Short sleep duration as a risk factor for hypercholesterolemia: analyses of the National Longitudinal Study of Adolescent Health

Sleep: important considerations for the prevention of cardiovascular disease

PURPOSE OF REVIEW

Sleep plays many roles in maintenance of cardiovascular health. This review summarizes the literature across several areas of sleep and sleep disorders in relation to cardiometabolic disease risk factors.

RECENT FINDINGS

Insufficient sleep duration is prevalent in the population and is associated with weight gain and obesity, inflammation, cardiovascular disease, diabetes, and mortality. Insomnia is also highly present and represents an important risk factor for cardiovascular disease, especially when accompanied by short sleep duration. Sleep apnea is a well-characterized risk factor for cardiometabolic disease and cardiovascular mortality. Other issues are relevant as well. For example, sleep disorders in pediatric populations may convey cardiovascular risks. Also, sleep may play an important role in cardiovascular health disparities.

SUMMARY

Sleep and sleep disorders are implicated in cardiometabolic disease risk. This review addresses these and other issues, concluding with recommendations for research and clinical practice.

Sleep Disturbances as a Risk Factor for Stroke

Sleep, a vital process of human being, is carefully orchestrated by the brain and consists of cyclic transitions between rapid eye movement (REM) and non-REM (NREM) sleep. Autonomic tranquility during NREM sleep is characterized by vagal dominance and stable breathing, providing an opportunity for the cardiovascular-neural axis to restore homeostasis, in response to use, distress or fatigue inflicted during wakefulness. Abrupt irregular swings in sympathovagal balance during REM sleep act as phasic loads on the resting cardiovascular system. Any causes of sleep curtailment or fragmentation such as sleep restriction, sleep apnea, insomnia, periodic limb movements during sleep, and shift work, not only impair cardiovascular restoration but also impose a stress on the cardiovascular system. Sleep disturbances have been reported to play a role in the development of stroke and other cardiovascular disorders. This review aims to provide updated information on the role of abnormal sleep in the development of stroke, to discuss the implications of recent research findings, and to help both stroke clinicians and researchers understand the importance of identification and management of sleep pathology for stroke prevention and care.

Association of sleep duration with apolipoproteins and the apolipoprotein B/A1 ratio: the China health and nutrition survey

Background

Short sleep duration has been related to established cardiovascular risk factors, likely obesity, diabetes, hypertension and dyslipidaemia. However, to the best of our knowledge, the associations between sleep duration and apolipoprotein concentrations and their ratios have not been investigated to date. This study aimed to explore the independent relationship of sleep duration with apolipoprotein (apo) A1, apoB and the apoB/apoA1 ratio in a Chinese adult population.

Methods

Data from 7381 participants, aged 18 to 75 years, from the National Health and Nutrition Survey 2009 were analysed in this cross-sectional study. Participants were divided into 3 categories according to sleep duration: ≤6, 7-8, and ≥9 h. Logistic regression analysis with odds ratios was employed to assess the association between sleep duration and apo profile.

Results

Using 7-8 h of sleep as a reference, short sleep duration was associated with significantly increased odds of elevated apoB (OR =1.75, 95% CI 1.12-2.72), whereas long sleep duration was correlated with a decreased (but not statistically significant) risk for elevated apoB (OR =0.86, 95% CI 0.54-1.38) among females after controlling for covariates. Among males, long sleep duration was only marginally related to decreased odds ratios for elevated apoB/apoA1 ratio after adjustment for covariates (OR =0.78, 95% CI 0.6-0.99).

Conclusions

These results indicate that short sleep duration is strongly associated with an increased risk of elevated apoB levels in women and that long sleep duration is correlated with decreased apoB/apoA1 levels in men. Sleep hygiene management could serve to treat and prevent cardiovascular diseases by altering unfavourable apo profile.

Association of sleep duration and quality with blood lipids: a systematic review and meta-analysis of prospective studies

OBJECTIVES

To assess the longitudinal evidence of the relationships between sleep disturbances (of quantity and quality) and dyslipidaemia in the general population and to quantify such relationships.

SETTING

Systematic review and meta-analysis following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

METHODS

We performed a systematic search of PubMed and Embase (up to 9 September 2017), complemented with manual searches, of prospective population studies describing the association between sleep duration and quality and the incidence of dyslipidaemias. Relative risks (95% CIs) were extracted and pooled using a random effects model. Subgroup analyses by lipid type were performed. Heterogeneity and publication bias were also assessed. Quality was assessed with Downs and Black score.

PARTICIPANTS

Studies were included if they were prospective, had measured sleep quantity and/or quality at baseline and either incident cases of dyslipidaemia or changes in blood lipid fractions assessed prospectively.

PRIMARY OUTCOME MEASURES

Incidence of dyslipidaemia and changes in lipid fractions. Dyslipidaemia was defined as a high total cholesterol, triglycerides, low-density lipoprotein cholesterol or low high-density lipoprotein cholesterol compared with the reference group.

RESULTS

Thirteen studies were identified (eight using sleep duration, four sleep quality and one both). There was heterogeneity in the sleep quality aspects and types of lipids assessed. Classification of sleep duration (per hour/groups) also varied widely. In the pooled analysis of sleep duration (6 studies, 16 cohort samples; 30 033 participants; follow-up 2.6-10 years), short sleep was associated with a risk of 1.01 (95% CI 0.93 to 1.10) of developing dyslipidaemia, with moderate heterogeneity (I2=56%, P=0.003) and publication bias (P=0.035). Long sleep was associated with a risk of 0.98 (95% CI 0.87 to 1.10) for dyslipidaemia, with heterogeneity (I2=63%, P<0.001) and no significant publication bias (P=0.248).

CONCLUSION

The present analysis was unable to find supportive evidence of a significant relationship between sleep duration and the development of dyslipidaemia. However, heterogeneity and small number of studies limit the interpretation.

PROSPERO REGISTRATION NUMBER

CRD42016045242.

Comprehensive assessment of the impact of life habits on sleep disturbance, chronotype, and daytime sleepiness among high-school students

OBJECTIVE

Sleep affects adolescents in various ways. However, the effects of multiple factors on sleep hygiene remain unclear. A comprehensive assessment of the effects of life habits on sleep in high-school students was conducted.

METHODS

A cross-sectional survey of 344 high school students (age range 15-17; 171 boys, 173 girls) in Tokyo, Japan was conducted in 2015. Complete responses were provided by 294 students. Demographic variables, Pittsburgh Sleep Quality Index (PSQI), diurnal type scale, Pediatric Daytime Sleepiness Scale (PDSS), and life habits such as dinnertime, viewing electronic displays, caffeine intake, sunlight in the morning, and the brightness of the room in the night were asked.

