Cardiac Autonomic Activity During Human Sleep: Analysis of Sleep Stages and Sleep Cycles

In this study characteristics of cardiac functioning were investigated in nine subjects during their nocturnal sleep. The pre-ejection period and the high frequency component of heart rate variability were used as indices of cardiac sympathetic and parasympathetic activity of the autonomic nervous system respectively. Heart rate and the autonomic indices were assessed across physiological determined sleep stages and consecutive temporal sleep cycles. Repeated measures ANOVA analyses indicated a significant pattern of heart rate as a function of sleep stages, which was mirrored by parasympathetic activity. Further, a significant decrease of heart rate as a function of sleep cycles was mirrored by an increase of sympathetic activity. Moreover, non-REM/REM differences revealed a dominant role of parasympathetic activity during sleep stages as well as sleep cycles. These findings demonstrate that sympathetic activity is influenced by time asleep, whereas parasympathetic activity is influenced by the depth of sleep.     

Effects of sleep pressure on endogenous cardiac autonomic activity and body temperature.

This study investigated the effects of variations in sleep pressure on cardiac autonomic activity and body temperature. In a counterbalanced design, 12 healthy, young subjects (6 men and 6 women) remained recumbent during 30 h of wakefulness (high sleep pressure) and 6 h of wakefulness (low sleep pressure). Both periods of wakefulness were immediately followed by a sleep opportunity, and the first 2 h of sleep were analyzed. During extended hours of wakefulness, a reduction in heart rate was mediated by a decline in cardiac sympathetic activity (measured via preejection period) and the maintenance of cardiac parasympathetic activity (measured via respiratory sinus arrhythmia). In subsequent high-pressure sleep, parasympathetic activity was amplified and sympathetic activity was negatively associated with electroencephalographic slow-wave activity. Sleep deprivation had no impact on foot temperature, but it did alter the pattern of change in core body temperature. A downregulation of cardiac autonomic activity during both extended hours of wakefulness and subsequent sleep may respectively provide "protection" and "recovery" from the temporal extension of cardiac demand.     

Noninvasive cardiac psychophysiology as a tool for translational science with marmosets

The importance of marmosets for comparative and translational science has grown in recent years because of their relatively rapid development, birth cohorts of twins, family social structure, and genetic tractability. Despite this, they remain understudied in investigations of affective processes. In this methodological note, we establish the validity of using noninvasive commercially available equipment to record cardiac physiology and compute indices of autonomic nervous system activity—a major component of affective processes. Specifically, we recorded electrocardiogram and impedance cardiogram, from which we derived heart rate, respiration rate, measures of high‐frequency heart rate variability (indices of parasympathetic autonomic nervous system activity), and ventricular contractility (an index of sympathetic autonomic nervous system activity). Our methods produced physiologically plausible data, and further, animals with increased heart rates during testing were also more reactive to isolation from their social partner and presentation of novel objects, though no relationship was observed between reactivity and specific indices of parasympathetic or sympathetic nervous system activity.     

Autonomic Activity Assessed by Heart Rate Spectral Analysis Varies with Fat Distribution in Obese Women

Obesity in humans has been associated with altered autonomic nervous system activity. The objective of this study was to examine the relationship between autonomic function and body fat distribution in 16 obese, postmenopausal women using power spectrum analysis of heart rate variability. Using this technique, a low frequency peak (0.04-0.12 Hz) reflecting mixed sympathetic and parasympathetic activity, and a high frequency peak (0.22-0.28 Hz) reflecting parasympathetic activity, were identified from 5-minute consecutive heart rate data (both supine and standing). Autonomic activity in upper body (UBO) vs. lower body obesity (LBO)(by waist-to-hip ratio) and subcutaneous vs. visceral obesity (by CT scan) was evaluated. Power spectrum data were log transformed to normalize the data. The results showed that standing, low-frequency power (reflecting sympathetic activity) and supine, high-frequency power (reflecting parasympathetic activity) were significantly greater in UBO than in LBO, and in visceral compared to subcutaneous obesity. Women with combined UBO and visceral obesity had significantly higher cardiac sympathetic and parasympathetic activity than any other subgroup. We conclude that cardiac autonomic function as assessed by heart rate spectral analysis varies in women depending on their regional body fat distribution.     

