associated with current and future risk of MetS and some of its components.

Healthy Sleep Every Day Keeps the Doctor Away

When one considers the big picture of their health, sufficient sleep may often go overlooked as a keystone element in this picture. Insufficient sleep in either quality or duration is a growing problem for our modern society. It is essential to look at what this means for our health because insufficient sleep increases our risks of innumerable lifechanging diseases. Beyond increasing the risk of developing these diseases, it also makes the symptoms and pathogenesis of many diseases worse. Additionally, consistent quality sleep can not only improve our physical health but has also been shown to improve mental health and overall quality of life. Substandard sleep health could be a root cause for numerous issues individuals may be facing in their lives. It is essential that physicians take the time to learn about how to educate their patients on sleep health and try to work with them on an individual level to help motivate lifestyle changes. Facilitating access to sleep education for their patients is one way in which physicians can help provide patients with the tools to improve their sleep health. Throughout this paper, we will review the mechanisms behind the relationship between insufficient sleep health and chronic disease and what the science says about how inadequate sleep health negatively impacts the overall health and the quality of our lives. We will also explain the lifechanging effects of sufficient sleep and how we can help patients get there.

The Impact of Online Learning System on Students Affected with Stroke Disease

Stroke, also known as a cerebrovascular accident, is a medical emergency that causes temporary or permanent behavioral dysfunction in people. Sleep deprivation affects our brains in a variety of ways. The advantages of sleep much justify the risks of not having enough sleep. Sleep deprivation (SD) includes a variety of factors, including prolonged awake. Neuroimaging investigates SD's impact on attention, working memory, mood, and hippocampal learning. We analyzed how this data enriches our mechanistic understanding of these alterations and the clinical illnesses linked with sleep disruption. We have used Cronbach's alpha to test the reliability of a scale, so we then have 19 individual attributes responding to 174 participants via survey. The evaluated result shows the reliability statistics; the value for Cronbach's alpha is .962, which is very excellent as it reaches 1. So, there is very strong reliability. If the value falls under .6, we look back to the mean and standard deviation table and remove the attribute with low values for mean or standard deviation and try the remaining attributes. Cronbach's alpha tells us which attribute or item to delete to increase the reliability, and we also have analyzed the correlation among the class students while watching the same video lecture. We have collected data for at least ten students watching the same video using a webcam. Once the data is collected, we then have applied some correlation techniques to determine the class students' behavior towards the same video lecture. This way, we can see the overall behavior of the class upon a specific video lecture. The study further reveals that subjective happiness is influenced by its efficiency, entertainment value, and effectiveness. Does the research offer an original emphasis on analyzing how does lack of sleep affect our brains? Sleep loss frameworks are minimal compared to the benefits of sleep.

Decrease in Sleep Duration and Poor Sleep Quality over Time Is Associated with an Increased Risk of Incident Non-Alcoholic Fatty Liver Disease

The impact of changes in sleep duration and sleep quality over time on the risk of non-alcoholic fatty liver disease (NAFLD) is not known. We investigated whether changes in sleep duration and in sleep quality between baseline and follow-up are associated with the risk of developing incident NAFLD. The cohort study included 86,530 Korean adults without NAFLD and with a low fibrosis score at baseline. The median follow-up was 3.6 years. Sleep duration and quality were assessed using the Pittsburgh Sleep Quality Index. Hepatic steatosis (HS) and liver fibrosis were assessed using ultrasonography and the fibrosis-4 index (FIB-4). Cox proportional hazard models were used to determine hazard ratios (HRs) and 95% confidence intervals (Cis). A total of 12,127 subjects with incident HS and 559 with incident HS plus intermediate/high FIB-4 was identified. Comparing the decrease in sleep duration of >1 h, with stable sleep duration, the multivariate-adjusted HR (95% CIs) for incident HS was 1.24 (1.15–1.35). The corresponding HRs for incident HS plus intermediate/high FIB-4 was 1.58 (1.10–2.29). Comparing persistently poor sleep quality with persistently good sleep quality, the multivariate-adjusted HR for incident HS was 1.13 (95% CI, 1.05–1.20). A decrease in sleep duration or poor sleep quality over time was associated with an increased risk of incident NAFLD, underscoring an important potential role for good sleep in preventing NAFLD risk.

