A Higher Proportion of Metabolic Syndrome in Chinese Subjects with Sleep-Disordered Breathing: A Case-Control Study Based on Electrocardiogram-Derived Sleep Analysis

Association of self-reported and objective sleep disturbance with the spectrum of gastroesophageal reflux disease

STUDY OBJECTIVES

The relationship between obstructive sleep apnea (OSA) and gastroesophageal reflux disease (GERD) is complex. We aimed to determine the association of self-reported and objective sleep parameters with diverse manifestations of the GERD spectrum.

METHODS

We prospectively recruited 561 individuals who underwent an electrocardiogram-based cardiopulmonary coupling for OSA screening during a health check-up. All participants received the Reflux Disease Questionnaire and an upper endoscopy to determine the presence of troublesome reflux symptoms and erosive esophagitis (EE). Sleep quality was evaluated by the Pittsburgh Sleep Quality Index and sleep dysfunction was defined as a Pittsburgh Sleep Quality Index score > 5. OSA was defined as a cardiopulmonary coupling-derived apnea-hypopnea index exceeding 15 events/h. Comparisons were made between participants on the GERD spectrum with respect to their various self-reported and objective sleep parameters.

RESULTS

Among the 277 patients with GERD (49.4%), 198 (35.3%) had EE. Patients with GERD had higher PSQI scores (6.99 ± 3.97 vs 6.07 ± 3.73, P = .005) and a higher prevalence of sleep dysfunction (60.6% vs 49.6%, P = .009). Patients with EE had a higher prevalence of OSA (42.9% vs 33.9%, P = .034). Along the GERD spectrum, symptomatic patients with EE had the highest PSQI scores and prevalence of sleep dysfunction (70.7%), while asymptomatic patients with EE had the highest prevalence of OSA (44%).

CONCLUSIONS

Our findings indicate a high prevalence of sleep dysfunction among individuals with GERD. Furthermore, patients on the GERD spectrum are prone to experiencing a range of self-reported and objective sleep disturbances.

CITATION

Hu K-Y, Tseng P-H, Hsu W-C, et al. Association of self-reported and objective sleep disturbance with the spectrum of gastroesophageal reflux disease. J Clin Sleep Med. 2024;20(6):911-920.

Association of allergic rhinitis with persistent obstructive sleep apnea: A secondary analysis of the childhood adenotonsillectomy trial

STUDY OBJECTIVES

Allergic rhinitis (AR) is frequently reported in children suffering from obstructive sleep apnea (OSA). This study aimed to assess whether children with AR are more likely to experience persistent OSA after AT.

METHODS

This study is a secondary analysis of a multi-center randomized clinical trial, the Childhood Adenotonsillectomy Trial. Children were categorized into the AR group or Non-AR group according to AR response. A subgroup analysis was conducted using a logistic regression model.

RESULTS

A total of 372 children (177 boys [47.6%]; median [IQR] age, 6.0 [5.0-8.0] years) were analyzed. Approximately 25% (93/372) of children presented with AR. Baseline data indicated higher PSQ scores and OSA-18 scores in the AR group. Children with AR demonstrated lower OSA resolution rates after AT (aOR, 0.43; 95% CI, 0.19 to 0.96). However, there was no significant difference in OSA resolution between the AR and Non-AR groups who underwent watchful waiting (aOR, 0.98; 95% CI, 0.50 to 1.93). Also, the AR group was more likely to maintain a PSQ score greater than 0.33 after AT (OR, 2.16; 95% CI, 1.01 to 4.61). There was no significant association between AR and higher follow-up OSA-18 scores after AT and watchful waiting.

CONCLUSIONS

In this secondary analysis, children with AR were more likely to experience persistent OSA, highlighting the importance of effective AR management even post-adenotonsillectomy. A purposefully designed, prospective randomized trial is needed to verify the association between AR and persistent OSA.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00560859.

Risk of Sleep Apnea Is Associated with Abdominal Obesity Among Asian Americans: Comparing Waist-to-Hip Ratio and Body Mass Index

OBJECTIVE

This study examines associations between the risk of sleep apnea and abdominal obesity (assessed by waist-to-hip ratio (WHR)) and general obesity (assessed by body mass index (BMI)) in a sample of Chinese and Korean American immigrants.

