Altered Cardiac Autonomic Regulation in Overweight and Obese Subjects: The Role of Age-and-Gender-Adjusted Statistical Indicators of Heart Rate Variability and Cardiac Baroreflex

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.

Assessing the cardiac autonomic response to bicycle exercise in Olympic athletes with different loads of endurance training: new insights from statistical indicators based on multilevel exploratory factor analysis

Aim: The mechanisms governing the organism's response to exercise are complex and difficult to study. Spectral analysis of heart rate variability (HRV) could represent a convenient methodology for studying humans' autonomic nervous system (ANS). However, difficulties in interpreting the multitude of correlated HRV-derived indices, mainly when computed over different time segments, may represent a barrier to its usage. This preliminary investigation addressed to elite athletes proposes a novel method describing the cardiac autonomic response to exercise based on multilevel exploratory factor analysis (MEFA), which reduces the multitude of HRV-derived indices to fewer uncorrelated ANS indicators capable of accounting for their interrelationships and overcoming the above difficulties. Methods: The study involved 30 Italian Olympic athletes, divided into 15 cyclists (prevalent high-intensity endurance training) and 15 shooters (prevalent technical training with low-intensity endurance component). All athletes underwent a complete test of a dynamic protocol, constituted by a rest-stand test followed by a stepwise bicycle stress test subdivided into a single bout of progressive endurance (from aerobic to anaerobic) exercise and recovery. Then, by spectral analysis, values of 12 ANS proxies were computed at each time segment (9 epochs in all) of the complete test. Results: We obtained two global ANS indicators (amplitude and frequency), expressing the athletes' overall autonomic response to the complete test, and three dynamic ANS indicators (amplitude, signal self-similarity, and oscillatory), describing the principal dynamics over time of the variability of RR interval (RRV). Globally, cyclists have significantly higher amplitude levels (median ± MAD: cyclists 69.9 ± 20.5; shooters 37.2 ± 19.4) and lower frequency levels (median ± MAD: cyclists 37.4 ± 14.8; shooters 78.2 ± 10.2) than shooters, i.e., a parasympathetic predominance compared to shooters. Regarding the RRV dynamics, the signal self-similarity and oscillatory indicators have the strongest sensitivity in detecting the rest-stand change; the amplitude indicator is highly effective in detecting the athletes' autonomic changes in the exercise fraction; the amplitude and oscillatory indicators present significant differences between cyclists and shooters in specific test epochs. Conclusion: This MEFA application permits a more straightforward representation of the complexity characterizing ANS modulation during exercise, simplifying the interpretation of the HRV-derived indices and facilitating the possible real-life use of this non-invasive methodology.

Effects of Endurance Exercise Intensities on Autonomic and Metabolic Controls in Children with Obesity: A Feasibility Study Employing Online Exercise Training

Exercise is one of the major determinants of a healthy lifestyle, which is particularly important in childhood and serves as a powerful preventive tool. On the other hand, obesity and arterial hypertension rates are increasing in children, representing a huge risk for developing major cardiovascular and metabolic diseases in adult life. Of fundamental importance is the modality and volume of exercise required to obtain benefits. In this feasibility study, we considered a group of obese children, studied before and after a 12-week online exercise training program, and subdivided the participants into two groups considering the volume of exercise performed (above or below 1200 MET·min/week). This threshold level was applied in two different ways: subdivision A considered the total weekly physical activity volume (considering both time spent walking for at least 10 min consecutively and time spent performing structured exercise) and subdivision B considered only the weekly volume of structured exercise. We assessed autonomic and metabolic control and auxological and lifestyle parameters. We observed that the improved volume of structured exercise was associated with reduced arterial pressure percentile only in subdivision B and an improvement in markers of vagal and metabolic control was evident. Moreover, the 12-week online exercise training program, defined considering individual fitness level and progressively adapted as the goal was reached, proved to be sustainable from an economical and organizational point of view.

