From wakefulness to excessive sleepiness: what we know and still need to know

Correntropy measures to detect daytime sleepiness from EEG signals

Excessive daytime sleepiness (EDS) is one of the main symptoms of several sleep related disorders and has a great impact on patients' lives. While many studies have been carried out in order to assess daytime sleepiness, automatic EDS detection still remains an open problem. In this work, a novel approach to this issue based on correntropy function analysis of EEG signals was proposed in order to detect patients suffering from EDS. Multichannel EEG signals were recorded during five Maintenance of Wakefulness Tests (MWT) and Multiple Sleep Latency Tests (MSLT) alternated throughout the day for patients suffering from sleep disordered breathing (SDB). A group of 20 patients with EDS was compared with a group of 20 patients without daytime sleepiness (WDS), by analyzing 60 s EEG windows in a waking state. Measures obtained from the cross-correntropy function (CCORR) and auto-correntropy function (ACORR) were calculated in the EEG frequency bands: δ, 0.1-4 Hz; θ, 4-8 Hz; α, 8-12 Hz; β, 12-30 Hz; total band TB, 0.1-45 Hz. These functions permitted the quantification of complex signal properties and the non-linear couplings between different areas of the scalp. Statistical differences between EDS and WDS groups were mainly found in the β band during MSLT events (p-value < 0.0001). The WDS group presented more complexity in the occipital zone than the EDS group, while a stronger nonlinear coupling between the occipital and frontal regions was detected in EDS patients than in the WDS group. At best, ACORR and CCORR measures yielded sensitivity and specificity above 80% and the area under ROC curve (AUC) was above 0.85 in classifying EDS and WDS patients. These performances represent an improvement with respect to classical EEG indices applied in the same database (sensitivity and specificity were never above 80% and AUC was under 0.75).

Cortical-subcortical interactions in hypersomnia disorders: mechanisms underlying cognitive and behavioral aspects of the sleep-wake cycle

Subcortical circuits mediating sleep–wake functions have been well characterized in animal models, and corroborated by more recent human studies. Disruptions in these circuits have been identified in hypersomnia disorders (HDs) such as narcolepsy and Kleine–Levin Syndrome, as well as in neurodegenerative disorders expressing excessive daytime sleepiness. However, the behavioral expression of sleep–wake functions is not a simple on-or-off state determined by subcortical circuits, but encompasses a complex range of behaviors determined by the interaction between cortical networks and subcortical circuits. While conceived as disorders of sleep, HDs are equally disorders of wake, representing a fundamental instability in neural state characterized by lapses of alertness during wake. These episodic lapses in alertness and wakefulness are also frequently seen in neurodegenerative disorders where electroencephalogram demonstrates abnormal function in cortical regions associated with cognitive fluctuations (CFs). Moreover, functional connectivity MRI shows instability of cortical networks in individuals with CFs. We propose that the inability to stabilize neural state due to disruptions in the sleep–wake control networks is common to the sleep and cognitive dysfunctions seen in hypersomnia and neurodegenerative disorders.

Cognitive behavioral treatment for narcolepsy: can it complement pharmacotherapy?

Sleep medicine in general and psychology in particular have recently developed cognitive behavioral treatment for narcolepsy (CBT-N). Despite a growing interest in this topic, most studies since 2007 have reviewed CBT applications for other sleep disorders. Currently, 6 reviews have been published on narcolepsy, with an expert consensus being reached that CBT represented an important adjunctive treatment for the disease. The current paper reviews the need for CBT applications for narcolepsy by generalizing the application of multicomponent treatments and performing studies that extrapolate the results obtained from multicenter studies. Nineteen studies were found in which the need-for-treatment guidelines identified the use of CBT for narcolepsy. Three additional studies were identified that evaluated the effectiveness of cognitive behavioral measures and multicomponent treatments for which treatment protocols have been proposed.

Determinants of daytime sleepiness in first-year nursing students: a questionnaire survey

BACKGROUND

Daytime sleepiness may affect student learning achievement. Research studies have found that daytime sleepiness is common in university students; however, information regarding the determinants of daytime sleepiness in this population is still lacking.

OBJECTIVES

The purpose of this study was to investigate the determinants of daytime sleepiness in first-year nursing students. In particular, we looked for the relationship between perceived symptoms, nocturnal sleep quality, and daytime sleepiness.

DESIGN

A cross-sectional and correlational design was employed.

PARTICIPANTS AND METHOD

Participants were recruited from two nursing programs at an institute of technology located in southern Taiwan. Ninety-three nursing students completed the questionnaires one month after enrollment into their program.

RESULTS

Approximately 35% of the participants experienced excessive daytime sleepiness at the beginning of the semester. Six variables (joining a student club, perceived symptoms, daytime dysfunction, sleep disturbances, sleep latency, and subjective sleep quality) were significantly correlated with daytime sleepiness. Among them, daytime dysfunction and perceived symptoms were two major determinants of daytime sleepiness, both accounting for 37.2% of the variance.

CONCLUSIONS

Daytime sleepiness in students should not be ignored. It is necessary to help first-year students identify and mitigate physical and psychological symptoms early on, as well as improve daytime functioning, to maintain their daytime performance and promote learning achievement.

Non-REM sleep EEG power distribution in fatigue and sleepiness

OBJECTIVES

The aim of this study is to contribute to the sleep-related differentiation between daytime fatigue and sleepiness.

METHODS

135 subjects presenting with sleep apnea-hypopnea syndrome (SAHS, n=58) or chronic fatigue syndrome (CFS, n=52) with respective sleepiness or fatigue complaints and a control group (n=25) underwent polysomnography and psychometric assessments for fatigue, sleepiness, affective symptoms and perceived sleep quality. Sleep EEG spectral analysis for ultra slow, delta, theta, alpha, sigma and beta power bands was performed on frontal, central and occipital derivations.

RESULTS

Patient groups presented with impaired subjective sleep quality and higher affective symptom intensity. CFS patients presented with highest fatigue and SAHS patients with highest sleepiness levels. All groups showed similar total sleep time. Subject groups mainly differed in sleep efficiency, wake after sleep onset, duration of light sleep (N1, N2) and slow wave sleep, as well as in sleep fragmentation and respiratory disturbance. Relative non-REM sleep power spectra distributions suggest a pattern of power exchange in higher frequency bands at the expense of central ultra slow power in CFS patients during all non-REM stages. In SAHS patients, however, we found an opposite pattern at occipital sites during N1 and N2.

