Cardiac Activity and Sympathovagal Balance During Sleep

Children with Down syndrome and sleep disordered breathing have altered cardiovascular control

BACKGROUND

Sleep disordered breathing (SDB) in typically developing (TD) children is associated with adverse cardiovascular effects. As children with Down syndrome (DS) are at increased risk for SDB, we aimed to compare the cardiovascular effects of SDB in children with DS to those of TD children with and without SDB.

METHODS

Forty-four children with DS (3-19 years) were age and sex matched with 44 TD children without SDB (TD-) and with 44 TD children with matched severity of SDB (TD+). Power spectral density was calculated from ECG recordings, for low frequency (LF), high frequency (HF), total power and the LF/HF ratio.

RESULTS

Children with DS had lower HF power, and higher LF/HF during sleep and when awake. There were no differences between groups for LF power. SpO₂ nadir, average SpO₂ drop and SpO₂ > 4% drop were larger in the DS group compared to the TD+ group (p < 0.05 for all).

CONCLUSIONS

Our findings demonstrate significantly reduced parasympathetic activity (reduced HF power) and increased LF/HF (a measure of sympathovagal balance) in children with DS, together with greater exposure to hypoxia, suggesting SDB has a greater effect in these children that may contribute to an increased risk of adverse cardiovascular outcomes.

IMPACT

Sleep disordered breathing in children with Down syndrome exacerbates impaired autonomic control and increases exposure to hypoxia, compared to typically developing children. In typically developing children sleep disordered breathing has adverse effects on autonomic cardiovascular control. The prevalence of sleep disordered breathing is very high in children with Down syndrome; however, studies on the effects on cardiovascular control are limited in this population. This study supports screening and early treatment of sleep disordered breathing in children with Down syndrome.

The value of cardiorespiratory parameters for sleep state classification in preterm infants: A systematic review

Cardiorespiratory activity is highly associated with infants' sleep duration and quality. We performed a systematic literature search of PubMed and EMBASE databases to investigate if and how cardiorespiratory parameters can be used for sleep state classification in preterm infants and in what way maturation influences this relation. All retrieved citations were screened against predetermined inclusion and exclusion criteria. Only studies of preterm infants (<37 wk postmenstrual age during sleep state classification) admitted to a neonatal ward and of whom at least one sleep state and one cardiorespiratory parameter was measured, were included. Two researchers independently reviewed the included studies on methodological quality. Of the 1097 initially retrieved studies, 23 were included for analysis. Heart rate and respiration frequency are strongly correlated with active sleep and quiet sleep. In quiet sleep, as compared to active sleep, respiratory frequency is more stable, and the heart rate is lower and less variable. This association, however, differed across preterm birth subtypes (i.e., extremely, very or late preterm), indicating that maturation - in the form of both gestational and postnatal age - influences the cardiorespiratory characteristics of preterm sleep states. The knowledge gained from this review can help improve behavioral sleep classification and automated sleep classification algorithms for preterm infants.

The effect of body position on maternal cardiovascular function during sleep and wakefulness in late pregnancy

INTRODUCTION

An association between the increased risk of late stillbirth and the maternal supine sleeping position has been recently established. The risk of stillbirth following supine sleep has been suspected to occur as a result of aortocaval compression by the gravid uterus. A number of studies conducted during wakefulness have reported compromised cardiovascular function during supine rest, as demonstrated by reductions in cardiac output, blood pressure and utero-placental blood flow. It remains unclear whether similar effects are also present during sleep, due to the presence of key sleep-specific changes in cardiovascular function.

OBJECTIVE

To investigate the changes in maternal cardiovascular function between the supine and left-lateral positions during wakefulness and non-rapid eye movement (NREM) sleep in late pregnancy.

