Cardiovascular regulation profile predicts developmental trajectory of BMI and pediatric obesity

Understanding risk and causal mechanisms for developing obesity in infants and young children: A National Institutes of Health workshop

Obesity in children remains a major public health problem, with the current prevalence in youth ages 2-19 years estimated to be 19.7%. Despite progress in identifying risk factors, current models do not accurately predict development of obesity in early childhood. There is also substantial individual variability in response to a given intervention that is not well understood. On April 29-30, 2021, the National Institutes of Health convened a virtual workshop on "Understanding Risk and Causal Mechanisms for Developing Obesity in Infants and Young Children." The workshop brought together scientists from diverse disciplines to discuss (1) what is known regarding epidemiology and underlying biological and behavioral mechanisms for rapid weight gain and development of obesity and (2) what new approaches can improve risk prediction and gain novel insights into causes of obesity in early life. Participants identified gaps and opportunities for future research to advance understanding of risk and underlying mechanisms for development of obesity in early life. It was emphasized that future studies will require multi-disciplinary efforts across basic, behavioral, and clinical sciences. An exposome framework is needed to elucidate how behavioral, biological, and environmental risk factors interact. Use of novel statistical methods may provide greater insights into causal mechanisms.

Integrated and diurnal indices of maternal pregnancy cortisol in relation to sex-specific parasympathetic responsivity to stress in infants

Maternal hypothalamic-pituitary-adrenal axis activity may prenatally program sex-specific stress-response pathways. We investigated associations between maternal cortisol during pregnancy and infant parasympathetic responsivity to stress among 204 mother-infant pairs. Cortisol indices included 3rd trimester hair cortisol, as well as diurnal slope and area under the curve, derived from saliva samples collected during pregnancy. Mother-infant dyads participated in the Repeated Still-Face Paradigm (SFP-R) at age 6 months. We calculated respiration-adjusted respiratory sinus arrhythmia (RSA_c ), an indicator of parasympathetic activation, from infant respiration and cardiac activity measured during the SFP-R. We used multivariable linear mixed models to examine each cortisol index in relation to infant RSA_c and investigated sex differences using cross-product terms. Diurnal cortisol indices were not associated with RSA_c . There was no association between hair cortisol and baseline RSA_c . However, hair cortisol was associated with sex-specific changes in RSA_c over the SFP-R such that, among girls, parasympathetic withdrawal was reduced with increasing prenatal exposure to cortisol. Consistently higher levels of prenatal cortisol exposure may lead to dampened parasympathetic responsivity to stress during infancy, particularly among girls. Maternal hair cortisol may be particularly valuable for studying the effects of prenatal cortisol exposure on infant autonomic reactivity.

Race and sex differences in cardiovascular autonomic regulation

Racial and ethnic differences in cardiovascular morbidity and mortality persist despite advances in risk factor identification and implementation of evidence-based treatment strategies. African American men and women are disproportionately affected by cardiovascular risk factors, particularly hypertension. In this context, previous studies have identified sex and racial differences in autonomic cardiovascular regulation which may contribute to the development of hypertension and its high morbidity burden among African Americans. In this review, we provide a comprehensive evaluation of the potential pathophysiological mechanisms of blood pressure control and their differences based on sex and race. These mechanisms include obesity-induced sympathetic activation, sympatho-vascular transduction, baroreflex sensitivity and adrenoreceptor vascular sensitivity, which have been the subjects of prior investigation in this field. Understanding the racial differences in the pathophysiology of hypertension and its co-morbid conditions would allow us to implement better treatment strategies tailored to African Americans, with the ultimate goal of reducing cardiovascular mortality in this population.