Relationship between Body Composition and Cardiac Autonomic Regulation in a Large Population of Italian Olympic Athletes

Athletic performance is determined by many factors, such as cardiorespiratory fitness, muscular strength and psychological features, which all interact simultaneously. The large Italian National Olympic Committee database of Olympic athletes offers a unique healthy population to verify the strength of the interplay among a number of major elements of training, including autonomic nervous system (ANS) modulation, biochemical indicators and body composition, in a system medicine approach. This observational, retrospective study involved 583 individuals. As part of the yearly precompetitive examination, cardiac autonomic (heart rate variability), psychological, physical (cycloergometer stress test), biochemical and body composition (BOD POD) evaluations were performed. In subsequent analysis, we first considered the relationship between body composition and single individual variables in a simple correlation matrix, including a multitude of variables; then, Exploratory Factor Analysis (EFA) restricted the information to six latent domains, each combining congruent information in relation to body composition. Finally, we employed a multiple quantile regression model to evaluate possible relationships between ANSIs (index capable of synthetizing ANS regulation) and the latent domains indicated by EFA reflecting body composition. We observed a clear relationship between ANS and body mass composition parameters, as indicated by both bivariate correlations and the quantile regression result of ANSIs versus the latent domain aggregating mainly body composition data expressed in % (p = 0.002). In conclusion, these results suggest that specific training may elicit parallel adaptation of ANS control and body composition. The analysis of Olympic athletes’ data allowed us to obtain a better understanding of the complex, multidimensional factors involved in determining sport performance. The latter appears to be determined by the simultaneous interaction not only of cardiorespiratory fitness, muscular strength and psychological features, but also of ANS cardiovascular modulation and body composition.

Progressive Additive Benefits of Prehabilitation and Subsequent Bariatric Surgery on Cardiac Autonomic Regulation as Assessed by Means of a Simple Unitary Composite Index: Preliminary Data from an Observational Study

Obesity is associated with an increased risk of several chronic comorbidities, which may also be determined by dysfunctional autonomic nervous system (ANS). The influence of bariatric surgery (BS) on ANS balance was explored in previous studies, but with high heterogeneity in both the assessment timing and methods employed. In the present observational study, we applied a clinical protocol which considers two subsequent phases. Twenty-nine non-diabetic obese subjects were studied at baseline (T0), after one month of lifestyle modification (prehabilitation) (phase 1-T1), and after eight months following BS (phase 2-T2). ANS regulation was assessed across the three study epochs by means of ANSI, a single composite percent-ranked proxy of autonomic balance, being free of gender and age bias, economical and simple to apply in a clinical setting. The aim of the present study was to investigate the effects of the clinical protocol based on prehabilitation and subsequent BS on the ANS regulation by means of ANSI. Potential intertwined correlations with metabolic parameters were also investigated. Notably, we observed a progressive improvement in ANS control, even by employing ANSI. Moreover, the reduction in the markers of sympathetic overactivity was found to significantly correlate with the amelioration in some metabolic parameters (fasting glucose, insulin levels, and waist circumference), as well as in stress and tiredness perception. In conclusion, this study provides convincing evidence that a unitary proxy of cardiac autonomic regulation (CAR) may reflect the progressive improvement in autonomic regulation following behavioral and surgical interventions in obese patients. Intriguingly, this might contribute to reducing cardiovascular and metabolic risk.

Interaction between Autonomic Regulation, Adiposity Indexes and Metabolic Profile in Children and Adolescents with Overweight and Obesity

Early obesity predicts initial modifications in cardiac and vascular autonomic regulation. The aim of this study was to assess the possible interaction between non-invasive measures of autonomic cardiovascular control and peripheral endothelium regulation in children with overweight and obesity. We involved 114 young subjects (77M/37F, 12.7 ± 2.2 years) with normal weight (NW, n = 46) to overweight or obesity (OB, n = 68). Multivariate statistical techniques utilizing a collection of modern indices of autonomic regulation, adiposity indexes and metabolic profile were employed. Resting values show substantial equivalence of data. Conversely, blood pressure variance is greater in NW/OB groups. The correlation matrix between major autonomic and metabolic/hemodynamic variables shows a clustered significant correlation between homogeneous indices. A significant correlation between metabolic indices and endothelial and autonomic control, mostly in its vascular end, was recorded. Particularly, the alpha index is significantly correlated with triglycerides (r = −0.261) and endothelial indices (RHI, r = 0.276). Children with obesity show a link between indices of autonomic and endothelial function, fat distribution and metabolic profile. The optimization of autonomic control, for instance by exercise/nutrition interventions, could potentially prevent/delay the occurrence of structural vascular damage leading to reduced cardiovascular health.