METHODS

The dataset included Chinese and Korean participants aged 50-75 who were recruited from primary care physicians' clinics from April 2018 to June 2020 in the Baltimore-Washington D.C. Metropolitan area (n = 394). Abdominal obesity was determined if WHR ≥ 0.9 in men and WHR ≥ 0.85 in women. General obesity was determined if BMI ≥ 30. The risk of sleep apnea was determined by using the Berlin questionnaire. Poisson regression models examined associations between sleep apnea risk and obesity. Models controlled for socio-demographic risk factors.

RESULTS

Twelve percent of the study participants were classified as a high risk for sleep apnea, and 75% had abdominal obesity whereas 6.4% had general obesity. High risk of sleep apnea was positively associated with abdominal obesity (PR = 1.31, 95% CI: 1.17-1.47) and general obesity (PR = 2.19, 95% CI: 0.90-5.32), marginally significant at p < 0.1).

CONCLUSIONS

Chinese and Korean immigrants living in the USA who are at high risk of sleep apnea have higher abdominal obesity, even after accounting for sociodemographic characteristics. Abdominal obesity may be a better indicator than general obesity when examining the risk of sleep apnea among Asian Americans.

INFORMATION ON CLINICAL TRIAL

Name: Screening To Prevent ColoRectal Cancer (STOP CRC) among At-Risk Asian American Primary Care Patients NCT Number: NCT03481296; Date of registration: March 29, 2018 URL: https://clinicaltrials.gov/ct2/show/NCT03481296?term=Sunmin+Lee&draw=2&rank=1.

Global trends and hotspots on childhood obstructive sleep apnea: a 10-year bibliometric analysis

Background

Obstructive sleep apnea (OSA) is children's most common sleep-related breathing disorder. It may develop a wide range of severe complications if not diagnosed promptly and treated effectively. However, Childhood OSA has not specifically been analyzed using a bibliometric approach.

Methods

We respectively collected the research results of childhood OSA from 2013 to 2022 through Web of Science and PubMed. Vosviewer, CiteSpace, and bibliometric online analysis platforms were used for visualizing and analyzing the literature. The MeSH terms were bi-clustered using the Bibliographic Item co-occurrence Matrix Builder (BICOMB) and graph clustering toolkit (gCLUTO) to identify the hotspots.

Results

4022 publications were finally identified on childhood OSA from 2013 to 2022. The United States has the largest number of publications (1902), accounting for 47.29%. University of Cincinnati is the most productive organization (196), followed by the University of Pennsylvania (151). The most prolific journal was the International Journal of Pediatric Otorhinolaryngology, with 311 documents published. In comparison, Pediatrics is the most cited journal (6936). Gozal D ranked highest among all authors in publication (192). Burst detection shows continuous positive airway pressure, Robin sequence, and nocturnal oximetry are recent keywords of great interest to researchers. Five hotspots were identified by co-word biclustering.

Conclusion

Research over the past ten years has been fruitful, establishing the foundation for childhood OSA. Clusters (0-4) of high-frequency Major Mesh topics have attracted extensive attention. Evaluation and treatment methods of childhood OSA remain major focuses. We believe this article will provide other researchers with new directions and may contribute to a future breakthrough in this field.

Effect of different head-high lateral extubation on adverse reactions in the peri-extubation period of pediatric OSAS surgery under general anesthesia

BACKGROUND

Children with OSAS are prone to various airway complications during tracheal extubation after tonsillectomy and adenoidectomy due to oropharyngeal secretions and oozing blood. However, few studies have examined the effect of position on airway complications after tracheal extubation in children with OSAS. The aim of this study was to investigate the appropriate position for extubation in children with OASA.

METHODS

A total of 459 children aged 3-14 years with OSAS who underwent tonsillectomy and adenoidectomy were recruited for this study. All children were treated with the same surgical approach and standard anesthesia methods of induction of anesthesia, tracheal intubation and maintenance of anesthesia. At the end of surgery, the children were delivered to the post anesthesia care unit and randomly divided into three groups: Group A: Head-high 0° in lateral position; Group B: Head-high 15° in lateral position; Group C: Head-high 30° in lateral position. The main outcomes of this study were the pulse oxygen saturation (SpO₂) and the Sedation-Agitation Scale (SAS) scores of the children after extubation, the outflow of oral-nasal secretions and the respiratory complications. Secondary outcomes were blood pressure, heart rate, end-respiratory carbon dioxide, respiratory rate, and post-operative awakening time of the children in three groups.

