Analysis of cardiac autonomic modulation in obese and eutrophic children

Autonomic Function in Obese Children and Adolescents: Systematic Review and Meta-Analysis

Background: Obesity is invariably accompanied by autonomic dysfunction, although data in pediatric populations are conflicting. Methods: We conducted a systematic review and meta-analysis of 12 studies (totaling 1102 participants) comparing obese and normal-weight subjects (5-18 years of age), defined as body mass index >95th or <85th percentile, respectively. Using a random-effects model, we report the standardized mean differences (SMD) of sympathetic and vagal indices of heart rate variability. Results: Autonomic dysfunction was present in the obesity group, based on the average SMD in the standard deviation of sinus intervals (at -0.5340), and on the ratio of low (LF)- to high (HF)-frequency spectra (at 0.5735). There was no difference in sympathetic activity, but the heterogeneity among the relevant studies weakens this result. SMD in HF (at 0.5876), in the root mean square of successive differences between intervals (at -0.6333), and in the number of times successive intervals exceeded 50 ms divided by the total number of intervals (at -0.5867) indicated lower vagal activity in the obesity group. Conclusions: Autonomic dysfunction is present in obese children and adolescents, attributed to lower vagal activity. Further studies are needed in various pediatric cohorts, placing emphasis on sympathetic activity.

Predictors of Cardiac Autonomic Dysfunction in Obesity-Related Hypertension

INTRODUCTION

Cardiac Autonomic Dysfunction (CAD) is an overlooked cardiovascular risk factor in individuals with obesity-related hypertension. Despite its clinical significance, there is a notable lack of clarity regarding the pathophysiological correlates involved in its onset and progression.

AIM

The present study aimed to identify potential predictors of CAD in obesity-related hypertension.

METHODS

A total of 72 participants (34 men and 38 women) were enrolled. Comprehensive evaluations were conducted, including cardiac autonomic function assessments, body composition estimation and biochemical analysis. Participants were categorized as CAD-positive or CAD-negative based on Ewing's criteria for autonomic dysfunction. Univariate logistic regression analysis was performed to identify potential predictors for CAD. Multivariate logistic regression models were further constructed by adjusting clinically relevant covariates to identify independent predictors of CAD.

RESULTS

Multivariate logistic regression analysis revealed that resting heart rate (HRrest), (odds ratio, confidence interval: 0.85, 0.78-0.93; p = 0.001) and percentage body fat (BF%), (odds ratio, confidence interval: 0.78, 0.64-0.96; p = 0.018) were significant independent predictors of CAD. Receiver Operating Characteristic curve analysis depicted optimal cut-off values for HRrest and BF% as > 74.1 bpm and > 33.6%, respectively. Multicolinearity analysis showed variance inflation factors (VIF) below the cautionary threshold of 3.

CONCLUSIONS

The HRrest and BF% emerged as significant independent predictors of CAD in obesity-related hypertension. Therapeutic strategies should target HRrest < 74.1 bpm and BF% < 33.6% to mitigate CAD risk in this population. Future trials are required to establish causal relationships and may consider additional confounding variables in obesity-related hypertension.

Cardiac autonomic dysfunction in school age children with overweight and obesity

BACKGROUND AND AIMS

We investigated cardiac autonomic function in overweight and obese school-age children.

METHODS AND RESULTS

Quantitative cross-sectional study conducted with children (n = 110) of both genders. Children were divided by normal weight (NW; n = 54), overweight (OW; n = 24) and obese (OB; n = 32). Systolic (SBP) and diastolic (DBP) blood pressure and electrocardiograms were recorded and analyzed for heart rate and the heart rate variability (HRV) in time (SDRR, RMSSD, PRR50, SD1 and SD2) and frequency domains (HF, LF and LF/HF). The OB group presented higher SBP (p ≤ 0.01) and DBP (p ≤ 0.01). For HRV, the OB group had a lower PRR50 (p ≤ 0.01) and HF (p ≤ 0.01), associated with higher LF (p ≤ 0.01). Moderate negative correlations were found between the HF, BMI (r = -0.37; p ≤ 0.01) and WC (r = -0.38; p ≤ 0.01). Positive moderate correlation were found between LF, LF/HF and BMI (LF: r = 0.32; p ≤ 0.01; LF/HF: r = 0.31; p ≤ 0.01) and WC (LF: r = 0.34; p ≤ 0.01; LF/HF: = 0.34; p ≤ 0.01). Multiple linear regression showed a positive association between body fat and the SDRR (β: 0.48; CI: 0.2-4.2; p = 0.02). No differences were observed in cardiac electrical activity.

CONCLUSION

Children with obesity but not overweight presented higher blood pressure and cardiac autonomic dysfunction, with sympathetic predominance on the heart rate. This fact was positively correlated with BMI and may be considered an important marker for cardiovascular risk in children.

Anthropometric Determinants of Respiratory Sinus Arrhythmia in Children

Background: The study was conducted to investigate the implications of anthropometry in school-aged children on the degree of respiratory sinus arrhythmia observed in clinical settings. Methods: In a cohort study, 626 healthy children (52% male) aged 10.8 ± 0.5 years attending primary school in a single town underwent a 12-lead electrocardiogram coupled with measurements of height, weight and blood pressure. Indices of respiratory sinus arrhythmia (pvRSA, RMSSD, RMSSDc) were derived from semi-automatic measurements of RR intervals. Height, weight, BMI, blood pressure as well as waist and hip circumferences were compared between subjects with rhythmic heart rate and respiratory sinus arrhythmia, and correlations between indices of sinus arrhythmia and anthropometry were investigated. Results: Respiratory sinus arrhythmia was recognized in 43% of the participants. Subjects with sinus arrhythmia had lower heart rate (p < 0.001), weight (p = 0.009), BMI (p = 0.005) and systolic (p = 0.018) and diastolic (p = 0.004) blood pressure. There were important inverse correlations of heart rate and indices of sinus arrhythmia (r = −0.52 for pvRSA and r = −0.58 for RMSSD), but not the anthropometry. Conclusion: Lower prevalence of respiratory sinus arrhythmia among children with overweight and obesity is a result of higher resting heart rate observed in this population.

Breakfast skipping and cardiometabolic risk factors in adolescents: Systematic review

OBJECTIVE

To systematically review the results of the association between breakfast skipping and cardiometabolic risk factors in adolescents.

METHODS

The articles were searched in May 2020 from PubMed, Virtual Health Library, Scopus, Web of Science and Scientific Electronic Library Online (SciELO). The review included observational studies conducted with adolescents (10-19 years old), which estimated the association of breakfast skipping with at least one outcome (markers of body adiposity, blood pressure, serum lipid and glucose levels). Regarding the risk of bias, the articles were evaluated using the Research Triangle Institute (RTI) Item Bank on bias risk and accuracy of observational studies. The quality of the evidence was assessed by the Grade rating.

RESULTS

A total of 43 articles involving 192,262 participants met the inclusion criteria and were considered in this review. The prevalence of breakfast skipping ranged from 0.7% to 94% and 60.5% of studies were classified with low risk of bias. The significant association between breakfast skipping and cardiometabolic risk factors was found in twenty-nine cross-sectional articles (n = 106,031) and four longitudinal articles (n = 5,162) for excess adiposity, in three articles (n = 8,511) for high total cholesterol levels, low-density lipoprotein and triglycerides, and in three studies (n = 6,303) for high blood pressure levels. However, there was no significant association between breakfast skipping and glycemic profile. According to the Grade rating, all the associations had low quality of evidence.

CONCLUSION

The results of this review suggest that breakfast skipping is associated with cardiometabolic risk factors in adolescents aged 10 to 19 years. However, considering the low quality of the evidence, the present results should be interpreted carefully. In addition, our findings highlight the importance of standardizing the definition of breakfast skipping and that more prospective studies are needed to determine how skipping breakfast can affect cardiometabolic risk factors in the long time.