CONCLUSIONS

Slow wave activity presents as a crossroad of fatigue and sleepiness with, however, different spectral power band distributions during non-REM sleep. The homeostatic function of sleep might be compromised in CFS patients and could explain why, in contrast to sleepiness, fatigue does not resolve with sleep in these patients. The present findings thus contribute to the differentiation of both phenomena.

The AWAKEN survey: knowledge of narcolepsy among physicians and the general population

Narcolepsy can be a debilitating sleep disorder resulting from the dysregulation of pathways that control the sleep and wake states of patients. Although overall knowledge of narcolepsy has increased, no previous studies characterize awareness and perceptions of this condition in the general population or among physicians. Our survey evaluated the understanding and perceptions of narcolepsy among individuals from the general population and from a sample of physicians, including sleep specialists. The Awareness and Knowledge of Narcolepsy (AWAKEN) survey included a sample of 1000 US adults, 300 primary care physicians (PCPs), and 100 sleep medicine specialists (36% board certified) and was conducted online by Harris Interactive in May 2012. Descriptive analysis was performed using 2-tailed t tests with a significance of P < 0.05. Although 70% of the general public respondents had heard of narcolepsy, it ranked lowest in awareness relative to other chronic diseases requiring long-term treatment. Overall, 62% of sleep specialists and 24% of PCPs considered themselves "very" or "extremely" knowledgeable about narcolepsy; however, only 42% and 9% of sleep specialists and PCPs, respectively, felt "very" or "extremely" comfortable diagnosing the disorder. Only 22% of sleep specialists and 7% of PCPs identified all 5 key narcolepsy symptoms; no participant in the general population could identify all 5 symptoms. Sixty-three percent of sleep specialists and 39% of PCPs recognized both of the most prominent narcolepsy symptoms, which are excessive daytime sleepiness and cataplexy. Substantial gaps exist in understanding narcolepsy and its symptoms, even among sleep medicine specialists. Our findings suggest a need for educational initiatives for physicians to improve recognition of narcolepsy symptoms.

Increased mortality in narcolepsy

OBJECTIVE

To evaluate the mortality rate in patients with narcolepsy.

DESIGN

Data were derived from a large database representative of the US population, which contains anonymized patient-linked longitudinal claims for 173 million individuals.

SETTING

Symphony Health Solutions (SHS) Source Lx, an anonymized longitudinal patient dataset.

PATIENTS/PARTICIPANTS

All records of patients registered in the SHS database between 2008 and 2010.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Identification of patients with narcolepsy was based on ≥ 1 medical claim with the diagnosis of narcolepsy (ICD-9 347.xx) from 2002 to 2012. Dates of death were acquired from the Social Security Administration via a third party; the third party information was encrypted in the same manner as the claims data such that anonymity is ensured prior to receipt by SHS. Annual all-cause mortality rates for 2008, 2009, and 2010 were calculated retrospectively for patients with narcolepsy and patients without narcolepsy in the database, and standardized mortality ratios (SMR) were calculated. Mortality rates were also compared with the general US population (Centers for Disease Control data). SMRs of the narcolepsy population were consistent over the 3-year period and showed an approximate 1.5-fold excess mortality relative to those without narcolepsy. The narcolepsy population had consistently higher mortality rates relative to those without narcolepsy across all age groups, stratified by age decile, from 25-34 years to 75+ years of age. The SMR for females with narcolepsy was lower than for males with narcolepsy.

CONCLUSIONS

Narcolepsy was associated with approximately 1.5-fold excess mortality relative to those without narcolepsy. While the cause of this increased mortality is unknown, these findings warrant further investigation.

Nocturnal frontal lobe epilepsy presenting as excessive daytime sleepiness

Excessive daytime sleepiness (EDS) is common in the general population. Etiologies include insufficient sleep and primary sleep disorders. Due to its high prevalence, physicians often overlook EDS as a significant problem. However, EDS may also be the presenting symptom of seizures, in particular Nocturnal Frontal Lobe Epilepsy (NFLE). Due to the clinical similarity between the nocturnal behaviors of NFLE and parasomnias, and poor patient-related history, NFLE remains a challenging diagnosis. We report the case of a patient with NFLE who presented with a primary complaint of EDS, and discuss the differential diagnosis and evaluation of patients with EDS associated with nocturnal behaviors. In the context of a patient presenting with EDS and stereotyped nocturnal events, clinical suspicion should be high for NFLE.

[Sleep medicine differential diagnostics in psychiatry and psychotherapy]

Complaints about disturbed sleep or increased daytime sleepiness are among the most frequent symptoms reported to psychiatrists by patients. Such complaints can be symptoms of an underlying psychiatric disorder or indicative of a separate or comorbid sleep disorder. Hence, basic knowledge in the differential diagnosis of sleep medicine pathologies is pivotal for psychiatrists and psychotherapists. In the present overview following a description of the diagnostic methods, the diagnostic work-up according to the major symptomatic clusters, namely disturbances in initiating and maintaining sleep, abnormal nocturnal movements and excessive daytime sleepiness will be presented.

Daytime sleepiness in renal transplant recipients is associated with immunosuppressive non-adherence: a cross-sectional, multi-center study

BACKGROUND

The aims of this study were to determine the prevalence of immunosuppressive non-adherence (NA) in renal transplant patients and describe whether the degree of daytime sleepiness (DS) and depressive symptomatology are associated with immunosuppressive NA.

METHODS

Using a cross-sectional design, 926 home-dwelling renal transplant recipients who were transplanted at one of three Swiss transplant centers provided data by self-report. The Basel Assessment of Adherence Scale for immunosuppressive was used to measure the following: taking, timing, and overall NA to immunosuppressive medication. DS was assessed with the Epworth Sleepiness Scale (ESS) (cut-off ≥6 for DS) and the Swiss Transplant Cohort Study DS item (cut-off ≥4 for DS), and depressive symptomatology was assessed with the Depression, Anxiety, and Stress Scale (cut-off>10). An ordinal logistical regression model was applied for statistical analysis.

RESULTS

The prevalence of the ESS-DS was 51%. NA for taking, timing, and the median overall NA level assessed by 0-100% visual analog scale (VAS) was 16%, 42%, and 0%, respectively. Based on the multivariate analysis, DS was significantly associated (p < 0.001) with taking (1.08 [1.04-1.13]), timing (1.07 [1.03-1.10]), and overall NA (1.09 [1.05-1.13]). Very similar results were found for the Swiss Transplant Cohort Study DS item.

CONCLUSION

DS is associated with immunosuppressive medication NA in renal transplant recipients. Admittedly, the association's strength is limited.

