Heart rate variability for determining autonomic nervous system effects of lifestyle behaviors in early life: A systematic review

Reliability of an "At-Home" Method for Monitoring Resting and Reactive Autonomic Nervous System Activity in Children: A Pilot Study

BACKGROUND

Heart rate variability (HRV), an index of the functional status of the autonomic nervous system (ANS), provides an opportunity for early detection of ANS dysfunction. Lower resting, vagally related HRV parameters are associated with increased risk of physical and mental illness. External factors influencing the ANS, such as the testing environment, may impact the interpretation of HRV. This study's main aim was to determine the reliability of HRV resting and reactivity tests performed at home with children aged 4-9 years.

METHODS

Fourteen healthy children (female n = 8) aged 6.8 ± 1.5 years participated. Two HRV tests were performed at home via online supervision 7 days apart using a Polar H10 heart rate monitor. The absolute and relative reliability of the pre-exercise resting (5 min) and sub-maximal exercise step test recovery (4 × 30 s segments) HRV time and frequency domains were calculated.

RESULTS

The Pearson correlation coefficients for day 1 versus day 7 for the vagal activity HRV domains (RMSSD log) at rest and in the first 30 s and 30-60 s of recovery indicated good-to-excellent relative reliability (r > 0.8, p < 0.01). Absolute reliability was moderate for the resting RMSSD log, with a coefficient of variation (CV) of 5.2% (90% CI: 3.9, 7.8%), high for the first 30 s of standing recovery, with a CV of 10.7% (90% CI: 8.2, 15.7%), and moderate for 30-60 s of recovery, with a CV of 8.7% (90% CI: 6.6, 12.9%).

CONCLUSIONS

The findings of this pilot study indicate that the resting and exercise recovery HRV measures of vagal activity can be measured reliably at home in children. This represents a novel "at-home" protocol for monitoring ANS health and development in children.

Heart rate variability to track autonomic nervous system health in young children: Effects of physical activity and cardiometabolic risk factors

Evidence for a key role of dysregulated autonomic nervous system (ANS) activity in maladaptive stress response/recovery and non-communicable disease development is extensive. Monitoring ANS activity via regular heart rate variability (HRV) measurement is growing in popularity in adult populations given that low HRV has been associated with ANS dysregulation, poor stress response/reactivity, increased cardiometabolic disease risk and early mortality. Although cardiometabolic disease may originate in early life, regular HRV measurement for assessing ANS activity in childhood populations, especially those consisting of children < 6 years of age, remains largely unpractised. A greater understanding of ANS activity modifiers in early life may improve analysis and interpretation of HRV measurements, thereby optimising its usefulness. Taking into consideration that HRV and ANS activity can be improved via daily engagement in physical activity (PA), this review will discuss the ANS and HRV, ANS activity modifiers, cardiometabolic disease risk factors and PA as they relate to childhood/adolescent populations (≤ 18 years old).

Association of lifestyle habits and cardiovascular risk among sedentary adults

This study aimed to analyze the association of lifestyle habits (physical activity, sleep habits, and eating habits) with cardiovascular risk (arterial stiffness and autonomic nervous system function) among sedentary adults. Sixty adults of sedentariness and physical activity were evaluated by accelerometers; sleep and eating habits were assessed by questionnaires; cardiovascular risks were assessed by pulse wave velocity (PWV), ankle-brachial index, flow mediated dilation, and heart rate variability; circulating biomarkers were also determined. Prolonged sitting (represented by longer maximum length of sedentary bouts, lower length of sedentary breaks, and more total time of sitting) were (P < .05) significantly associated with matrix metalloproteinases, neuropeptide Y, C-reactive protein, peptide Y, ghrelin, and leptin; significant associations (P < .05) were also observed of total time in physical activity with most circulating biomarkers except interleukin-6, tumor necrosis factor-α, and adiponectin. Sleep habits, especially sleep efficiency, were (P < .05) significantly associated with PWV, ankle-brachial index, and circulating biomarkers. Eating habits (including emotional overeating and enjoyment of food) were (P < .05) significantly associated with PWVs and flow mediated dilation; satiety responsiveness and enjoyment of food were (P < .05) significantly associated with low-frequency spectral component expressed in normalized units, high frequency spectral component expressed in normalized units, and ratio between low-frequency/high frequency spectral component expressed in normalized units. The findings indicated that several lifestyle habits among sedentary adults were closely associated with increased cardiovascular risk. Sedentary people were encouraged to live with sufficient physical activity, good sleep, and healthy eating habits for decreasing arterial stiffness and balancing autonomic nervous function.