Relationship between heart rate variability and body mass index: A cross-sectional study of preschool children

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Heart rate variability and BMI are inversely related in preschool children.

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One unit increase in BMI resulted in a reduction in RMSSD(ln) of 0.06%

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Age, sex and physical activity levels did not influence this relationship.

Reduced heart rate variability (HRV) is associated with overweight and obesity in adults. However, little is known about this relationship in early childhood. We investigated the relationship between resting vagally-mediated HRV and body mass index (BMI) in Australian preschool children. Children were recruited from 13 non-government early learning centres located in Queensland and New South Wales, Australia. From this population-based sample, data from 146 healthy children (58 females) between 3 and 5 years of age (mean age 4.35 ± 0.44 years) were analysed. BMI was calculated from child body weight and height. Physical activity was recorded using an Actigraph wGT3x accelerometer worn at the waist of participants over 3 consecutive days. A Polar H10 chest strap measured seated, resting RR intervals for the calculation of HRV with the root mean square of successive differences (RMSSD) reflecting vagally-mediated activity. The relationship between HRV and BMI was analysed using a linear mixed model adjusted for age, sex and physical activity. Analysis revealed that RMSSD (ln) demonstrated a significant inverse relationship with BMI (β = -0.06; 95% CI = -0.12 – −0.01; p = 0.032), and the model accounted for 23% of the variance in RMSSD (ln). Notably, a one unit increase in BMI resulted in a reduction in RMSDD (ln) of 0.06. This investigation demonstrated evidence for a significant inverse linear relationship between vagally-mediated HRV and BMI in 3 – 5-year-old Australian children, similar to that of adults. Furthermore, this relationship was independent of age, sex and physical activity levels. Results may indicate that the cardiometabolic health of preschool children is, in part, influenced by the relationship between vagally-mediated HRV and weight status.

Heart Rate Variability Reactivity to Food Image Stimuli is Associated with Body Mass Index

Appetitive control is driven by the hedonic response to food and affected by several factors. Heart rate variability (HRV) signals have been used to index autonomic activity and arousal levels towards visual stimuli. The current research aimed to examine the influence of body mass index (BMI), disordered eating behaviors, and sex on the HRV reactivity to food in a nonclinical sample. Thirty-eight healthy male and sixty-one healthy female participants completed questionnaires assessing disordered eating symptoms. HRV was recorded when the participants received visual stimuli of high-calorie food, neutral and negative emotional signals. Generalized estimating equation models were used to investigate the associations between HRV, BMI, disordered eating behaviors, and sex across the three stimulus types. Male participants demonstrated a higher ratio of low-frequency power to high-frequency power (LF/HF) than females across all the stimulus types. An increase in LF/HF reactivity to food signals was observed in all the study subjects. The moderation effect of BMI on LF/HF in response to food signals was also observed. Our study suggests that body weight may play a role in the interaction between sympathetic activity and food stimuli; however, how the interaction between sympathetic activity and food stimuli contributes to diet control warrants further investigation.

Evaluation of autonomic modulation of lung function and heart rate in children with cystic fibrosis

The autonomic nervous system (ANS) plays an important role in modulating bronchial smooth muscle contractility, which is altered in cystic fibrosis (CF). A convenient approach to probe ANS regulation is the quantitative analysis of heart rate variability (HRV). The purpose of this study was to evaluate ANS regulation in children with CF and to investigate the influence of colonization by Pseudonomas aeruginosa via assessment of HRV in colonized CF (CCF) children and noncolonized CF (NCCF) children. Sixteen children with CF (7 CCF and 9 NCCF) and seven healthy age-matched control children were enrolled in the study. Heart rate was recorded for 10 min at rest in the supine and standing positions and HRV analysis was carried out using autoregressive spectral analysis. The CCF group was characterized by lower forced expiratory volume than NCCF, indicating an impairment of respiratory function. The HRV parameters further confirmed the possible sympathetic overactivity in CCF. Children with CF exhibited hyperactivity of the sympathetic nervous system. In particular, the CCF group presented a greater impairment of ANS modulation. Both CCF and NCCF children showed lower supine vagal activation in the HRV indices related to sympathetic activation and reduction of indices indicating vagal activity with the postural change from supine to standing when compared to the NCCF group.

The Relationship between Autonomic Regulation of Cardiovascular Function and Body Composition

Background

We investigated whether the results of autonomic function tests correlate with body composition and shape in healthy young people.

Methods

We conducted cardiovascular reflex tests (heart rate [HR] and blood pressure [BP] responses to the Valsalva maneuver and HR response to deep breathing) and the tilt table test with 32 subjects (19 males; mean age, 22.1±1.9 years). Participants also completed an anthropometric measurement sequence (weight; height; upper arm, hips, and waist circumference; triceps and subscapular skinfold), bioelectric impedance testing, and hand grip strength measurements.

Results

Markers of obesity, other anthropometric measures, functional measures, and the basal metabolic rate (BMR) were significantly positively correlated with systolic BP (SBP) and diastolic BP (DBP) in both the supine and tilted positions. There was a positive correlation between the difference in HR (ΔHR) between the tilt and supine body positions and markers of obesity, the functional marker of dominant handgrip strength, and BMR. Participants with a body mass index (BMI) <25 kg/m² had significantly lower median values of ΔHR, DBP in the tilt-test, SBP at rest, and SBP in the tilt-test than participants who had a BMI ≥25 kg/m² (10.55 vs. 21.95 bpm, P=0.003; 77.55 vs. 90.05 mmHg, P=0.045; 113.45 vs. 140.55 mmHg, P=0.013; 117.00 vs. 135.25 mmHg, P=0.006, respectively). Body fat percentage was identified as an independent positive predictor (β=0.993; 95% confidence interval [CI], 0.070 to 1.916; P=0.036) and body water percentage was an independent negative predictor of tilted SBP (β=-1.370; 95% CI, -2.634 to 0.106; P=0.035).

Conclusion

High sympathetic activity, as evaluated by cardiovascular regulation, correlates with a high share of adipose tissue in young healthy persons.

Respiratory Sinus Arrhythmia Mechanisms in Young Obese Subjects

Autonomic nervous system (ANS) activity and imbalance between its sympathetic and parasympathetic components are important factors contributing to the initiation and progression of many cardiovascular disorders related to obesity. The results on respiratory sinus arrhythmia (RSA) magnitude changes as a parasympathetic index were not straightforward in previous studies on young obese subjects. Considering the potentially unbalanced ANS regulation with impaired parasympathetic control in obese patients, the aim of this study was to compare the relative contribution of baroreflex and non-baroreflex (central) mechanisms to the origin of RSA in obese vs. control subjects. To this end, we applied a recently proposed information-theoretic methodology - partial information decomposition (PID) - to the time series of heart rate variability (HRV, computed from RR intervals in the ECG), systolic blood pressure (SBP) variability, and respiration (RESP) pattern measured in 29 obese and 29 age- and gender-matched non-obese adolescents and young adults monitored in the resting supine position and during postural and cognitive stress evoked by head-up tilt and mental arithmetic. PID was used to quantify the so-called unique information transferred from RESP to HRV and from SBP to HRV, reflecting, respectively, non-baroreflex and RESP-unrelated baroreflex HRV mechanisms, and the redundant information transferred from (RESP, SBP) to HRV, reflecting RESP-related baroreflex RSA mechanisms. Our results suggest that obesity is associated: (i) with blunted involvement of non-baroreflex RSA mechanisms, documented by the lower unique information transferred from RESP to HRV at rest; and (ii) with a reduced response to postural stress (but not to mental stress), documented by the lack of changes in the unique information transferred from RESP and SBP to HRV in obese subjects moving from supine to upright, and by a decreased redundant information transfer in obese compared to controls in the upright position. These findings were observed in the presence of an unchanged RSA magnitude measured as the high frequency (HF) power of HRV, thus suggesting that the changes in ANS imbalance related to obesity in adolescents and young adults are subtle and can be revealed by dissecting RSA mechanisms into its components during various challenges.