RESULTS

The mean scores were PSQI: 5.9 (±2.3), PDSS: 19.0 (±5.8), and the diurnal type scale: 16.7 (±3.4). Using an electronic display in bed (OR = 3.01; (95%CI) 1.24-7.30), caffeine intake at night always (OR = 2.22; 1.01-4.90), and waking up before dawn (OR = 3.25; 1.34-7.88) were significantly associated with sleep disturbance. Irregular timing of the evening meal (OR = 2.06; 1.10-3.84) and display viewing within 2 h before bedtime (OR = 2.50; 1.01-6.18) or in bed (OR = 3.60; 1.41-9.21) were significantly associated with excessive daytime sleepiness. Using an electronic display within 2 h before bedtime (OR = 2.64; 1.10-6.38) or in bed (OR = 3.50; 1.40-8.76) and a living room which is bright at night (OR = 1.89; 1.06-3.36) were significantly associated with eveningness.

CONCLUSION

Each type of sleep-related problem had its own associated life habit factors.

Contribution of short sleep duration to ethnic differences in cardiovascular disease: results from a cohort study in the Netherlands

OBJECTIVES

We analysed association between short sleep duration and prevalence of cardiovascular disease (CVD) in a multiethnic population living in the Netherlands, and the contribution of short sleep to the observed ethnic differences in the prevalence of CVD, independent of CVD risk factors.

METHODS

20 730 participants (aged 18-71 years) of the HELIUS (Healthy Life in an Urban Setting) Study were investigated. Self-reported sleep duration was classified as: short (<7 hours/night) and healthy (7-9 hours/night). Prevalence of CVD was assessed using the Rose Questionnaire on angina pectoris, intermittent claudication and possible myocardial infarction. Association of short sleep duration with prevalent CVD and the contribution of short sleep to the observed ethnic differences in the prevalence of CVD were analysed using adjusted prevalence ratio(s) (PRs) with 95% CI.

RESULTS

Results indicate that short sleep was associated with CVD among all ethnic groups with PRs ranging from 1.44 (95% CI 1.20 to 1.71) in Moroccans to 1.74 (95% CI 1.28 to 2.36) in Dutch after adjustment for age, sex and conventional CVD risk factors. The independent contributions of short sleep (in percentage) to ethnic differences in CVD compared with Dutch were 12%, 16%, 6%, 19% and 6% in South-Asian Surinamese, African-Surinamese, Ghanaian, Turkish and Moroccan, respectively.

CONCLUSION

Short sleep contributed to ethnic differences in CVD independent of well-known CVD risk factors particularly in Surinamese and Ghanaian groups. Reducing sleep deprivation may be a relevant entry point for reducing increased CVD risks among the various ethnic minority groups.

Prevalence of sleep duration among Saudi adults

Objectives:

To examine the associations between sleep duration and a variety of demographic and clinical variables in a sample of Saudi adults.

Methods:

A cross-sectional study among 2,095 participants was conducted at King Abdulaziz Medical City, Riyadh, Kingdom of Saudi Arabia, between May and October 2014. A questionnaire was administered to collect data related to clinical health outcomes and demographic characteristics. Participants were asked to report their average sleep duration per night in hours.

Results:

One-third (33.8%) reported short sleep duration of less than 7 hours/night. Short sleep duration was more prevalent in females (37.3% versus 31.4%, p=0.004). The most common medical problems reported were obesity with body mass index of >30 Kg/m² (39.1%), hypertension (33.9%), diabetes mellitus (20.8%), depression (4.3%), asthma (17.3%), COPD (6.6%), and hyperlipidemia (2.7%). Diabetes mellitus was associated with long sleep of more than 9 hours/night (25.4%, p=0.011) and hypertension (54.2%, p=0.001). The linear regression model tend to reduce their sleep duration by roughly 22 minutes in female gender, 66 minutes in participants with hyperlipidemia, and 70 minutes in participants with poor sleep quality.

Conclusions:

Short sleep duration per night was prevalent, it affects one in every 3 Saudi adults. Long sleep duration of more than 9 hours was associated with increased comorbid conditions.

Exploring associations between state education initiatives and teachers' sleep: A social-ecological approach

Social policies that are not specifically aimed at impacting health can still have health consequences. State education reforms, such as standardized testing and stringent accountability for schools and teachers, may affect teacher health by changing their working conditions. This study explores associations between state education initiatives and teachers' sleep, an important predictor of productivity and chronic health conditions. The Behavioral Risk Factor Surveillance System 2013 and 2014 data sets provided sleep and demographic data for 7836 teachers in 29 states in the United States. We linked the teacher data to state education reform data from the U.S. Department of Education. Logistic regression was used to estimate odds ratios (ORs) of reporting inadequate sleep (i.e., <6.5 h and <5.5 h) associated with state education policies after adjusting for demographic characteristics. Teachers had significantly higher odds of reporting inadequate sleep if their state financed professional development, sanctioned or rewarded schools based on student performance, and regulated classroom materials for state-wide common core standards (ORs ranging from 1.25 to 1.84). More strictly defined inadequate sleep (<5.5 h) had generally higher ORs than less strict definition (<6.5 h). The Race-to-the-Top award, a US federal grant designed to encourage states to implement reforms through regulations and legislations, was also associated with inadequate sleep (OR = 1.41, p < 0.01, for <6.5 h; OR = 1.55, p < 0.01, for <5.5 h). Although this exploratory study did not have district- and school-level implementation data, the results suggest that some state education policies may have impacts on teacher sleep. Consequences of education reform for teacher health deserve more attention.

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.

Relationship between Sleep Duration and Risk Factors for Stroke

Stroke is a leading cause of death and disability worldwide. While various risk factors have been identified, sleep has only been considered a risk factor more recently. Various epidemiologic studies have associated stroke with sleep such as sleep duration, and laboratory and clinical studies have proposed various underlying mechanisms. The pathophysiology is multifactorial, especially considering sleep affects many common risk factors for stroke. This review aims to provide an outline of the effect of sleep duration on common stroke risk factors. Appropriate sleep duration, especially in patients who have stroke risk factors, and increasing awareness and screening for sleep quality may contribute to primary prevention of stroke.