Feeding During Infancy: Interpersonal Behavior, Physiology, and Obesity Risk

Infancy is a sensitive developmental period that presents both opportunities and challenges for caregivers to feed their infants in ways that support healthy growth and development. The capacity to eat in a way that supports energy (caloric) intake aligned with the body's physiologic need for growth and development appear to diminish in the years following infancy, but the reasons for this and whether this is developmentally typical are unclear. Feeding interactions that undermine infants' ability to regulate their intake in response to hunger and satiety are thought to confer risk for obesity in infancy and beyond. In this integrative review, we consider what we know about the emergence of self-regulation of behavior and emotion from both a behavioral and a physiological perspective. Then, we apply this information to our emerging understanding of how self-regulation of energy intake may be derailed through feeding interactions between caregivers and infants.

Prenatal Exposure to PM2.5 and Cardiac Vagal Tone during Infancy: Findings from a Multiethnic Birth Cohort

BACKGROUND

The autonomic nervous system plays a key role in maintaining homeostasis and responding to external stimuli. In adults, exposure to fine particulate matter (PM2.5) has been associated with reduced heart rate variability (HRV), an indicator of cardiac autonomic control.

OBJECTIVES

Our goal was to investigate the associations of exposure to fine particulate matter (PM2.5) with HRV as an indicator of cardiac autonomic control during early development.

METHODS

We studied 237 maternal-infant pairs in a Boston-based birth cohort. We estimated daily residential PM2.5 using satellite data in combination with land-use regression predictors. In infants at 6 months of age, we measured parasympathetic nervous system (PNS) activity using continuous electrocardiogram monitoring during the Repeated Still-Face Paradigm, an experimental protocol designed to elicit autonomic reactivity in response to maternal interaction and disengagement. We used multivariable linear regression to examine average PM2.5 exposure across pregnancy in relation to PNS withdrawal and activation, indexed by changes in respiration-corrected respiratory sinus arrhythmia (RSAc)-an established metric of HRV that reflects cardiac vagal tone. We examined interactions with infant sex using cross-product terms.

RESULTS

In adjusted models we found that a 1-unit increase in PM2.5 (in micrograms per cubic meter) was associated with a 3.53% decrease in baseline RSAc (95% CI: -6.96, 0.02). In models examining RSAc change between episodes, higher PM2.5 was generally associated with reduced PNS withdrawal during stress and reduced PNS activation during recovery; however, these associations were not statistically significant. We did not observe a significant interaction between PM2.5 and sex.

DISCUSSION

Prenatal exposure to PM2.5 may disrupt cardiac vagal tone during infancy. Future research is needed to replicate these preliminary findings. https://doi.org/10.1289/EHP4434.

Temperamental vulnerability to emotion dysregulation and risk for mental and physical health challenges

Emotion dysregulation characterizes many forms of psychopathology. Patterns of dysregulation occur as a function of a developmental process in which normative and adaptive emotion regulation skills fail to become part of the child's behavioral repertoire due to biological, psychological, and contextual processes and experiences. Here we highlight the processes involved in the dysregulation of temperamental anger and frustration that become core features of externalizing problems and place children at risk for more serious forms of psychopathology. We imbed these processes in a larger self-regulatory framework, and we discuss how they influence mental as well as physical health, using data from our 20-year longitudinal study following a large cohort of children into young adulthood. Recommendations are made for future research involving the integration of biological systems with mental and physical health outcomes.

Night-time cardiac autonomic modulation as a function of sleep-wake stages is modified in otherwise healthy overweight adolescents

OBJECTIVE

Even though sympathetic dominance during the daytime period is well known, currently, scarce data exist on autonomic nervous system (ANS) regulation during sleep in pediatric obesity. We aimed to evaluate sleep cardiac ANS regulation in normal-weight (NW) and overweight and obese (OW) adolescents.

PATIENTS/METHODS

In this study, 60 healthy adolescents (15.7 ± 0.7 years) belonging to a birth cohort since infancy were classified based on body mass index percentiles criteria as: OW (N = 27) or NW (N = 33). Sleep was evaluated by polysomnography (PSG) during two consecutive in-lab overnight sessions. Non-rapid eye movement (non-REM) sleep stages (stages 1, 2, and slow-wave sleep [SWS]), rapid eye movement (REM) sleep, and wakefulness (Wake) were scored. R-waves were detected automatically in the electrocardiographic (ECG) signal. An all-night heart rate variability analysis was conducted in the ECG signal, with several time- and frequency-domain measures calculated for each sleep-wake stage. Sleep time was divided into thirds (T1, T2, T3). The analysis was performed using a mixed-effects linear regression model.