Four-second dynamic exercise testing (T4S) for the assessment of cardiac vagal modulation in obese adolescents

BACKGROUND

Reduced vagal activity is often present in obese adolescents. Simple and practical strategies for the assessment of isolate parasympathetic outflow in this population are therefore useful.

OBJECTIVES

To compare the methods derived from heart rate variability (HRV) analysis at rest and 4 s exercise testing (T4S) for the assessment of cardiac parasympathetic modulation in adolescents classified as obese (OB) or with normal weight (NW). Additionally, associations between total and trunk fat versus autonomic modulation determined by the two methods were calculated.

APPROACH

A cross-sectional study was conducted with 50 adolescents (26 OB and 24 NW, 14.7  ±  1.5 years), comparing autonomic indices provided by HRV and T4S. Body fractioning was determined employing dual-energy x-ray absorptiometry (DXA).

MAIN RESULTS

The cardiac vagal index (CVI) obtained from T4S and standard time- and frequency-domain HRV measures were lower in OB versus NW (P  ⩽  0.05). Correlations between CVI and HRV indices of cardiac vagal modulation were as follows: CVI versus RMSSD (r  =  0.44; P  =  0.003); CVI versus pNN50 (r  =  0.32; P  =  0.04); CVI versus HF (r  =  0.35; P  =  0.02). Associations between body fat, android/gynoid ratio, and percent trunk fat versus CVI were of similar magnitude and direction than versus HRV indices.

SIGNIFICANCE

The T4S proved to be adequate to detect cardiac parasympathetic impairment in obese adolescents. Moreover, vagal modulation assessed by HRV and T4S inversely correlated with visceral adipose tissue. These findings along with the simplicity and safety of the T4S should encourage its use in the assessment of cardiac parasympathetic modulation in obese pediatric populations.

Longitudinal associations between overweight/obesity and stress biology in low-income children

Background/Objectives

Associations between overweight and altered stress biology have been reported cross-sectionally during childhood, but it is unclear whether overweight precedes altered stress biology or if altered stress biology predicts greater likelihood of overweight over time. The current longitudinal study investigates associations between overweight/obesity, salivary alpha amylase and cortisol morning intercept, diurnal slope, and reactivity to social stress in a cohort of low-income children during preschool and middle childhood.

Subjects/Methods

Children were recruited through Head Start and were observed and followed into middle childhood (N = 257; M = 8.0 years). Height and weight were measured at both time points. Saliva samples were collected across the day and in response to a social challenge at both ages for alpha amylase and cortisol determination.

Results

Cross-lagged panel analyses indicated that overweight/obesity at preschool predicted lower morning alpha amylase (β = −0.18, 95% CI: −0.34, −0.03; p = .023), lower morning cortisol (β = −0.22, 95% CI: −0.38, −0.06; p = .006), lower sAA diurnal slope (β = −0.18, 95% CI: −0.34, −0.03; p = .021), and lower cortisol stress reactivity (β = −0.19, 95% CI: −0.35, −0.02; p = .031) in middle childhood. Lower alpha amylase reactivity at preschool was the only biological factor that predicted higher likelihood of overweight/obesity at middle childhood (β = −0.20, 95% CI: −0.38, −0.01; p = .035).

Conclusions

These findings suggest that overweight/obesity may be driving changes in stress biology across early to middle childhood, particularly in down-regulation of morning levels of stress hormones, diurnal sAA slope, and cortisol reactivity to stress, rather than stress biology driving overweight/obesity.

The Role of Heart Rate on the Associations Between Body Composition and Heart Rate Variability in Children With Overweight/Obesity: The ActiveBrains Project

BACKGROUND

Heart rate variability (HRV) is negatively associated with body mass index and adiposity in several populations. However, less information is available about this association in children with overweight and obesity, especially severe/morbid obesity, taking into consideration the dependence of HRV on heart rate (HR).

OBJECTIVES

(1) to examine associations between body composition measures and HRV, (2) to study differences in HRV between children with overweight and severe/morbid obesity; and (3) to test whether relationships and differences tested in objectives 1 and 2, respectively are explained by the dependency of HRV on HR.

METHODS

A total of 107 children with overweight/obesity (58% boys, 10.03 ± 1.13 years) participated in this study. Body composition measures were evaluated by Dual-energy X-ray absorptiometry (DXA). HRV parameters were measured with Polar RS800CX®.

RESULTS

Body composition measures were negatively associated with HRV indicators of parasympathetic activity (β values ranging from -0.207 to -0.307, all p < 0.05). Children with severe/morbid obesity presented lower HRV values with respect to children with overweight/mild obesity in HRV parameters indicators of parasympathetic activity (p = 0.035). All associations disappeared after further adjustment for HR (all p > 0.05).

CONCLUSION

All associations between adiposity/obesity and HRV could be explained by HR, suggesting a key confounding role of HR in HRV studies in children with weight disturbances.

Childhood growth patterns and cardiovascular autonomic modulation in midlife: Northern Finland 1966 Birth Cohort Study

OBJECTIVES

To test the hypothesis that age and body mass index (BMI) at BMI peak during infancy and at BMI rebound in childhood are related to cardiovascular autonomic modulation in adulthood.

METHODS

At the age of 46 years, a sample (n = 5861) of the participants of the Northern Finland Birth Cohort 1966 took part in follow-up examinations. Heart rate variability (HRV), baroreflex sensitivity (BRS) and low-frequency oscillations of systolic blood pressure (LF_SBP) were measured during sympathetic stimulus by standing. BMI at various ages was calculated from frequent anthropometric measurements collected from child welfare clinical records. BRS and LF_SBP were available for 1243 participants with BMI peak data and 1524 participants with BMI rebound data, and HRV for 2137 participants with BMI peak data and 2688 participants with BMI rebound data.

RESULTS

Age at BMI rebound had a significant inverse association with LF_SBP (beta = -0.071, p = 0.006) after all adjustments (p < 0.001) and was also directly associated with BRS (beta = 0.082, p = 0.001) independently of birth and maternal factors (p = 0.023). BMI at BMI peak and at BMI rebound was inversely associated with high-frequency component of HRV (HF) (beta = -0.045, p = 0.036 for BMI at peak; beta = -0.043, p = 0.024 for BMI at rebound) and directly associated with the ratio of low- and high-frequency components of HRV (LF/HF ratio) (beta = 0.084, p = < 0.001 for BMI at peak; beta = 0.069, p < 0.001 for BMI at rebound). These associations remained significant after all adjustments (p < 0.05 for all).

CONCLUSIONS

This novel study shows that younger age at BMI rebound and higher BMI at BMI peak and at BMI rebound are associated with higher levels in markers suggestive of augmented sympathetic and reduced vagal cardiovascular modulation in midlife.

Autonomic responses induced by aerobic submaximal exercise in obese and overweight adolescents

BACKGROUND

Graded exercises tests are performed in adult populations; nonetheless, the use of this type of assessment is greatly understudied in overweight and obese adolescents.

OBJECTIVE

To investigate heart rate autonomic responses to submaximal aerobic exercise in obese and overweight adolescents.

METHODS

We recruited 40 adolescents divided into two groups: (1) overweight group comprising 10 boys and 10 girls between Z-score +1 and +2 and (2) obese group comprising 10 boys and 10 girls above Z-score &gt;+2. Heart rate variability was analysed before (T1) and after exercise (T2-T4) on treadmill at a slope of 0%, with 70% of the maximal estimated heart rate (220 - age) for 20 minutes.

