Cardiovascular Implications of Poor Sleep

Sleep is Essential for Cardiovascular Health: An Analytic Review of the Relationship Between Sleep and Cardiovascular Mortality

The American Heart Association recently included sleep health as one of eight factors that define cardiovascular health. Restorative sleep is a pillar of lifestyle medicine influenced by sleep duration, quality, and disorders. Short and long sleep duration are associated with greater risk of cardiovascular disease. Short sleep appears causally related to cardiovascular risk. Long sleep is more strongly predictive of cardiovascular risk, which may be due to comorbidities and other risk factors. Good-quality sleep appears to protect against the increased risk and is independently associated with risk of cardiovascular disease (CVD). Insomnia, particularly difficulty falling asleep and non-restorative sleep, is associated with an increase in cardiac events. Obstructive sleep apnea (OSA) is associated with cardiac risk and outcomes, which is typically observed in the context of contributing comorbidities. However, treating OSA with continuous positive airway pressure (CPAP) may not improve prognosis. Further research is needed to understand the causal mechanisms connecting sleep health with CVD and whether modifying sleep can improve outcomes. Sleep health should be considered as part of a holistic approach to improving cardiovascular health, as reflected in the scoring of LE8 and as one of the interrelated components of lifestyle medicine.

Co-ordination of brain and heart oscillations during non-rapid eye movement sleep

Oscillatory activities of the brain and heart show a strong variation across wakefulness and sleep. Separate lines of research indicate that non‐rapid eye movement (NREM) sleep is characterised by electroencephalographic slow oscillations (SO), sleep spindles, and phase–amplitude coupling of these oscillations (SO–spindle coupling), as well as an increase in high‐frequency heart rate variability (HF‐HRV), reflecting enhanced parasympathetic activity. The present study aimed to investigate further the potential coordination between brain and heart oscillations during NREM sleep. Data were derived from one sleep laboratory night with polysomnographic monitoring in 45 healthy participants (22 male, 23 female; mean age 37 years). The associations between the strength (modulation index [MI]) and phase direction of SO–spindle coupling (circular measure) and HF‐HRV during NREM sleep were investigated using linear modelling. First, a significant SO–spindle coupling (MI) was observed for all participants during NREM sleep, with spindle peaks preferentially occurring during the SO upstate (phase direction). Second, linear model analyses of NREM sleep showed a significant relationship between the MI and HF‐HRV (F = 20.1, r² = 0.30, p < 0.001) and a tentative circular‐linear correlation between phase direction and HF‐HRV (F = 3.07, r² = 0.12, p = 0.056). We demonstrated a co‐ordination between SO–spindle phase–amplitude coupling and HF‐HRV during NREM sleep, presumably related to parallel central nervous and peripheral vegetative arousal systems regulation. Further investigating the fine‐graded co‐ordination of brain and heart oscillations might improve our understanding of the links between sleep and cardiovascular health.

Are Spouses' Sleep Problems a Mechanism Through Which Health is Compromised? Evidence Regarding Insomnia and Heart Disease

BACKGROUND

Symptoms of insomnia have been widely identified as risk factors for health, including heart disease. Despite the expansive and growing literature on health concordance among coupled individuals, few studies have examined insomnia as a shared risk factor for heart disease among middle-aged and older couples.

PURPOSE

This study examined the association between insomnia and incident heart disease among couples. A dyadic modeling approach was employed to investigate the relationships between one's own insomnia and partners' insomnia for the risk of incident heart disease for each partner.

METHODS

Data from the 2010, 2012, and 2014 Health and Retirement Study were utilized in a prospective research design (N = 3,221 couples). Actor-partner interdependence models were employed to estimate actor and partner effects of insomnia symptoms for incident heart disease over the 4 year observation period.

RESULTS

Insomnia symptoms measured at baseline were related to an increased risk for heart disease for husbands, whereas for wives the association was attenuated after other health measures were controlled. Wives' insomnia was related to an increased risk of incident heart disease for husbands but husbands' insomnia was not related to wives' risk of heart disease.