RESULTS

Sleep organization was comparable except for reduced REM sleep percentage in the OW group (p < 0.04). Shorter R-R intervals were found for all sleep stages in the OW group; time-domain measured standard deviation of all R-R intervals (RRSD) was lower during stage 2, SWS and REM sleep (all p < 0.05). The square root of the mean of the sum of the squares of differences between adjacent R-R intervals (RMSSD) was also lower only during wake after sleep onset (WASO) in T1 and T3 (p < 0.05). The OW group had increased very low- and low-frequency (LF) power during WASO (in T1 and T2), and LF power during stage 2 and REM sleep (in T2). During WASO in the OW group, high-frequency (HF) power was lower (in T1 and T2), and LF/HF ratio was higher (in T2, p < 0.007).

CONCLUSIONS

Several sleep-stage-dependent changes in cardiac autonomic regulation characterized the OW group. As sleep-related ANS balance was disturbed in the absence of concomitant metabolic alterations in this sample of otherwise healthy OW adolescents, their relevance for pediatric obesity should be further explored throughout development.

Polymorphic variation in the SLC5A7 gene influences infant autonomic reactivity and self-regulation: A neurobiological model for ANS stress responsivity and infant temperament

OBJECTIVE

To examine the impact of polymorphic variation in the solute carrier family 5 member 7 (SLC5A7) gene on autonomic nervous system (ANS) reactivity indexed by respiratory sinus arrhythmia (RSA) and heart rate (HR) in infants during a dyadic stressor, as well as maternal report of infant self-regulation. Given evidence of race differences in older individuals, race was specifically examined.

METHODS

RSA and HR were collected from 111 infants during the still-face paradigm (SFP). Mothers completed the Infant Behavior Questionnaire-Revised short-form. Multi-level mixed effects models examined the impact of SLC5A7 genotype on RSA and HR across the SFP. Linear models tested the influence of genotype on the relation between RSA, HR, and maternal report of infant self-regulation.

RESULTS

SLC5A7 genotype significantly predicted RSA stress responsivity (β = -0.023; p = 0.028) and HR stress responsivity (β = 0.004; p = 0.002). T-allele carriers exhibited RSA suppression and HR acceleration in response to stress while G/G homozygotes did not suppress RSA and exhibited less HR acceleration. All infants exhibited modest RSA augmentation and HR deceleration during recovery. Race-stratified analyses revealed that White T-allele carriers drove the overall results for both RSA (β = -0.044; p = 0.007) and HR (β = 0.006; p = 0.008) with no relation between SLC5A7 genotype and RSA or HR in Black infants. Maternal report of infant orienting/regulation was predicted by the interaction of SLC5A7 genotype and both RSA recovery (β = 0.359; p = 0.001) and HR recovery (β = -1.659; p = 0.020). RSA augmentation and HR deceleration during recovery were associated with higher maternal reports of self-regulation among T-allele carriers, a finding again primarily driven by White infants.

CONCLUSIONS

Early in development, genetic contributions to ANS are evident and predict maternal report of infant self-regulation within White infants, consistent with prior literature. The lack of associations in Black infants suggest that race differences in physiological reactivity and self-regulation are emerging during the first year of life potentially providing early evidence of disparities in health risk trajectories.

Vagal Regulation of Cardiac Function in Early Childhood and Cardiovascular Risk in Adolescence

OBJECTIVE

Poor behavioral self-regulation in the first 2 decades of life has been identified as an important precursor of disease risk in adulthood. However, physiological regulation has not been well studied as a disease risk factor before adulthood. We tested whether physiological regulation at the age of 2 years, in the form of vagal regulation of cardiac function (indexed by respiratory sinus arrhythmia [RSA] change), would predict three indicators of cardiovascular risk at the age of 16 years (diastolic and systolic blood pressure and body mass index).