RESULTS

Heart rate in the overweight group was: 93.2±10.52 bpm versus 120.8±13.49 bpm versus 94.6±11.65 bpm versus 93.0±9.23 bpm, and in the obese group was: 92.0±15.41 bpm versus 117.6±16.31 bpm versus 92.1±12.9 bpm versus 91.8±14.33 bpm. High frequency in the overweight group was: 640±633.1 ms2 versus 84±174.66 ms2 versus 603.5±655.31 ms2 versus 762.6±807.21 ms2, and in the obese group was: 628.4±779.81 ms2 versus 65.4±119.34 ms2 versus 506.2±482.70 ms2 versus 677.9±939.05 ms2; and root mean square of successive differences in the overweight group was: 37.9±18.81 ms versus 10.9±8.41 ms versus 32.8±24.07 ms versus 36.7±21.86 ms, and in the obese group was: 38.7±23.17 ms versus 11.5±8.62 ms versus 32.3±16.74 ms versus 37.3±24.21 ms. These values significantly changed during exercise compared with resting values in overweight and obese groups. Moreover, we also reported no significant difference of resting parasympathetic control of heart rate between obese and overweight adolescents.

CONCLUSION

There was no significant difference of autonomic responses elicited by submaximal aerobic exercise between overweight and obese adolescents.

Heart rate variability in individuals with Down syndrome - A systematic review and meta-analysis

INTRODUCTION

Down syndrome (DS) results in many changes, including dysfunction in cardiac autonomic modulation. Heart rate variability (HRV) analysis evaluates the autonomic function and it is a predictor of adverse cardiovascular events.

OBJECTIVE

To present results of a systematic review and a meta-analysis about heart rate variability in individuals with DS.

METHOD

A systematic review was performed on PubMed, PubMed Central and Web of science databases. We included articles that exhibited all the terms: "Down Syndrome", "heart rate variability", "autonomic nervous system", "autonomic dysfunction" and "cardiac autonomic modulation". We conducted the meta-analysis to compare "DS" to "controls" during rest. Random effects models were used, as were appropriate tests for heterogeneity.

RESULTS

From 271 studies, 13 were included in our review. These are conducted with volunteers from a wide age range, of either gender, and not taking medications. Meta-analysis displayed that there were no significant differences between the groups at rest, except the RMSSD, which revealed a significant (Z = -2.80, p = 0.005) main effect (Hedge's g = -0.55, 95% CI [-0.93; -0.16]), indicating difference in individuals with DS compared with controls.

CONCLUSION

There is autonomic dysfunction in individuals with DS, which may or may not be expressed at rest, but it is usually demonstrated in an autonomic task. Meta-analysis specified that there was no significant alteration between DS and the controls during rest, except RMSSD index which was lower in DS than controls.

PROSPERO

CRD42017068647.

Physical Activity and Heart Rate Variability in Adolescents with Abdominal Obesity

Physical activity is a protective factor for autonomic dysfunction. However, whether this occurs in adolescents with abdominal obesity is still unclear. Thus, the aim of this study was to analyze the association between physical activity and heart rate variability (HRV) in adolescents with and without abdominal obesity. This cross-sectional study included 1152 boys (age: 17 ± 1 years). HRV measures of time (root mean square of the squared differences between adjacent normal RR intervals-RMSSD and the percentage of adjacent intervals over 50 ms-PNN50) and frequency domains (balance sympathetic-vagal-LF/HF) were evaluated, as well as total physical activity, commuting physical activity, leisure-time physical activity, and abdominal obesity. All physical activity domains were associated with better RMSSD, PNN50, and LF/HF in normal weight adolescents (p < 0.05), whereas in adolescents with abdominal obesity only leisure-time physical activity was associated with better PNN50 (b = 0.174, p = 0.035) independent of age, period of the day, body mass index, and blood pressure. In conclusion, higher leisure-time physical activity, but not total and commuting physical activity levels, was associated with improved HRV in adolescents with abdominal obesity.

The relationship between erythrocyte membrane fatty acid levels and cardiac autonomic function in obese children

OBJECTIVE

Childhood obesity is a worldwide health concern. Studies have shown autonomic dysfunction in obese children. The exact mechanism of this dysfunction is still unknown. The aim of this study was to assess the relationship between erythrocyte membrane fatty acid (EMFA) levels and cardiac autonomic function in obese children using heart rate variability (HRV).

METHODS

A total of 48 obese and 32 healthy children were included in this case-control study. Anthropometric and biochemical data, HRV indices, and EMFA levels in both groups were compared statistically.

RESULTS

HRV parameters including standard deviation of normal-to-normal R-R intervals (NN), root mean square of successive differences, the number of pairs of successive NNs that differ by >50 ms (NN50), the proportion of NN50 divided by the total number of NNs, high-frequency power, and low-frequency power were lower in obese children compared to controls, implying parasympathetic impairment. Eicosapentaenoic acid and docosahexaenoic acid levels were lower in the obese group (p<0.001 and p=0.012, respectively). In correlation analysis, in the obese group, body mass index standard deviation and linoleic acid, arachidonic acid, triglycerides, and high-density lipoprotein levels showed a linear correlation with one or more HRV parameter, and age, eicosapentaenoic acid, and systolic and diastolic blood pressure correlated with mean heart rate. In linear regression analysis, age, dihomo-gamma-linolenic acid, linoleic acid, arachidonic acid, body mass index standard deviation, systolic blood pressure, triglycerides, low-density lipoprotein and high-density lipoprotein were related to HRV parameters, implying an effect on cardiac autonomic function.

CONCLUSION

There is impairment of cardiac autonomic function in obese children. It appears that levels of EMFAs such as linoleic acid, arachidonic acid and dihomo-gamma-linolenic acid play a role in the regulation of cardiac autonomic function in obese children.

Cardiovascular Response of an Acute Exergame Session in Prepubertal Obese Children

PURPOSE

We aimed to analyze the acute autonomic response of obese and eutrophic prepubertal boys to an exergame (EXG) session.

MATERIALS AND METHOD

Nine eutrophic (8.89 ± 2.71 years of age and 16.42% ± 6.30% body fat) and nine obese boys (8.70 ± 1.16 years of age and 40.76% ± 4.2% body fat) participated. Nutritional state was determined using World Health Organization guidelines. Variables were collected at rest, immediately post (IP), and 60 minutes after a 20 minutes EXG session. Autonomic nervous system (ANS) activity was assessed using heart rate variability in time and frequency domains, and data were analyzed using Shapiro-Wilk and ANOVA tests with Tukey post hoc.

RESULTS

The obese group demonstrated an increased sympathetic activity at rest when compared with the eutrophic group (P < 0.05). The obese group also demonstrated an increased parasympathetic activity 60 minutes after the EXG session when compared with the eutrophic group (P < 0.05).

CONCLUSION

We concluded that an acute session of EXG promoted ANS super compensation. We encourage research on chronic ANS response to EXG.

Time domain parameters of heart rate variability in children born as small-for-gestational age

According to metabolic programming theory, small-for-gestational age patients are at high risk of cardiovascular diseases also because of the possible malfunction of the autonomic nervous system. Autonomic disorders can be assessed by heart rate variability. The aims of this study were to compare time domain parameters of heart rate variability in children born as small-for-gestational age and appropriate-for-gestational age and to assess the correlation of the postnatal and current somatic parameters with the time domain parameters. The small-for-gestational age group consisted of 68 children aged 5-10 years who were born with birth weight below the 10th percentile. The appropriate-for-gestational age group consisted of 30 healthy peers, matched in terms of gender and age. On the basis of Holter monitoring, slightly higher average heart rate was observed in the small-for-gestational age group than in the appropriate-for-gestational age group. It was found that all the time domain parameters (SDNN, SDNNi, SDANNi, rMSSD, pNN50) were lower in the small-for-gestational age group than in the appropriate-for-gestational age group. In the small-for-gestational age group, girls had lower heart rate and some of the heart rate variability parameters (SDNN, SDNNi, SDANNi) in comparison with boys. Children born as small-for-gestational age have impaired function of the autonomic nervous system. Moreover, in the small-for-gestational age group, autonomic balance moved towards the sympathetic component, which was evidenced by higher heart rate. Children with faster heart rate and lower heart rate variability parameters may be at risk of cardiovascular disease.