METHODS

Twenty-nine women with a singleton pregnancy between 24.7 and 36.7 weeks' gestation participated in a single overnight sleep study. Physiological measures (blood pressure, heart rate, heart rate variability - HRV, and pulse arrival time - PAT) were measured and recorded throughout the night using standard polysomnography equipment and the Portapres Model-2 device. As the present study evaluated cardiovascular changes during natural rest and sleep in pregnancy, participants were not given explicit instructions on which position to adopt. Body position was continuously recorded using a position monitor and verified with video recording.

RESULTS

No changes in systolic, diastolic or mean arterial blood pressure were observed between the left-lateral and supine positions during wakefulness or sleep. However, heart rate was significantly higher in the supine position compared to the left during wakefulness (p= .03), with a similar trend present during sleep (p= .11). A significantly shorter PAT was measured in the supine position (compared to the left) during wakefulness (p= .01) and sleep (p= .01). No change in HRV measures was observed between the left and supine positions in either state.

CONCLUSION

Blood pressure did not appear to differ significantly between the left-lateral and supine positions during wakefulness and sleep. The lack of blood pressure differences may reflect elevated sympathetic activity during rest and sleep in the supine position (compared to the left), suggesting that some degree of compensation for aortocaval compression may still be possible during sleep.

Reducing bedtime physiological arousal levels using immersive audio-visual respiratory bio-feedback: a pilot study in women with insomnia symptoms

Hyperarousal is a critical component of insomnia, particularly at bedtime when individuals are trying to fall asleep. The current study evaluated the effect of a novel, acute behavioral experimental manipulation (combined immersive audio-visual relaxation and biofeedback) in reducing bedtime physiological hyperarousal in women with insomnia symptoms. After a clinical/adaptation polysomnographic (PSG) night, sixteen women with insomnia symptoms had two random-order PSG nights: immersive audio-visual respiratory bio-feedback across the falling asleep period (manipulation night), and no pre-sleep arousal manipulation (control night). While using immersive audio-visual respiratory bio-feedback, overall heart rate variability was increased and heart rate (HR) was reduced (by ~ 5 bpm; p < 0.01), reflecting downregulation of autonomic pre-sleep arousal, relative to no-manipulation. HR continued to be lower during sleep, and participants had fewer awakenings and sleep stage transitions on the manipulation night relative to the control night (p < 0.05). The manipulation did not affect sleep onset latency or other PSG parameters. Overall, this novel behavioral approach targeting the falling asleep process emphasizes the importance of pre-sleep hyperarousal as a potential target for improving sleep and nocturnal autonomic function during sleep in insomnia.

The Sleep of the Ring: Comparison of the ŌURA Sleep Tracker Against Polysomnography

Objective/Background: To evaluate the performance of a multisensor sleep-tracker (ŌURA ring) against polysomnography (PSG) in measuring sleep and sleep stages. Participants: Forty-one healthy adolescents and young adults (13 females; Age: 17.2 ± 2.4 years). Methods: Sleep data were recorded using the ŌURA ring and standard PSG on a single laboratory overnight. Metrics were compared using Bland-Altman plots and epoch-by-epoch (EBE) analysis. Results: Summary variables for sleep onset latency (SOL), total sleep time (TST), and wake after sleep onset (WASO) were not different between ŌURA ring and PSG. PSG-ŌURA discrepancies for WASO were greater in participants with more PSG-defined WASO (p < .001). Compared with PSG, ŌURA ring underestimated PSG N3 (~20 min) and overestimated PSG REM (~17 min; p < .05). PSG-ŌURA differences for TST and WASO lay within the ≤ 30 min a-priori-set clinically satisfactory ranges for 87.8% and 85.4% of the sample, respectively. From EBE analysis, ŌURA ring had a 96% sensitivity to detect sleep, and agreement of 65%, 51%, and 61%, in detecting "light sleep" (N1), "deep sleep" (N2 + N3), and REM sleep, respectively. Specificity in detecting wake was 48%. Similarly to PSG-N3 (p < .001), "deep sleep" detected with the ŌURA ring was negatively correlated with advancing age (p = .001). ŌURA ring correctly categorized 90.9%, 81.3%, and 92.9% into PSG-defined TST ranges of < 6 hr, 6-7 hr, > 7 hr, respectively. Conclusions: Multisensor sleep trackers, such as the ŌURA ring have the potential for detecting outcomes beyond binary sleep-wake using sources of information in addition to motion. While these first results could be viewed as promising, future development and validation are needed.