Effects of glucagon-like peptide-1, yohimbine, and nitrergic modulation on sympathetic and parasympathetic activity in humans

Glucagon-like peptide-1 (GLP-1), an incretin, which is used to treat diabetes mellitus in humans, inhibited vagal activity and activated nitrergic pathways. In rats, GLP-1 also increased sympathetic activity, heart rate, and blood pressure (BP). However, the effects of GLP-1 on sympathetic activity in humans are unknown. Our aims were to assess the effects of a GLP-1 agonist with or without alpha(2)-adrenergic or -nitrergic blockade on autonomic nervous functions in humans. In this double-blind study, 48 healthy volunteers were randomized to GLP-1-(7-36) amide, the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-l-arginine acetate (l-NMMA), the alpha(2)-adrenergic antagonist yohimbine, or placebo (i.e., saline), alone or in combination. Hemodynamic parameters, plasma catecholamines, and cardiac sympathetic and parasympathetic modulation were measured by spectral analysis of heart rate. Thereafter, the effects of GLP-1-(7-36) amide on muscle sympathetic nerve activity (MSNA) were assessed by microneurography in seven subjects. GLP-1 increased (P = 0.02) MSNA but did not affect cardiac sympathetic or parasympathetic indices, as assessed by spectral analysis. Yohimbine increased plasma catecholamines and the low-frequency (LF) component of heart rate power spectrum, suggesting increased cardiac sympathetic activity. l-NMMA increased the BP and reduced the heart rate but did not affect the balance between sympathetic and parasympathetic activity. GLP-1 increases skeletal muscle sympathetic nerve activity but does not appear to affect cardiac sympathetic or parasympathetic activity in humans.     

Application of Chaos Theory in Analyzing the Cardiac Rhythm in Healthy Subjects at Different Sleep Stages

The changes in the chaotic element of the cardiac rhythm (CR) were quantitated at different sleep stages by calculating the correlation dimension (D2) in 26 healthy subjects of both sexes (mean age 29.2 years), including 7 trained and 19 untrained subjects. Three untrained subjects took part in tests with autonomic nervous system blockers (atropine and propranolol). The study demonstrated a correlation between the changes in D2 at different sleep stages and the level of the autonomic regulation of CR. As the influence of the parasympathetic system on CR increased from one stage of slow wave sleep to another, D2 increased; during rapid eye movement (REM) sleep, this influence weakened and D2 decreased. The character of changes differed in the trained and untrained subjects and depended on the initial level of the autonomic regulation of CR. In the trained subjects, characterized by predominance of the parasympathetic regulation of CR, the initial and subsequent D2 values were higher than in the untrained subjects. Both during wakefulness and at all stages of sleep, D2 increased when the sympathetic regulation of CR was blocked, decreased when the parasympathetic regulation was blocked, and reached the lowest level when both of them were blocked. This showed that the chaotic element of CR, expressed numerically by D2, depends on the regulating effects of the autonomic nervous system.     

Plastic surgeon's life: marvelous for mind, exhausting for body

Surgery is accepted as one of the most demanding professions that create both physical and mental strain on the performers. Therefore, the authors aimed to elucidate the mental burden of surgeons, which is dedicated to operative stress. They also tested the hypotheses that participating in surgery creates mental stress on surgeons that leads to cardiovascular changes, and that this stress is more pronounced for actual operators than for first assistants. The method chosen for this purpose was an analysis of heart rate variability. Twelve surgeons (five plastic surgery staff and seven plastic surgery residents) were monitored by a digital ambulatory Holter recorder on at least two occasions. Half of the recordings were carried out on operating days and the other half on office days. Heart rate variability indices (low frequency, high frequency, high frequency/low frequency ratio, and heart rate) were analyzed from those recordings using computerized research tool software. The heart rate variability indices of the operators showed statistically significant differences between operating days and office hours in favor of an increased sympathetic and decreased parasympathetic activity for the former. For first assistants, three of the parameters, with the exception of heart rate, changed in favor of a sympathetic predominance over parasympathetic activity; these changes were also statistically significant. These results showed a sympathetic hyperactivity for both operators and first assistants during the operations. When the sympathovagal balance of the actual operators was compared with that of assistants, the former group showed a more pronounced sympathetic arousal. This difference is accepted as a proof for the mental stress of the surgery being the main factor responsible for the sympathetic hyperactivity that we detected during the operations. Surgeons continuously face a unique mental strain that other professions rarely bring forth, and these psychological stressors are associated with alterations in cardiac autonomic control that may contribute to the development of cardiac disease. Prolonged sympathetic hyperactivity could anticipate cardiac discomfort in more experienced surgeons with marginal cardiac reserve. Such cardiac diseases would be reconsidered as occupation-related illnesses, which might be reimbursed to the physician. In addition, the legal responsibility of surgeons concerning their unfavorable results might be assessed with more understanding with a realization of their undue working conditions.     