Associations between stress biology indicators and overweight across toddlerhood

Biological stress responses are proposed as a pathway through which stress exposure can "get under the skin" and lead to health problems, specifically obesity. Yet, it is not clear when such associations may emerge or whether they are bidirectional. Cortisol and salivary alpha amylase (sAA) were considered indicators of the biological stress response. We tested the longitudinal association between cortisol and sAA and weight in 215 low-income children at ages 21, 27, and 33 months (52% male; 46% non-Hispanic white). sAA and cortisol intercept and slope (representing morning level and rate of change across the day) were calculated for each age point using random effect models. Children were weighed and length measured and categorized as overweight versus normal weight (overweight defined as weight-for-length z-score ≥85th percentile for age and sex). Cross-lagged models stratified by sex and controlling for birthweight z-score tested the concurrent and cross-lagged associations between each of 4 indices of stress biology individually (cortisol and sAA intercept and slope) and overweight. Overweight status was correlated across time. Cortisol and sAA were correlated across occasions of measurement, though somewhat less strongly in boys. There were no concurrent associations between stress indicators and overweight. sAA at 27 months predicted greater risk of overweight at 33 months in girls, such that both lower sAA intercept and more rapidly increasing sAA at 27 months predicted greater risk of overweight at 33 months (β=-0.64, p<0.05 and β=1.09, p<0.05, respectively). For boys only, overweight at 21 months predicted lower sAA intercept at 27 months (β=-0.35, p<0.05). Findings suggest that longitudinal associations of stress biology and weight status may be present only on a limited basis very early in the lifespan.

Cardiac Autonomic Function at Baseline and under Stress and Its Relationship to Circulatory Markers of Inflammation in Obese Compared to Nonobese Children: A Pilot Study

BACKGROUND/AIMS

The autonomic nervous system (ANS) provides neurogenic control of inflammatory reactions. ANS changes in obesity may result in inflammation. This study sought to gain insight into cardiac autonomic dysfunction and inflammation in childhood obesity, and to gather pilot data on the potential relationship between altered ANS and inflammation.

METHODS

Fifteen obese children and adolescents without metabolic complications and 15 nonobese controls underwent heart rate variability and impedance cardiography testing during rest, mental stress, and physical stress. Inflammatory cytokines and immune reactivity were measured.

RESULTS

There was no statistically significant difference between groups in cardiac ANS testing at rest or in response to stress. Median high-sensitivity C-reactive protein (hsCRP) was higher in the obese group [obese 2.6 mg/l (IQR 1.6-11.9); nonobese 0.3 mg/l (IQR 0.2-0.7); p < 0.001]. Interleukin-6 and tumour necrosis factor-α were similar between groups. Immune reactivity testing (in vitro Toll-like receptor stimulation) revealed a strong, but comparable, inflammatory response in both groups.

CONCLUSIONS

Obese children and adolescents without metabolic complications did not have cardiac ANS dysfunction. While hsCRP was elevated, systemic cytokines were not raised. Compared to prior studies, which often focused on children with obesity and its complications, it is encouraging that obese children without metabolic complications may not yet have autonomic dysfunction.

TESTE DE CAMINHADA DE SEIS MINUTOS: DESEMPENHO DE CRIANÇAS COM EXCESSO DE PESO

RESUMO Introdução: O teste de caminhada de seis minutos (TC6') tem sido utilizado para avaliar a capacidade funcional do exercício em crianças. Objetivo: Comparar o desempenho no teste de caminhada de seis minutos em escolares na faixa etária entre 8 a 10 anos, conforme a classificação nutricional, com base em dois diferentes critérios. Métodos: A amostra de 226 crianças entre 8 a 10 anos foi dividida em três grupos (eutrófico, sobrepeso e obeso), de acordo com os critérios de classificação nutricional propostos pela Organização Mundial da Saúde (OMS) e pela International Obesity Task Force (IOTF) e avaliada por meio do teste de caminhada de seis minutos. Resultados: A prevalência de sobrepeso e obesidade na amostra foi de 42,48% de acordo com o critério da OMS e 38,94% pelo critério da IOTF. Não ocorreram diferenças estatisticamente significantes entre os grupos eutrófico, sobrepeso e obeso, quando os resultados do TC6' foram comparados, tanto na distância percorrida quanto no percentual do predito para a criança, de acordo com os valores de referência, e também de acordo com os dois critérios de classificação nutricional. A frequência cardíaca final do teste foi estatisticamente maior nos grupos sobrepeso e obeso, tanto pelo critério OMS (p = 0,0015), quanto pelo critério IOTF (p = 0,0160) . Conclusões: Na amostra estudada não houve diferença no desempenho do TC6' entre crianças eutróficas, com sobrepeso e obesas. Porém, a frequência cardíaca final do teste foi significantemente maior entre as crianças com excesso de peso. Os resultados ressaltam que medidas de prevenção, acompanhamento e tratamento são necessárias, promovendo hábitos saudáveis.

Is the algorithm used to process heart rate variability data clinically relevant? Analysis in male adolescents

Objective

To analyze whether the algorithm used for the heart rate variability assessment (fast Fourier transform versus autoregressive methods) influenced its association with cardiovascular risk factors in male adolescents.

Methods

This cross-sectional study included 1,152 male adolescents (aged 14 to 19 years). The low frequency, high frequency components (absolute numbers and normalized units), low frequency/high frequency ratio, and total power of heart rate variability parameters were obtained using the fast Fourier transform and autoregressive methods, while the adolescents were resting in a supine position.

Results

All heart rate variability parameters calculated from both methods were different (p<0.05). However, a low effect size (<0.1) was found for all parameters. The intra-class correlation between methods ranged from 0.96 to 0.99, whereas the variation coefficient ranged from 7.4 to 14.8%. Furthermore, waist circumference was negatively associated with high frequency, and positively associated with low frequency and sympatovagal balance (p<0.001 for both fast Fourier transform and autoregressive methods in all associations). Systolic blood pressure was negatively associated with total power and high frequency, whereas it was positively associated with low frequency and sympatovagal balance (p<0.001 for both fast Fourier transform and autoregressive methods in all associations). Body mass index was negatively associated with high frequency, while it was positively associated with low frequency and sympatovagal balance (p values ranged from <0.001 to 0.007).

Conclusion

There are significant differences in heart rate variability parameters obtained with the fast Fourier transform and autoregressive methods in male adolescent; however, these differences are not clinically significant.

Relation of Heart Rate and its Variability during Sleep with Age, Physical Activity, and Body Composition in Young Children

Background: Recent studies have claimed a positive effect of physical activity and body composition on vagal tone. In pediatric populations, there is a pronounced decrease in heart rate with age. While this decrease is often interpreted as an age-related increase in vagal tone, there is some evidence that it may be related to a decrease in intrinsic heart rate. This factor has not been taken into account in most previous studies. The aim of the present study was to assess the association between physical activity and/or body composition and heart rate variability (HRV) independently of the decline in heart rate in young children.

Methods: Anthropometric measurements were taken in 309 children aged 2–6 years. Ambulatory electrocardiograms were collected over 14–18 h comprising a full night and accelerometry over 7 days. HRV was determined of three different night segments: (1) over 5 min during deep sleep identified automatically based on HRV characteristics; (2) during a 20 min segment starting 15 min after sleep onset; (3) over a 4-h segment between midnight and 4 a.m. Linear models were computed for HRV parameters with anthropometric and physical activity variables adjusted for heart rate and other confounding variables (e.g., age for physical activity models).

Results: We found a decline in heart rate with increasing physical activity and decreasing skinfold thickness. HRV parameters decreased with increasing age, height, and weight in HR-adjusted regression models. These relationships were only found in segments of deep sleep detected automatically based on HRV or manually 15 min after sleep onset, but not in the 4-h segment with random sleep phases.

Conclusions: Contrary to most previous studies, we found no increase of standard HRV parameters with age, however, when adjusted for heart rate, there was a significant decrease of HRV parameters with increasing age. Without knowing intrinsic heart rate correct interpretation of HRV in growing children is impossible.