Nocturnal rapid eye movement sleep latency for identifying patients with narcolepsy/hypocretin deficiency

IMPORTANCE

Narcolepsy, a disorder associated with HLA-DQB1*06:02 and caused by hypocretin (orexin) deficiency, is diagnosed using the Multiple Sleep Latency Test (MSLT) following nocturnal polysomnography (NPSG). In many patients, a short rapid eye movement sleep latency (REML) during the NPSG is also observed but not used diagnostically.

OBJECTIVE

To determine diagnostic accuracy and clinical utility of nocturnal REML measures in narcolepsy/hypocretin deficiency.

DESIGN, SETTING, AND PARTICIPANTS

Observational study using receiver operating characteristic curves for NPSG REML and MSLT findings (sleep studies performed between May 1976 and September 2011 at university medical centers in the United States, China, Korea, and Europe) to determine optimal diagnostic cutoffs for narcolepsy/hypocretin deficiency compared with different samples: controls, patients with other sleep disorders, patients with other hypersomnias, and patients with narcolepsy with normal hypocretin levels. Increasingly stringent comparisons were made. In a first comparison, 516 age- and sex-matched patients with narcolepsy/hypocretin deficiency were selected from 1749 patients and compared with 516 controls. In a second comparison, 749 successive patients undergoing sleep evaluation for any sleep disorders (low pretest probability for narcolepsy) were compared within groups by final diagnosis of narcolepsy/hypocretin deficiency. In the third comparison, 254 patients with a high pretest probability of having narcolepsy were compared within group by their final diagnosis. Finally, 118 patients with narcolepsy/hypocretin deficiency were compared with 118 age- and sex-matched patients with a diagnosis of narcolepsy but with normal hypocretin levels.

MAIN OUTCOME AND MEASURES

Sensitivity and specificity of NPSG REML and MSLT as diagnostic tests for narcolepsy/hypocretin deficiency. This diagnosis was defined as narcolepsy associated with cataplexy plus HLA-DQB1*06:02 positivity (no cerebrospinal fluid hypocretin-1 results available) or narcolepsy with documented low (≤ 110 pg/mL) cerebrospinal fluid hypocretin-1 level.

RESULTS

Short REML (≤15 minutes) during NPSG was highly specific (99.2% [95% CI, 98.5%-100.0%] of 516 and 99.6% [95% CI, 99.1%-100.0%] of 735) but not sensitive (50.6% [95% CI, 46.3%-54.9%] of 516 and 35.7% [95% CI, 10.6%-60.8%] of 14) for patients with narcolepsy/hypocretin deficiency vs population-based controls or all patients with sleep disorders undergoing a nocturnal sleep study (area under the curve, 0.799 [95% CI, 0.771-0.826] and 0.704 [95% CI, 0.524-0.907], respectively). In patients with central hypersomnia and thus a high pretest probability for narcolepsy, short REML remained highly specific (95.4% [95% CI, 90.4%-98.3%] of 132) and similarly sensitive (57.4% [95% CI, 48.1%-66.3%] of 122) for narcolepsy/hypocretin deficiency (area under the curve, 0.765 [95% CI, 0.707-0.831]). Positive predictive value in this high pretest probability sample was 92.1% (95% CI, 83.6%-97.0%).

CONCLUSIONS AND RELEVANCE

Among patients being evaluated for possible narcolepsy, short REML (≤15 minutes) at NPSG had high specificity and positive predictive value and may be considered diagnostic without the use of an MSLT; absence of short REML, however, requires a subsequent MSLT.

The relationship between excessive daytime sleepiness and depressive and anxiety disorders in women

OBJECTIVE

Excessive daytime sleepiness (EDS) is a common clinical symptom that affects women more than men. However, the association of excessive sleepiness with depressive and anxiety disorders in the broader population is unclear. The aim of this study was, therefore, to examine the association between excessive daytime sleepiness as measured by the Epworth Sleepiness Scale, and depressive and anxiety disorders in a population-based sample of women.

METHODS

Using the Structured Clinical Interview for DSM-IV Disorders (Non-Patient) (SCID-I/NP), 944 women aged 20-97 years (median 49 years, IQR 33-65 years) were assessed for depressive and anxiety disorders as part of the Geelong Osteoporosis Study. EDS was assessed using the Epworth Sleepiness Scale (ESS, cut-off > 10). Lifestyle factors were documented by self-report, height and weight were measured, and socioeconomic status categorised according to the Index of Relative Socio-Economic Advantage and Disadvantage.

RESULTS

Overall, 125 (13.2%) of the women were identified with EDS. EDS was associated with an increased likelihood for both current (OR = 2.11, 95% CI 1.10-4.06) and lifetime history (OR = 1.95, 95% CI 1.28-2.97) of depressive disorders, but not anxiety disorders, independent of age and alcohol consumption. These findings were not explained by antidepressant or sedative use, body mass index, physical activity, smoking, or socioeconomic status.

CONCLUSIONS

These results suggest that excessive daytime sleepiness is associated with current and lifetime depressive, but not anxiety disorders. Clinically, this highlights the need to take into account the possible bidirectional relationship between depressive disorders and excessive sleepiness when assessing mental health issues in patients with EDS.

Excessive sleep duration and quality of life

OBJECTIVE

Using population-based data, we document the comorbidities (medical, neurologic, and psychiatric) and consequences for daily functioning of excessive quantity of sleep (EQS), defined as a main sleep period or 24-hour sleep duration ≥ 9 hours accompanied by complaints of impaired functioning or distress due to excessive sleep, and its links to excessive sleepiness.

METHODS

A cross-sectional telephone study using a representative sample of 19,136 noninstitutionalized individuals living in the United States, aged ≥ 18 years (participation rate = 83.2%). The Sleep-EVAL expert system administered questions on life and sleeping habits; health; and sleep, mental, and organic disorders (Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision; International Classification of Sleep Disorders: Diagnostic and Coding Manual II, International Classification of Diseases and Related Health Problems, 10th edition).

RESULTS

Sleeping at least 9 hours per 24-hour period was reported by 8.4% (95% confidence interval = 8.0-8.8%) of participants; EQS (prolonged sleep episode with distress/impairment) was observed in 1.6% (1.4-1.8%) of the sample. The likelihood of EQS was 3 to 12× higher among individuals with a mood disorder. EQS individuals were 2 to 4× more likely to report poor quality of life than non-EQS individuals as well as interference with socioprofessional activities and relationships. Although between 33 and 66% of individuals with prolonged sleep perceived it as a major problem, only 6.3 to 27.5% of them reported having sought medical attention.