Impact of objectively-measured sleep duration on cardiometabolic health: A systematic review of recent evidence

Cardiometabolic disease is a spectrum of diseases including, cardiovascular diseases, and metabolic syndrome. It is the leading cause of morbidity and mortality worldwide, with premature deaths being preventable. Currently, sleep has emerged as a potential target for cardiometabolic disease prevention. Several epidemiological studies have provided ample evidence that objectively measured short sleep duration increases the risk of cardiometabolic disease. However, the findings are inconsistent, and few studies measure sleep duration on cardiometabolic profiles objectively. Therefore, in this review, we focused on the recently published literature that explored the association between objectively measured sleep duration and cardiometabolic profiles (cardiovascular diseases, type 2 diabetes mellitus, and metabolic syndrome), seeking more insights regarding the applicability and, in turn, the impact of objectively measured sleep duration on cardiometabolic health, which is relatively understudied. We retrieved the information manually from PubMed, Google Scholar, HINARI, and the Cochrane Library from 2015 to 2022 using appropriate search terms, we included 49 articles. In this review, we found a strong relationship between objectively measured sleep duration and the risk of cardiometabolic disease, indicating that objectively measured short sleep durations increase cardiometabolic risks. In general, the association between objectively measured sleep duration and increased cardiometabolic risks (CMR) has been well-documented in higher-income countries. Several studies found that longer sleep duration was associated with a more favorable cardiometabolic profile in early adolescence, independent of other risk factors. On the other hand, objectively measured short sleep duration is associated with adverse cardiometabolic health outcomes such as coronary heart disease, hypertension, type 2 diabetes mellitus, and metabolic syndrome.

Causal Roles of Sleep Duration in Osteoporosis and Cardiometabolic Diseases: A Mendelian Randomization Study

Sleep duration suggests some association with osteoporosis and cardiometabolic diseases, but it is unknown if these associations are causal or confounded. In this two-sample Mendelian randomization (MR) study, we included the largest genome-wide association studies (GWASs) associated with sleep duration and the outcome measures of osteoporosis and cardiometabolic diseases. Finally, 25 single nucleotide polymorphisms (SNPs) associated with short sleep duration and 7 SNPs associated with long sleep duration obtained the genome-wide significance (P < 5 × 10^-8) and were used as instrumental variables. Genetic predisposition to short sleep duration was strongly associated with increased risk of coronary artery disease (beta-estimate: 0.199, 95% confidence interval CI: 0.081 to 0.317, standard error SE:0.060, P value = 0.001) and heart failure (beta-estimate: 0.145, 95% CI: 0.025 to 0.264, SE:0.061, P value = 0.017), which were both confirmed by the sensitivity analyses. Both short and long sleep duration may reduce the estimated bone mineral density (eBMD, beta-estimate: -0.086, 95% CI: -0.141 to -0.031, SE:0.028, P value = 0.002 for short sleep duration; beta-estimate: -0.080, 95% CI: -0.120 to -0.041, SE:0.020, P value < 0.0001 for long sleep duration). There was limited evidence of associations between sleep duration and fracture, type 2 diabetes, atrial fibrillation, fasting glucose, fasting insulin, or HbA1c. This study provides robust evidence that short sleep duration is causally associated with high risk of coronary artery disease and heart failure and suggests that short sleep duration should be avoided to prevent these two cardiovascular diseases. Short and long sleep duration show some MR association with reduced eBMD, which indicates that both short and long sleep duration may be prevented to reduce the incidence of osteoporosis.

Sleep duration and metabolic syndrome: An updated systematic review and meta-analysis