CONCLUSIONS

This study showed how subjective insomnia symptoms among middle-aged and older adults in intimate partnerships are associated with their heart disease risk. Further research is needed to verify the results with objective measures of sleep problems and heart disease.

Posttraumatic stress disorder diagnosis is associated with reduced parasympathetic activity during sleep in US veterans and military service members of the Iraq and Afghanistan wars

Study Objectives

To determine whether high-frequency heart rate variability (HF-HRV) during sleep differs between those with and without posttraumatic stress disorder (PTSD) as a function of sleep type (non-rapid eye movement [NREM] vs. rapid eye movement [REM]), and to explore this relationship across successive sleep cycles. Participants with PTSD were hypothesized to have lower HF-HRV across both REM and NREM sleep.

Methods

Sixty-two post-9/11 military veterans and service members completed self-report measures of sleep quality, insomnia severity, and disruptive nocturnal behaviors. Participants then completed a laboratory-based polysomnographic study night with concurrent HRV assessment.

Results

Participants with PTSD (N = 29) had lower HF-HRV in overall NREM sleep relative to those without PTSD (N = 33) (F(1, 54) = 4.24, p = .04). Groups did not differ on overall HF-HRV during REM sleep. HF-HRV increased over the night for the sample as a whole during both NREM and REM sleep. PTSD status did not moderate the association between HF-HRV and sleep cycles. However, the PTSD group had lower HF-HRV in the first t(155) = 2.67, p = .008, and fourth NREM cycles, t(155) = 2.11, p = .036, relative to participants without PTSD.

Conclusions

Findings suggest blunted parasympathetic modulation during NREM sleep in a young cohort of military veterans and service-members with PTSD. Findings are concerning considering the increased risk of incident cardiovascular events associated with impaired parasympathetic nervous system function. Reduced parasympathetic modulation may be one mechanism underlying the increased prevalence of cardiovascular disease (CVD) among veterans with PTSD.

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.

EEG beta power and heart rate variability describe the association between cortical and autonomic arousals across sleep

Cortical and autonomic arousals have been found to be closely associated. As arousal events are not evenly dispersed across sleep, we hypothesized the relationship between high frequency electroencephalogram (EEG) power and autonomic arousal indices differ between non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. One night of polysomnographic recording was performed on a group of 18 subjects using a portable recorder. The EEG was collected from C3/Fz. Sleep stages and cortical arousals were visually scored. Cardiac autonomic modulation was assessed from heart rate variability, where the high frequency power (HF) indicates parasympathetic modulation, and the low frequency to high frequency power ratio (LF/HF) represents sympathetic modulation. During NREM sleep, EEG beta power was significantly correlated with LF/HF (r=0.40 ± 0.06), and the relationships were more positive than during REM sleep (LF/HF: r=0.20 ± 0.08; EOG power: r=-0.13 ± 0.05). The relationship of beta power with LF/HF was associated with the incidence of cortical arousal, particularly during NREM sleep. With respect to alpha power, it was only marginally related to HF or LF/HF. In addition, the coefficients of determination were lower for alpha power than for beta power in terms of the relationships to HF, LF/HF and EOG power. This study shows a higher relationship between cortical and autonomic activation during NREM sleep, and the association is better described by beta power. This finding suggests NREM sleep may be of greater therapeutic potential in view of reducing cardiovascular disease associated with sleep fragmentation, and beta power may provide a better index to evaluate the effect.

[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.