Effects of bright light and melatonin on sleep propensity, temperature, and cardiac activity at night.

Melatonin increases sleepiness, decreases core temperature, and increases peripheral temperature in humans. Melatonin may produce these effects by activating peripheral receptors or altering autonomic activity. The latter hypothesis was investigated in 16 supine subjects. Three conditions were created by using bright light and exogenous melatonin: normal endogenous, suppressed, and pharmacological melatonin levels. Data during wakefulness from 1.5 h before to 2.5 h after each subject's estimated melatonin onset (wake time + 14 h) were analyzed. Respiratory sinus arrhythmia (cardiac parasympathetic activity) and preejection period (cardiac sympathetic activity) did not vary among conditions. Pharmacological melatonin levels significantly decreased systolic blood pressure [5.75 +/- 1.65 (SE) mmHg] but did not significantly change heart rate. Suppressed melatonin significantly increased rectal temperature (0.27 +/- 0.06 degrees C), decreased foot temperature (1.98 +/- 0.70 degrees C), and increased sleep onset latency (5.53 +/- 1.87 min). Thus melatonin does not significantly alter cardiac autonomic activity and instead may bind to peripheral receptors in the vasculature and heart. Furthermore, increases in cardiac parasympathetic activity before normal nighttime sleep cannot be attributed to the concomitant increase in endogenous melatonin.     

The link between cardiac autonomic activity and sleep delta power is altered in men with sleep apnea-hypopnea syndrome

We hypothesize that sleep apnea-hypopnea alters interaction between cardiac vagal modulation and sleep delta EEG. Sleep apnea-hypopnea syndrome (SAHS) is related to cardiovascular complications in men. SAHS patients show higher sympathetic activity than normal subjects. In healthy men, non-rapid eye movement (NREM) sleep is associated with cardiac vagal influence, whereas rapid eye movement (REM) sleep is linked to cardiac sympathetic activity. Interaction between cardiac autonomic modulation and delta sleep EEG is not altered across a life span nor is the delay between appearances of modifications in both signals. Healthy controls, moderate SAHS, and severe SAHS patients were compared across the first three NREM-REM cycles. Spectral analysis was applied to ECG and EEG signals. High frequency (HF) and low frequency (LF) of heart rate variability (HRV), ratio of LF/HF, and normalized (nu) delta power were obtained. A coherency analysis between HF(nu) and delta was performed, as well as a correlation analysis between obstructive apnea index (AI) or hypopnea index (HI) and gain, coherence, or phase shift. HRV components were similar between groups. In each group, HF(nu) was larger during NREM, while LF(nu) predominated across REM and wake stages. Coherence and gain between HF(nu) and delta decreased from controls to severe SAHS patients. In SAHS patients, the delay between modifications in HF(nu) and delta did not differ from zero. AI and HI correlated negatively with coherence, while HI correlated negatively with gain only. Apneas-hypopneas affect the link between cardiac sympathetic and vagal modulation and delta EEG demonstrated by the loss of cardiac autonomic activity fluctuations across shifts in sleep stages. Obstructive apneas and hypopneas alter the interaction between both signals differently.     

Bradyarrythmias in the obstructive sleep apnea sundrome: a dangerous complication or defense mechanism?

Sleep is characterized by cycling and consecutive alternation of different phases and stages, each of which features intrinsic changes in autonomic regulation with heart rate oscillations; this may cause heart rhythm disorders, especially in the presence of comorbidities. This review addresses the issues of interrelationship between cardiac conduction disorders and obstructive sleep apnea. It is shown that some mechanisms of bradyarrythmia emergence (first of all, features of autonomic regulation with increases in parasympathetic tone) under respiratory arrest during sleep are also inherent to human divers as well as aquatic or para-aquatic mammals that have to hold their breath when diving or staying under water for a long time. These mechanisms may fulfill the defense function.     