RESULTS

Data from a total of 423 children were statistically analyzed, 141 in Group A, 142 in Group B, and 140 in Group C. The main results showed a significant decrease in choking response after extubation in Group B (46.5%) and Group C (40.7%) compared to Group A (60.3%) (P < 0.05). The SAS score for postoperative agitation was higher in Group A (4.6 [Formula: see text] 0.9) than in Group B (4.4 [Formula: see text] 0.7) and Group C (4.3 [Formula: see text] 0.6) (P < 0.05). Also the SpO₂ after extubation was higher in Group B (97.2%) and Group C (97.1%) than in Group A (95.8%) (P < 0.05). In contrast, there was no difference in the occurrence of respiratory complication and postoperative agitation in children between Group B and Group C (all P > 0.05). In addition, there was no difference in the amount of oral-nasal secretions among the children in the three groups (all P > 0.05).

CONCLUSION

The head-high 15° lateral position and head-high 30° lateral position can reduce the incidence of airway complications and agitation and provide safe and comfortable extubation conditions for children during the peri-extubation period after tonsillectomy and adenoidectomy, which has certain clinical guidance value.

TRIAL REGISTRATION

Registration Number: NO.ChiCTR2200055835(20,01,2022) https://www.chictr.org.cn.

Debates in pediatric obstructive sleep apnea treatment

Pediatric obstructive sleep apnea (OSA) is among the most common sleep-disordered breathing (SDB) diseases in children. Its high prevalence and multiple systemic complications lead to increasing numbers of children and families affected by OSA. Timely diagnosis and effective intervention in children with this condition is extremely important in improving their prognosis. The major approaches in the treatment of OSA in children are to eliminate the causes of upper airway obstruction and prevent and treat complications. Considering the specific individual differences in children's growth and development, as well as the diversity of etiologies in children's OSA, pediatric treatment strategies need to be precise, multidisciplinary, and individualized. First-line clinical treatment consists of surgical (adenotonsillectomy) and non-surgical therapies [including anti-inflammatory medications and non-invasive ventilation (NIV)]. However, a considerable controversy exists concerning the indications, treatment standards, and the evaluation of the efficacy of the aforementioned treatment methods. In this review, reviews and assessment of literature studies and multidisciplinary clinical experience were performed to analyze the application of each treatment and discuss controversial issues and future research directions. We suggest that the above interventions should be tailored to each child's needs, comorbidities, and the availability and expertise of the practitioner. The ideal case is when a multidisciplinary team of doctors together with the patients and their parents, or guardians, have a thorough discussion regarding the benefits and risks of all available treatment options and all agree on an effective treatment plan.

Time-dependence and comparison of regional and overall anthropometric features between Asian and Caucasian populations with obstructive sleep apnea: a cumulative meta-analysis

Background

Anthropometric measurements are simple and reachable tools for self-evaluating and screening patients with a high risk of obstructive sleep apnea (OSA). However, the accumulated relationship of obesity on the anthropometric characteristics of OSA is not well understood. The aim of the study was to show the time-dependent trend of OSA patients and compare overall and regional anthropometric between two ethnicities.

Methods

A cumulative meta-analysis was performed to assess obesity metrics in patients with and without OSA between Asians and Caucasians. We searched PubMed, Web of Science, Embase, and Scopus up to Jun 2020. Included studies used body mass index (BMI), neck circumference (NC), waist circumference (WC) and waist-to-hip ratio (WHR) as measures of anthropometric features in the adult OSA population and controls, utilized in-lab polysomnography or home sleep testing with apnea-hypopnea index (AHI) or respiratory disturbance index (RDI) classification, reported ethnicity/race, and were published in English. Any studies lacking one of these criteria or sufficient data were excluded.