We examined the association between self-reported sleep duration and metabolic syndrome (MetS). Data were collected from 36 cross-sectional and 9 longitudinal studies with a total of 164,799 MetS subjects and 430,895 controls. Odds ratios (ORs) for prevalent MetS and risk ratios (RRs) for incident MetS were calculated through meta-analyses of adjusted data from individual studies. Short sleep duration was significantly associated with increased prevalent MetS (OR = 1.11, 95% CI = 1.05-1.18) and incident MetS (RR = 1.28, 95% CI = 1.07-1.53) in cross-sectional and longitudinal studies, respectively. Furthermore, long sleep duration was significantly associated with increased prevalent MetS in cross-sectional studies (OR = 1.14, 95% CI = 1.05-1.23), but not incident MetS (RR = 1.16, 95% CI = 0.95-1.41) in longitudinal studies. Interestingly, the association between long sleep and prevalent MetS was found in sleep duration defined by 24-h sleep (including naps) rather than nighttime sleep. Our findings suggest 1) a "U-shape" relationship between sleep duration and MetS in cross-sectional studies and 2) association between short sleep duration, but not long sleep duration with incident MetS. Future studies should shed light on the underlying mechanisms related to the association between sleep duration and MetS and examine if normalizing sleep duration reduces MetS risk in the general population.

Association of Sleep Duration With Atrial Fibrillation and Heart Failure: A Mendelian Randomization Analysis

Both short (<7 h per night) and long (≥9 h per night) sleep durations are related to atrial fibrillation (AF) and heart failure (HF), but their causality has not been confirmed. We applied Mendelian randomization (MR) approaches to estimate the causal association between genetically determined sleep duration and the risk of AF and HF. We performed two-sample MR analysis to obtain the effect of sleep duration on AF and HF. Instrumental variables were constructed using genetic variants known to be associated with continuous sleep duration, short sleep duration, and long sleep duration. MR estimates of the effect of sleep duration on AF and HF were derived based on two large meta-analyses of genome-wide association studies. The pooled MR estimate demonstrated a significant protective effect of continuous sleep duration on HF [odds ratio (OR) = 0.765, 95% confidence interval (CI) = 0.675–0.867; P = 2.64 × 10^–5] and a suggestive inverse association of continuous sleep duration with AF (OR = 0.893, 95% CI = 0.804–0.991; P = 0.034). In addition, the results showed a suggestive detrimental effect of short sleep duration on the risk of AF (OR = 1.108, 95% CI = 1.017–1.207; P = 0.019) and HF (OR = 1.136, 95% CI = 1.025–1.258; P = 0.015). Conversely, there is no significant evidence for the causal protective effect of long sleep duration on AF (OR = 0.956, P = 0.410) and HF (OR = 0.921, P = 0.202). This MR study indicated that genetically determined continuous sleep duration has a significant protective effect on HF and a suggestive inverse association with AF. Short sleep duration is positively associated with the risk of AF and HF. Nevertheless, there is no significant evidence for the causal protective effect of long sleep duration on AF and HF. Larger intervention studies are required to confirm the effectiveness of improving sleep on reducing the incidence of AF and HF.

Sleep Duration and the Risk of Metabolic Syndrome in Adults: A Systematic Review and Meta-Analysis

Objective: Epidemiological studies have reported inconsistent findings for the association between sleep duration and metabolic syndrome. We aimed to clarify the effects of short and long sleep durations on metabolic syndrome in adults by performing a meta-analysis. Methods: Adopting random-effects models, this study analyzed the effects of short and long sleep durations based on data from prospective cohort studies and cross-sectional studies retrieved from four electronic databases from inception to May 2020. Results: We collected data from 235,895 participants included in nine prospective cohort studies and 340,492 participants included in 27 cross-sectional studies. In cohort studies, short sleep duration was associated with an increased risk of metabolic syndrome (RR, 1.15; 95% CI, 1.05-1.25, I 2 = 63.1%, P < 0.001) compared with normal sleep duration. While long sleep duration was not associated with new-onset metabolic syndrome (RR, 1.02, 0.85-1.18, I 2 = 38.0%, P = 0.491). In cross-sectional studies, both short (OR, 1.06, 95% CI, 1.01-1.11, I 2 = 66.5%, P < 0.001) and long (OR, 1.11, 95% CI, 1.04-1.17, I 2 = 73.8%, P < 0.001) sleep durations were associated with a high prevalence of metabolic syndrome. Conclusions: Only a short sleep duration was associated with an increased risk of metabolic syndrome. Future studies should address whether the association is casual and modifiable.

Longitudinal association between sleep and 5-year incident metabolic syndrome in older Chinese adults: a community-based cohort study

PURPOSE

Our aim was to investigate the association between sleep and the development of metabolic syndrome (MetS) in Chinese older adults and to accumulate evidence for the prevention of MetS through sleep management.