METHODS

Data came from 229 children who participated in a community-based longitudinal study. At the age of 2 years, children were assessed for RSA baseline and RSA change (ln(ms)) in response to a series of challenge tasks. These same children were assessed again at the age of 16 years for diastolic and systolic blood pressure (millimeters of mercury), height (meters), and weight (kilogram).

RESULTS

Regression analyses revealed that less RSA withdrawal at the age of 2 years predicted higher diastolic blood pressure at the age of 16 years, adjusting for demographic characteristics (B = -3.07, M [S E] = 1.12, p = .006). Follow-up analyses demonstrated that these predictions extended to clinically significant levels of diastolic prehypertension (odds ratio = 0.43, 95% confidence interval = 0.22-0.89). RSA withdrawal did not significantly predict adolescent body mass index or systolic blood pressure.

CONCLUSIONS

Vagal regulation of cardiac function in early childhood predicts select indicators of cardiovascular risk 14 years later. Early signs of attenuated vagal regulation could indicate an increased risk for elevated blood pressure before adulthood. Future research should test biological, behavioral, and psychological mechanisms underlying these long-term predictions.

Parent-Child Interaction, Self-Regulation, and Obesity Prevention in Early Childhood

This paper describes the epidemiologic evidence linking parent-child relationships, self-regulation, and weight status with a focus on early childhood. The emotional quality of parent-child interactions may influence children's risk for obesity through multiple pathways. Prospective studies linking observer ratings of young children's self-regulation, particularly inhibitory control, to future weight status are discussed. Although findings are preliminary, promoting positive relationships between parents/caregivers and young children holds promise as a component of efforts to prevent childhood obesity. Multi-disciplinary collaborations between researchers with training in developmental science and child health should be encouraged.

Obesity-associated sympathetic overactivity in children and adolescents: the role of catecholamine resistance in lipid metabolism

BACKGROUND

Obesity in children and adolescents is characterized by chronic sympathetic overdrive and reduced epinephrine-stimulated lipolysis. This resistance to catecholamines occurs during the dynamic phase of fat accumulation. This review will focus on the relationship between sympathetic-adrenal activity and lipid metabolism, thereby highlighting the role of catecholamine resistance in the development of childhood obesity.

RESULTS AND CONCLUSIONS

Catecholamine resistance causes lipid accumulation in adipose tissue by reducing lipolysis, increasing lipogenesis and impeding free fatty acid (FFA) transportation. Exercise improves catecholamine resistance, as evidenced by attenuated systemic sympathetic activity, reduced circulating catecholamine levels and enhanced β-adrenergic receptor signaling. Insulin resistance is mostly a casual result rather than a cause of childhood obesity. Therefore, catecholamine resistance in childhood obesity may promote insulin signaling in adipose tissue, thereby increasing lipogenesis. This review outlines a series of evidence for the role of catecholamine resistance as an upstream mechanism leading to childhood obesity.

Cardiac Autonomic Nervous System Activation and Metabolic Profile in Young Children: The ABCD Study

Background

In adults, increased sympathetic and decreased parasympathetic nervous system activity are associated with a less favorable metabolic profile. Whether this is already determined at early age is unknown. Therefore, we aimed to assess the association between autonomic nervous system activation and metabolic profile and its components in children at age of 5–6 years.

Methods

Cross-sectional data from an apparently healthy population (within the ABCD study) were collected at age 5–6 years in 1540 children. Heart rate (HR), respiratory sinus arrhythmia (RSA; parasympathetic activity) and pre-ejection period (PEP; sympathetic activity) were assessed during rest. Metabolic components were waist-height ratio (WHtR), systolic blood pressure (SBP), fasting triglycerides, glucose and HDL-cholesterol. Individual components, as well as a cumulative metabolic score, were analyzed.