Association between obesity and heart rate variability indices: an intuition toward cardiac autonomic alteration - a risk of CVD

BACKGROUND

Obese people have a higher prevalence of cardiovascular disease, which is supposed to be due to autonomic dysfunction and/or metabolic disorder. The alterations in cardiac autonomic functions bring out the changes in the heart rate variability (HRV) indicators, an assessing tool for cardiac autonomic conditions.

OBJECTIVE

To compare the cardiac autonomic activity between obese and normal weight adults and find out the highest association between the indices of HRV and obesity.

METHODS

The study was conducted in 30 adult obese persons (body mass index [BMI] >30 kg/m²) and 29 healthy normal weight controls (BMI 18-24 kg/m²). Short-term HRV variables were assessed using standard protocol. Data were compared between groups using Mann-Whitney U test. Obesity indices such as waist circumference, hip circumference, waist-hip ratio (WHR), and BMI were measured and calculated, and they were correlated with HRV indices using Spearman's correlation analysis.

RESULTS

In the obese group, there was a significant increase in the mean heart rate, whereas the HRV parasympathetic indicators were less (eg, root mean square of differences of successive RR intervals [28.75 {16.72-38.35} vs 41.55 {30.6-56.75} ms, p=0.018], number of RR intervals that differ by >50 ms, that is, NN50 [15.5 {2-39} vs 83.5 {32.75-116.25}, p=0.010], etc) and the sympathetic indicator low frequency (LF)/high frequency (HF) ratio (1.2 [0.65-2.20] vs 0.79 [0.5-1.02], p=0.045) was more than that of the normal weight group. Spearman's correlation between HRV and obesity indices showed significant positive correlation of WHR with LF in normalized unit (r=0.478, p<0.01) and LF/HF ratio (r=0.479, p<0.01), whereas it had significant negative correlation with high frequency power ms² (r=-0.374, p<0.05) and HF in normalized unit (r=-0.478, p<0.01). There was a nonsignificant correlation of BMI with HRV variables in obese individuals.

CONCLUSION

Increased WHR, by far an indicator of visceral adiposity, was strongly associated with reduced cardiac parasympathetic and increased sympathetic activity in obese individuals defined by BMI. However, BMI itself has a weak relationship with HRV cardiac autonomic markers. Thus, even with a slight increase in WHR in an individual, there could be a greater risk of cardiovascular morbidity and mortality brought about by cardiac autonomic alterations.

Impact of malnutrition on cardiac autonomic modulation in children

OBJECTIVE

To compare the autonomic behavior between malnourished children and a control group using analysis of heart rate variability (HRV).

METHOD

Data were analyzed from 70 children who were divided into two groups: malnourished and eutrophic, according to the Z-score nutritional status for height and age. For analysis of HRV indices, heart rate was recorded beat to beat with the child in the supine position for 20min. The analysis of these indices was performed using linear methods, analyzed in the time and frequency domains. Student's t-test for unpaired data and the Mann-Whitney test were used to compare variables between groups, with a significance level of 5%.

RESULTS

A reduction in systolic and diastolic blood pressure and an increase in heart rate were found in malnourished children compared to eutrophic children. The HRV indices suggested that malnourished children present reductions in both sympathetic and parasympathetic autonomic nervous system activity. The SDNN, rMSSD, NN50, pNN50, SD1, SD2, TINN, LF (ms²), and HF (ms²) indices were lower in malnourished children.

CONCLUSION

Malnourished children present changes in cardiac autonomic modulation, characterized by reductions in both sympathetic and parasympathetic activity, as well as increased heart rate and decreased blood pressure.

Effect of a weight reduction program on baseline and stress-induced heart rate variability in children with obesity

OBJECTIVE

Autonomic dysregulation is a well-established feature in adults with obesity but not in children. Since this dysregulation could contribute to weight dynamics, this study aimed to compare autonomic regulation in children with obesity and normal-weight peers and to track autonomic status during weight reduction.

METHODS

Sixty children with obesity and 27 age- and sex-matched normal-weight healthy participants were included. Heart rate variability (HRV) was assessed at baseline and during a mental stress test and a subsequent recovery period. Children with obesity were investigated both upon admission and discharge.

RESULTS

Upon admission, no significant differences in HRV parameters were found for normal-weight participants and those with obesity. Inpatient treatment led to significant changes in HRV with increase in general variability (standard deviation of the normal-to-normal interval (SDNN), P < 0.001) as well as of parasympathetic regulation (root mean square successive difference (RMSSD) and high frequency power (logHF), P < 0.01). Children with obesity had sympathetic activation similar to normal-weight controls during mental stress with subsequent return to baseline values, and weight loss did not affect this profile.

CONCLUSIONS

A weight reduction program induced a change in autonomic activity in children with obesity toward parasympathetic dominance but had no influence on autonomic nervous system reactivity during stress conditions.

Breakfast frequency, adiposity, and cardiovascular risk factors as markers in adolescents

OBJECTIVE

To analyse the relationship between skipping breakfast and haemodynamic, metabolic, inflammatory, and cardiovascular risk factors in adolescents.

METHODS

A cross-sectional study was carried out with information from an ongoing cohort study in Presidente Prudente, São Paulo, Brazil. The sample comprised of 120 adolescents (11.7±0.8 years old) who met the following inclusion criteria: age between 11 and 14 years; enrolled in the school unit of elementary education; absence of any known disease; and no drug consumption. The parents or legal guardians of the patients signed a formal informed consent. Skipping breakfast was self-reported through face-to-face interviews. Blood pressure, intima-media thickness, trunk fatness, total and fractional cholesterol levels - high-density lipoprotein cholesterol and low-density lipoprotein cholesterol - triacylglycerol levels, and high-sensitivity C-reactive protein levels were measured.

RESULTS

In this study, 47.5% (95% CI: 38.5-56.4%) of the adolescents reported skipping breakfast at least 1 day/week. Adolescents who skipped breakfast had higher values of trunk fatness and systolic blood pressure. Breakfast frequency was negatively related to systolic blood pressure (β -1.99 [-3.67; -0.31]) and z score dyslipidaemia (β -0.46 [-0.90; -0.01]), but this relationship was mediated by trunk fatness.

CONCLUSION

Skipping breakfast is related to cardiovascular risk factors in adolescents, and this relationship was mainly mediated by trunk fatness.

Obesity and Prader-Willi Syndrome Affect Heart Rate Recovery from Dynamic Resistance Exercise in Youth

Following exercise, heart rate decline is initially driven by parasympathetic reactivation and later by sympathetic withdrawal. Obesity delays endurance exercise heart rate recovery (HRR) in both children and adults. Young people with Prader-Willi Syndrome (PWS), a congenital cause for obesity, have shown a slower 60-s endurance exercise HRR compared to lean and obese children, suggesting compromised regulation. This study further evaluated effects of obesity and PWS on resistance exercise HRR at 30 and 60 s in children. PWS (8–18 years) and lean and obese controls (8–11 years) completed a weighted step-up protocol (six sets x 10 reps per leg, separated by one-minute rest), standardized using participant stature and lean body mass. HRR was evaluated by calculated HRR value (HRRV = difference between HR at test termination and 30 (HRRV30) and 60 (HRRV60) s post-exercise). PWS and obese had a smaller HRRV30 than lean (p < 0.01 for both). Additionally, PWS had a smaller HRRV60 than lean and obese (p = 0.01 for both). Obesity appears to delay early parasympathetic reactivation, which occurs within 30 s following resistance exercise. However, the continued HRR delay at 60 s in PWS may be explained by either blunted parasympathetic nervous system reactivation, delayed sympathetic withdrawal and/or poor cardiovascular fitness.