Results

Forty studies with a total of 19,142 subjects were investigated. Comparison of changes between patients with and without OSA showed that OSA patients had a higher BMI [mean difference (MD) 3.12, 95% confidence interval (CI): 2.51–3.73], NC (MD 3.10, 95% CI: 2.70–3.51), WC (MD 9.84, 95% CI: 8.42–11.26) and waist-hip ratio (MD 0.04, 95% CI: 0.03–0.05) than the control subjects. The accumulated time-dependent increase in population with OSA was significantly apparent with all anthropometric features. BMI increased from 2000 (MD 0.50) to 2012 (MD 3.08–3.48) and remained stable afterwards (MD 2.70–3.17), NC increased from 2000 (MD 0.40) to 2013 (MD 3.09) and remained stable afterwards too (MD 3.06–3.21). WC increased from 2000 (MD 2.00) to 2012 (MD 9.37–10.03) and also remained stable afterwards (MD 8.99–9.84). WHR was stable from 2000 to 2004 with an MD of 0.01 and then stable from 2007 onwards with an increased MD of 0.03–0.04. Compared with Caucasian patients, Asian patients had lower obesity relevant variates.

Conclusions

BMI, NC, WC and WHR are associated with OSA in both ethnic groups. Anthropometry for overall and regional obesity could facilitate differentiation of patients with OSA from individuals without OSA by ethnicity.

Electrocardiogram-based sleep analysis for sleep apnea screening and diagnosis

PURPOSE

Despite the increasing number of research studies of cardiopulmonary coupling (CPC) analysis, an electrocardiogram-based technique, the use of CPC in underserved population remains underexplored. This study aimed to first evaluate the reliability of CPC analysis for the detection of obstructive sleep apnea (OSA) by comparing with polysomnography (PSG)-derived sleep outcomes.

METHODS

Two hundred five PSG data (149 males, age 46.8 ± 12.8 years) were used for the evaluation of CPC regarding the detection of OSA. Automated CPC analyses were based on ECG signals only. Respiratory event index (REI) derived from CPC and apnea-hypopnea index (AHI) derived from PSG were compared for agreement tests.

RESULTS

CPC-REI positively correlated with PSG-AHI (r = 0.851, p < 0.001). After adjusting for age and gender, CPC-REI and PSG-AHI were still significantly correlated (r = 0.840, p < 0.001). The overall results of sensitivity and specificity of CPC-REI were good.

CONCLUSION

Compared with the gold standard PSG, CPC approach yielded acceptable results among OSA patients. ECG recording can be used for the screening or diagnosis of OSA in the general population.

Obstructive sleep apnea: personal, societal, public health, and legal implications

Introduction Obstructive sleep apnea (OSA) is a widely prevalent sleep-related breathing disorder, which leads to several life-threatening diseases. OSA has systemic effects on various organ systems. Untreated OSA is associated with long-term health consequences including hypertension, heart disease, diabetes, depression, metabolic disorders, and stroke. In addition, untreated OSA is reported to be associated with cognitive dysfunction, impaired productivity at the workplace and in an increased risk of motor vehicle accidents (MVAs) resulting in injury and fatality. Other consequences of OSA include, but are not limited to, impaired vigilance, daytime somnolence, performance deficits, morning headaches, mood disturbances, neurobehavioral impairments, and general malaise. Additionally, OSA has become an economic burden on most health systems all over the world. Many driving license regulations have been developed to reduce MVAs among OSA patients. Methods Studies of the personal, societal, public health, and legal aspects of OSA are reviewed. Data were collected through the following databases: MEDLINE, Google Scholar, Scopus, SAGE Research Methods, and ScienceDirect. Conclusion OSA leads to worsening of patients' personal relationships, decreasing work productivity, and increasing occupational accidents as well as MVAs. The costs of undiagnosed and untreated OSA to healthcare organizations are excessive. Thus, proper management of OSA will benefit not only the patient but will also provide widespread benefits to the society as a whole.

Systematic investigation of childhood sleep-disordered breathing (SDB) in Beijing: validation of survey methodology

OBJECTIVE

To systematically investigate and validate the survey methodology for the epidemiological study of childhood sleep-disordered breathing (SDB) in mainland China using the Mandarin version of the Pediatric Sleep Questionnaire-Sleep-Related Breathing Disorder (PSQ-SRBD).

DESIGN

A cross-sectional study using randomised, stratified, multistage, cluster sampling method.

SETTING

A total of 11 kindergartens, 7 primary schools and 8 middle schools from 7 districts of Beijing, China.

PARTICIPANTS

A total of 9198 children with valid questionnaires (4736 boys and 4462 girls; age range 3.0-14.4 years) were included.