Longitudinal Analysis of Sleep Duration and Cardiometabolic Risk in Young Children

BACKGROUND

The aim of this study is to determine if sleep duration in early childhood is associated with cardiometabolic risk (CMR) in later childhood as assessed by a CMR cluster score [sum of age- and sex-standardized z-scores of waist circumference (WC), systolic blood pressure, triglycerides, glucose, and (inverse) high-density lipoprotein (HDL)]. Secondary objectives included examining sleep duration and the individual CMR factors and BMI z-score.

PATIENTS AND METHODS

A prospective cohort study was conducted using data from the TARGet Kids! practice-based research network in Toronto, Canada. Children (n = 597) with parent-reported 24-hour sleep duration in early childhood (12-36 months) and a follow-up visit (36-96 months) with all five CMR factors were included in the analysis. Multivariable linear regression was used to assess the relationship between early childhood sleep duration and later childhood CMR, adjusting for relevant covariates.

RESULTS

Average 24-hour sleep duration in early childhood [mean age: 28.1 (6.6) months] was 11.8 (1.4) hours, with 87% meeting or exceeding total sleep recommendations for their age. Sleep duration in early childhood was not associated with the CMR cluster score in later childhood. Shorter sleep duration was associated with higher HDL concentrations [adjusted β = -0.028 (95% confidence interval: -0.049 to -0.007), p = 0.009].

CONCLUSIONS

Further research is needed to determine if early childhood sleep duration is associated with HDL in later childhood. Future studies, which investigate sleep quality in addition to sleep duration, may be helpful.

Work, sleep, and cholesterol levels of U.S. long-haul truck drivers

Long-haul truck drivers in the United States experience elevated cardiovascular health risks, possibly due to hypercholesterolemia. The current study has two objectives: 1) to generate a cholesterol profile for U.S. long-haul truck drivers; and 2) to determine the influence of work organization characteristics and sleep quality and duration on cholesterol levels of long-haul truck drivers. Survey and biometric data were collected from 262 long-haul truck drivers. Descriptive analyses were performed for demographic, work organization, sleep, and cholesterol measures. Linear regression and ordinal logistic regression analyses were conducted to examine for possible predictive relationships between demographic, work organization, and sleep variables, and cholesterol outcomes. The majority (66.4%) of drivers had a low HDL (<40 mg/dL), and nearly 42% of drivers had a high-risk total cholesterol to HDL cholesterol ratio. Sleep quality was associated with HDL, LDL, and total cholesterol, and daily work hours were associated with LDL cholesterol. Workday sleep duration was associated with non-HDL cholesterol, and driving experience and sleep quality were associated with cholesterol ratio. Long-haul truck drivers have a high risk cholesterol profile, and sleep quality and work organization factors may induce these cholesterol outcomes. Targeted worksite health promotion programs are needed to curb these atherosclerotic risks.

Sleep duration is associated with increased risk for cardiovascular outcomes: a pilot study in a sample of community dwelling adults in Ghana

BACKGROUND

Associations between sleep duration and cardiovascular disease (CVD) risk factors have been demonstrated in past studies. However, previous studies have not investigated these relationships using objective sleep measures in sub-Saharan Africa. Our objective was to investigate the association between sleep duration and cardiovascular risk factors in a sample of community-dwelling Ghanaian adults.

METHODS

We used wrist actigraphy along with a seven-day sleep diary to measure sleep duration, wake after sleep onset, sleep latency, and sleep quality. Participants were randomly selected from among those participating in the RODAM study in rural and urban Ghana. Outcome measurements included 10-year risk of CVD events, prevalent CVD, and metabolic syndrome. Additional participant characteristics were assessed using a structured questionnaire. Linear and logistic regression analyses were used to assess the relationships between sleep measures and CVD risk.

RESULTS

A total of 263 participants from rural and urban Ghana participated. Total sleep time was positively associated with a 10-year CVD risk; this association remained after adjusting for age, sex, urban vs rural location, socio-economic status, physical activity, and sleep disturbance (β = 0.990, p = 0.015). Short sleep, defined as sleeping less than seven hours per night on average, was negatively associated with a 10-year CVD risk, and this relationship remained in the fully adjusted model (β = -2.100, p = 0.011). Sleep duration was not associated with prevalence of CVD or metabolic syndrome.

CONCLUSION

Using actigraphy to measure sleep duration among a population of community-dwelling adults in sub-Saharan Africa is feasible. We found a positive association between sleep and CVD risk. No association was found between sleep duration and prevalent CVD or metabolic syndrome. The implications and new directions relating to these findings are stated.

Sleep Problems as Predictors in Attention-Deficit Hyperactivity Disorder: Causal Mechanisms, Consequences and Treatment

Attention-deficit hyperactivity disorder (ADHD) is notorious for its debilitating consequences and early age of onset. The need for early diagnosis and intervention has frequently been underscored. Previous studies have attempted to clarify the bidirectional relationship between ADHD and sleep problems, proposing a potential role for sleep problems as early predictors of ADHD. Sleep deprivation, sleep-disordered breathing, and circadian rhythm disturbances have been extensively studied, yielding evidence with regard to their induction of ADHD-like symptoms. Genetic-phenotypic differences across individuals regarding the aforementioned sleep problems have been elucidated along with the possible use of these characteristics for early prediction of ADHD. The long-term consequences of sleep problems in individuals with ADHD include obesity, poor academic performance, and disrupted parent-child interactions. Early intervention has been proposed as an approach to preventing these debilitating outcomes of ADHD, with novel treatment approaches ranging from melatonin and light therapy to myofunctional therapy and adjustments of the time point at which school starts.

Association of Subjective and Objective Sleep Duration as well as Sleep Quality with Non-Invasive Markers of Sub-Clinical Cardiovascular Disease (CVD): A Systematic Review

Aim: Abnormal daily sleep duration and quality have been linked to hypertension, diabetes, stroke, and overall cardiovascular disease (CVD) morbidity & mortality. However, the relationship between daily sleep duration and quality with subclinical measures of CVD remain less well studied. This systematic review evaluated how daily sleep duration and quality affect burden of subclinical CVD in subjects free of symptomatic CVD.

Methods: Literature search was done via MEDLINE, EMBASE, Web of Science until June 2016 and 32 studies met the inclusion criteria. Sleep duration and quality were measured either via subjective methods, as self-reported questionnaires or Pittsburg Sleep Quality Index (PSQI) or via objective methods, as actigraphy or polysomnography or by both. Among subclinical CVD measures, coronary artery calcium (CAC) was measured by electron beam computed tomography, Carotid intima-media thickness (CIMT) measured by high-resolution B-mode ultrasound on carotid arteries, endothelial/microvascular function measured by flow mediated dilation (FMD) or peripheral arterial tone (PAT) or iontophoresis or nailfold capillaroscopy, and arterial stiffness measured by pulse wave velocity (PWV) or ankle brachial index (ABI).