Causal coherence analysis of cardiovascular variables in obese preadolescents and adolescents

Obesity during adulthood has been associated with cardiovascular disease, but its adverse effects during adolescence are less well established. The aim of this study was to probe cardiovascular control in obese adolescence by studying causal coherence between cardiovascular variables. Sixty minutes of resting ECG and finger blood pressure were recorded in 19 obese and 19 non-obese subjects in the supine position to measure pair-wise spectral coherence in the low frequency band between heart rate, systolic and diastolic blood pressure, pulse pressure, total peripheral resistance and left ventricular ejection time. We observed that causal coherences in {systolic blood pressure → total peripheral resistance} and {left ventricular ejection time → systolic blood pressure} directions were significantly decreased in obese preadolescents and adolescents when compared to the healthy control group, despite the lack of difference in the magnitude of oscillations of cardiovascular variables. In conclusion, causal coherence analysis of cardiovascular variables may give new insight into cardiovascular dysregulation in young obese subjects.

Effects of exercise on cardiac autonomic modulation in children: literature update

AbstractIntroduction It is known that physical exercise is beneficial and precipitates adjustments to the autonomic nervous system. However, the effect of exercise on cardiac autonomic modulation in children, despite its importance, is poorly investigated.Objective To bring together current information about the effects of exercise on heart rate variability in healthy and obese children.Methods The literature update was performed through a search for articles in the following databases; PubMed, PEDro, SciELO and Lilacs, using the descriptors “exercise” and “child” in conjunction with the descriptors “autonomic nervous system”, “sympathetic nervous system”, “parasympathetic nervous system” and also with no descriptor, but the key word of this study, “heart rate variability”, from January 2005 to December 2012.Results After removal of items that did not fit the subject of the study, a total of 9 articles were selected, 5 with healthy and 4 with obese children.Conclusion The findings suggest that exercise can act in the normalization of existing alterations in the autonomic nervous system of obese children, as well as serve as a preventative factor in healthy children, enabling healthy development of the autonomic nervous system until the child reaches adulthood.

Sympathetic Activity Assessed during Exercise Recovery in Young Obese Females

OBJECTIVE

To evaluate differences in sympathetic activity, as assessed by an exercise recovery index (ERI; heart rate/oxygen consumption [VO2] plateau), between black and white obese female adolescents. An additional aim was to determine the association of ERI with insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR]), cardiovascular fitness per fat-free mass (VO2 per fat-free mass), systolic blood pressure (SBP), and percent body fat (%FAT) in both black and white obese adolescents.

STUDY DESIGN

Sixty-one females volunteered to participate in this study. HOMA-IR, SBP, and %FAT were assessed during resting conditions in black (n = 49, 13.7 ± 1.6 years, 38.1 ± 6.1 kg/m(2)) and white (n = 12, 13.3 ± 2.2 years, 34.3 ± 4.9 kg/m(2)) obese adolescents. An ERI was calculated during a 5-minute passive recovery period immediately following a graded treadmill exercise test to exhaustion.

RESULTS

The ERI was significantly greater in black compared with white obese adolescent females (29.8 ± 6.4 vs 24.1 ± 3.1 bpm·mLO2(-1)·min(-1), P = .004). Using multiple linear regression modeling, there was a significant independent association between ERI and VO2 per fat-free mass (r = -0.310, P = .027) and %FAT (r = 0.326, P = .020) in black obese adolescents after controlling for HOMA-IR and SBP.

CONCLUSIONS

These results suggest that black obese adolescent females have greater sympathetic activity, as assessed by an ERI, than white obese adolescent females. These findings support the need for weight management efforts aimed at both reducing %FAT and improving fitness in obese adolescents, specifically black females.

TRIAL REGISTRATION

Registered with Clinicaltrials.gov: NCT00562293.

Heart rate variability is reduced in underweight and overweight healthy adult women

Heart rate variability (HRV) is altered in obese subjects, but whether this is true also in underweight (UW) subjects is still under debate. We investigated the HRV profile in a sample of healthy adult women and its association with adiposity. Five-minute resting state electrocardiographic activity was recorded in 69 subjects grouped according to their body mass index, [23 normal weight (NW), 23 overweight/obese (OW) and 23 UW). Body fat mass (FM) was measured by bio-impedance. Frequency- and time-domain analyses were performed. Compared to NW, UW and OW subjects showed a significant decrease in HRV indices, as revealed by spectral analysis. No differences were observed between UW and OW subjects. A second-order polynomial regression unveiled an inverted U-shaped relationship between FM extent and HRV indices. A decrease of HRV indices was associated with changes in FM extent, proving that in UW and OW subjects, the adaptive flexibility of autonomic cardiac function was reduced. These findings provide important clues to guide future studies addressed to determine how changes in adiposity and autonomic cardiac function may contribute to health risk.

Metabolic syndrome burden in apparently healthy adolescents is adversely associated with cardiac autonomic modulation--Penn State Children Cohort

BACKGROUND

Reduced cardiac autonomic modulation (CAM) has been associated with metabolic syndrome (MetS) in adults. However, the association between MetS component cluster and CAM has not been examined in adolescents.

METHODS

We conducted a cross-sectional analysis using data from the Penn State Child Cohort follow-up examination. CAM was assessed by heart rate variability (HRV) analysis of 39-h RR intervals, including frequency (high frequency, HF; low frequency, LF; and LF/HF ratio) and time (SDNN, standard deviation of all RR intervals; RMSSD, square root of the mean of the sum of the squares of differences between adjacent RR intervals; and HR, heart rate) domain variables. To assess the MetS burden, we used continuous MetS score (cMetS)--sum of the age and sex-adjusted standardized residual (Z-score) of five established MetS components. Linear mixed-effect models were used to analyze the association between cMetS and CAM in the entire population and stratified by gender.

RESULTS

After adjusting for age, sex, and race, cMetS was significantly associated with reduced HRV and higher HR. With 1 standard deviation increase in cMetS, there was a significant decrease in HF (-0.10 (SE = 0.02)), LF (-0.07 (SE = 0.01)), SDNN (-1.97 (SE = 0.50)), and RMSSD (-1.70 (SE = 0.72)), and increase in LF/HF (0.08 (SE = 0.02)) and HR (1.40 (SE = 0.26)). All cMetS components, with the exception of high-density lipoprotein (HDL), were associated with significantly decreased HRV and increased HR. High blood pressure (MAP) and triglyceride (TG) levels were also associated with an increase in LF/HF and decrease in RMSSD. An increase in high-density lipoprotein was only associated with higher LF and SDNN. Moreover, cMetS and HRV associations were more pronounced in males than in females. The associations between HRV and. MAP, TG, and HDL were more pronounced in females.

CONCLUSIONS

cMetS score is associated with lower HRV, suggesting an adverse impact on CAM, even in apparently healthy adolescents.

Resting state Rolandic mu rhythms are related to activity of sympathetic component of autonomic nervous system in healthy humans

We tested the hypothesis of a relationship between heart rate variability (HRV) and Rolandic mu rhythms in relaxed condition of resting state. Resting state eyes-closed electroencephalographic (EEG) and electrocardiographic (ECG) data were recorded (10-20 System) in 42 healthy adults. EEG rhythms of interest were high-frequency alpha (10.5-13Hz) and low-frequency beta (13-20Hz), which are supposed to form Rolandic mu rhythms. Rolandic and occipital (control) EEG sources were estimated by LORETA software. Results showed a statistically significant (p<0.05, corrected) negative correlation across all subjects between Rolandic cortical sources of low-frequency beta rhythms and the low-frequency band power (LF, 0.04-0.15Hz) of tachogram spectrum as an index of HRV. The lower the amplitude of Rolandic sources of low-frequency beta rhythms (as a putative sign of activity of somatomotor cortex), the higher the LF band power of tachogram spectrum (as a putative sign of sympathetic activity). This effect was specific as there was neither a similar correlation between these EEG rhythms and high-frequency band power of tachogram spectrum (as a putative sign of parasympathetic vagal activity) neither between occipital sources of low-frequency beta rhythms (as a putative sign of activity of visual cortex) and LF band power of tachogram spectrum. These results suggest that Rolandic low-frequency beta rhythms are related to sympathetic activity regulating heart rate, as a dynamic neurophysiologic oscillatory mechanism sub-serving the interaction between brain neural populations involved in somatomotor control and brain neural populations regulating ANS signals to heart for on-going homeostatic adaptations.