Dynamic coupling between the central and autonomic nervous systems during sleep: A review

Sleep is characterized by coordinated cortical and cardiac oscillations reflecting communication between the central (CNS) and autonomic (ANS) nervous systems. Here, we review fluctuations in ANS activity in association with CNS-defined sleep stages and cycles, and with phasic cortical events during sleep (e.g., arousals, K-complexes). Recent novel analytic methods reveal a dynamic organization of integrated physiological networks during sleep and indicate how multiple factors (e.g., sleep structure, age, sleep disorders) affect "CNS-ANS coupling". However, these data are mostly correlational and there is a lack of clarity of the underlying physiology, making it challenging to interpret causality and direction of coupling. Experimental manipulations (e.g., evoking K-complexes or arousals) provide information on the precise temporal sequence of cortical-cardiac activity, and are useful for investigating physiological pathways underlying CNS-ANS coupling. With the emergence of new analytical approaches and a renewed interest in ANS and CNS communication during sleep, future work may reveal novel insights into sleep and cardiovascular interactions during health and disease, in which coupling could be adversely impacted.

Altered nocturnal blood pressure profiles in women with insomnia disorder in the menopausal transition

OBJECTIVE

Insomnia disorder is a risk factor for cardiovascular (CV) pathology. It is unknown whether insomnia that develops in the context of the menopausal transition (MT) impacts the CV system. We assessed nocturnal blood pressure (BP) and heart rate (HR) profiles in women with insomnia disorder in the MT.

METHODS

Twelve women meeting DSM-IV criteria for insomnia in the MT (age, mean ± SD: 50.5 ± 3.6 y) and 11 controls (age, mean ± SD: 49.0 ± 3.0 y) had polysomnographic recordings on one or two nights during which beat-to-beat BP and HR were assessed and analyzed hourly from lights-out across the first 6 hours of the night and according to sleep stage. Physiological hot flashes were identified from fluctuations in sternal skin conductance.

RESULTS

Women with insomnia and controls had similar distributions of sleep stages and awakenings/arousals across hours of the night, although insomnia participants tended to have more wakefulness overall. More women in the insomnia group (7 of 12) than in the control group (2 of 11) had at least one physiological hot flash at night (P < 0.05). Both groups showed a drop in BP in the first part of the night; however, systolic and diastolic BP patterns diverged later, remaining low in controls but increasing in insomnia participants 4 to 6 hours after lights-out (P < 0.05). Both groups showed a similar pattern of decline in HR across the night.

CONCLUSIONS

Our findings suggest altered regulatory control of BP during sleep in the MT insomnia. The causes and long-term consequences of this altered nocturnal BP profile remain to be determined.

Heart rate variability during sleep in children with autism spectrum disorder

PURPOSE

Autonomic dysfunction has been reported in autism spectrum disorders (ASD). Less is known about autonomic function during sleep in ASD. The objective of this study is to provide insight into the autonomic cardiovascular control during different sleep stages in ASD. We hypothesized that patients with ASD have lower vagal and higher sympathetic modulation with elevated heart rate, as compared to typical developing children (TD).

METHODS

We studied 21 children with ASD and 23 TD children during overnight polysomnography. Heart rate and spectral parameters were calculated for each vigilance stage during sleep. Data from the first four sleep cycles were used to avoid possible effects of different individual sleep lengths and sleep cycle structures. Linear regression models were applied to study the effects of age and diagnosis (ASD and TD).

RESULTS

In both groups, HR decreased during non-REM sleep and increased during REM sleep. However, HR was significantly higher in stages N2, N3 and REM sleep in the ASD group. Children with ASD showed less high frequency (HF) modulation during N3 and REM sleep. LF/HF ratio was higher during REM. Heart rate decreases with age at the same level in ASD and in TD. We found an age effect in LF in REM different in ASD and TD.