Association between vitamin B12 status and heart rate variability in patients with ischemic stroke

Autonomic dysfunction is common in patients with ischemic stroke. An ischemic stroke may induce abnormalities in autonomic tone, resulting in poor heart rate regulation and an increased risk of severe cardiac arrest and sudden death. Heart rate variability (HRV) is a reliable index for evaluating autonomic dysfunction. Vitamin B12 deficiency is frequent among older adults and is a known risk factor for ischemic stroke. As vitamin B12 deficiency affects the peripheral nerves and the central nervous system, it can lead to autonomic dysfunction. However, no study has been published on the correlation between HRV and vitamin B12 status in patients with ischemic stroke. This study aimed to investigate the relationship between HRV and vitamin B12 status and to determine whether the serum vitamin B12 level can be a predictor of HRV parameters. This retrospective study enrolled patients with ischemic stroke between January 2015 and December 2022. The patients underwent serum vitamin B12 level measurements and 24-h Holter monitoring. Pearson correlation analysis was used to investigate the correlation between serum vitamin B12 levels and HRV parameters. The impact of serum vitamin B12 status on HRV parameters was determined using multiple linear regression analysis. A total of 87 patients with ischemic stroke were included in this study. HRV parameters were significantly correlated with serum vitamin B12 status in the frequency domain. In multiple linear regression analysis, the serum vitamin B12 status was a significant predictor of HRV parameters. HRV parameters may be correlated with serum vitamin B12 status in patients with ischemic stroke. Therefore, the serum vitamin B12 status may be a significant predictor of autonomic dysfunction. Our results may provide objective evidence for the impact of serum vitamin B12 status on autonomic dysfunction in patients with ischemic stroke.

Effects of Occupational Stress and Health Behaviors on Heart Rate Variability in Live-Fire Instructors

OBJECTIVES

This study aimed to identify the association between the healthrelated characteristics and the subscales of occupational stress of live fire instructors and heart rate variability (HRV).

METHODS

We conducted questionnaire survey on a general health checkup for 15 live fire instructors. Occupational stress and HRV parameters were measured to determine the association between health behavior, including smoking, drinking, exercise, and sleep-related disorders, and occupational stress of live fire instructors and HRV parameters using Spearman's rank correlation coefficient.

RESULTS

Smoking, insomnia, and job insecurity, a subscale of occupational stress measurement, showed negative Spearman rank correlations with HRV.

CONCLUSIONS

Insomnia, smoking, and job insecurity (due to occupational stress) among live fire instructors were associated with decreased HRV.

Heart rate variability improves in 3-5-year-old children following a 6-month physical activity-based intervention: the Active Early Learning (AEL) cluster randomised controlled trial

Heart rate variability (HRV) measurement provides non-invasive assessment of autonomic stability and cardiometabolic disease risk. Insufficient physical activity in early childhood may contribute to negative cardiometabolic health. The Active Early Learning (AEL) study was a 6-month randomised controlled trial investigating the effects of a physical activity-based program incorporating movement within the daily curriculum of preschool children. The current study assessed the effects of the AEL intervention on HRV as a measure of cardiac vagal control. Children aged between 3-5 years and enrolled in a preschool with an attendance of ≥15 children were eligible. 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 HRV with the HF-band and RMSSD representing cardiac vagal control. After 6 months of the AEL trial, linear mixed model analyses revealed a significant intervention effect for increased HF (p = 0.044). The control group did not demonstrate changes in cardiac vagal control after the intervention ceased. Independent of age, sex, physical activity and BMI, the AEL study elicited significant improvements in the cardiac vagal control of participants who received the intervention. Findings highlight the importance of investigating HRV for assessing the cardiometabolic health in young children. ANZCTR trial registration number: ACTRN12619000638134. Novelty: The AEL curriculum improved child HRV independent of age, sex, physical activity and BMI. Heart rate and RR intervals did not demonstrate changes for the intervention and control groups. Multivariate programs for developing physical competence, confidence, knowledge and motivation may improve child health.