Cardiac autonomic modulation of children with Down syndrome

The aim of this study is to analyze the autonomic modulation in children with Down syndrome (DS). The study was conducted with a convenience sample of children with DS and without heart disease, from the Genetics Clinic of the Hospital Infantil Darcy Vargas and APAE São Paulo, São Paulo, SP, Brazil. The control group was matched for sex and age. The analysis of autonomic modulation was performed using the indices of heart rate variability (HRV). The children remained in the supine position with spontaneous breathing for 20 min. Heart rate was recorded beat-to-beat. HRV analysis was performed in time and frequency domain. For data analysis, we used Student's t test: unpaired and Mann-Whitney. It was considered statistically significant at p < 0.05. From 75 children with DS, 50 were excluded, a total of 25 children [16 boys, 8.6 (1.4) years] participated in this study, and the control group also consisted of 25 children [16 boys, 9.0 (1.2) years] without the syndrome. The BMI of the volunteers with DS was higher than the controls [19.1 (2.9) vs. 15.8 (1.2), p < 0.0001]. There were differences between groups in the indices in frequency domain: LFms(2) [1242.1 (788.25) vs. 786.44 (481.90), p = 0.040], LFun [69.104 (11.247) vs. 57.348 (11.683), p = 0.0004], HFun [30.896 (11.247) vs. 42.520 (11.634), p = 0.0004] and LF/HF [2.594 (1.104) vs. 1.579 (0.9982), p = 0.0004]. No differences were observed in time domain indices. The results indicate increased indices representing the sympathetic branch of the autonomic nervous system and those that indicate the overall modulation in children with DS.

The circadian pattern of cardiac autonomic modulation and obesity in adolescents

PURPOSE

To assess the impact of obesity and population attributes on the circadian pattern of cardiac autonomic modulation (CAM) in a population-based sample of adolescents.

METHODS

We used data from 421 adolescents who completed the follow-up exam in the Penn State Children Cohort study. CAM was assessed by heart rate variability (HRV) analysis of beat-to-beat, normal R-R intervals from a 24-hour ECG, on a 30-minute basis. The HRV indices included frequency-domain (HF, LF, and LF/HF ratio) and time-domain (SDNN, RMSSD, and HR) variables. Nonlinear mixed-effect models were used to calculate a cosine periodic curve, each having three parameters quantifying its circadian period: M (mean levels of the HRV variables), Â (amplitude of the oscillation), and θ (the time of the highest oscillation).

RESULTS

The mean (SD) age was 16.9 (2.2) years, with 54 % male and 77 % white. The mean BMI percentile was 66, with 16 % obese (BMI percentile ≥ 95). Overall, HF (a marker of parasympathetic modulation) gradually increased from the late afternoon, reached peak amplitude around 3 a.m., and then decreased throughout the daytime until late afternoon. In contrast, obesity had adverse effects on all circadian parameters. The age, sex and race showed varying differences on the CAM circadian parameters. The adjusted means (95 %Cls) of M, Â, and θ for HF were 5.99 (5.79-6.19), 0.77 (0.66-0.89), 3:15 (2:15-4:15) a.m., and 6.21 (6.13-6.29), 0.66 (0.61-0.70), 2:45 (2:30-3:15) a.m. for obese and non-obese subjects, respectively.

CONCLUSION

The circadian pattern of CAM can be quantified by the three cosine parameters. Obesity is associated with lower HRV even in young individuals like children/adolescents.

The influence of age and weight status on cardiac autonomic control in healthy children: a review

Heart rate variability (HRV) analyses can provide a non-invasive evaluation of cardiac autonomic activity. How autonomic control normally develops in childhood and how this is affected by obesity remain incompletely understood. In this review we examine the evidence that childhood age and weight status influence autonomic control of the heart as assessed using HRV. Electronic databases (Pubmed, EMBASE and Cochrane Library) were searched for studies examining HRV in healthy children from birth to 18 years who adhered to the Task Force (1996) guidelines. Twenty-four studies met our inclusion criteria. Seven examined childhood age and HRV. A reduction in 24-hour LF:HF was reported from birth to infancy (1 year), while overall HRV (SDNN) showed a marked and progressive increase. From infancy to early-to-late childhood (from 12 months to 15 years) LF:HF ratio was reported to decline further albeit at a slower rate, while RMSSD and SDNN increased. Twenty studies examined the effects of weight status and body composition on HRV. In a majority of studies, obese children exhibited reductions in RMSSD (n = 8/13), pNN50% (n = 7/9) and HF power (n = 14/18), no difference was reported for LF (n = 10/18), while LF:HF ratio was elevated (n = 10/15). HRV changes during childhood are consistent with a marked and progressive increase in cardiac parasympathetic activity relative to sympathetic activity. Obesity disrupts the normal maturation of cardiac autonomic control.

Childhood obesity and autonomic dysfunction: risk for cardiac morbidity and mortality

OPINION STATEMENT

The epidemic of childhood obesity is becoming a major predictor for risk of cardiovascular diseases (CVD) and mortality during adulthood. Alterations in the morphology of the heart due to obesity could be a predictor for the dysfunction of cardiac autonomic modulation (CAM). A number of epidemiologic studies have evaluated the effect of obesity and CAM in children, finding that obesity impaired the balance of CAM toward a sympathetic overflow and reduced parasympathetic modulation, a significant predictor of CVD morbidity and mortality in adults. Lifestyle modifications, for example long-term exercise programs, have been shown to improve CAM in the obese. This review discusses the recent evidence on childhood and adolescent obesity and its impact on CAM, as well as how early lifestyle changes could help improve CAM, which may in turn reduce the burden of CVD in adults.

Analysis of cardiac autonomic modulation of children with attention deficit hyperactivity disorder

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is characterized by decreased attention span, impulsiveness, and hyperactivity. Autonomic nervous system imbalance was previously described in this population. We aim to compare the autonomic function of children with ADHD and controls by analyzing heart rate variability (HRV).

METHODS

Children rested in supine position with spontaneous breathing for 20 minutes. Heart rate was recorded beat by beat. HRV analysis was performed in the time and frequency domains and Poincaré plot.

RESULTS

Twenty-eight children with ADHD (22 boys, aged 9.964 years) and 28 controls (15 boys, age 9.857 years) participated in this study. It was determined that the mean and standard deviation of indexes which indicate parasympathetic activity is higher in children with ADHD than in children without the disorder: high frequency in normalized units, 46.182 (14.159) versus 40.632 (12.247); root mean square of successive differences, 41.821 (17.834) versus 38.150 (18.357); differences between adjacent normal-to-normal intervals greater than 50 milliseconds, 199.75 (144.00) versus 127.46 (102.21) (P<0.05); percentage of differences between adjacent normal-to-normal intervals greater than 50 milliseconds, 23.957 (17.316) versus 16.211 (13.215); standard deviation of instantaneous beat-to-beat interval, 29.586 (12.622) versus 26.989 (12.983).

CONCLUSION

Comparison of the autonomic function by analyzing HRV suggests an increase in the activity of the parasympathetic autonomic nervous systems in children with ADHD in relation to the control group.

Childhood obesity and cardiovascular dysfunction

Obesity-related cardiovascular disease in children is becoming more prevalent in conjunction with the rise in childhood obesity. Children with obesity are predisposed to an increased risk of cardiovascular morbidity and mortality in adulthood. Importantly, research in children with obesity over the last decade has demonstrated that children may exhibit early signs of cardiovascular dysfunction as a result of their excess adiposity, often independent of other obesity-related comorbidities such as dyslipidemia and insulin resistance. The clinical evidence is accumulating to suggest that the cardiovascular damage, once observed only in adults, is also occurring in obese children. The objective of this review is to provide a synopsis of the current research on cardiovascular abnormalities in children with obesity and highlight the importance and need for early detection and prevention programs to mitigate this potentially serious health problem.