CONCLUSION

Our findings suggest possible deficits in vagal influence to the heart during sleep, especially during REM sleep. Children with ASD may have higher sympathetic dominance during sleep but rather due to decreased vagal influence.

K-Complexes: Interaction between the Central and Autonomic Nervous Systems during Sleep

STUDY OBJECTIVES

To investigate the relationship between K-complexes (KCs) and cardiac functioning.

METHODS

Forty healthy adolescents aged 16-22 y (19 females) participated in the study. Heart rate (HR) fluctuations associated with spontaneous and evoked KCs were investigated on two nights, one with (event-related potential night) and one without auditory tones presented across the night.

RESULTS

There was a clear biphasic cardiac response to evoked and spontaneous KCs, with an initial acceleration in HR followed by a deceleration (P < 0.001). HR acceleration occurred immediately to KCs in response to tones presented in the first third of the interbeat interval, but was delayed a beat when the tone occurred later in the cardiac cycle (P < 0.05). Sex differences were also evident. Pretone baseline HR was higher, and the magnitude of the HR response was blunted and delayed, in female compared to male adolescents (P < 0.001). Also, pretone baseline HR was lower when a tone elicited a KC compared to when it did not (P < 0.001), suggesting that KCs are possibly more likely to be elicited by external stimuli in states of reduced cardiac activation.

CONCLUSIONS

The strict dependency observed between KCs and cardiac control indicates a potential role of KCs in modulating the cardiovascular system during sleep. Sex differences in the KC-cardiac response indicate the sensitivity of this measure in capturing sex differences in cardiac regulatory physiology.

Acute stress alters autonomic modulation during sleep in women approaching menopause

Hot flashes, hormones, and psychosocial factors contribute to insomnia risk in the context of the menopausal transition. Stress is a well-recognized factor implicated in the pathophysiology of insomnia; however the impact of stress on sleep and sleep-related processes in perimenopausal women remains largely unknown. We investigated the effect of an acute experimental stress (impending Trier Social Stress Task in the morning) on pre-sleep measures of cortisol and autonomic arousal in perimenopausal women with and without insomnia that developed in the context of the menopausal transition. In addition, we assessed the macro- and micro-structure of sleep and autonomic functioning during sleep. Following adaptation to the laboratory, twenty two women with (age: 50.4 ± 3.2 years) and eighteen women without (age: 48.5 ± 2.3 years) insomnia had two randomized in-lab overnight recordings: baseline and stress nights. Anticipation of the task resulted in higher pre-sleep salivary cortisol levels and perceived tension, faster heart rate and lower vagal activity, based on heart rate variability measures, in both groups of women. The effect of the stress manipulation on the autonomic nervous system extended into the first 4 h of the night in both groups. However, vagal tone recovered 4-6 h into the stress night in controls but not in the insomnia group. Sleep macrostructure was largely unaltered by the stress, apart from a delayed latency to REM sleep in both groups. Quantitative analysis of non-rapid eye movement sleep microstructure revealed greater electroencephalographic (EEG) power in the beta1 range (15-≤23 Hz), reflecting greater EEG arousal during sleep, on the stress night compared to baseline, in the insomnia group. Hot flash frequency remained similar on both nights for both groups. These results show that pre-sleep stress impacts autonomic nervous system functioning before and during sleep in perimenopausal women with and without insomnia. Findings also indicate that women with insomnia had increased EEG arousal and lacked recovery in vagal activity across the stress night suggesting a greater sensitivity to stress in this group.

The role of variability in night-time mean heart rate on the prediction of ventricular arrhythmias and all-cause mortality in implantable cardioverter defibrillator patients

AIMS

This study was to use implantable cardioverter defibrillator (ICD) home monitoring (HM) feature to evaluate the role of mean night-time heart rate (MNHR) in the occurrence of ventricular arrhythmias (VAs) and mortality.