INTERPRETATION

EQS is widespread in the general population, co-occurring with a broad spectrum of sleep, medical, neurologic, and psychiatric disorders. Therefore, physicians must recognize EQS as a mixed clinical entity indicating careful assessment and specific treatment planning.

Narcolepsy is complicated by high medical and psychiatric comorbidities: a comparison with the general population

BACKGROUND

Individuals affected with narcolepsy represent a vulnerable segment of the population. However, we only have a partial understanding of this vulnerability. Our study aims to examine psychiatric disorders and medical conditions associated with narcolepsy.

METHODS

A total of 320 narcoleptic participants were interviewed regarding sleeping habits, health, medication consumption, medical conditions (International Statistical Classification of Diseases and Related Health Problems, 10th edition), sleep disorders (International Classification of Sleep Disorders, second edition [ICSD-2]) and mental disorders (Diagnostic and Statistical Manual of Mental Disorders, fourth edition, text revision [DSM-IV-TR]) using Sleep-EVAL. A general population comparison sample (N=1464) matched for age, sex, and body mass index (BMI) and interviewed with the same instrument was used to estimate odds ratios (OR).

RESULTS

Five diseases were more frequently observed among narcoleptic participants, including hypercholesterolemia (OR, 1.51), diseases of the digestive system (OR, 3.27), heart diseases (OR, 2.07), upper respiratory tract diseases (OR, 2.52), and hypertension (OR, 1.32). Most frequent psychiatric disorders among the narcolepsy group were major depressive disorder (MDD) (OR, 2.67) and social anxiety disorder (OR, 2.43), both affecting nearly 20% of narcoleptic individuals. However, most mood and anxiety disorders were more prevalent among the narcoleptic group. Alcohol abuse or alcohol dependence was comparable between groups.

CONCLUSIONS

Narcolepsy is associated with a high comorbidity of both medical conditions and psychiatric disorders that need to be addressed when developing a treatment plan.

Daytime sleepiness, sleep disturbance and functioning impairment in bipolar disorder

OBJECTIVE

To verify the prevalence and clinical impact of excessive daytime sleepiness (EDS) in outpatients with bipolar disorder.

METHODS

Eighty-one outpatients with bipolar disorder and 79 healthy control subjects were recruited. Patients were required not to be acutely manic or depressed. We used the Epworth Sleepiness Scale, the Pittsburgh Sleep Quality Index and the Functioning Assessment Short Test to assess sleepiness, sleep problems and functioning, respectively.

RESULTS

Patients had a higher prevalence of sleepiness (40%) than the control group (18%). Sleepiness and sleep disturbance had independent impacts on disability in the multivariable model.

CONCLUSIONS

This study suggests that EDS is a relevant clinical dimension in patients with bipolar disorder. It is a frequent symptom that often overlaps with other sleep disturbances. This study also reveals that once present it has the potential to increase functional impairment.

Joint associations of sleep duration and insomnia symptoms with subsequent sickness absence: The Helsinki Health Study

Aims: We aimed to examine the joint associations of sleep duration and insomnia symptoms with subsequent sickness absence of various lengths while considering several covariates. Methods: Baseline surveys among 40–60-year-old employees of the City of Helsinki, Finland, ( N = 6535) were prospectively linked with employer’s personnel register data comprising short self-certified (1–3 days), medically-certified intermediate (4–14 days) and long (15 days or more) sickness absence spells. Average follow-up time was 4.1 years. Sleep duration, insomnia symptoms, sociodemographics, working conditions, health behaviours and health were self-reported in the surveys. Poisson regression analysis was used. Results: Insomnia symptoms were associated with sickness absence at all levels of sleep duration. Adjusting for gender and age, U-shaped associations regarding sleep hours were found. Thus, those reporting short or long sleep and reporting insomnia symptoms had a higher risk for medically-certified intermediate and long sickness absence as compared to those reporting 7 hours of sleep without insomnia symptoms. Also, those reporting 6, 7, and 8 hours of sleep had a higher risk for such sickness absence, if they reported insomnia. Weak associations were also found for self-certified sickness absence, and for those reporting short and long sleep without insomnia. Adjustments attenuated the associations, but they mainly remained. Conclusions: These results suggest primacy of the effects of insomnia symptoms over sleep duration on sickness absence. Although insomnia dominated the joint association, U-shaped associations suggest that both sleep duration and insomnia symptoms need to be considered to promote work ability.

Hypersomnia and depressive symptoms: methodological and clinical aspects

The associations between depressive symptoms and hypersomnia are complex and often bidirectional. Of the many disorders associated with excessive sleepiness in the general population, the most frequent are mental health disorders, particularly depression. However, most mood disorder studies addressing hypersomnia have assessed daytime sleepiness using a single response, neglecting critical and clinically relevant information about symptom severity, duration and nighttime sleep quality. Only a few studies have used objective tools such as polysomnography to directly measure both daytime and nighttime sleep propensity in depression with normal mean sleep latency and sleep duration. Hypersomnia in mood disorders, rather than a medical condition per se, is more a subjective sleep complaint than an objective finding. Mood symptoms have also been frequently reported in hypersomnia disorders of central origin, especially in narcolepsy. Hypocretin deficiency could be a contributing factor in this condition. Further interventional studies are needed to explore whether management of sleep complaints improves mood symptoms in hypersomnia disorders and, conversely, whether management of mood complaints improves sleep symptoms in mood disorders.

A case-control study of physical activity patterns and risk of non-fatal myocardial infarction

Background

The interactive effects of different types of physical activity on cardiovascular disease (CVD) risk have not been fully considered in previous studies. We aimed to identify physical activity patterns that take into account combinations of physical activities and examine the association between derived physical activity patterns and risk of acute myocardial infarction (AMI).

Methods

We examined the relationship between physical activity patterns, identified by principal component analysis (PCA), and AMI risk in a case-control study of myocardial infarction in Costa Rica (N=4172), 1994-2004. The component scores derived from PCA and total METS were used in natural cubic spline models to assess the association between physical activity and AMI risk.

Results

Four physical activity patterns were retained from PCA that were characterized as the rest/sleep, agricultural job, light indoor activity, and manual labor job patterns. The light indoor activity and rest/sleep patterns showed an inverse linear relation (P for linearity=0.001) and a U-shaped association (P for non-linearity=0.03) with AMI risk, respectively. There was an inverse association between total activity-related energy expenditure and AMI risk but it reached a plateau at high levels of physical activity (P for non-linearity=0.01).

Conclusions

These data suggest that a light indoor activity pattern is associated with reduced AMI risk. PCA provides a new approach to investigate the relationship between physical activity and CVD risk.