METHODS

This prospective study followed 3005 participants aged over 60 derived from the Weitang Geriatric Diseases Study who were without MetS at baseline. MetS was defined according to the Adult Treatment Panel III (ATP III) criteria. Logistic regression models were fit to assess the association between sleep and MetS incident and a linear regression model was used to examine the impact of sleep duration on every component of MetS. Data on sleep-related parameters were obtained based on a self-reported questionnaire.

RESULTS

After five-year follow-up, 13.51% participants developed MetS, of which 46.86% were women. The incidence of MetS was highest among adults who slept 6 h or less and lowest among those who slept 7 h after adjusted for multiple variables. Subgroup analyses showed no gender specificity. The variation of fasting plasma glucose (FBG) for ≥9 h per night was significantly lower than that for 7.01-7.99 h per night (β = -0.18, P < 0.05). Sleeping for 8-8.99 h also decreased the variation of diastolic blood pressure (DBP) compared to 7.01-7.99 h (β = -0.84, P < 0.05).

CONCLUSION

We conclude that both short and long sleep duration are risk factors for MetS incident in older adults.

The Association Between Sleep and Metabolic Syndrome: A Systematic Review and Meta-Analysis

PURPOSE

Sleep duration is thought to play a key role in the development of metabolic syndrome. However, the results have been inconsistent.

METHODS

We conducted a systematic review and meta-analysis of cohort studies and searched publications in PubMed, Embase, Cochrane Central Register of Controlled Trials, and Clinicaltrials.gov. The summary relative risks (RRs) were estimated using a random model. The sensitivity analysis was performed by sequentially excluding each study to test the robustness of the pooled estimates.

FINDING

We included 13 studies involving 300,202 patients in which short sleep and long sleep significantly increased the risk of metabolic syndrome 15% (RR = 1.15, 95%CI = 1.09-1.22, p < 0.001) and 19% (RR = 1.19, 95%CI = 1.05-1.35, p < 0.001). Moreover, the relationship between sleep duration and metabolic syndrome risk presented a U-shaped curve. Short and long sleep increased the risk of obesity by 14% (RR = 1.14, 95%CI = 1.07-1.22, p<0.001) and 15% (RR = 1.15, 95%CI = 1.00-1.30, p = 0.04), and high blood pressure 16% (RR = 1.16, 95%CI = 1.02-1.31, p = 0.03) and 13% (RR = 1.13, 95%CI = 1.04-1.24, p = 0.01), respectively. Short sleep can potentially increase the risk of high blood sugar by 12% (RR = 1.12, 95%CI = 1.00-1.15, P = 0.05).

IMPLICATIONS

Based on our findings, sleep is a behavior that can be changed and is economical. Clinically doctors and health professionals should be encouraged to increase their efforts to promote healthy sleep for all people.

Exploration of Sleep as a Specific Risk Factor for Poor Metabolic and Mental Health: A UK Biobank Study of 84,404 Participants

PURPOSE

Short and long sleep durations have adverse effects on physical and mental health. However, most studies are based on self-reported sleep duration and health status. Therefore, this longitudinal study aims to investigate objectively measured sleep duration and subsequent primary health care records in older adults to investigate the impact of sleep duration and fragmentation on physical and mental health.

METHODS

Data on objective sleep duration were measured using accelerometry. Primary care health records were then obtained from the UK Biobank (n=84,404). Participants (mean age, 62.4 years) were divided into five groups according to their sleep duration derived from the accelerometry data: <5 hours, 5-6 hours, 6-7 hours, 7-8 hours and >8 hours. ICD-10 codes were used for the analysis of primary care data. Wake after sleep onset, activity level during the least active 5 hours and episodes of movement during sleep were analysed as an indication for sleep fragmentation. Binary regression models were adjusted for age, gender and Townsend deprivation score.

RESULTS

A "U-shaped" relationship was found between sleep duration and diseases including diabetes, hypertension and heart disease and depression. Short and long sleep durations and fragmented sleep were associated with increased odds of disease.

CONCLUSION

Six to eight hours of sleep, as well as less fragmented sleep, predicted better long-term metabolic and mental health.