PRIMARY AND SECONDARY OUTCOME MEASURES

Data on sociodemographic characteristics and PSQ-SRBD were collected. The score on PSQ-SRBD and the included factors were calculated with the effective data after data cleaning. Logistic regression and factor analysis with the principal components method were used to evaluate the validity of the questionnaire; reliability was assessed by retesting 5% of the respondents after 2±4 weeks of the initial test, and the intraclass correlation coefficient was calculated.

RESULTS

The effective response rate of80.54% matched the sociodemographic characteristics of the respondents with respect to age group ratio and sex ratio in Beijing. With regard to construct validity of the PSQ-SRBD, the item score, except that of 'delayed growth', was highly correlated to the SRBD score as assessed by the logistic regression model. The exploratory factor analysis displayed a credible construct validity, with majority of the items grouped as the original dimensions. The test-retest reliability coefficient of each dimension's score ranged from 0.758 to 0.901, with an SRBD score of 0.730 indicating significant retest reliability.

CONCLUSIONS

This study conducted and validated a successful survey methodology for investigation of childhood SDB in Beijing, China. The questionnaire demonstrated credible construct validity and retest reliability, thereby supporting the applicability and generalisability of the PSQ-SRBD in a large epidemiological survey of childhood SDB in China.

Associations Between the Prevalence of Metabolic Syndrome and Sleep Parameters Vary by Age

OBJECTIVE

To examine whether the relationship between the metabolic syndrome (MetS) and various sleep parameters [sleep duration, symptoms of sleep-disordered breathing (SDB), and sleep disturbances] varies by age.

METHODS

Waist circumference, blood pressure, triglycerides, high-density lipoprotein cholesterol, and fasting glucose were used to determine MetS status in a cohort (N = 19,691) of middle-aged (aged 45-64 years) and older (aged ≥65 years) subjects. Habitual sleep duration (short, ≤6 h/day; normal, 7-8 h/day; and long ≥9 h/day), sleep disturbances (such as problems with falling and staying asleep), and symptoms of sleep-disordered breathing (SDB, such as snoring and sleep apneas) were measured by questionnaires.

RESULTS

Among the participants, 4,941 subjects (25.1%) fulfilled the criteria for MetS. In the entire sample, both short and long sleep durations were associated with higher prevalence of MetS as compared to normal sleep duration. When stratified by age, a similar pattern was observed for middle-aged subjects (<65 years old; prevalence ratio (PR) [95% CI], 1.13 [1.06-1.22] for short sleep and 1.26 [1.06-1.50] for long sleep duration). In contrast, in older individuals (≥65 years old), only long sleep duration was linked to a higher prevalence of MetS (1.26 [1.12-1.42]; P < 0.01 for sleep duration × age). In the entire cohort, having at least one SDB symptom ≥4 times per week was linked to an increased prevalence of MetS; however, the PR was higher in middle-aged subjects compared with older subjects (1.50 [1.38-1.63] vs. 1.36 [1.26-1.47], respectively; P < 0.001 for SDB × age). Finally, independent of subjects' age, reports of sleep disturbances (i.e., at least one symptom ≥4 times per week) were associated with a higher likelihood of having MetS (1.12 [1.06-1.18]; P > 0.05 for sleep disturbance × age).

CONCLUSION

Our results suggest that age may modify the associations between some sleep parameters and the prevalence of MetS.

Quality and readability of online information resources on insomnia

The internet is a major source for health information. An increasing number of people, including patients with insomnia, search for remedies online; however, little is known about the quality of such information. This study aimed to evaluate the quality and readability of insomnia-related online information. Google was used as the search engine, and the top websites on insomnia that met the inclusion criteria were evaluated for quality and readability. The analyzed websites belonged to nonprofit, commercial, or academic organizations and institutions such as hospitals and universities. Insomnia-related websites typically included definitions (85%), causes and risk factors (100%), symptoms (95%), and treatment options (90%). Cognitive behavioral therapy for insomnia (CBT-I) was the most commonly recommended approach for insomnia treatment, and sleep drugs are frequently mentioned. The overall quality of the websites on insomnia is moderate, but all the content exceeded the recommended reading ease levels. Concerns that must be addressed to increase the quality and trustworthiness of online health information include sharing metadata, such as authorship, time of creation and last update, and conflicts of interest; providing evidence for reliability; and increasing the readability for a layman audience.