Results

In analysis adjusted for child’s physical activity, sleep, anxiety score and other potential confounders, increased HR and decreased RSA were associated with higher WHtR (P< 0.01), higher SBP (p<0.001) and a higher cumulative metabolic score (HR: p < 0.001; RSA: p < 0.01). Lower PEP was only associated with higher SBP (p <0.05). Of all children, 5.6% had 3 or more (out of 5) adverse metabolic components; only higher HR was associated with this risk (per 10 bpm increase: OR = 1.56; p < 0.001).

Conclusions

This study shows that decreased parasympathetic activity is associated with central adiposity and higher SBP, indicative of increased metabolic risk, already at age 5–6 years.

Autonomic dysfunction: a possible pathophysiological pathway underlying the association between sleep and obesity in children at-risk for obesity

While mounting evidence suggests that sleep plays an important role in the etiology of obesity, the underlying pathogenic pathways are complex and unresolved. Experimental sleep deprivation studies demonstrate sympathovagal imbalance, indicative of diminished parasympathetic activity and/or heightened sympathetic activity, is consequent to poor sleep. Further, obese children exhibit sympathovagal imbalance, particularly during the night, compared to non-obese children. The question remains whether sympathovagal imbalance is one potential pathophysiological pathway underlying the association between sleep and obesity. The aim of the present study was to examine whether sympathovagal imbalance contributed to the association between sleep and obesity in children. Participants included 564 children aged 10 to 12 years (M = 11.67, SD = 0.95; 43.5% girls) from the QUALITY Cohort, a longitudinal study of children at-risk for the development of obesity. While children were at-risk due to confirmed parental obesity status, 57.7% of children were of normal body mass index (5-85th percentile). Sleep duration, sleep timing, and sleep disturbances were based on child- and parent-report. Anthropometrics were measured for central adiposity (waist circumference) and body composition (body mass index, fat mass index). Sympathovagal imbalance was derived from heart rate variability spectral analyses. Estimated path coefficients revealed that sympathovagal imbalance partially contributed to the association between poor sleep (later bedtimes, sleep-disordered breathing) and obesity. These findings highlight the importance of better understanding sympathovagal imbalance and its role in the etiology and maintenance of obesity. Future research should consider investigating nocturnal sympathovagal balance in youth.

Latino children's body mass index at 2-3.5 years predicts sympathetic nervous system activity at 5 years

BACKGROUND

To understand whether the relationship between young children's autonomic nervous system (ANS) responses predicted their BMI, or vice versa, the association between standardized BMI (zBMI) at 2, 3.5, and 5 years of age and ANS reactivity at 3.5-5 years of age, and whether zBMI predicts later ANS reactivity or whether early ANS reactivity predicts later zBMI, was studied.

METHODS

Low-income, primarily Latino children (n=112) were part of a larger cohort study of mothers recruited during early pregnancy. Study measures included maternal prenatal weight, children's health behaviors (i.e., time watching television, fast food consumption, and time playing outdoors), children's height and weight at 2, 3.5, and 5 years, and children's ANS reactivity at 3.5 and 5 years. ANS measures of sympathetic nervous system (i.e., pre-ejection period) and parasympathetic nervous system (i.e., respiratory sinus arrhythmia) activity were monitored during rest and four challenges. Reactivity was calculated as the difference between mean challenge response and rest. Structural equation models analyzed the relationship between children's zBMI at 2, 3.5, and 5 years and ANS reactivity at 3.5 and 5 years, adjusting for mother's BMI, children's behaviors, and changes in height.

RESULTS

There was no association between zBMI and ANS cross-sectionally. Children with high zBMI at 2 or 3.5 years or large zBMI increases from 2 to 3.5 years of age had decreased sympathetic activity at 5 years. Neither sympathetic nor parasympathetic reactivity at 3.5 years predicted later zBMI.

CONCLUSIONS

Increased zBMI early in childhood may dampen young children's SNS responses later in life.