AI-Based Stroke Disease Prediction System Using Real-Time Electromyography Signals

Stroke is a leading cause of disabilities in adults and the elderly which can result in numerous social or economic difficulties. If left untreated, stroke can lead to death. In most cases, patients with stroke have been observed to have abnormal bio-signals (i.e., ECG). Therefore, if individuals are monitored and have their bio-signals measured and accurately assessed in real-time, they can receive appropriate treatment quickly. However, most diagnosis and prediction systems for stroke are image analysis tools such as CT or MRI, which are expensive and difficult to use for real-time diagnosis. In this paper, we developed a stroke prediction system that detects stroke using real-time bio-signals with artificial intelligence (AI). Both machine learning (Random Forest) and deep learning (Long Short-Term Memory) algorithms were used in our system. EMG (Electromyography) bio-signals were collected in real time from thighs and calves, after which the important features were extracted, and prediction models were developed based on everyday activities. Prediction accuracies of 90.38% for Random Forest and of 98.958% for LSTM were obtained for our proposed system. This system can be considered an alternative, low-cost, real-time diagnosis system that can obtain accurate stroke prediction and can potentially be used for other diseases such as heart disease.

Long sleep duration and risk of increased arterial stiffness in a Chinese population

To examine the relationship between self-reported sleep duration and arterial stiffness in a large Chinese population from Kailuan.From July 2010 to December 2015, a total of 17,018 participants aged 18 to 98 years were enrolled after excluding those with a history of cerebrovascular events and coronary artery disease. Participants were divided into 5 categories according to self-reported night sleep duration: ≤5.0, 6.0, 7 (ref), 8, and ≥9.0 hours. A brachial-ankle pulse wave velocity ≥1400 cm/s was considered to represent arterial stiffness. Multivariate logistic regression models were used to calculate the odds ratio (OR) and confidence interval (CI) for arterial stiffness according to the sleep duration.Using 7 hours of sleep as the reference group, the multivariable adjusted ORs (95% CI) for arterial stiffness were 1.00 (0.87-1.16), 1.00 (0.90-1.11), 1.0 (ref), 1.03 (0.93-1.14), and 1.48 (1.05-2.08) from the lowest to highest category of sleep duration, respectively. Secondary analysis showed no evidence of interactions between sleep duration and age/sex on the risk of arterial stiffness (P-interaction = .390/.198).A long night sleep duration was associated with increased arterial stiffness.

Sleep Apnea and Sleep Habits: Relationships with Metabolic Syndrome

Excess visceral adiposity is a primary cause of metabolic syndrome and often results from excess caloric intake and a lack of physical activity. Beyond these well-known etiologic factors, however, sleep habits and sleep apnea also seem to contribute to abdominal obesity and metabolic syndrome: Evidence suggests that sleep deprivation and behaviors linked to evening chronotype and social jetlag affect eating behaviors like meal preferences and eating times. When circadian rest and activity rhythms are disrupted, hormonal and metabolic regulations also become desynchronized, and this is known to contribute to the development of metabolic syndrome. The metabolic consequences of obstructive sleep apnea syndrome (OSAS) also contribute to incident metabolic syndrome. These observations, along with the first sleep intervention studies, have demonstrated that sleep is a relevant lifestyle factor that needs to be addressed along with diet and physical activity. Personalized lifestyle interventions should be tested in subjects with metabolic syndrome, based on their specific diet and physical activity habits, but also according to their circadian preference. The present review therefore focuses (i) on the role of sleep habits in the development of metabolic syndrome, (ii) on the reciprocal relationship between sleep apnea and metabolic syndrome, and (iii) on the results of sleep intervention studies.

Sleep problems are a strong predictor of stress-related metabolic changes in police officers. A prospective study

OBJECTIVE

Previous studies have shown that workers chronically exposed to occupational stress have an increased risk of metabolic syndrome (MetS) and sleep problems (SPs). The purpose of this study was to verify whether SPs mediate the relationship between stress and MetS.

METHOD

A 5-year prospective cohort study included 242 police officers from a rapid response unit engaged exclusively in maintaining law and order. Perceived stress levels were measured repeatedly with the demand-control-support and the effort-reward-imbalance questionnaires; insomnia symptoms were assessed with the Pittsburgh Sleep Quality Index; excessive daytime sleepiness was measured using the Epworth Sleepiness Scale. MetS and its components were evaluated at baseline and at follow-up.