Results: Subjective short sleep duration was associated with CAC and CIMT, but variably associated with endothelial dysfunction (ED) and arterial stiffness; however, subjective long sleep duration was associated with CAC, CIMT and arterial stiffness, but variably associated with ED. Objective short sleep duration was positively associated with CIMT and variably with CAC but not associated with ED. Objective long sleep duration was variably associated with CAC and CIMT but not associated with ED. Poor subjective sleep quality was significantly associated with ED and arterial stiffness but variably associated with CAC and CIMT. Poor objective sleep quality was significantly associated with CIMT, and ED but variably associated with CAC.

Conclusions: Overall, our review provided mixed results, which is generally in line with published literature, with most of the studies showing a significant relationship with subclinical CVD, but only some studies failed to demonstrate such an association. Although such mechanistic relationship needs further evaluation in order to determine appropriate screening strategies in vulnerable populations, this review strongly suggested the existence of a relationship between abnormal sleep duration and quality with increased subclinical CVD burden.

Sleep Duration and Diabetes Risk: Population Trends and Potential Mechanisms

Sleep is important for regulating many physiologic functions that relate to metabolism. Because of this, there is substantial evidence to suggest that sleep habits and sleep disorders are related to diabetes risk. In specific, insufficient sleep duration and/or sleep restriction in the laboratory, poor sleep quality, and sleep disorders such as insomnia and sleep apnea have all been associated with diabetes risk. This research spans epidemiologic and laboratory studies. Both physiologic mechanisms such as insulin resistance, decreased leptin, and increased ghrelin and inflammation and behavioral mechanisms such as increased food intake, impaired decision-making, and increased likelihood of other behavioral risk factors such as smoking, sedentary behavior, and alcohol use predispose to both diabetes and obesity, which itself is an important diabetes risk factor. This review describes the evidence linking sleep and diabetes risk at the population and laboratory levels.

Gut microbiota and glucometabolic alterations in response to recurrent partial sleep deprivation in normal-weight young individuals

Objective

Changes to the microbial community in the human gut have been proposed to promote metabolic disturbances that also occur after short periods of sleep loss (including insulin resistance). However, whether sleep loss affects the gut microbiota remains unknown.

Methods

In a randomized within-subject crossover study utilizing a standardized in-lab protocol (with fixed meal times and exercise schedules), we studied nine normal-weight men at two occasions: after two nights of partial sleep deprivation (PSD; sleep opportunity 02:45–07:00 h), and after two nights of normal sleep (NS; sleep opportunity 22:30–07:00 h). Fecal samples were collected within 24 h before, and after two in-lab nights, of either NS or PSD. In addition, participants underwent an oral glucose tolerance test following each sleep intervention.

Results

Microbiota composition analysis (V4 16S rRNA gene sequencing) revealed that after two days of PSD vs. after two days of NS, individuals exhibited an increased Firmicutes:Bacteroidetes ratio, higher abundances of the families Coriobacteriaceae and Erysipelotrichaceae, and lower abundance of Tenericutes (all P < 0.05) – previously all associated with metabolic perturbations in animal or human models. However, no PSD vs. NS effect on beta diversity or on fecal short-chain fatty acid concentrations was found. Fasting and postprandial insulin sensitivity decreased after PSD vs. NS (all P < 0.05).

Discussion

Our findings demonstrate that short-term sleep loss induces subtle effects on human microbiota. To what extent the observed changes to the microbial community contribute to metabolic consequences of sleep loss warrants further investigations in larger and more prolonged sleep studies, to also assess how sleep loss impacts the microbiota in individuals who already are metabolically compromised.

•

Possibly the first results of how short sleep impacts the human gut microbiota.

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Two nights of short sleep do not significantly impact beta diversity.

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The Firmicutes to Bacteroidetes ratio is significantly affected by sleep loss.

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Fecal short-chain fatty acid levels do not change depending on sleep duration.

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Increased insulin resistance after sleep loss is unrelated to alterations in the microbiota.

Differences in sleep habits, study time, and academic performance between US-born and foreign-born college students

PURPOSE

To inform the design of a sleep improvement program for college students, we assessed academic performance, sleep habits, study hours, and extracurricular time, hypothesizing that there would be differences between US-born and foreign-born students.

METHODS

Questionnaires queried participants on bedtimes, wake times, nap frequency, differences in weekday and weekend sleep habits, study hours, grade point average, time spent at paid employment, and other extracurricular activities. Comparisons were made using chi square tests for categorical data and t tests for continuous data between US-born and foreign-born students.

RESULTS

Of 120 participants (55 % women) with racial diversity (49 whites, 18 blacks, 26 Hispanics, 14 Asians, and 13 other), 49 (41 %) were foreign-born. Comparisons between US-born and foreign-born students showed no differences in average age or gender though US-born had more whites. There were no differences between US-born and foreign-born students for grade point averages, weekday bedtimes, wake times, or total sleep times. However, US-born students averaged 50 min less study time per day (p = 0.01), had almost 9 h less paid employment per week (14.5 vs 23.4 h per week, p = 0.001), and stayed up to socialize more frequently (63 vs 43 %, p = 0.03). Foreign-born students awakened an hour earlier and averaged 40 min less sleep per night on weekends.

CONCLUSIONS

Cultural differences among college students have a profound effect on sleep habits, study hours, and extracurricular time. The design of a sleep improvement program targeting a population with diverse cultural backgrounds must factor in such behavioral variations in order to have relevance and impact.

Sleep and Lipid Profile During Transition from Childhood to Adolescence

OBJECTIVES

To assess the longitudinal effects of sleep duration and quality on lipid profiles during the transition from childhood to early adolescence, over a 4-year-period.

STUDY DESIGN

A cohort study of children born in 1998 examined at 8 years of age (SD, 0.3; n = 105) and 12 years of age (SD, 0.5; n = 190). Sleep duration, wake after sleep onset, sleep efficiency, and weekend catch-up sleep were measured with actigraphs for 7 (8 years of age) and 8 (12 years of age) nights. Fasting serum samples were collected at 12 years of age. Covariates included age, pubertal development, socioeconomic status, body mass index, and physical activity.