METHODS AND RESULTS

This study retrospectively analysed clinical and ICD device data in 318 ICD patients. Data of the first 30-day MNHR (recorded 02:00-06:00 am) by HM were collected. The average and standard deviation of 30-day MNHR (AVHR and SDHR, respectively) were then determined in each patient. The primary endpoint was appropriate ICD treatment of VAs. The secondary endpoint was all-cause mortality. During a mean follow-up period of 32 ± 10 months, 179 of the 318 patients (56.3%) experienced VAs, 123 patients (38.7%) were treated by ICD shocks, and 37 patients (11.6%) died. The overall SDHR in this study cohort was 4.5 ± 3.0 bpm. Based on the receiver operating characteristic curve, the cut-off value of SDHR = 3.685 bpm was identified to predict VAs. In the Kaplan-Meier survival, SDHR ≥ 3.685 bpm was associated with increased VAs [hazard ratio (HR) = 1.885; 95% confidence interval (CI) = 1.362-2.609; P < 0.001], shock events (HR = 1.637; 95% CI = 1.11-2.414; P = 0.013), all-cause mortality (HR = 2.42; 95% CI = 1.266-4.627; P = 0.008), and the combined endpoints (HR = 1.872; 95% CI = 1.365-2.567; P < 0.001). In univariate and multivariate Cox models (adjusting for clinical factors), SDHR ≥ 3.685 bpm was still an independent predictor for all endpoints.

CONCLUSION

In ICD population, SDHR ≥ 3.685 bpm was an independent predictor for VAs and all-cause mortality.

Vagal withdrawal during hot flashes occurring in undisturbed sleep

OBJECTIVE

Little is known about the impact of hot flashes on cardiac autonomic regulation, particularly vagal control. Therefore, we assessed the cardiac autonomic profile associated with physiological hot flashes occurring in undisturbed sleep.

METHODS

Eleven perimenopausal women (45-56 y) had overnight laboratory recordings of polysomnography, electrocardiography, and skin conductance. Eighteen hot flashes that occurred in stable non-rapid eye movement sleep undisturbed by arousals were analyzed. Heart rate variability measures were obtained for three consecutive 2-minute windows starting from 4 minutes before (baseline and preflash periods) to 2 minutes after the onset of hot flashes (hot flash period).

RESULTS

Heart rate increased by, on average, 4 beats/minute with the occurrence of a hot flash compared with both baseline (P < 0.001) and preflash (P < 0.001). High-frequency power was reduced, reflecting a decrease in vagal activity, at the onset of a hot flash compared with baseline (P < 0.001) and preflash (P < 0.001). There was no change in sympathovagal balance with the onset of a hot flash. The magnitude of the hot flash (ie, skin conductance amplitude) was associated with increased heart rate (r = 0.78, P < 0.001) and decreased vagal tone (r = -0.56, P = 0.014).

CONCLUSIONS

Physiological hot flashes per se, recorded during undisturbed sleep periods and independent of any arousals, are associated with increased heart rate and decreased cardiac autonomic vagal activity. These data support the hypothesis that the parasympathetic branch of the autonomic nervous system is involved in the cardiac response to a hot flash.

Autonomic regulation across phases of the menstrual cycle and sleep stages in women with premenstrual syndrome and healthy controls

