The interaction between respiratory and autonomic function during sleep-related changes in pharyngeal airway patency

Multimodal transcutaneous auricular vagus nerve stimulation: An option in the treatment of sleep bruxism in a "polyvagal" context

OBJECTIVE

To consider the possible role of the vagus nerve (VN) in the pathophysiology of sleep bruxism (SB) and introduce a multimodal protocol of transcutaneous auricular stimulation of the VN in the treatment of SB patients.

METHODS

Ten patients with SB underwent four sessions of electric transcutaneous auricular vagus nerve stimulation (ta-VNS) in specific auricular areas. The patients were advised to manually stimulate the same areas between sessions. Masticatory muscle activity and sleep parameters were measured by a polysomnography (PSG) before and after the treatment. Heart rate variability (HRV) parameters were measured during each stimulation.

RESULTS

PSG analysis revealed a statistically significant reduction in tonic SB index and tonic contraction time. HRV parameters showed a statistically significant increase in mean values of the vagal tone after each session of stimulation. No side effect was reported.

CONCLUSION

The stimulation of the VN might have a role in the treatment of SB.

Cardiac and sympathetic activation are reduced in children with Down syndrome and sleep disordered breathing

STUDY OBJECTIVES

Sleep disordered breathing (SDB) occurs at an increased incidence in children with Down Syndrome (DS) compared to the general pediatric population. We hypothesized that, compared with typically developing (TD) children with SDB, children with DS have a reduced cardiovascular response with delayed reoxygenation after obstructive respiratory events, and reduced sympathetic drive, providing a potential explanation for their increased risk of pulmonary hypertension.

DESIGN

Beat-by-beat heart rate (HR) was analyzed over the course of obstructive events (pre, early, late, post-event) and compared between groups. Also compared were the time for oxygen resaturation post-event and overnight urinary catecholamines.

SETTING

Pediatric sleep laboratory.

PATIENTS

Sixty-four children aged 2-17 y referred for investigation of SDB (32 DS; 32 TD) matched for age and obstructive apnea/hypopnea index.

MEASUREMENT AND RESULTS

Children underwent overnight polysomnography with overnight urine collection. Compared to TD children, those with DS had significantly reduced HR changes post-event during NREM (DS: 21.4% ± 1.8%, TD: 26.6% ± 1.6%, change from late to post-event, P < 0.05). The time to resaturation post-event was significantly increased in the DS group (P < 0.05 for both NREM and REM sleep). Children with DS had significantly reduced overnight urinary noradrenaline (P < 0.01), adrenaline (P < 0.05) and dopamine levels (P < 0.01) compared with TD children.

CONCLUSION

Children with DS and SDB exhibit a compromised acute cardio-respiratory response and dampened sympathetic response to SDB compared with TD children with SDB. These data may reflect autonomic dysfunction in children with DS that may place them at increased risk for cardiovascular complications such as pulmonary hypertension.

The reciprocal interaction between obesity and obstructive sleep apnoea

Obesity is a significant risk factor in the pathogenesis of obstructive sleep apnoea (OSA) altering airway anatomy and collapsibility, and respiratory control. The association between obesity and OSA has led to an increasing focus on the role of weight loss as a potential treatment for OSA. To date, most discussion of obesity and OSA assumes a one-way cause and effect relationship, with obesity contributing to the pathogenesis of OSA. However, OSA itself may contribute to the development of obesity. OSA has a potential role in the development and reinforcement of obesity via changes to energy expenditure during sleep and wake periods, dietary habits, the neurohormonal mechanisms that control satiety and hunger, and sleep duration arising from fragmented sleep. Thus, there is emerging evidence that OSA itself feeds back into a complex mechanism that leads either to the development or reinforcement of the obese state. Whilst current evidence does not confirm that treatment of OSA directly influences weight loss, it does suggest that the potential role OSA plays in obesity and weight loss deserves further research.

Do rheumatoid arthritis patients have a higher risk for sleep apnea?

OBJECTIVE

Patients with rheumatoid arthritis (RA) have an increased risk for developing cardiovascular disease (CVD) compared to subjects in the general population. The development of CVD has also been linked to chronic sleep apnea. The purpose of this study was to examine the risk for sleep apnea in patients with RA compared to subjects without RA.