RESULTS

In girls, shorter sleep duration at 8 and 12 years of age was associated with lower high-density lipoprotein-cholesterol and higher triglycerides at 12 years of age. Poorer sleep quality at 8 years of age and longer weekend catch-up sleep at 12 years of age was associated with higher triglycerides at 12 years of age. From 8 to 12 years of age, improvement in sleep quality associated with higher total cholesterol, and a decrease in sleep duration with lower lipid levels. In boys, longer sleep duration at 8 years of age, and a larger decrease in sleep duration from 8 to 12 years of age was associated with higher levels of triglycerides at 12 years of age.

CONCLUSIONS

Poorer sleep during transition to early adolescence is associated with an atherogenic lipid profile in early adolescent girls, and such effects are less prominent in boys. Poor sleep may have long-term associations with health, which are not mitigated by the amount of physical activity.

Onset of Impaired Sleep and Cardiovascular Disease Risk Factors: A Longitudinal Study

STUDY OBJECTIVES

Impaired sleep has been linked to increased risk of cardiovascular disease (CVD), but the underlying mechanisms are still unsettled. We sought to determine how onset of impaired sleep affects the risk of established physiological CVD risk factors (i.e., hypertension, diabetes, and dyslipidemia).

METHODS

In a longitudinal cohort study with 3 survey waves (2000, 2004, 2008) from the Finnish Public Sector study we used repeated information on sleep duration and disturbances to determine onset of impaired sleep. Information on development of CVD risk factors, as indicated by initiation of medication for hypertension, diabetes, and dyslipidemia was derived from electronic medical records within 8 years of follow-up. Data on 45,647 participants was structured as two data-cycles to examine the effect of change in sleep (between two waves) on incident CVD events. We applied strict inclusion and exclusion criteria to determine temporality between changes in sleep and the outcomes.

RESULTS

While we did not find consistent effects of onset of short or long sleep, we found onset of disturbed sleep to predict subsequent risk of hypertension (hazard ratio = 1.22, 95% CI: 1.04-1.44) and dyslipidemia (HR = 1.17, 95% CI: 1.07-1.29) in fully adjusted analyses.

CONCLUSIONS

Results suggest that onset of sleep disturbances rather than short or long sleep mark an increase in physiological risk factors, which may partly explain the higher risk of CVD observed among impaired sleepers.

COMMENTARY

A commentary on this paper appears in this issue on page 1629.

Role of sleep quality in the metabolic syndrome

Emerging evidence has assigned an important role to sleep as a modulator of metabolic homeostasis. The impact of variations in sleep duration, sleep-disordered breathing, and chronotype to cardiometabolic function encompasses a wide array of perturbations spanning from obesity, insulin resistance, type 2 diabetes, the metabolic syndrome, and cardiovascular disease risk and mortality in both adults and children. Here, we critically and extensively review the published literature on such important issues and provide a comprehensive overview of the most salient pathophysiologic pathways underlying the links between sleep, sleep disorders, and cardiometabolic functioning.

A Pilot Study of the Association of Markers of Cholesterol Synthesis with Disturbed Sleep in Smith-Lemli-Opitz Syndrome

OBJECTIVE

Smith-Lemli-Opitz syndrome (SLOS) is a rare genetic disorder characterized by cholesterol synthesis impairment. A host of physical, developmental, and behavioral presentations are associated with SLOS, many of which have been related with disorder severity. Sleep disturbance is commonly reported in SLOS. This study is the first to examine the association between sleep disturbance and biomarkers of cholesterol synthesis defect.

METHOD

Twenty youth with SLOS participated. Biomarkers of cholesterol synthesis were obtained, including plasma sterols (i.e., 7-dehydrocholesterol, 8-dehydrocholesterol, and cholesterol), mevalonic acid, and 24-S hydroxycholsterol. A ratio of plasma cholesterol precursors to cholesterol levels was used as a measure of biochemical severity. Parents reported their children's sleep problems using the Children's Sleep Habits Questionnaire.

RESULTS

Most markers of cholesterol synthesis disruption were associated with overall sleep disturbance. Biochemical severity of SLOS was also associated with specific sleep problems (e.g., decreased sleep duration and increased sleep onset delay) and was identified as a significant predictor of these factors.

CONCLUSION

This study is the first to demonstrate associative relationships between cholesterol levels and sleep disturbance in youth with SLOS. These results add to the current understanding of how cholesterol levels may contribute to the behavioral phenotype of SLOS. These findings may inform future studies related to the role cholesterol synthesis defects play in the behavioral phenotype of SLOS and, subsequently, modalities of intervention for behavioral symptoms.

Dietary Macronutrients and Sleep

This study examined the effects of macronutrient diets on sleep quantity and quality. Using a repeated-measures, randomized crossover study design, 36 young adults served as their own control, and consumed high protein, carbohydrate, fat, and control diets. Treatment orders were counterbalanced across the dietary groups. Following consumption of the study diets, sleep measures were examined for within-subject differences. Fatty acid intakes and serum lipids were further analyzed for differences. Sleep actigraphs indicated wake times and wake minutes (after sleep onset) were significantly different when comparing consumption of macronutrient diets and a control diet. Post hoc testing indicated high carbohydrate intakes were associated with significantly shorter (p < .001) wake times. Also, the Global Pittsburgh Sleep Quality Index© post hoc results indicated high fat intake was associated with significantly better (p < .05) sleep in comparison with the other diets. These results highlight the effects that dietary manipulations may have on sleep.

Is there an association between short sleep duration and adolescent anxiety disorders?

OBJECTIVE

The purpose of this study is to provide the first data on the prospective, reciprocal association between short sleep duration and DSM-IV anxiety disorders among adolescents.

METHODS

A community-based two-wave cohort study included 4175 youths aged 11-17 years at baseline, with 3134 of these followed up a year later, drawn from a metropolitan area with a population of over 4 million. Anxiety is defined as any DSM-IV anxiety disorder in the past year generalized anxiety: panic disorder, agoraphobia without panic, social phobia, and post-traumatic stress disorder. Short sleep duration is defined as ≤6 h of sleep per night.

RESULTS/CONCLUSIONS

In multivariate analyses, short sleep duration every night at baseline predicted anxiety disorders at follow-up, controlling for anxiety at baseline. Examining the reciprocal association, anxiety disorders at baseline did not predict short sleep duration at follow-up. We are the first to examine the reciprocal effects for anxiety disorders and sleep duration among adolescents using prospective data. The data suggest that reduced quantity of sleep may increase risk for anxiety, but anxiety does not increase risk for decreased sleep duration.