To investigate the influence of menstrual cycle phase and the presence of severe premenstrual symptoms on cardiac autonomic control during sleep, we performed heart rate variability (HRV) analysis during stable non-rapid eye movement (NREM) and REM sleep in 12 women with severe premenstrual syndrome and 14 controls in the mid-follicular, mid-luteal, and late-luteal phases of the menstrual cycle. Heart rate was higher, along with lower high frequency (HF) power, reflecting reduced vagal activity, and a higher ratio of low frequency (LF) to high frequency power, reflecting a shift to sympathetic dominance, in REM sleep compared with NREM sleep in both groups of women. Both groups of women had higher heart rate during NREM and REM sleep in the luteal phase recordings compared with the mid-follicular phase. HF power in REM sleep was lowest in the mid-luteal phase, when progesterone was highest, in both groups of women. The mid-luteal phase reduction in HF power was also evident in NREM sleep in control women but not in women with PMS, suggesting some impact of premenstrual syndrome on autonomic responses to the hormone environment of the mid-luteal phase. In addition, mid-luteal phase progesterone levels correlated positively with HF power and negatively with LF/HF ratio in control women in NREM sleep and with the LF/HF ratio during REM sleep in both groups of women. Our findings suggest the involvement of female reproductive steroids in cardiac autonomic control during sleep in women with and without premenstrual syndrome.

Relationships between clinical characteristics and nocturnal cardiac autonomic activity in Parkinson's disease

BACKGROUND

The aim of the present study was to explore the association between Parkinson's disease (PD) clinical characteristics and cardiac autonomic control across sleep stages.

METHODS

Frequency-domain heart rate variability (HRV) measures were estimated in 18 PD patients undergoing a night of polysomnography.

RESULTS

Significant relationships were found between PD severity and nocturnal HRV indices. The associations were restricted to rapid eye movement (R) sleep.

CONCLUSIONS

The progressive nocturnal cardiac autonomic impairment occurring with more severe PD can be subclinical emerging only during conditions requiring active modulation of physiological functions such as R-sleep.

Nocturnal cardiovascular activity in essential hypotension: evidence of differential autonomic regulation

OBJECTIVE

Essential hypotension represents a form of chronic low blood pressure (BP) not explained by medical or orthostatic conditions. The pathogenesis of essential hypotension may involve sympathetic hypoactivation and other forms of autonomic dysregulation. The aim of the current study was to investigate autonomic and cardiovascular activity during sleep in individuals with essential hypotension.

METHODS

A case-control study was conducted in 14 individuals with essential hypotension (mean [standard error] = 23.4 [0.6] years, all women) and 14 controls (mean [standard error] age = 22.2 [0.4] years, all women). The following measures were collected over a night of sleep: BP, heart rate (HR), stroke volume, cardiac output (CO), preejection period (PEP), total peripheral resistance, and time-domain measures of HR variability.

RESULTS

Hypotensive participants had consistently lower BP, HR, and CO than did normotensives. Cardiac autonomic variables revealed enhanced parasympathetic tone (proportion of adjacent normal-to-normal intervals that differed in length by more than 50 milliseconds = 40.8 [6.3] versus 23.4 [4.5], p = .03) and reduced sympathetic drive in hypotensives (PEP = 99.4 [3.6] versus 86.1 [4.3], p = .02). Analysis of temporal profiles showed that HR, stroke volume, and CO decreased throughout the night in both groups, whereas PEP and HR variability increased. Unlike controls, BP remained essentially unchanged in hypotensives, as the decrease in CO was counterbalanced by a parallel rise in total peripheral resistance.

CONCLUSIONS

These findings suggest that nocturnal cardiac sympathetic withdrawal combined with vagal hyperactivity is a characteristic of the autonomic regulation in essential hypotension.

Nighttime cardiac sympathetic hyper-activation in young primary insomniacs

PURPOSE

A growing literature supports the association between insomnia and cardiovascular risk. Since only few studies have provided empirical evidence of hyper-activation of the cardiovascular system in insomniacs, the aim of the present study was to analyze cardiac autonomic responses in primary insomnia.

METHODS

Impedance cardiography and heart rate variability (HRV) measures were assessed in 9 insomniacs and 9 good sleepers during a night of polysomnographic recording.

RESULTS

Insomniacs were found to be characterized by a constant sympathetic hyper-activation which was maintained all night, as suggested by a faster pre-ejection period (PEP) compared to good sleepers. In addition, only insomniacs showed a strong reduction in heart rate in the transition from wake to sleep. Both groups exhibited a reduction in cardiac output and sympathovagal balance, i.e., reductions in low-frequency/high-frequency ratio and increases in high-frequency normalized units of HRV, across the night. In addition, in our sample, a high physiological sympathetic activation (fast PEP) at night was found to be directly associated with low quality of sleep.