Increased risk of Eustachian tube disorders in patients with sleep-disordered breathing

Sleep-disordered breathing (SDB) and Eustachian tube disorders (ETDs) share the same risk factors. The specific aim of this study was to determine the correlation between these 2 conditions and to determine whether treatments for SDB reduce the risk of ETD.This is a retrospective and large population-based cohort study. According to Taiwan's National Health Insurance Research Database, out of 1,000,000 insured patients, 24,251 patients were newly diagnosed with SDB from year 2000 through 2009. The control group for this study comprised 96,827 patients without SDB who were randomly selected from the same database at a ratio of 1:4, frequency matched for sex, age, and index year of SDB. The incidence of developing ETD was compared between these 2 groups; the main covariates were demographic data, interventions, and medical comorbidities.There was an increased risk of developing ETD among the SDB cohort compared with the control group (hazard ratio = 1.51, 95% confidence interval = 1.41-1.63). Compared with SDB patients who did not receive treatment, those who received the treatment, that is, pharyngeal or nasal surgery, CPAP, or multiple modalities (both surgery and CPAP), had a significantly reduced risk of developing ETD.This study showed that patients with SDB are at an increased risk of developing ETD and other comorbidities. The risk of developing ETD can be reduced by implementing prompt treatment for SDB. Multidisciplinary evaluation including ETD should be conducted in the management of patients presenting with SDB.

Evaluation of pulse oximeter derived photoplethysmographic signals for obstructive sleep apnea diagnosis

High prevalence of obstructive sleep apnea (OSA) has increased the demands for more convenient and accessible diagnostic devices other than standard in-lab polysomnography (PSG). Despite the increasing utility of photoplethysmograph (PPG), it remains understudied in underserved populations. This study aimed to evaluate the reliability of a standard pulse oximeter system with an automated analysis based on the PPG signal for the diagnosis of OSA, as compared with PSG derived measures.Consecutive out-patients with suspect OSA completed a PPG monitoring simultaneous with an overnight in-lab standard PSG. Forty-nine OSA patients (38 males, age 43.5 ± 16.9 years, BMI 26.9 ± 0.5 kg/m) were included in this study. Automated analyses were based on PPG and oximetry signals only. The PPG calculated measures were compared with PSG derived measures for agreement tests.Respiratory events index derived from PPG significantly correlated with PSG-derived apnea-hypopnea index (r = 0.935, P < .001). The calculation of total sleep time and oxygen desaturation index from PPG and PSG also significantly correlated (r = 0.418, P = .003; r = 0.933, P < .001, respectively). Bland-Altman plots showed good agreement between the PPG and the PSG measures. The overall sensitivity and specificity of PPG are good, especially in moderate and severe OSA groups.The tested PPG approach yielded acceptable results compared to the gold standard PSG among moderate to severe OSA patients. A pulse oximeter system with PPG recording can be used for the diagnosis or screening of OSA in high risk population.

Cardiac Autonomic Alteration and Metabolic Syndrome: An Ambulatory ECG-based Study in A General Population

Metabolic syndrome (MetS) has been associated with chronic damage to the cardiovascular system. This study aimed to evaluate early stage cardiac autonomic dysfunction with electrocardiography (ECG)-based measures in MetS subjects. During 2012–2013, 175 subjects with MetS and 226 healthy controls underwent ECG recordings of at least 4 hours starting in the morning with ambulatory one-lead ECG monitors. MetS was diagnosed using the criteria defined in the Adult Treatment Panel III, with a modification of waist circumference for Asians. Conventional heart rate variability (HRV) analysis, and complexity index (CI_1–20) calculated from 20 scales of entropy (multiscale entropy, MSE), were compared between subjects with MetS and controls. Compared with the healthy controls, subjects with MetS had significantly reduced HRV, including SDNN and pNN20 in time domain, VLF, LF and HF in frequency domain, as well as SD2 in Poincaré analysis. MetS subjects have significantly lower complexity index (CI_1–20) than healthy subjects (1.69 ± 0.18 vs. 1.77 ± 0.12, p < 0.001). MetS severity was inversely associated with the CI_1–20 (r = −0.27, p < 0.001). MetS is associated with significant alterations in heart rate dynamics, including HRV and complexity.