Sleep Patterns among South Korean Infants and Toddlers: Global Comparison

The purpose of this study was to examine sleep patterns in a large sample of infants and toddlers (ages birth to 36 months) in Korea, and to compare sleep patterns, sleep problems, sleep ecology, and parental behaviors to global sleep data on young children in both predominantly Asian (P-A) and predominantly Caucasian (P-C) countries/regions. We additionally examined parent and child demographic information, parental behaviors, and aspects of the sleep ecology as predictors of sleep patterns among infants and toddlers in Korea. Parents/caregivers of 1,036 Korean infants and toddlers completed an expanded, internet-based version of the brief infant sleep questionnaire. Consistent with other studies of sleep in early childhood, sleep/wake patterns became increasingly consolidated with older child age for the Korea sample. Compared to both P-A and P-C infants and toddlers, children in Korea had the latest bedtimes, shortest total sleep and daytime sleep durations, and the least frequent rates of napping. Even though half of parents perceive their children's sleep problematic, parental perceptions of severe child sleep problems were the lowest. Within Korea, breastfeeding and bottle-feeding at sleep resumption were associated with increased nocturnal awakenings. Evening television viewing was associated with later bedtimes, which may have implications for sleep hygiene recommendations in clinical practice. The current study provides important information about sleep/wake patterns, parental behaviors, and aspects of the sleep ecology for infants and toddlers for physicians to support healthy sleep in Korea.

Restriction of rapid eye movement sleep during adolescence increases energy gain and metabolic efficiency in young adult rats

NEW FINDINGS

What is the central question of this study? Sleep curtailment in infancy and adolescence may lead to long-term risk for obesity, but the mechanisms involved have not yet been determined. This study examined the immediate and long-term metabolic effects produced by sleep restriction in young rats. What is the main finding and its importance? Prolonged sleep restriction reduced weight gain (body fat stores) in young animals. After prolonged recovery, sleep-restricted rats tended to save more energy and to store more fat, possibly owing to increased gross food efficiency. This could be the first step to understand this association. Sleep curtailment is associated with obesity and metabolic changes in adults and children. The aim of the present study was to evaluate the immediate and long-term metabolic alterations produced by sleep restriction in pubertal male rats. Male Wistar rats (28 days old) were allocated to a control (CTL) group or a sleep-restricted (SR) group. This was accomplished by the single platform technique for 18 h per day for 21 days. These groups were subdivided into the following four time points for assessment: sleep restriction and 1, 2 and 4 months of recovery. Body weight and food intake were monitored throughout the experiment. At the end of each time period, blood was collected for metabolic profiling, and the carcasses were processed for measurement of body composition and energy balance. During the period of sleep restriction, SR animals consumed less food in the home cages. This group also displayed lower body weight, body fat, triglycerides and glucose levels than CTL rats. At the end of the first month of recovery, despite eating as much as CTL rats, SR animals showed greater energy and body weight gain, increased gross food efficiency and decreased energy expenditure. At the end of the second and fourth months of recovery, the groups were no longer different, except for energy gain and gross food efficiency, which remained higher in SR animals. In conclusion, sleep restriction affected weight gain of young animals, owing to reduction of fat stores. Two months were sufficient to recover this deficit and to reveal that SR rats tended to save more energy and to store more fat.

Is there an association between adolescent sleep restriction and obesity

OBJECTIVE

This is the first prospective study of the reciprocal association between sleep restriction and weight among adolescents. Evidence on sleep duration and obesity in youth is sparse and the results have been equivocal.

METHODS

Data are from a community-based, two-wave cohort study. The setting was a metropolitan area with a population of over 4 million. The cohort consisted of 4175 youths 11-17 at baseline and 3134 of these followed up a year later. Obesity was defined as body mass index >95th percentile for children of the same age and sex. Sleep restriction was defined as 6 or fewer hours of sleep per night on weeknights or on both weekends and weeknights. Covariates examined were age, gender, family income and depression.

RESULTS

Results clearly demonstrated that there was no association between sleep restriction and obesity at baseline. In prospective analyses, sleep restriction did not increase future risk of obesity, nor did obesity increase risk of future sleep restriction.

CONCLUSIONS

These findings call into question previous research based primarily on cross-sectional data suggesting a positive correlation between sleep restriction and obesity. However, the results for adolescents in this study are supported by one study of adolescents and by studies of adults using prospective designs. At this point, there appears to be little evidence for a temporal relation between sleep duration and obesity among adults or adolescents.

Exposure to long-term air pollution and road traffic noise in relation to cholesterol: A cross-sectional study

BACKGROUND

Exposure to traffic noise and air pollution have both been associated with cardiovascular disease, though the mechanisms behind are not yet clear.

OBJECTIVES

We aimed to investigate whether the two exposures were associated with levels of cholesterol in a cross-sectional design.

METHODS

In 1993–1997, 39,863 participants aged 50–64 year and living in the Greater Copenhagen area were enrolled in a population-based cohort study. For each participant, non-fasting total cholesterol was determined in whole blood samples on the day of enrolment. Residential addresses 5-years preceding enrolment were identified in a national register and road traffic noise (Lden) were modeled for all addresses. For air pollution, nitrogen dioxide (NO2) was modeled at all addresses using a dispersion model and PM2.5 was modeled at all enrolment addresses using a land-use regression model. Analyses were done using linear regression with adjustment for potential confounders as well as mutual adjustment for the three exposures.

RESULTS

Baseline residential exposure to the interquartile range of road traffic noise,NO2 and PM2.5 was associated with a 0.58 mg/dl (95% confidence interval: −0.09; 1.25), a 0.68 mg/dl (0.22; 1.16) and a 0.78 mg/dl (0.22; 1.34) higher level of total cholesterol in single pollutant models, respectively. In two pollutant models with adjustment for noise in air pollution models and vice versa, the association between air pollution and cholesterol remained for both air pollution variables (NO2: 0.72 (0.11; 1.34); PM2.5: 0.70 (0.12; 1.28) mg/dl), whereas there was no association for noise (−0.08mg/dl). In three-pollutant models (NO2, PM2.5 and road traffic noise), estimates for NO2 and PM2.5 were slightly diminished (NO2: 0.58 (−0.05; 1.22); PM2.5: 0.57 (−0.02; 1.17) mg/dl).

CONCLUSIONS

Air pollution and possibly also road traffic noise may be associated with slightly higher levels of cholesterol, though associations for the two exposures were difficult to separate.