Individual specificity of the autonomic support of purposive activity in students performing computer-aided tests

The autonomic correlates of individual differences in the effectiveness of purposive activity during a computer-aided sensorimotor test and computer-aided testing of the level of knowledge of students were studied. Students who reached high results of sensorimotor and academic tests were characterized by lability of autonomic indices, which manifests itself in a change in the absolute values and relationship of the characteristics of heart rate and hemodynamics in accordance with activity stages. These changes were specific for each form of activity and were connected with the results of the tests. The physiological prerequisites of the high lability of autonomic characteristics which ensures the ability of the subject to successfully adapt to the conditions of the activity included high initial values of TP and power of LF- and HF-ranges of heart rate variability at a LF/HF ratio close to unity, reflecting a high level of balanced sympathetic and parasympathetic effects on cardiovascular functions.     

Heart Rate Variability in Sleeping Preterm Neonates Exposed to Cool and Warm Thermal Conditions

Sudden infant death syndrome (SIDS) remains the main cause of postneonatal infant death. Thermal stress is a major risk factor and makes infants more vulnerable to SIDS. Although it has been suggested that thermal stress could lead to SIDS by disrupting autonomic functions, clinical and physiopathological data on this hypothesis are scarce. We evaluated the influence of ambient temperature on autonomic nervous activity during sleep in thirty-four preterm neonates (mean ± SD gestational age: 31.4±1.5 weeks, postmenstrual age: 36.2±0.9 weeks). Heart rate variability was assessed as a function of the sleep stage at three different ambient temperatures (thermoneutrality and warm and cool thermal conditions). An elevated ambient temperature was associated with a higher basal heart rate and lower short- and long-term variability in all sleep stages, together with higher sympathetic activity and lower parasympathetic activity. Our study results showed that modification of the ambient temperature led to significant changes in autonomic nervous system control in sleeping preterm neonates. The latter changes are very similar to those observed in infants at risk of SIDS. Our findings may provide greater insight into the thermally-induced disease mechanisms related to SIDS and may help improve prevention strategies.     

Daytime cardiac autonomic activity during one week of continuous night shift

Shift workers encounter an increased risk of cardiovascular disease compared to their day working counterparts. To explore this phenomenon, the effects of one week of simulated night shift on cardiac sympathetic (SNS) and parasympathetic (PNS) activity were assessed. Ten (5m; 5f) healthy subjects aged 18-29 years attended an adaptation and baseline night before commencing one week of night shift (2300-0700 h). Sleep was recorded using a standard polysomnogram and circadian phase was tracked using salivary melatonin data. During sleep, heart rate (HR), cardiac PNS activity (RMSSD) and cardiac SNS activity (pre-ejection period) were recorded. Night shift did not influence seep quality, but reduced sleep duration by a mean of 52 +/- 29 min. One week of night shift evoked a small chronic sleep debt of 5 h 14 +/- 56 min and a cumulative circadian phase delay of 5 h +/- 14 min. Night shift had no significant effect on mean HR, but mean cardiac SNS activity during sleep was consistently higher and mean cardiac PNS activity during sleep declined gradually across the week. These results suggest that shiftwork has direct and unfavourable effects on cardiac autonomic activity and that this might be one mechanism via which shiftwork increases the risk of cardiovascular disease. It is postulated that sleep loss could be one mediator of the association between shiftwork and cardiovascular health.     

Sympathetic nervous system representation in time and frequency domain indices of heart rate variability

This study evaluated the contributions of sympathetic and parasympathetic modulation to heart rate variability during situations in which vagal and sympathetic tone predominated. In a placebo-controlled, randomized, double blind blockade study, six young healthy male individuals received propranolol (0.2 mg x kg(-1)), atropine (0.04 mg x kg(-1)), propranolol plus atropine, or placebo infusions over 4 days. Time-domain indices were calculated during 40 min of rest and 20 min of exercise at 70% of maximal exercise intensity. Spectrum analysis, using fast Fourier transformation, was also performed at rest and during the exercise. The time-domain indices standard deviation of R-R intervals, mean of the standard deviations of all R-R intervals for all 5-min segments, percentage of number of pairs of adjacent R-R intervals differing by more than 50 ms, and square root of the mean of the sum of squares of differences between adjacent R-R intervals were reduced after atropine and propranolol plus atropine. Propranolol alone caused no appreciable change in any of the time-domain indices. At rest, all spectrum components were similar after placebo and propranolol infusions, but following parasympathetic and double autonomic blockade there was a reduction in all components of the spectrum analysis, except for the low:high ratio. During exercise, partial and double blockade did not change significantly any of the spectrum components. Thus, time and frequency-domain indices of heart rate variability were able to detect vagal activity, but could not detect sympathetic activity. During exercise, spectrum analysis is not capable of evaluating autonomic modulation of heart rate.     