RESULTS

During 5-year follow-up period, 26 new cases of MetS were identified. Both occupational stress and SPs were significantly related to incident cases of MetS. Insomnia symptoms showed a highly significant association with MetS (aOR 11.038; CI95% 2.867-42.493). Mediation analysis confirmed that SPs mediate the relationship between stress and MetS. A reciprocal relationship was found between job stress and SPs. Work-related stress was a significant predictor of insomnia symptoms, short sleep duration, sleep dissatisfaction, and sleepiness. Compared to the reference group, police officers with SPs at baseline had significantly higher odds of reporting high stress at follow-up.

CONCLUSION

SPs play a mediating role in the relationship between occupational stress and MetS. Prevention of MetS must include the control of stress factors and an increase in the resilience of workers, but correct sleep hygiene is also an essential factor.

Association between high-density lipoprotein cholesterol and all-cause mortality in the general population of northern China

Recent studies proposed reasonable doubts about the good prognosis of very high levels of high-density lipoprotein cholesterol (HDL-c). We aimed to investigate the association between HDL-c levels and all-cause mortality using data from an observational cohort study in northern China from 2006 to 2015. The study population was stratified into six groups by HDL-c levels in mg/dl (<40, 40–49, 50–59, 60–69, 70–79, ≥80). Cox hazards regression models were used to estimate the association between HDL-c levels and all-cause mortality. In total, 100,070 participants (aged 51.9 ± 12.7 years) were included in the current analysis. During a mean follow-up of 8.76 years, 7,362 deaths were identified (mortality rate, 8.40 per 1000 person-years). There was a significant interaction effect between age and HDL-c levels (P for interaction < 0.001). Among individuals aged 65 and older, no significant association was found between HDL-c levels and total mortality. In contrast, HDL-c levels showed a U-shaped relationship with all-cause mortality in younger participants (<65 years old), and very high HDL-c levels (≥80 mg/dl) were independently associated with increased total mortality risk compared with the reference level (60 to 69 mg/dl). These findings suggest that very high HDL-c levels may not represent a good prognosis, especially in younger individuals.

Sleep Duration and Risk of Atrial Fibrillation: a Systematic Review

Background

Little is known about a possible association between sleep duration and the incidence of atrial fibrillation (AF), in healthy people. In this systematic review, we conducted a literature search to examine possible association between sleep duration and the incidence of AF.

Methods

Scientific databases (PubMed, Web of Knowledge and Embase) were searched using relevant Medical Subject Headings and keywords, to retrieve studies written in English and published until November 2017. Only observational studies were included. Since sleep duration categories were not consistent, it was feasible to run a meta-analysis.

Results

Six eligible studies were included. Long sleep duration (≥ 8 hours) was found to be associated with an increased risk of AF (adjusted hazard ratio (aHR) = 1.13; 95% CI: 1.00-1.27 and aHR= 1.5, 95% CI: 1.07-2.10) in two studies. One study reported that sleep duration less than 6 hours was associated with an increased risk of AF (aHR= 1.58, 95% CI: 1.18 -2.13) compared to sleeping for 6-7 hours. In two studies, mean sleep duration was lower in AF groups compared to the non-AF group. Insomnia was associated with an increased risk of AF in another study (aHR= 1.33, 95% CI: 1.25-1.41).

Conclusions

Unhealthy sleep duration, defined as either less than 6 hours or more than 8 hours, may be associated with an increased risk of AF.

Prospective associations among objectively and subjectively assessed sleep and the metabolic syndrome

OBJECTIVE

Subjective sleep disturbances have been associated with greater risk for concurrent and incident metabolic syndrome (MetS). Previous studies have not examined prospective associations among polysomnography-assessed sleep and the MetS, despite knowledge that self-reported sleep is subject to reporting bias, and that subjectively and objectively assessed sleep are weakly correlated.

METHOD

In the current study, objectively-assessed (polysomnography) and subjectively-assessed (Pittsburgh Sleep Quality Index, PSQI) sleep was measured in 145 adults at two timepoints, separated by 12-30 years. A continuous measure of the MetS was assessed at the second time point. Statistical analyses were adjusted for age, sex, lifetime history of major depressive disorder, follow-up time, and apnea-hypopnea index.