[Sleep duration and metabolism]

Sleep duration has gradually diminished during the last decade while obesity and type 2 diabetes have become epidemics. Experimental sleep curtailment leads to increased appetite, hormonal disturbances and, especially, insulin resistance. Numerous epidemiological studies have therefore examined whether habitual short sleep is associated with obesity and type 2 diabetes. A large majority of cross-sectional studies have confirmed an association between short, and also long sleep duration and obesity in adults more than in the elderly. Short sleep is strongly associated to obesity in children and adolescents. Prospective studies, including studies in children, are not conclusive with regard to the effect of short sleep on the incidence of obesity. Both short and long sleep durations are associated with diabetes, but only short sleep duration seems predictive of future diabetes. Insomnia seems to be a strong contributor to short sleep duration but the association of insomnia with obesity is not clear. Insomnia is associated with type 2 diabetes and also predictive of a higher incidence. Other studies have shown that short sleep duration and insomnia are associated with, and sometime predictive of, other components of the metabolic syndrome, especially hypertension and the risk of coronary disease. The treatment of short sleep duration and insomnia with regard to their effects on the metabolic syndrome merits further study.

The relationship between insomnia with short sleep duration is associated with hypercholesterolemia: a cross-sectional study

AIM

To examine the association between insomnia with short sleep duration and hypercholesterolemia in Taiwanese adults.

BACKGROUND

Previous studies mostly focused on the association between sleep duration and hyperlipidemia, but the results were not consistent. Besides, very few studies extensively examined the association between insomnia and hypercholesterolemia. This study hypothesized that insomnia with short sleep duration is associated with hypercholesterolemia.

DESIGN

Secondary data analysis. This study analysed the latest database of the cross-sectional Nutrition and Health Survey in Taiwan which was released on 2011 (data collected between 2005-2008) and collected data using stratified three-staged probability sampling design.

METHODS

This study analysed 1533 participants aged between 19-64 (733 males and 800 females) and used logistic regression model to calculate the odds ratio and the 95% confidence interval of insomnia with short sleep duration to hypercholesterolemia. Controlled confounders included age, gender, sample weight, body mass index, waist circumference, fasting plasma glucose, hypertension and diabetes.

RESULTS

Insomnia with 5-6 hours of sleep duration was significantly associated with hypercholesterolemia. The odds ratio of mild insomnia or moderate/severe insomnia with 5-6 hours of sleep duration to hypercholesterolemia was higher, compared with the reference group (without insomnia and >6 hours of sleep duration).

CONCLUSION

Insomnia with short sleep duration was associated with increased odds of hypercholesterolemia. Caregivers in clinical practice should watch out for the effect brought by this novel factor.

Sleep Duration and Waist Circumference in Adults: A Meta-Analysis

BACKGROUND

Previous research has demonstrated a relation between insufficient sleep and overall obesity. Waist circumference (WC), a measure of central adiposity, has been demonstrated to improve prediction of health risk. However, recent research on the relation of insufficient sleep duration to WC in adults has yielded inconsistent findings.

OBJECTIVES

To assess the magnitude and the consistency of the relation of insufficient sleep and WC.

METHODS

A systematic search of Internet and research databases using Google Scholar, Medline, PubMed, and PsycINFO through July 2013 was conducted. All articles in English with adult human subjects that included measurements of WC and sleep duration were reviewed. A random effects meta-analysis and regression analyses were performed. Heterogeneity and publication bias were checked. Results are expressed as Pearson correlations (r; 95% confidence interval).

RESULTS

Of 1,376 articles, 30 met inclusion criteria and 21 studies (22 samples for a total of 56,259 participants) provided sufficient data for meta-analysis. Results showed a significant negative relation between sleep duration and WC (r = -0.10, P < 0.0001) with significant heterogeneity related to sleep comparison method. Potential moderators of the relation between sleep duration and WC were not significant. Funnel plots showed no indication of publication bias. In addition, a fail-safe N calculation indicated that 418 studies with null effects would be necessary to bring the overall mean effect size to a trivial value of r = -0.005.

CONCLUSIONS

Internationally, cross-sectional studies demonstrate a significant negative relation between sleep duration and waist circumference, indicating shorter sleep durations covary with central adiposity. Future research should include prospective studies.

Sleep characteristics and cardiovascular risk in children and adolescents: an enumerative review

Cardiovascular risk factors develop in childhood and adolescence. This enumerative review addresses whether sleep characteristics, including sleep duration, continuity, quality, and daytime sleepiness, are associated with cardiovascular risk factors in young people. Thirty-nine studies were identified, which examined the following risk factors: metabolic syndrome, glucose and insulin, lipids, blood pressure, and cardiovascular responses to psychological stressors. Due to the availability of other reviews, 16 longitudinal studies of obesity published in 2011 and later were also included in this report. Excluded from the review were studies of participants with suspected or diagnosed sleep disorders and reports from sleep deprivation experiments. Combining studies, evidence was strongest for obesity, followed by glucose, insulin, blood pressure (especially ambulatory blood pressure), and parasympathetic responses to psychological stressors. There was little evidence for metabolic syndrome cluster, lipids, and blood pressure responses to psychological stressors. The more positive associations were obtained for studies that incorporated objective measures of sleep and that included adolescents. The foundational evidence is almost entirely cross-sectional, except for work on obesity. In summary, available evidence suggests that the associations between sleep characteristics and cardiovascular risk vary by risk factor. It is time to conduct studies to determine antecedent and consequent relationships, and to expand risk factors to include markers of inflammation.

School Start Time and Adolescent Sleep Patterns: Results From the U.S. National Comorbidity Survey--Adolescent Supplement

OBJECTIVES

We estimated associations between school start time and adolescent weeknight bedtime, weeknight sleep duration, and weekend compensatory sleep and assessed whether associations differ by age, sex, or urbanicity.

METHODS

We used a subsample of a nationally representative, cross-sectional survey of 7308 students aged 13 to 18 years attending 245 schools to estimate associations of school start time, reported by school principals, with weeknight bedtime and sleep duration and weekend compensatory sleep, reported during adolescent face-to-face interviews.

RESULTS

Start time was positively associated with weeknight bedtime. Associations between start time and weeknight sleep duration were nonlinear and were strongest for start times of 8:00 am and earlier. Associations differed by sex and urbanicity, with the strongest association among boys in major metropolitan counties. Start time was negatively associated with sleep duration among boys in nonurban counties. Start time was not associated with weekend compensatory sleep.

CONCLUSIONS

Positive overall associations between school start time and adolescent sleep duration at the national level support recent policy recommendations for delaying school start times. However, the impact of start time delays may differ by sex and urbanicity.