METHODS

We recruited RA patients and non-RA subjects who were age and sex matched from the same population. These persons completed the Berlin Sleep Questionnaire, which evaluated their level of risk (high or low) for sleep apnea. In addition, there were 3 subscales evaluating snoring, fatigue, and relevant comorbidities [i.e., high blood pressure and obesity [body mass index (BMI) > or = 30 kg/m(2))]. Chi-squared tests were used for comparisons.

RESULTS

The study population consisted of 164 patients with RA and 328 patients without RA. Age, sex and BMI were similar for both groups. There was no difference in snoring (p = 0.31) or in the comorbidities subscale (p = 0.37). However, RA patients reported more fatigue (38%) than subjects without RA (13%; p < 0.001). Overall, the risk for sleep apnea was significantly higher for the RA patients (50%) than the non-RA subjects (31%; p < 0.001).

CONCLUSION

Patients with RA may be at a higher risk for sleep apnea compared to non-RA subjects. This apparent risk difference may be attributed to reports of fatigue in RA patients, which may be associated with sleep apnea or RA disease itself.

Sleep quality and elevated blood pressure in adolescents

BACKGROUND

We assessed whether insufficient sleep is associated with prehypertension in healthy adolescents.

METHODS AND RESULTS

We undertook a cross-sectional analysis of 238 adolescents, all without sleep apnea or severe comorbidities. Participants underwent multiple-day wrist actigraphy at home to provide objective estimates of sleep patterns. In a clinical research facility, overnight polysomnography, anthropometry, and 9 blood pressure measurements over 2 days were made. Exposures were actigraphy-defined low weekday sleep efficiency, an objective measure of sleep quality (low sleep efficiency < or =85%), and short sleep duration (< or =6.5 hours). The main outcome was prehypertension (> or =90th percentile for age, sex, and height), with systolic and diastolic blood pressures as continuous measures as secondary outcomes. Prehypertension, low sleep efficiency, and short sleep duration occurred in 14%, 26%, and 11% of the sample, respectively. In unadjusted analyses, the odds of prehypertension increased 4.5-fold (95% CI, 2.1 to 9.7) in adolescents with low sleep efficiency and 2.8-fold (95% CI, 1.1 to 7.3) in those with short sleep. In analyses adjusted for sex, body mass index percentile, and socioeconomic status, the odds of prehypertension increased 3.5-fold (95% CI, 1.5. 8.0) for low sleep efficiency and 2.5-fold (95% CI, 0.9 to 6.9) for short sleep. Adjusted analyses showed that adolescents with low sleep efficiency had on average a 4.0+/-1.2-mm Hg higher systolic blood pressure than other children (P<0.01).

CONCLUSIONS

Poor sleep quality is associated with prehypertension in healthy adolescents. Associations are not explained by socioeconomic status, obesity, sleep apnea, or known comorbidities, suggesting that inadequate sleep quality is associated with elevated blood pressure.

Apnea promotes glutamate-induced excitotoxicity in hippocampal neurons

Patients with obstructive sleep apnea (OSA) exhibit hippocampal damage and cognitive deficits. To determine the effect of apnea on the synaptic transmission in the hippocampus, we performed electrophysiological studies in an in vivo guinea pig model of OSA. Specifically, we determined the cornu ammonis region 1 (CA1) field excitatory postsynaptic potential (fEPSP) response to cornu ammonis region 3 (CA3) stimulation and examined the presynaptic mechanisms underlying the changes in the fEPSP. Single episodes of apnea resulted in a maximal potentiation of the fEPSPs at 1 to 3 min after the termination of each episode of apnea. The mean amplitude and slope of the post-apneic fEPSP was significantly larger compared with the pre-apneic control. These changes were accompanied by a significant decrease in the paired-pulse facilitation ratio during the post-apneic period compared with the pre-apneic control. The N-methyl-D-aspartate (NMDA) glutamate receptor antagonist MK-801, when applied locally to the CA1 recording site by pressure ejection, blocked the apnea-induced potentiation of the fEPSP. In the experimental animals that were subjected to extended periods of recurrent apnea, CA1 neurons exhibited positive immunoreactivity for fragmented DNA strands, which indicates apoptotic cell death. The present results demonstrate that apnea-induced potentiation of the hippocampal CA1 fEPSP is mediated by an NMDA receptor mechanism. We therefore conclude that recurrent apnea produces abnormally high levels of glutamate that results in the apoptosis of CA1 neurons. We hypothesize that this damage is reflected by the cognitive deficits that are commonly observed in patients with breathing disorders such as OSA.