RESULTS

Polysomnography-assessed sleep duration, latency, efficiency, and slow wave sleep were not significantly prospectively associated with the MetS (ps ≥ 0.16). Self-reported longer sleep latency was prospectively associated with higher MetS scores in unadjusted (β = 0.29, p = 0.002) and adjusted models (β = 0.25, p = 0.009). Longer sleep latency was associated with higher fasting glucose levels (β = 0.47, p < 0.001).

CONCLUSION

Our study provides evidence that subjective and objective measures of sleep may differ in their ability to prospectively predict MetS.

Working in Shifts and the Metabolic Syndrome: Epidemiological Evidence and Physiopathological Mechanisms

The Metabolic syndrome (MetS) is considered as an association of the abdominal obesity, abnormal metabolism of the lipids and glucose (high level of triglycerides, low level of HDL-cholesterol and high level of glycemia) and high values of blood pressure, determined by an underlying mechanism of insulin resistance. As a result of environmental-gene interaction, MetS is associated with unhealthy nutrition, smoking, alcohol abuse, lack of physical activity, shorter sleep duration and desynchronization of the circadian rhytm caused by working in shifts. The aim of this article is to review the effects of working in shifts on the MetS through the epidemiological evidence and the perspective of the physiopathological mechanisms.

A dose-response association of night sleep duration with hypertension in a Chinese rural population: the Henan Rural Cohort Study

The purpose of the study was to determine if there was a relationship between night sleep duration and hypertension, and to evaluate as to whether blood lipid levels played a role in this relationship. A total of 37,317 participants aged 18-79 years were included in this study. Night sleep duration was classified as <5, 5-, 6-, 7-, 8-, 9-, and ≥10 hours. Logistic regression and restricted cubic spline analysis was carried out to evaluate the association of sleep duration with hypertension. Compared with reference sleep duration (7 hours), in males, the multivariate odds ratios (ORs) (95% confidence interval [95% CI]) of the groups with longest sleep duration (≥10 hours) and shortest sleep duration (<5 hours) for hypertension was 1.52 (1.25-1.84) and 1.07 (0.80-1.44), respectively. Similarly, the longest sleep duration was associated with diagnosed hypertension (1.21, 1.00-1.45) in females. The OR for an indirect effect of sleep duration through low-density lipoprotein cholesterol (LDL-C) on hypertension was 1.085 (95% CI 1.038-1.137). Overall, a 3.5% possibility of hypertension being associated with sleep duration was attributable to LDL-C. In summary, a relationship between sleep duration and hypertension was observed in this rural population. LDL-C appeared to partially mediate the effect of sleep duration on hypertension in males.

Night Sleep Duration and Risk of Incident Anemia in a Chinese Population: A Prospective Cohort Study

The purpose was to study the association between sleep duration and the prevalence of anemia in Chinese people. There were 84,791 participants (men: 79.1%; women: 20.9%) aged 18–98 years in the prospective study. We divided the participants into five categories based on the individual sleep duration: ≤5 h, 6 h, 7 h(reference), 8 h, and ≥9 h. Anemia was defined based on hemoglobin <12 g/dL for men and <11 g/dL for women. The Cox proportional hazards model was used to assess the association between sleep duration and anemia. During median follow-up of 7.9 years, 2698 cases of anemia had occurred. The HRand (95% CI) of anemia (7 h as the reference group) for individuals reporting ≤5 h, 6 h, 8 h, and ≥9 h were 1.23(1.04–1.45), 1.26(1.11–1.44), 1.04(0.92–1.16) and 1.42(1.08–1.86), respectively. It showed that there was a significant interaction on the risk of anemia between sleep duration and sex in the secondary analysis (p < 0.001).The significant association between long sleepduration and anemia was found in women (HR, 2.29; 95% CI, 1.56–3.37), not in men(HR, 0.90; 95% CI, 0.60–1.34). Both short and long night sleep duration were associated with increased risk of anemia.

Associations Between the Prevalence of Metabolic Syndrome and Sleep Parameters Vary by Age

OBJECTIVE

To examine whether the relationship between the metabolic syndrome (MetS) and various sleep parameters [sleep duration, symptoms of sleep-disordered breathing (SDB), and sleep disturbances] varies by age.