The Role of the Suprachiasmatic Nucleus in Cardiac Autonomic Control during Sleep

Background

The suprachiasmatic nucleus (SCN) may play an important role in central autonomic control, since its projections connect to (para)sympathetic relay stations in the brainstem and spinal cord. The cardiac autonomic modifications during nighttime may therefore not only result from direct effects of the sleep-related changes in the central autonomic network, but also from endogenous circadian factors as directed by the SCN. To explore the influence of the SCN on autonomic fluctuations during nighttime, we studied heart rate and its variability (HRV) in a clinical model of SCN damage.

Methods

Fifteen patients in follow-up after surgical treatment for nonfunctioning pituitary macroadenoma (NFMA) compressing the optic chiasm (8 females, 26–65 years old) and fifteen age-matched healthy controls (5 females, 30–63 years) underwent overnight ambulatory polysomnography. Eleven patients had hypopituitarism and received adequate replacement therapy. HRV was calculated for each 30-second epoch and corrected for sleep stage, arousals, and gender using mixed effect regression models.

Results

Compared to controls, patients spent more time awake after sleep onset and in NREM1-sleep, and less in REM-sleep. Heart rate, low (LF) and high frequency (HF) power components and the LF/HF ratio across sleep stages were not significantly different between groups.

Conclusions

These findings suggest that the SCN does not play a dominant role in cardiac autonomic control during sleep.     

Exposure to bright light modifies HRV responses to mental tasks during nocturnal sleep deprivation

This study was intended to determine the effects of continuous bright light exposure on cardiovascular responses, particularly heart rate variability (HRV), at rest and during performance of mental tasks with acute nocturnal sleep deprivation. Eight healthy male subjects stayed awake from 21.00 to 04.30 hours under bright (BL, 2800 lux) or dim (DL, 120 lux) light conditions. During sleep deprivation, mental tasks (Stroop color-word conflict test: CWT) were performed for 15 min each hour. Blood pressure, electrocardiogram, respiratory rate, urinary melatonin concentrations and rectal temperature were measured. During sleep deprivation, BL exposure depressed melatonin secretion in comparison to DL conditions. During sleep deprivation, exposure to BL delayed the decline in heart rate (HR) for 4 h in resting periods. A significant increment of HR induced by each CWT was detected, especially at 03.00 h and later, under DL conditions only. In addition, at 04.00 h, an index of sympathetic activity and sympatho-vagal balance on HRV during CWT increased significantly under DL conditions. In contrast, an index of parasympathetic activity during CWT decreased significantly under DL conditions. However, the indexes of HRV during CWT did not change throughout sleep deprivation under BL conditions. Our results suggest that BL exposure not only delays the nocturnal decrease in HR at rest but also maintains HR and balance of cardiac autonomic modulation to mental tasks during nocturnal sleep deprivation.     

Evidence of dominant parasympathetic nervous activity of great cormorants (<Emphasis Type="Italic">Phalacrocorax carbo</Emphasis>)

The characteristics of autonomic nervous activity were examined on captive great cormorants Phalacrocorax carbo hanedae, using a power spectral analysis of heart rate variability. Heart rates were calculated from recordings of the electrocardiograms of the birds via embarked data loggers. We investigated the effects of blockades of the sympathetic or parasympathetic nervous systems using the indices of autonomic nervous activity such as high frequency (0.061–1.5 Hz) component, low frequency (0.02–0.060 Hz) component and the low frequency power component to high frequency power component ratio. Resting heart rate (85.5 ± 6.1 bpm) was lower than the intrinsic heart rate (259.2 ± 15.3 bpm). The heart rate drastically increased after the injection of the parasympathetic nervous blocker, on the other hand it slightly decreased after the injection of the sympathetic nervous blocker. The sympathetic, parasympathetic and net autonomic nervous tones calculated from heart rate with and without blockades were 40.9 ± 27.6, −44.5 ± 7.4 and −29.5 ± 9.0%, respectively. The effect of the parasympathetic nervous blockade on low frequency and high frequency power was greater than that of the sympathetic nervous blockade. Those data suggested that the parasympathetic nervous activity was dominant for great cormorants.     