Prevalence and factors associated with dyslipidemia after liver transplantation

OBJECTIVE

to determine the prevalence of abnormal total cholesterol (TC), low density lipoprotein (LDL), high density lipoprotein (HDL) and triglycerides in patients undergoing liver transplantation (LTx) and to identify predictors of these disorders.

METHODS

cross-sectional study to assess the prevalence of dyslipidemia in patients undergoing LTx. Demographic, socioeconomic, clinical, anthropometric and dietetic data were collected to determine the association with dyslipidemia using univariate and multivariate statistical analysis.

RESULTS

136 patients were evaluated, 68.1% of which had at least one type of dyslipidemia. The triglyceride level was high in 32.4% of cases, with low HDL in 49.3% of patients and high LDL levels in only 8.8%. High total cholesterol was observed in 16.2% of the study population and was associated with the recommendation for transplantation due to ethanolic cirrhosis (OR = 2.7) and a greater number of hours slept per night (OR = 1.5).

CONCLUSION

many patients presented dyslipidemia after transplantation, demonstrating the need for interventions in relation to modifiable factors associated with dyslipidemias that can mitigate or prevent these disorders.

Predictors of screening for hyperlipidemia in an urban pediatric tertiary care center

INTRODUCTION

It is unknown how the conflicting recommendations of the American Academy of Pediatrics and the US Preventive Services Task Force on pediatric hyperlipidemia affect screening.

OBJECTIVES

(a) Identify clinical predictors for screening for hyperlipidemia, (b) assess the adherence to the 2008 American Academy of Pediatrics guidelines, and (c) determine the efficacy of reminder cards in increasing the adherence to the aforementioned guidelines.

METHODS

Retrospective chart review in the resident, attending, and adolescent medicine clinics during a 3-month period. Reminder cards on each patient chart outlining guidelines for lipid screening for the same clinics were inserted and prospectively assessed for adherence during the following 3 months.

RESULTS

Older age and higher body mass index increased likelihood (odds ratio = 1.2 and 12.7, respectively) for lipid screening. Reminder cards improved adherence in the resident clinic only (χ2 P = .016).

CONCLUSIONS

Age and body mass index were the most significant predictors for lipid screening. Reminder cards modestly improved adherence among resident physicians.

The metabolic burden of sleep loss

In parallel with the increasing prevalence of obesity and type 2 diabetes, sleep loss has become common in modern societies. An increasing number of epidemiological studies show an association between short sleep duration, sleep disturbances, and circadian desynchronisation of sleep with adverse metabolic traits, in particular obesity and type 2 diabetes. Furthermore, experimental studies point to distinct mechanisms by which insufficient sleep adversely affects metabolic health. Changes in the activity of neuroendocrine systems seem to be major mediators of the detrimental metabolic effects of insufficient sleep, through favouring neurobehavioural outcomes such as increased appetite, enhanced sensitivity to food stimuli, and, ultimately, a surplus in energy intake. The effect of curtailed sleep on physical activity and energy expenditure is less clear, but changes are unlikely to outweigh increases in food intake. Although long-term interventional studies proving a cause and effect association are still scarce, sleep loss seems to be an appealing target for the prevention, and probably treatment, of metabolic disease.

Circadian rhythms and sleep in bipolar disorder: implications for pathophysiology and treatment

PURPOSE OF REVIEW

Multiple lines of evidence support the conceptualization of bipolar disorder as a disorder of circadian rhythms. Considering bipolar disorder in the framework of circadian disturbances also helps understand the clinical phenomenology pointing toward a multisystemic involvement.

RECENT FINDINGS

Patients with bipolar disorder show altered rhythmicity in body temperature and melatonin rhythms, high day-to-day variability in activity and sleep timing, persistent disturbances of sleep or wake cycles, including disturbances of sleep continuity. The internal clocks are, indeed, responsible for regulating a variety of physiologic functions, including appetitive behaviors, cognitive functions and metabolism.

SUMMARY

An underlying circadian pathology in bipolar disorder is a unifying explicatory model for the high psychiatric and medical comorbidity observed during the long-term course of the disorder. This model also provides a rationale for therapeutic interventions aimed at re-entraining the internal clock.

Prevalence of dyslipidemia and its association with insomnia in a community based population in China

BACKGROUND

Studies of the prevalence of dyslipidemia and its association with insomnia are scarce in China. This study investigated the prevalence of dyslipidemia and its association with insomnia in a community based Chinese population.

METHODS

We conducted a cross-sectional survey in Beijing and recruited 10054 participants aged ≥ 18 years. The association between self-reported insomnia and dyslipidemia was determined by multiple logistic regression models. Age, gender, education, obesity, body mass index, physical activity, current smoking, current drinking, diabetes, and hypertension were adjusted as confounders. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were reported as effect measurements.

RESULTS

The prevalence of dyslipidemia in those with no insomnia, occasional insomnia, and frequent insomnia were 53.3%, 54.3%, and 54.5% in men and 52.0%, 54.8%, and 61.2% in women. Compared with subjects with no insomnia, the multivariate adjusted ORs and 95% CIs for those with occasional insomnia and frequent insomnia were 1.07(0.86 ~ 1.34) and 1.19(0.89 ~ 1.60) for men, and 1.00(0.86 ~ 1.14) and 1.23(1.03 ~ 1.47) for women.

CONCLUSIONS

These observations indicate that frequent insomnia was associated with a higher prevalence of dyslipidemia in women. This association was not significant in men.

A review of evidence for the link between sleep duration and hypertension

There are lines of evidence from experimental sleep deprivation studies, population-based epidemiological studies, and an interventional study that point to the potential efficacy of adequate quality sleep to prevent and treat hypertension. Experimental sleep restriction has been shown to raise blood pressure and heart rate. Insufficient sleep on a chronic basis can raise average 24-hour blood pressure and lead to structural adaptations that entrain the cardiovascular system to operate at an elevated blood pressure equilibrium and increase the risk for hypertension. Disruptions in the timing and duration of sleep could also disrupt circadian rhythmicity and autonomic balance, which can increase the prevalence of the nondipping pattern, disturb diurnal rhythm of cardiac output, and increase blood pressure variability. Short sleep duration has been found to be associated with higher blood pressure and hypertension in both cross-sectional and longitudinal epidemiological studies. The association appears stronger in middle-aged adults and in women. Experimental sleep extension has been shown to significantly reduce blood pressure in individuals with prehypertension or stage 1 hypertension. The observed association between sleep duration and hypertension raises the hypothesis that interventions to extend sleep and improve sleep quality could serve as effective primary, secondary, and tertiary preventive measures for hypertension.