CONCLUSIONS

These preliminary findings suggest that a constant cardiac sympathetic hyper-activation throughout the night is a main feature of primary insomnia. Our evidences support the association between insomnia and increased risk for cardiovascular diseases.

Hemodynamic and autonomic modifications during sleep stages in young hypotensive women

This study examined cardiovascular activity and autonomic involvement during sleep in essential hypotension. We compared young female hypotensives and normotensives using ambulatory blood pressure monitoring, impedance cardiography, and frequency-domain analysis of heart rate variability during a night of polysomnographic recording. Hypotensives, as compared to normotensives, exhibited lower blood pressure, reduced myocardial contractility and reduced sympathovagal balance across the whole night. Both groups exhibited a reduction in cardiovascular involvement from wake to sleep with similar cardiovascular activity during wake and REM. No group difference was observed in sleep architecture suggesting similar sleeping quality in hypotensives and normotensives. The lower blood pressure and reduced myocardial contractility associated with a lower sympathovagal balance in hypotensives, as compared to normotensives, suggest a night-time hypoactivation of the cardiovascular system supporting the hypothesis of impairment in autonomic control in essential hypotension.

Sleep and cardiovascular regulation

Normal sleep has a profound effect on the cardiovascular system, reducing cardiovascular activity throughout non-rapid eye movement sleep; changes that are modified and augmented by circadian system influence. There is also evidence that sleep-initiated changes in autonomic balance may in turn modify the development of sleep within a night, particularly the development of slow wave sleep. It is assumed that the cardiovascular changes that accompany sleep reflect a functional aspect of sleep, although the precise functional role has not been agreed upon. Nevertheless, there is good evidence that the cardiovascular changes that occur during normal sleep are beneficial for the cardiovascular system. Arousals from sleep, which are common even in normal sleep, are associated with a surge in activity in cardiorespiratory systems, with marked effects on the sleep-related pattern of cardiovascular activity when they occur frequently. Despite the importance of this aspect of sleep, controversy remains as to both the nature of the activation response and the circumstances under which it is elicited. The concept that sleep-related changes in cardiovascular activity are beneficial leads to the corollary that sleep disturbance would result in adverse cardiovascular consequences. While there is strong empirical evidence for such a relationship, it remains unclear whether this is a direct effect or, as has been suggested recently, the effect of disturbed sleep is mediated via stress-related modification of neuroendocrine systems.

The effect of lavender aromatherapy on autonomic nervous system in midlife women with insomnia

The objective of this study is to determine the effects of 12 weeks of lavender aromatherapy on self-reported sleep and heart rate variability (HRV) in the midlife women with insomnia. Sixty-seven women aged 45–55 years, with a CPSQI (Chinese version of Pittsburgh Sleep Quality Index) greater than 5, were recruited from communities in Taiwan. The experimental group (n = 34) received lavender inhalation, 20 min each time, twice per week, for 12 weeks, with a total of 24 times. The control group (n = 33) received health education program for sleep hygiene with no intervention. The study of HRV was analyzed by time- and frequency-domain methods. Significant decrease in mean heart rate (HR) and increases in SDNN (standard deviation of the normal-to-normal (NN) intervals), RMSDD (square root of the mean squared differences of successive NN intervals), and HF (high frequency) of spectral powers analysis after lavender inhalation were observed in the 4th and 12th weeks of aromatherapy. The total CPSQI score of study subjects was significantly decreased in the experimental group (P < 0.001), while no significant difference was observed across the same time period (P = 0.776) in the control group. Resting HR and HRV measurements at baseline 1 month and 3 months after allocation showed no significant difference between the experimental and control groups. The study demonstrated that lavender inhalation may have a persistent short-term effect on HRV with an increase in parasympathetic modulation. Women receiving aromatherapy experienced a significant improvement in sleep quality after intervention. However, lavender aromatherapy does not appear to confer benefit on HRV in the long-term followup.