Prenatal adversities and Latino children's autonomic nervous system reactivity trajectories from 6 months to 5 years of age

The purpose of the study was to determine whether mothers' adversities experienced during early pregnancy are associated with offspring's autonomic nervous system (ANS) reactivity trajectories from 6 months to 5 years of age. This cohort study of primarily Latino families included maternal interviews at 13-14 weeks gestation about their experience of a range of adversities: father's absence, general social support, poverty level, and household density. ANS measures of heart rate, respiratory sinus arrhythmia (parasympathetic nervous system) and preejection period (sympathetic nervous system) were collected during resting and challenging conditions on children at 6 months and 1, 3.5 and 5 years of age. Reactivity measures were calculated as the mean of the responses to challenging conditions minus a resting condition. Fixed effects models were conducted for the 212 children with two or more timepoints of ANS measures. Interactions between maternal prenatal adversity levels and child age at time of ANS protocol were included in the models, allowing the calculation of separate trajectories or slopes for each level of adversity. Results showed no significant relations between mothers' prenatal socioeconomic or social support adversity and offspring's parasympathetic nervous system trajectories, but there was a statistically significant relationship between social support adversity and offspring's heart rate trajectories (p<.05) and a borderline significant relationship between socioeconomic adversity and offspring's sympathetic nervous system trajectories (p = .05). Children whose mothers experienced one, not two, social support adversity had the smallest increases in heart rate reactivity compared to children whose mothers experienced no adversity. The children whose mothers experienced no social support and no socioeconomic adversity had the largest increases in heart rate and preejection period respectively from 6 months to 5 years showing the most plasticity. Mothers' prenatal adverse experiences may program their children's physiologic trajectory to dampen their heart rate or sympathetic responsivity to challenging conditions.

Cardiac vagal control and children's adaptive functioning: a meta-analysis

Polyvagal theory has influenced research on the role of cardiac vagal control, indexed by respiratory sinus arrhythmia withdrawal (RSA-W) during challenging states, in children's self-regulation. However, it remains unclear how well RSA-W predicts adaptive functioning (AF) outcomes and whether certain caveats of measuring RSA (e.g., respiration) significantly impact these associations. A meta-analysis of 44 studies (n=4996 children) revealed small effect sizes such that greater levels of RSA-W were related to fewer externalizing, internalizing, and cognitive/academic problems. In contrast, RSA-W was differentially related to children's social problems according to sample type (community vs. clinical/at-risk). The relations between RSA-W and children's AF outcomes were stronger among studies that co-varied baseline RSA and in Caucasian children (no effect was found for respiration). Children from clinical/at-risk samples displayed lower levels of baseline RSA and RSA-W compared to children from community samples. Theoretical/practical implications for the study of cardiac vagal control are discussed.

Respiratory sinus arrhythmia and auditory processing in autism: modifiable deficits of an integrated social engagement system?

The current study evaluated processes underlying two common symptoms (i.e., state regulation problems and deficits in auditory processing) associated with a diagnosis of autism spectrum disorders. Although these symptoms have been treated in the literature as unrelated, when informed by the Polyvagal Theory, these symptoms may be viewed as the predictable consequences of depressed neural regulation of an integrated social engagement system, in which there is down regulation of neural influences to the heart (i.e., via the vagus) and to the middle ear muscles (i.e., via the facial and trigeminal cranial nerves). Respiratory sinus arrhythmia (RSA) and heart period were monitored to evaluate state regulation during a baseline and two auditory processing tasks (i.e., the SCAN tests for Filtered Words and Competing Words), which were used to evaluate auditory processing performance. Children with a diagnosis of autism spectrum disorders (ASD) were contrasted with aged matched typically developing children. The current study identified three features that distinguished the ASD group from a group of typically developing children: 1) baseline RSA, 2) direction of RSA reactivity, and 3) auditory processing performance. In the ASD group, the pattern of change in RSA during the attention demanding SCAN tests moderated the relation between performance on the Competing Words test and IQ. In addition, in a subset of ASD participants, auditory processing performance improved and RSA increased following an intervention designed to improve auditory processing.