Regulation of sleepiness: the role of the arousal system

Sleepiness is a widespread phenomenon in the busy industrial countries, and many studies have identified its significant negative impacts on individuals and society. Particularly important are the data that associate sleepiness with the risk of accidents at workplace and in transport, pointing to shift workers as the most vulnerable population. It is generally accepted that two basic physiological processes regulate sleepiness: homeostatic and circadian rhythmic processes. Recent research has proposed the third component regulating sleepiness, that is, the wake drive or the arousal system. The role of the arousal system in regulating sleepiness has partly been addressed by the studies of the pathophysiology of insomnia, which is often described as a disorder of hyperarousal. Experimental and correlational studies on the relation between sleepiness and arousal in good sleepers have generally indicated that both physiological and cognitive arousal are related to the standard measures of sleepiness. Taking into account the role of the arousal system in regulating sleepiness widens the possibilities for the management of sleep disorders and could also help in solving the problem of excessive sleepiness at work and the wheel.

Clinical pharmacology in sleep medicine

The basic treatment goals of pharmacological therapies in sleep medicine are to improve waking function by either improving sleep or by increasing energy during wakefulness. Stimulants to improve waking function include amphetamine derivatives, modafinil, and caffeine. Sleep aids encompass several classes, from benzodiazepine hypnotics to over-the-counter antihistamines. Other medications used in sleep medicine include those initially used in other disorders, such as epilepsy, Parkinson's disease, and psychiatric disorders. As these medications are prescribed or encountered by providers in diverse fields of medicine, it is important to recognize the distribution of adverse effects, drug interaction profiles, metabolism, and cytochrome substrate activity. In this paper, we review the pharmacological armamentarium in the field of sleep medicine to provide a framework for risk-benefit considerations in clinical practice.

Screening for obstructive sleep apnea among individuals with severe mental illness at a primary care clinic

OBJECTIVE

Obstructive sleep apnea (OSA) is linked to significant morbidity and mortality. OSA has received more attention recently, but the literature on OSA is scant in patients with severe mental illness (SMI). This project was undertaken to improve clinician knowledge and screening of OSA in persons with SMI.

METHOD

One hundred SMI patients attending a primary care clinic were screened for symptoms and risk factors associated with OSA. The Epworth Sleepiness Scale was used to assess daytime sleepiness, and the STOP-Bang score was used to classify those at high risk for OSA.

RESULTS

Sixty-nine percent of patients were found to be at high risk for OSA. Sixteen percent had a previously confirmed diagnosis of OSA. Most patients reported that OSA was never discussed with them, and 71% of those at high risk were willing to be referred for a sleep evaluation.

CONCLUSIONS

Patients with SMI are at high risk for OSA, and screening for OSA appears to be inadequate. This screening can be done easily, seems acceptable to patients and may prove very beneficial as OSA diagnosis and treatment can improve mental and physical health outcomes in SMI patients.

Sleep phenotyping in a mouse model of extreme trait anxiety

Background

There is accumulating evidence that anxiety impairs sleep. However, due to high sleep variability in anxiety disorders, it has been difficult to state particular changes in sleep parameters caused by anxiety. Sleep profiling in an animal model with extremely high vs. low levels of trait anxiety might serve to further define sleep patterns associated with this psychopathology.

Methodology/Principal Findings

Sleep-wake behavior in mouse lines with high (HAB), low (LAB) and normal (NAB) anxiety-related behaviors was monitored for 24 h during baseline and recovery after 6 h sleep deprivation (SD). The amounts of each vigilance state, sleep architecture, and EEG spectral variations were compared between the mouse lines. In comparison to NAB mice, HAB mice slept more and exhibited consistently increased delta power during non-rapid eye movement (NREM) sleep. Their sleep patterns were characterized by heavy fragmentation, reduced maintenance of wakefulness, and frequent intrusions of rapid eye movement (REM) sleep. In contrast, LAB mice showed a robust sleep-wake rhythm with remarkably prolonged sleep latency and a long, persistent period of wakefulness. In addition, the accumulation of delta power after SD was impaired in the LAB line, as compared to HAB mice.

Conclusions/Significance

Sleep-wake patterns were significantly different between HAB and LAB mice, indicating that the genetic predisposition to extremes in trait anxiety leaves a biological scar on sleep quality. The enhanced sleep demand observed in HAB mice, with a strong drive toward REM sleep, may resemble a unique phenotype reflecting not only elevated anxiety but also a depression-like attribute.

[Review on sleep and awakening disorders]

Insomnia is the most prevalent sleep disorders and affects severely 10% of adults worldwide. From poor sleep to insomnia, the severity of sleep disorders should be assessed clinically and by the use of validated questionnaires based on international consensual definitions. One main sign of insomnia is impaired daytime functioning. Insomnia may be treated with hypnotics only for a limited duration. Behavioural and cognitive therapies have been found efficient on chronic insomnia. Sleepiness is also a common sleep disorders due to altered sleep schedules, sleep deprivation, sleep disorders or as an adverse effect of some treatments. The risk of car accidents and the impaired quality of daytime functioning are the main consequences of sleepiness. The aim of this paper is to give some recommendations for the diagnosis and treatment of insomnia and sleepiness.

Determining the level of sleepiness in the American population and its correlates

OBJECTIVE

To assess the prevalence, to determine the risk factors and to evaluate the impacts of excessive sleepiness in the general population.

METHOD

It is a cross-sectional telephone study using a representative sample consisting of 8937 non-institutionalized individuals aged 18 or over living in Texas, New York and California. They represented a total of 62.8 million inhabitants. The participation rate was 85.6% in California, 81.3% in New York and 83.2% in Texas. Interviews were managed by the Sleep-EVAL expert system. The questionnaire included questions on sleeping habits, life habits, health, DSM-IV mental disorders, DSM-IV and ICSD sleep disorders.

RESULTS

As many as 19.5% of the sample reported having moderate excessive sleepiness and 11.0% reported severe excessive sleepiness. Moderate excessive sleepiness was comparable between men and women but severe excessive sleepiness was higher in women (8.6% vs. 13.0%). Factors associated with moderate excessive sleepiness were sleeping 6 h or less per main sleep episode (OR:2.0); OSAS (OR:2.0); insomnia disorder (OR:2.4); Restless Legs Syndrome (OR: 1.8) major depressive disorder (OR: 1.7); anxiety disorder (OR:1.5) and use of tricyclic antidepressant (OR: 2.1) presence of heart disease (OR: 1.5), cancer (1.8) and chronic pain (1.3). Factors associated with severe excessive sleepiness were similar with the addition of being a woman (OR:1.5), alcohol dependence (OR: 1.4), bipolar disorder (OR: 2.1), use of over-the-counter sleeping pills (OR: 2.5), narcotic analgesics (OR: 3.4), Antidepressants (other than SSRI or tricyclic) and presence of gastro-esophageal reflux disease (OR:1.6). Sleepy individuals were twice as likely than non-sleepy participants to have had accidents while they were at the wheel of a vehicle during the previous year.