Cardiovascular variability during periodic leg movements in sleep in children

STUDY OBJECTIVES

Periodic leg movements in sleep (PLMS) are episodes of repetitive and stereotypic leg movements occurring during sleep. In adults, research indicates that PLMS affects sleep quality and duration and are associated with a shift to relatively greater sympathetic influence over cardiovascular variables. However, little research has been performed to investigate the effect of PLMS episodes on cardiac autonomic control in children. This study aimed to quantify the effect of PLMS episodes during NREM2 sleep on heart rate variability (HRV) measures of sympathovagal balance in children.

PARTICIPANTS

Overnight polysomnography data from 20 children (7-12 y) referred for assessment of sleep disordered breathing (SDB) were analyzed retrospectively. Ten children with episodes of PLMS were matched for age and SDB severity with a control group of 10 children without PLMS episodes.

RESULTS

The LF/HF ratio was significantly higher in the PLM+ compared with both the PLM- periods from PLMS subjects (P < 0.001) and the periods from the control group (P < 0.001). However, this effect could not be parsimoniously interpreted due to the likelihood that leg movements had a direct effect on the lower frequencies. Analysis of the ratio PLM+ to PLM+ plus PLM- indicated parasympathetic inhibition during periods of periodic leg movement and the onset of individual leg movements were associated with cardiac acceleration followed by a return to pre-movement levels.

CONCLUSION

This study identified vagal inhibition in association with episodes of PLMS in children. Rapid cardiac acceleration occurring concurrently with the onset of individual leg movements also suggested decreased vagal activity associated with the movements.

Effect of mood during daily life on autonomic nervous activity balance during subsequent sleep

RR-interval and eight types of mood level were recorded for 48 h from 40 normal male subjects. Sympathovagal balance was evaluated by calculating the normalized high-frequency power (HFnu) of RR-interval variability. The mean mood levels during 6 h before bedtime and the mean HFnu during 3 h after bedtime were compared. The data were normalized individually and the differences from the first night (Deltamood and DeltaHFnu) were taken. The correlation coefficient between Deltadepression and DeltaHFnu was -0.53, and that between Deltaworry and DeltaHFnu was -0.44. This implies that both daily depression and worry shift toward sympathetic dominance during subsequent sleep.

Reduced parasympathetic activity during sleep in the symptomatic phase of severe premenstrual syndrome

OBJECTIVE

Severe premenstrual syndrome (PMS) is a common distressing disorder in women that manifests during the premenstrual (late-luteal) phase of the ovulatory menstrual cycle. There is some evidence that altered autonomic function may be an important component of PMS, but few studies have used heart rate variability (HRV) as a sensitive marker of autonomic activity in severe PMS, and findings are conflicting.

METHODS

We investigated HRV during sleep, a state that is relatively free of external disruptions, in 9 women with severe PMS and 12 controls.

RESULTS

The normal-to-normal (NN) RR interval was shorter during the sleep period in women with PMS than in controls in both the follicular and the late-luteal phases of the menstrual cycle. The standard deviation of all NN intervals, a measure of total variability in the interbeat interval, was lower during the sleep period in the late-luteal phase than in the follicular phase in women with PMS. The square root of the mean of the sum of the squares of differences between adjacent NN intervals, a measure reflecting high-frequency (HF) activity, showed a similar pattern. HF power, a marker of parasympathetic activity, was lower during non-rapid eye movement (non-REM) and REM sleep in the late-luteal phase than in the follicular phase in women with severe PMS. Controls had a shorter NN interval, but similar HRV measures, in the late-luteal phase compared with the follicular phase.

CONCLUSION

These results suggest that women with severe PMS have decreased parasympathetic activity during sleep in association with their premenstrual symptoms in the late-luteal phase compared with the follicular phase when they are symptom-free.