Predominance of Intrinsic Mechanism of Resting Heart Rate Control and Preserved Baroreflex Sensitivity in Professional Cyclists after Competitive Training

Different season trainings may influence autonomic and non-autonomic cardiac control of heart rate and provokes specific adaptations on heart’s structure in athletes. We investigated the influence of transition training (TT) and competitive training (CT) on resting heart rate, its mechanisms of control, spontaneous baroreflex sensitivity (BRS) and relationships between heart rate mechanisms and cardiac structure in professional cyclists (N = 10). Heart rate (ECG) and arterial blood pressure (Pulse Tonometry) were recorded continuously. Autonomic blockade was performed (atropine—0.04 mg.kg^-1; esmolol—500 μg.kg^-1 = 0.5 mg). Vagal effect, intrinsic heart rate, parasympathetic (n) and sympathetic (m) modulations, autonomic influence, autonomic balance and BRS were calculated. Plasma norepinephrine (high-pressure liquid chromatography) and cardiac structure (echocardiography) were evaluated. Resting heart rate was similar in TT and CT. However, vagal effect, intrinsic heart rate, autonomic influence and parasympathetic modulation (higher n value) decreased in CT (P≤0.05). Sympathetic modulation was similar in both trainings. The autonomic balance increased in CT but still showed parasympathetic predominance. Cardiac diameter, septum and posterior wall thickness and left ventricular mass also increased in CT (P<0.05) as well as diastolic function. We observed an inverse correlation between left ventricular diastolic diameter, septum and posterior wall thickness and left ventricular mass with intrinsic heart rate. Blood pressure and BRS were similar in both trainings. Intrinsic heart rate mechanism is predominant over vagal effect during CT, despite similar resting heart rate. Preserved blood pressure levels and BRS during CT are probably due to similar sympathetic modulation in both trainings.     

The effects of bright light and nighttime melatonin administration on cardiac activity

Although melatonin has an important physiological role in the facilitation of sleep, its precise mechanism of action is not clear. To investigate the potential contribution of melatonin to influence cardiac autonomic activity in the evening, 16 young healthy subjects participated in a repeated measures design where cardiac autonomic activity, heart rate and blood pressure were examined during three experimental conditions. An initial baseline condition involved dim light exposure (< 10 lux), permitting the normal nocturnal rise in endogenous melatonin. In other sessions, subjects were exposed to bright light (> 3000 lux) to suppress melatonin secretion and administered a placebo or melatonin (5 mg) capsule at the estimated time of increase in endogenous melatonin (wake time + 14 hours). Heart rate, pre-ejection period (a measure of cardiac sympathetic activity) and respiratory sinus arrhythmia (a measure of parasympathetic activity) were not significantly altered in response to the three melatonin levels. While melatonin had no effect on diastolic blood pressure, systolic blood pressure was maximally decreased by 6 +/- 1.93 mmHg (mean +/- SEM, p < 0.005) 150 minutes after exogenous melatonin. The results indicate that melatonin does not directly modulate cardiac autonomic activity, but may rather act directly on the cardiovascular system.     

Autonomic Dysregulation in Headache Patients

To analyze autonomic nervous system activity in headache subjects, measurements of heart rate variability (HRV), skin temperature, skin conductance, and respiration were compared to a matched control group. HRV data were recorded in time and frequency domains. Subjects also completed self-report questionnaires assessing psychological distress, fatigue, and sleep dysfunction. Twenty-one headache and nineteen control subjects participated. In the time domain, the number of consecutive R-to-R intervals that varied by more than 50 ms and the standard deviation of the normalized R-to-R intervals, both indices of parasympathetic nervous system activity, were significantly lower in the headache group than the control group. Groups did not differ statistically on HRV measures in the frequency domain. Self-report measures showed significantly increased somatization, hostility, anxiety, symptom distress, fatigue, and sleep problems in the headache group. The results suggest headache subjects have increased sympathetic nervous system activity and decreased parasympathetic activity compared to non-headache control subjects. Headaches subjects also showed greater emotional distress, fatigue, and sleep problems. The results indicate an association between headaches and cardiovascular functioning suggestive of sympathetic nervous system activation in this sample of mixed migraine and tension-type headache sufferers.