CONCLUSIONS

Excessive sleepiness is highly prevalent in the American population. It was strongly associated with insufficient sleep and various sleep disorders as well as mental and organic diseases.

Excessive daytime sleepiness and narcolepsy--an approach to investigation and management

Excessive daytime sleepiness is a common presentation to physicians both in general practice and hospital settings. In this review, we provide an update on the latest theories on the pathogenesis of the condition, and discuss the approach to investigation of the sleepy patient, with particular reference to narcolepsy. Recommended therapy is reviewed for both narcolepsy and cataplexy, to provide physicians with an important reference on the investigation and management of these troubling conditions.

Operational definitions and algorithms for excessive sleepiness in the general population: implications for DSM-5 nosology

CONTEXT

Excessive sleepiness (ES) is poorly defined in epidemiologic studies, although its adverse implications for safety, health, and optimal social and vocational functioning have been extensively reported.

OBJECTIVE

To determine the importance of ES definition, measurement, and prevalence in the general population, together with its coexisting conditions.

DESIGN

Cross-sectional telephone study.

PARTICIPANTS

A total of 15 929 individuals representative of the adult general population of 15 states in the United States.

MAIN OUTCOME MEASURES

Interviews were carried out using Sleep-EVAL, a knowledge-based expert system for use in epidemiologic studies, focusing on sleep, as well as physical and mental disorders, according to classification in DSM-IV and the second edition of the International Classification of Sleep Disorders. The interviews elicited information on ES, naps, frequency, duration, impairment, and distress associated with ES symptoms.

RESULTS

Excessive sleepiness was reported by 27.8% (95% CI, 27.1%-28.5%) of the sample. Excessive sleepiness with associated symptoms was found in 15.6% of the participants (95% CI, 15.0%-16.2%). Adding an ES frequency of at least 3 times per week for at least 3 months despite normal sleep duration dropped the prevalence to 4.7% of the sample (95% CI, 4.4%-5.0%). The proportion of individuals having social or professional impairment and psychological distress increased with the frequency of ES symptoms during the week and within the same day. In multivariate models, the number of ES episodes per day and severity of ES were identified as the best predictors for impairment/distress. Prevalence of hypersomnia disorder was 1.5% of the participants (95% CI, 1.3%-1.7%). The most common coexisting conditions were mood and substance use disorders.

CONCLUSIONS

Excessive sleepiness is an important problem in the US population, even when using restrictive criteria to define it. Hypersomnia disorder is more prevalent than previously estimated. Excessive sleepiness has to be recognized and given attention by public health authorities, scientists, and clinicians.

Reliability of a single objective measure in assessing sleepiness

STUDY OBJECTIVES

To evaluate reliability of single objective tests in assessing sleepiness.

DESIGN

Subjects who completed polysomnography underwent a 4-nap multiple sleep latency test (MSLT) the following day. Prior to each nap opportunity on MSLT, subjects performed the psychomotor vigilance test (PVT) and divided attention driving task (DADT). Results of single versus multiple test administrations were compared using the intraclass correlation coefficient (ICC) and adjusted for test administration order effects to explore time of day effects. Measures were explored as continuous and binary (i.e., impaired or not impaired).

SETTING

Community-based sample evaluated at a tertiary, university-based sleep center.

PARTICIPANTS

372 adult commercial vehicle operators oversampled for increased obstructive sleep apnea risk.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

AS CONTINUOUS MEASURES, ICC WERE AS FOLLOWS: MSLT 0.45, PVT median response time 0.69, PVT number of lapses 0.51, 10-min DADT tracking error 0.87, 20-min DADT tracking error 0.90. Based on binary outcomes, ICC were: MSLT 0.63, PVT number of lapses 0.85, 10-min DADT 0.95, 20-min DADT 0.96. Statistically significant time of day effects were seen in both the MSLT and PVT but not the DADT. Correlation between ESS and different objective tests was strongest for MSLT, range [-0.270 to -0.195] and persisted across all time points.

CONCLUSIONS

Single DADT and PVT administrations are reliable measures of sleepiness. A single MSLT administration can reasonably discriminate individuals with MSL < 8 minutes. These results support the use of a single administration of some objective tests of sleepiness when performed under controlled conditions in routine clinical care.

Probabilistic sleep architecture models in patients with and without sleep apnea

Sleep fragmentation of any cause is disruptive to the rejuvenating value of sleep. However, methods to quantify sleep architecture remain limited. We have previously shown that human sleep-wake stage distributions exhibit multi-exponential dynamics, which are fragmented by obstructive sleep apnea (OSA), suggesting that Markov models may be a useful method to quantify architecture in health and disease. Sleep stage data were obtained from two subsets of the Sleep Heart Health Study database: control subjects with no medications, no OSA, no medical co-morbidities and no sleepiness (n = 374); and subjects with severe OSA (n = 338). Sleep architecture was simplified into three stages: wake after sleep onset (WASO); non-rapid eye movement (NREM) sleep; and rapid eye movement (REM) sleep. The connectivity and transition rates among eight 'generator' states of a first-order continuous-time Markov model were inferred from the observed ('phenotypic') distributions: three exponentials each of NREM sleep and WASO; and two exponentials of REM sleep. Ultradian REM cycling was accomplished by imposing time-variation to REM state entry rates. Fragmentation in subjects with severe OSA involved faster transition probabilities as well as additional state transition paths within the model. The Markov models exhibit two important features of human sleep architecture: multi-exponential stage dynamics (accounting for observed bout distributions); and probabilistic transitions (an inherent source of variability). In addition, the model quantifies the fragmentation associated with severe OSA. Markov sleep models may prove important for quantifying sleep disruption to provide objective metrics to correlate with endpoints ranging from sleepiness to cardiovascular morbidity.