Characterising acute coronary syndrome-associated depression: Let the data speak

Depression in the context of acute coronary syndrome (ACS) is understood to confer increased morbidity and mortality risk. The pathophysiological mechanisms underlying this association remain poorly understood, although several candidates including inflammation, cardiac autonomic dysregulation, and behavioural factors are viewed as of key importance. No single bio-behavioural explanatory model of ACS-associated depression has emerged, likely due the substantial heterogeneity across both conditions. We studied 344 patients with ACS; 45 fulfilled diagnostic (DSM-IV) criteria for a major depressive episode occurring within 1-month of ACS, and 13 had ongoing major depression that pre-dated ACS and continued through to 1 month post-ACS. We employed two statistical methods (multinomial logistic regression; and latent class analysis) and a range of immunological, autonomic and nutritional markers in an attempt to characterise a biological basis for ACS-associated depression. Regression modelling failed to accurately predict categorical group membership of ACS-associated depression. An alternative data-driven approach produced a three-class solution, with the derived classes differing on measure of C-reactive protein, vitamin D, omega-6:omega-3 ratio, heart rate variability, and age (all p⩽0.004). The majority of participants with ACS-associated and ongoing depression were members of the class characterised by the greatest biological disturbance. Patients with depression differed from those without depression on a range of psychological trait and state variables; additionally reporting poorer sleep quality, higher levels of social isolation, and functional impairment, but had similar biological profiles. Patients with ongoing depression generally had higher scores on these psychological/behavioural measures. Our novel analytic approach identified a combination of biomarkers suggestive of a role for immune, autonomic, and nutritional pathways in the manifestation of depression during ACS, in the context of additional psychosocial and behavioural vulnerabilities. Further studies are required to confirm the causal role of these factors in perpetuating depression and increasing risk of poor-health outcomes.

Insomnia and its impact on physical and mental health

In contrast to the association of insomnia with mental health, its association with physical health has remained largely unexplored until recently. Based on findings that insomnia with objective short sleep duration is associated with activation of both limbs of the stress system and other indices of physiological hyperarousal, which should adversely affect physical and mental health, we have recently demonstrated that this insomnia phenotype is associated with a significant risk of cardiometabolic and neurocognitive morbidity and mortality. In contrast, insomnia with normal sleep duration is associated with sleep misperception and cognitive-emotional arousal, but not with signs of physiological hyperarousal or cardiometabolic or neurocognitive morbidity. Interestingly, both insomnia phenotypes are associated with mental health, although most likely through different pathophysiological mechanisms. We propose that objective measures of sleep duration may become part of the routine evaluation and diagnosis of insomnia, and that these two insomnia phenotypes may respond differentially to biological versus psychological treatments.

Insomnia with Short Sleep Duration: Nosological, Diagnostic, and Treatment Implications

The diagnosis of insomnia is based solely on subjective complaints. This has contributed to the low reliability and validity of the current nosology of insomnia as well as to its lack of firm association with clinically relevant outcomes such as cardiometabolic and neurocognitive morbidity. We review evidence that insomnia with objective short sleep duration is associated with physiological hyperarousal, higher risk for hypertension, diabetes, neurocognitive impairment, and mortality as well as with a persistent course. It also appears that objective short sleep duration in poor sleepers is a biological marker of genetic predisposition to chronic insomnia. In contrast, insomnia with objective normal sleep duration is associated with cognitive-emotional and cortical arousal and sleep misperception but not with signs of physiological hyperarousal or medical complications. Thus, short sleep duration in insomnia may be a reliable marker of the biological severity and medical impact of the disorder. We propose that (a) objective measures of sleep be included in the diagnosis of insomnia and its subtypes, (b) objective measures of sleep obtained in the home environment of the patient would become part of the routine assessment and diagnosis of insomnia in a clinician's office setting, and (c) insomnia with short sleep duration may respond better to biological treatments, whereas insomnia with normal sleep duration may respond primarily to psychological therapies.