Novel pharmacotherapy for fibromyalgia

Fibromyalgia is a common disorder that is characterized by chronic widespread pain, tenderness to light palpation, fatigue and sleep disturbances. The present lack of a well-accepted model of the disorder has hampered progress towards adequate treatment. A review of potential models to explain the pathophysiology underlying its primary symptom (i.e., chronic widespread pain) lends insight on the therapeutic potential of novel therapies. Following this, a mechanistic evaluation of those medications that are under consideration for the treatment of the disorder is offered. Adequate treatment will be likely to involve the identification of biologic subgroups within the greater fibromyalgia construct. Key insights from basic research are the basis for increased optimism for effective relief among patients and clinicians.

Awakenings change results of nighttime ambulatory blood pressure monitoring

OBJECTIVE

Investigate the effect of distinguishing nighttime and sleep on nocturnal blood pressure results in ambulatory blood pressure monitoring.

METHODS

We recruited 36 patients, 29 men, with suspected obstructive sleep apnea/hypopnea syndrome attending a sleep clinic for diagnostic polysomnography and who agreed to wear a Spacelabs 90207 ambulatory blood pressure monitor during polysomnography. Their mean age was 45+/-11 years; body mass index (BMI), 30.8+/-5.4 kg/m; apnea-hypopnea index, 35+/-29 AH/h; 13 had a history of hypertension. A microphone attached to the ambulatory blood pressure monitor recorded its sounds in the polygraph and allowed us to classify each ambulatory blood pressure monitoring measurement as being made in electrographically-determined wake (e-wake) or sleep state (e-sleep).

RESULTS

Patients were asleep during (mean+/-SD) 61+/-24% (range 0-100%) of the 14+/-1 nighttime blood pressure measurements. Systolic and diastolic ambulatory blood pressure monitoring readings were significantly higher during e-wake (121+/-12/73+/-9 mmHg) than during total nighttime (119+/-11/70+/-8 mmHg) and e-sleep (116+/-13/68+/-9 mmHg). On the basis of nighttime measurements, 22 patients (61%) had nocturnal hypertension. On the basis of measurements made during e-sleep, nocturnal hypertension was diagnosed in 12 patients (33%; chi2=5.54; P=0.018). A multiple linear regression model showed that the percentage of measurements made in e-sleep was the only variable that significantly explained the difference between nighttime and e-sleep blood pressure figures, when controlling for sex, age, BMI, apnea-hypopnea index, and lowest SaO2.

CONCLUSION

During ambulatory blood pressure monitoring, nighttime blood pressure readings are higher than during e-sleep and this changes dipping and nocturnal hypertension classification.

Sex-specific densities of estrogen receptors alpha and beta in the subnuclei of the nucleus tractus solitarius, hypoglossal nucleus and dorsal vagal motor nucleus weanling rats

In rats ventilatory responses to N-methyl-d-aspartate (NMDA) receptor modulation are sexually dimorphic and may be altered by manipulating brain levels of estrogen receptors. Here we used image analysis and immunohistochemistry in weanling male and female rats to quantitate areas and densities of ER alpha and ER beta-positive neurons within medullary regions associated with cardiopulmonary regulation including the hypoglossal nucleus, subnuclei of the nucleus of the solitary tract (NTS), and the dorsal motor nucleus of the vagus. Weanling rats were selected because ventilation, metabolic rate, and body and brain weights are comparable at this age and there are no large fluctuations in plasma hormone levels. Females, relative to males, had smaller areas in the A2 region and parts of the NTS. Counts and densities for ER alpha were greater in females than males in almost all regions studied. In contrast sex differences in ER beta were found in fewer nuclei, but in those higher counts and densities were noted in females. In general, ER beta-positive neurons in the brainstem regions examined were less prevalent than ER alpha neurons. Thus, in weanling rats sex affected ER alpha and ER beta neuronal densities in brainstem regions associated with cardiopulmonary regulation that may be responsible for sex differences in control of breathing.