Determinants of excessive daytime sleepiness and fatigue in adults with heart failure

Little is known about excessive daytime sleepiness (EDS) in heart failure (HF). The aim of this cross-sectional descriptive study was to describe the prevalence of EDS and factors associated with it in HF. A secondary purpose was to explore the correlates of fatigue. We enrolled a consecutive sample of 280 adults with a confirmed diagnosis of chronic HF from three outpatient settings in the northeastern United States. Patients with major depressive illness were excluded. Clinical, sociodemographic, behavioral, and perceptual factors were explored as possible correlates of EDS. Using an Epworth Sleepiness Scale score > 10, the prevalence of EDS was 23.6%. Significant determinants of EDS were worse sleep quality (p = .048), worse functional class (p = .004), not taking a diuretic (p = .005), and lack of physical activity (p = .04). Only sleep quality was associated with fatigue (p < .001). Sleep-disordered breathing was not significantly associated with EDS or with fatigue. These factors may be amenable to intervention.

Insomnia subtypes and their relationship to excessive daytime sleepiness in Brazilian community-dwelling older adults

STUDY OBJECTIVES

To investigate the association between different types of insomnia as exposures and excessive daytime sleepiness (EDS) as a binary outcome in older Brazilian residents.

DESIGN

The baseline examination of the Bambuí Health and Ageing Study (BHAS), which is an ongoing population-based prospective cohort study of older adults.

SETTING

Bambuí (15,000 inhabitants), a city in the State of Minas Gerais, Southeast Brazil

PARTICIPANTS

All residents aged ≥ 60 years were eligible to take part in the BHAS baseline. Of 1742 residents identified who were ≥ 60 years, 1606 (92.2%) were interviewed and received comprehensive examinations of health status.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

EDS was defined as the presence of sleepiness ≥ 3 times per week in the last month, causing any interference in usual activities. All insomnia subtypes were significantly associated with EDS in unadjusted analyses, and these associations were only modestly altered after adjusting incrementally for the other covariates. In a final model, the 3 insomnia subtypes were entered into a fully adjusted model simultaneously to investigate mutual independence, giving prevalence ratios of 1.63 (95% CI 1.14-2.31) for initial insomnia, 2.13 (95% CI 1.48-3.07) for middle insomnia, and 1.36 (95% CI 0.94-1.96) for terminal insomnia. The population attributable fractions for initial, middle, and terminal insomnia on prevalence of EDS were 17.6%, 32.9%, and 9.7%, respectively.

CONCLUSIONS

Middle insomnia emerged as the insomnia subtype most strongly associated with EDS. Further research is required to clarify causal pathways underlying this cross-sectional association.

Sleep disorders, medical conditions, and road accident risk

Sleep disorders and various common acute and chronic medical conditions directly or indirectly affect the quality and quantity of one's sleep or otherwise cause excessive daytime fatigue. This article reviews the potential contribution of several prevalent medical conditions - allergic rhinitis, asthma, chronic obstructive pulmonary disease, rheumatoid arthritis/osteoarthritis - and chronic fatigue syndrome and clinical sleep disorders - insomnia, obstructive sleep apnea, narcolepsy, periodic limb movement of sleep, and restless legs syndrome - to the risk for drowsy-driving road crashes. It also explores the literature on the cost-benefit of preventive interventions, using obstructive sleep apnea as an example. Although numerous investigations have addressed the impact of sleep and medical disorders on quality of life, few have specifically addressed their potential deleterious effect on driving performance and road incidents. Moreover, since past studies have focused on the survivors of driver crashes, they may be biased. Representative population-based prospective multidisciplinary studies are urgently required to clarify the role of the fatigue associated with common ailments and medications on traffic crash risk of both commercial and non-commercial drivers and to comprehensively assess the cost-effectiveness of intervention strategies.

Excessive daytime sleepiness is associated with poor medication adherence in adults with heart failure

BACKGROUND

A relationship between excessive daytime sleepiness (EDS) and poor treatment adherence has been suspected but not confirmed. We hypothesized that medication adherence would be poorer in adults with heart failure (HF) and EDS and that cognitive status would be the mechanism of effect.

METHODS AND RESULTS

A sample of 280 adults with chronic HF were enrolled into a prospective cohort comparison study. We identified a cohort with EDS and a control group without EDS and further divided both groups into those with and without mild cognitive decline. Data on medication adherence were obtained at baseline and 3 and 6 months by using the Basel Assessment of Adherence Scale. Regression analysis was used to clarify the contribution of EDS and cognition to medication adherence and to assess relationships over 6 months after adjusting for age, enrollment site, gender, race, functional class, depression, and premorbid intellect. At baseline, 62% of subjects were nonadherent to their medication regime. Nonadherence was significantly more common in those with EDS, regardless of cognitive status (P = .035). The odds of nonadherence increased by 11% for each unit increase in EDS (adjusted odds ratio 1.11; 95% confidence interval 1.05-1.19; P = .001). In longitudinal models, there was a 10% increase in the odds of nonadherence for each unit increase in EDS (P = .008). The only cognition measure significantly associated with medication adherence was attention (P = .047).

CONCLUSIONS

Adults with HF and EDS are more likely to have problems adhering to their medication regimen than those without EDS, regardless of their cognitive status. Identifying and correcting factors that interfere with sleep may improve medication adherence.

Excessive sleepiness: under-recognized and essential marker for sleep/wake disorder management

BACKGROUND

Research during the past few decades has provided substantial evidence indicating that excessive sleepiness (ES) and associated sleep/wake disorders can result in significant morbidity and mortality. However, symptomatology (e.g., ES) and the relationships among common morbidities (e.g., cardiovascular disease, metabolic disorders, mood impairment) and sleep/wake disorders remain under-recognized in clinical practice, particularly in primary care. Yet assessment of sleep/wakefulness and associated symptoms can often be easily conducted in the primary care setting, providing valuable information to facilitate the diagnosis and management of sleep/wake disorders.

OBJECTIVE

To provide a conceptual and educational framework that helps primary care physicians comprehensively assess, differentially diagnosis, and appropriately manage patients presenting with ES or ES-related sleep/wake disorders.

METHODS

Comprised of six sleep specialists and six primary care physicians, the Sleep/Wake Disorders Working Group (SWG) used a modified, two-round Delphi approach to create and harmonize consensus recommendations for the assessment, diagnosis, treatment, and ongoing management of patients with common sleep/wake disorders related to ES.

RESULTS

After a review of the relevant literature, the SWG arrived at consensus on a number of clinical recommendations for the assessment and management ES and some of the most commonly associated sleep/wake disorders. Ten consensus statements – five each for assessment/diagnosis and treatment/ongoing care – were created for ES, insomnia, obstructive sleep apnea, circadian rhythm disorders, restless legs syndrome, and narcolepsy.

CONCLUSION

ES and ES-related sleep/wake disorders are commonly encountered in the primary care setting. By providing an educational framework for primary care physicians, the SWG hopes to improve patient outcomes by emphasizing recognition, prompt diagnosis, and appropriate ongoing management of ES and associated sleep/wake disorders.