Insomnia with objective short sleep duration: the most biologically severe phenotype of the disorder

Until recently, the association of chronic insomnia with significant medical morbidity was not established and its diagnosis was based solely on subjective complaints. We present evidence that insomnia with objective short sleep duration is the most biologically severe phenotype of the disorder, as it is associated with cognitive-emotional and cortical arousal, activation of both limbs of the stress system, and a higher risk for hypertension, impaired heart rate variability, diabetes, neurocognitive impairment, and mortality. Also, it appears that objective short sleep duration is a biological marker of genetic predisposition to chronic insomnia. In contrast, insomnia with objective normal sleep duration is associated with cognitive-emotional and cortical arousal and sleep misperception but not with signs of activation of both limbs of the stress system or medical complications. Furthermore, the first phenotype is associated with unremitting course, whereas the latter is more likely to remit. We propose that short sleep duration in insomnia is a reliable marker of the biological severity and medical impact of the disorder. Objective measures of sleep obtained in the home environment of the patient would become part of the routine assessment of insomnia patients in a clinician's office setting. We speculate that insomnia with objective short sleep duration has primarily biological roots and may respond better to biological treatments, whereas insomnia with objective normal sleep duration has primarily psychological roots and may respond better to psychological interventions alone.

Perceptions of short and long sleep duration and comorbid conditions: the PLATINO study

OBJECTIVES

We aimed to describe the distribution of self-reported sleep duration in adults over the age of 40 years and to analyze the associated risk factors, comorbid conditions, and quality of life (QoL).

METHODS

Our study was constructed as a cross-sectional population-based study and is part of the PLATINO (Spanish acronym for the Latin American Project for Research in Pulmonary Obstruction) study. It includes data from Mexico City (Mexico), Montevideo (Uruguay), Santiago (Chile), and Caracas (Venezuela). Data from 4533 individuals were analyzed using a single questionnaire entitled, PLATINO, which was designed to collect data on self-reported sleep symptoms. Spirometry also was performed in accordance with international standards. All statistical analyses took the study design into consideration with adjustments for each city.

RESULTS

The prevalence of subjects who reported sleeping <7h was 38.4%, ≥ 7 to <9h was 51.4%, and ≥ 9h was 10.2%. In the multivariate analysis, individuals with shorter sleep duration had higher frequencies of insomnia, increased forced expiratory volume in one second in liters and percentage/forced vital capacity in liters (FEV1/FVC) of predicted ratios, and a higher presence of coughing and phlegm. The main risk factor associated with longer duration of sleep was the number of comorbidities.

CONCLUSIONS

Self-reported sleep duration discriminated among groups that differed in sleep-related symptoms, respiratory symptoms, QoL and comorbid conditions.

Sleep disturbance and baroreceptor sensitivity in women with posttraumatic stress disorder

In a previous study, women with posttraumatic stress disorder (PTSD) had greater objective sleep disturbance than those without PTSD. In a separate previous study, women with PTSD were also found to have lower baroreceptor sensitivity (BRS), an index of blood pressure regulation. In the present study, the authors concurrently assessed BRS and objective sleep by diagnostic status. A comparison of 32 women with PTSD with 21 women without PTSD revealed an interaction between BRS and sleep efficiency, wake after sleep onset percentage, and sleep fragmentation. Lower BRS was associated with poorer sleep in women with PTSD, but not in those without. Future research should investigate causal relationships between sleep and blood pressure regulation in those with PTSD.

Hyperarousal and insomnia: state of the science

In the past few years it has become increasingly clear that insomnia is a chronic disease that interacts with many other medical conditions. As our ability to examine complex physiological activity during sleep has increased, additional evidence continues to suggest that insomnia is associated with inappropriate physiological arousal. It is now known that patients with primary insomnia have increased high-frequency EEG activation, abnormal hormone secretion, increased whole body and brain metabolic activation, and elevated heart rate and sympathetic nervous system activation during sleep. This activation can be measured throughout the day and night and is chronic. Other research suggests that insomnia, probably based upon the associated chronic physiologic arousal, is associated with increased risk for medical disorders such as depression, hypertension, or cardiac disease. An animal model that has used odor stress to produce poor sleep in rats has identified specific activated brain sites similar to those found in human brain metabolic studies to suggest that insomnia is a state in which sleep and arousal systems are both simultaneously active. The animal studies have also shown that the inappropriate arousal can be blocked by lesions in the limbic and arousal systems. It is hoped that these findings can be extended to identify new compounds that improve insomnia by acting at these sites of abnormal brain activation.