METHODS

Waist circumference, blood pressure, triglycerides, high-density lipoprotein cholesterol, and fasting glucose were used to determine MetS status in a cohort (N = 19,691) of middle-aged (aged 45-64 years) and older (aged ≥65 years) subjects. Habitual sleep duration (short, ≤6 h/day; normal, 7-8 h/day; and long ≥9 h/day), sleep disturbances (such as problems with falling and staying asleep), and symptoms of sleep-disordered breathing (SDB, such as snoring and sleep apneas) were measured by questionnaires.

RESULTS

Among the participants, 4,941 subjects (25.1%) fulfilled the criteria for MetS. In the entire sample, both short and long sleep durations were associated with higher prevalence of MetS as compared to normal sleep duration. When stratified by age, a similar pattern was observed for middle-aged subjects (<65 years old; prevalence ratio (PR) [95% CI], 1.13 [1.06-1.22] for short sleep and 1.26 [1.06-1.50] for long sleep duration). In contrast, in older individuals (≥65 years old), only long sleep duration was linked to a higher prevalence of MetS (1.26 [1.12-1.42]; P < 0.01 for sleep duration × age). In the entire cohort, having at least one SDB symptom ≥4 times per week was linked to an increased prevalence of MetS; however, the PR was higher in middle-aged subjects compared with older subjects (1.50 [1.38-1.63] vs. 1.36 [1.26-1.47], respectively; P < 0.001 for SDB × age). Finally, independent of subjects' age, reports of sleep disturbances (i.e., at least one symptom ≥4 times per week) were associated with a higher likelihood of having MetS (1.12 [1.06-1.18]; P > 0.05 for sleep disturbance × age).

CONCLUSION

Our results suggest that age may modify the associations between some sleep parameters and the prevalence of MetS.

Diet and Sleep Physiology: Public Health and Clinical Implications

This mini-review examines the complex relationship between diet and sleep and explores the clinical and public health implications of the current evidence. Dietary quality and intake of specific nutrients can impact regulatory hormonal pathways to alter sleep quantity and quality. Sleep, in turn, affects the intake of total energy, as well as of specific foods and nutrients, through biological and behavioral mechanisms. Initial research in this field focused primarily on the effects of short sleep duration on nutritional quality. However, more recent studies have explored the dynamic relationship between long sleep duration and diet. Current evidence suggests that extremes of sleep duration alter sleep patterns, hormonal levels, and circadian rhythms, which contribute to weight-related outcomes and obesity, and other risk factors for the development of chronic disease such as type 2 diabetes and cardiovascular disease. These patterns may begin as early as childhood and have impacts throughout the life course. Given that non-communicable diseases are among the leading causes of death globally, deeper understanding of the interactions between sleep and nutrition has implications for both public health and clinical practice.

Long Sleep Duration Is an Independent Risk Factor for Incident Atrial Fibrillation in a Chinese Population: A Prospective Cohort Study

There is limited information on the relation between sleep duration and incident atrial fibrillation. We aimed to investigate this association in a Chinese population using cohort data from a study in Kailuan. The analysis included 87,693 participants (age range, 18–98 years) free of atrial fibrillation at the baseline survey. Participants were divided into three categories according to self-reported sleep duration: ≤6.0 hours, 7 hours (ref), ≥8.0 hours. Atrial fibrillation diagnosis was made on a standard 12-lead electrocardiogram and via self-reported history. Cox proportional hazards models were used to calculate hazard ratio (HR) and confidence interval (CI) for atrial fibrillation, according to sleep duration. During median follow-up of 7.89 (range, 6.36–8.57) years, 322 cases of atrial fibrillation had occurred. Using 7 hours of sleep as the reference group, multivariable adjusted HRs (95% CI) for atrial fibrillation were 1.07 (0.75–1.53), 1.0 (ref), and 1.50 (1.07–2.10), from lowest to highest category of sleep duration. Secondary analysis showed no evidence of interactions between sleep duration and sex and snoring on the risk of incident atrial fibrillation (p = 0.75/0.25). We conclude long sleep duration may be a potential predictor/marker for incident atrial fibrillation.