Obstructive sleep apnea alters sleep stage transition dynamics

INTRODUCTION

Enhanced characterization of sleep architecture, compared with routine polysomnographic metrics such as stage percentages and sleep efficiency, may improve the predictive phenotyping of fragmented sleep. One approach involves using stage transition analysis to characterize sleep continuity.

METHODS AND PRINCIPAL FINDINGS

We analyzed hypnograms from Sleep Heart Health Study (SHHS) participants using the following stage designations: wake after sleep onset (WASO), non-rapid eye movement (NREM) sleep, and REM sleep. We show that individual patient hypnograms contain insufficient number of bouts to adequately describe the transition kinetics, necessitating pooling of data. We compared a control group of individuals free of medications, obstructive sleep apnea (OSA), medical co-morbidities, or sleepiness (n = 374) with mild (n = 496) or severe OSA (n = 338). WASO, REM sleep, and NREM sleep bout durations exhibited multi-exponential temporal dynamics. The presence of OSA accelerated the "decay" rate of NREM and REM sleep bouts, resulting in instability manifesting as shorter bouts and increased number of stage transitions. For WASO bouts, previously attributed to a power law process, a multi-exponential decay described the data well. Simulations demonstrated that a multi-exponential process can mimic a power law distribution.

CONCLUSION AND SIGNIFICANCE

OSA alters sleep architecture dynamics by decreasing the temporal stability of NREM and REM sleep bouts. Multi-exponential fitting is superior to routine mono-exponential fitting, and may thus provide improved predictive metrics of sleep continuity. However, because a single night of sleep contains insufficient transitions to characterize these dynamics, extended monitoring of sleep, probably at home, would be necessary for individualized clinical application.

Development and validation of patient-reported outcome measures for sleep disturbance and sleep-related impairments

STUDY OBJECTIVES

To develop an archive of self-report questions assessing sleep disturbance and sleep-related impairments (SRI), to develop item banks from this archive, and to validate and calibrate the item banks using classic validation techniques and item response theory analyses in a sample of clinical and community participants.

DESIGN

Cross-sectional self-report study.

SETTING

Academic medical center and participant homes.

PARTICIPANTS

One thousand nine hundred ninety-three adults recruited from an Internet polling sample and 259 adults recruited from medical, psychiatric, and sleep clinics.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

This study was part of PROMIS (Patient-Reported Outcomes Information System), a National Institutes of Health Roadmap initiative. Self-report item banks were developed through an iterative process of literature searches, collecting and sorting items, expert content review, qualitative patient research, and pilot testing. Internal consistency, convergent validity, and exploratory and confirmatory factor analysis were examined in the resulting item banks. Factor analyses identified 2 preliminary item banks, sleep disturbance and SRI. Item response theory analyses and expert content review narrowed the item banks to 27 and 16 items, respectively. Validity of the item banks was supported by moderate to high correlations with existing scales and by significant differences in sleep disturbance and SRI scores between participants with and without sleep disorders.

CONCLUSIONS

The PROMIS sleep disturbance and SRI item banks have excellent measurement properties and may prove to be useful for assessing general aspects of sleep and SRI with various groups of patients and interventions.

Approaches to unravel the genetics of sleep

Sleep and circadian rhythms are complex and inter-connected physiological processes. Relative to the remarkable progress made in identifying the genetic basis of circadian rhythms and some specific sleep disorders, efforts to identify genetic variants associated with normal variation in sleep have progressed more slowly. Two key issues concerning the design of such studies must be addressed in order to facilitate further progress. The first concerns the sleep related traits to be targeted. The second issue is the choice of the gene-mapping method (linkage, candidate gene association or genome-wide association). This paper discusses these issues, reviews published studies of sleep phenotypes, and recommends cost-effective methods to advance knowledge of the genetic determinants of normal sleep patterns.

Lack of association of the APOE epsilon 4 allele with the risk of obstructive sleep apnea: meta-analysis and meta-regression

STUDY OBJECTIVES

Reports on the association of polymorphisms in the gene encoding apolipoprotein E (APOE)--a vital macromolecule in cholesterol metabolism--with obstructive sleep apnea (OSA) have provided conflicting results. Our objective was to meta-analytically synthesize the existing evidence for the association of the APOE epsilon4 allele with the risk of OSA.

DESIGN

Random effects meta-analysis and meta-regression.

SETTING

Genetic epidemiological studies reporting the association of APOE epsilon4 allele with OSA susceptibility.

PATIENTS OR PARTICIPANTS

Synthesis of APOE epsilon4 allele data from 6,508 subjects including 1,901 cases of OSA and 4,607 controls.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Eight studies were included in the random effects meta-analysis; the summary effect size measured as odds ratio (OR) for association of the APOE epsilon4 allele with the risk of OSA was found to be 1.13 (95% confidence interval 0.86-1.47). There was a statistically significant heterogeneity (I2 = 72%, P = 0.001) across study results that was not explained by the mean age, proportion of males, or the proportion possessing the APOE epsilon4 allele or when grouped based on the geographic location of the study.

CONCLUSIONS

The hypothesis that the APOE epsilon4 allele may be causally associated with OSA cannot be supported on the basis of published literature.

Joint effect of self-reported sleep problems and three components of the metabolic syndrome on risk of coronary heart disease

OBJECTIVE

This study explored the joint effect of two epidemics, sleep problems and metabolic syndrome (MetS), on the risk of coronary heart disease (CHD).

METHODS

The study group is part of the Finnish middle-aged men who participated in the first screening for the Helsinki Heart Study (HHS) in 1981-1982. At that time, three components of MetS were measured: body mass index, HDL cholesterol, and blood pressure. Later, in 1986-1988, they were given a psychosocial questionnaire including items on sleep problems. Of the respondents, 2753 formed our study group and were followed up using population-based registers until 1995. The relative risks (RR) of CHD were estimated using Cox's regression models.

RESULTS

When several sleep problems were present simultaneously, some increased CHD risk was observed. However, when considered jointly with MetS, insomnia or daytime fatigue approximately doubled the CHD risk and the presence of insufficient sleep more than tripled the risk. Among those who had MetS only, the RR was 2.55, and among those with both insufficient sleep and MetS the RR was 9.36 (95% confidence interval: 4.60-19.04; P for interaction 0.09) when compared to those with no insufficient sleep and no components of MetS.

CONCLUSION

The interaction occurred when all three measured MetS components were present, suggesting that co-occurrence of these two epidemics may predict growing public health problems.