Julian Koenig

Sex differences in healthy human heart rate variability: A meta-analysis.

The present meta-analysis aimed to quantify current evidence on sex differences in the autonomic control of the heart, indexed by measures of heart rate variability (HRV) in healthy human subjects. An extensive search of the literature yielded 2020 titles and abstracts, of which 172 provided sufficient reporting of sex difference in HRV. Data from 63,612 participants (31,970 females) were available for analysis. Meta-analysis yielded a total of 1154 effect size estimates (k) across 50 different measures of HRV in a cumulated total of 296,247 participants. Females showed a significantly lower mean RR interval and standard deviation of RR intervals (SDNN). The power spectral density of HRV in females is characterized by significantly less total power that contains significantly greater high- (HF) and less low-frequency (LF) power. This is further reflected by a lower LF/HF ratio. Meta-regression revealed significant effects of age, respiration control and the length of recording available for analysis. Although women showed greater mean heart rate, they showed greater vagal activity indexed by HF power of HRV. Underlying mechanisms of these findings are discussed.

Resting heart rate variability predicts self-reported difficulties in emotion regulation: a focus on different facets of emotion regulation

The Model of Neurovisceral Integration suggests that vagally mediated heart rate variability (vmHRV) represents a psychophysiological index of inhibitory control and thus, is associated with emotion regulation capacity. Over the past decade, growing empirical evidence supports this notion, showing that those with higher resting vmHRV can regulate negative emotions more adequately. However, to our knowledge, no study has previously examined how resting vmHRV may relate to everyday perceived difficulties in emotion regulation. The present study attempts to examine such relationship in 183 undergraduate students (98 female, 60 minority, mean Age = 19.34). Resting vmHRV was collected during a 5-min resting baseline period, and everyday difficulties in emotion regulation were assessed using the Difficulties in Emotion Regulation Scale (DERS). Controlling for potential covariates (including both trait anxiety and rumination), results revealed a negative relationship between resting vmHRV and DERS such that lower resting vmHRV was associated with greater difficulties in emotional regulation, especially a lack of emotional clarity and impulse control, as indicated by the respective subscales of the DERS. These findings provide further evidence for the Neurovisceral Integration Model, suggesting that emotion regulation and autonomic regulation share neural networks within the brain. Moreover, the present study extends prior research by highlighting two distinct facets of emotion regulation (impulse control and emotional clarity) that should be of particular interest when investigating the link between emotion regulation, resting vmHRV, and related health outcomes including morbidity and mortality.

Autonomic nervous system activity and workplace stressors—A systematic review

AIM This systematic review evaluates and summarizes the evidence of the association between psychosocial work environment as indicated by several work-stress models such as Job-Demand-Control (JDC), Effort-Reward-Imbalance (ERI), or Organizational Justice (OJ) and autonomic nervous system (ANS) function as indexed by heart rate variability (HRV). METHOD We conducted a systematic literature search following the PRISMA-Statement in eleven databases including Medline, Web of Science and PsycINFO to address medical as well as psychological aspects of the relation between psychosocial work-stress models and HRV. RESULTS We identified 19 publications with a total of 8382 employees from ten countries reporting data from the years 1976-2008. Overall, nine of all studies report a negative and significant association between vagally-mediated HRV and measures of stress at work, while eight of all studies report a negative and significant association to mixed sympathetic and parasympathetic measures of HRV. CONCLUSIONS This systematic review provides evidence that adverse psychosocial work conditions are negatively associated with ANS function as indexed by HRV.

Heart rate variability and experimentally induced pain in healthy adults: A systematic review

Reactivity of the autonomic nervous system to experimental pain stimuli has been extensively studied using measures of heart rate and blood pressure. Heart rate variability (HRV) attempts to tease out the relative contributions of sympathetic and parasympathetic activity in the autonomic control of the heart and may therefore be more appropriate to investigate autonomic response to short‐term nociceptive stimulation in detail. The current evidence on HRV and experimentally induced pain has not yet been synthesized within a systematic review.

Body mass index is related to autonomic nervous system activity as measured by heart rate variability--a replication using short term measurements.

ObjectivesThe present analysis is a replication of previous findings presenting first evidence of an association between body mass index (BMI) and autonomic nervous system (ANS) activity as measured by heart rate variability (HRV), in healthy non-obese adults.DesignA total of fifty-nine apparently healthy male (M) and female (F) individuals (M/F = 15/44) were included in the trial. HRV data for analysis was derived from 5 minutes of baseline recordings, while the subject was sitting on a comfortable chair. Subjects’ body measures (weight and height) were taken and BMI was obtained according to common calculation (kg/m2).ResultsBMI was inversely related to pNN50 and RMSSD components of HRV. Statistically significant differences between stratified groups (BMI<20, BMI 20–25, BMI >25) only occurred for analysis of pNN50 components. The pNN50 components and RMSSD are strongly associated with cardiac vagal influence, and thus represents parasympathetic activity.ConclusionsThe present data supports previous findings, that sympatho-vagal balance is related to BMI in non-obese, healthy individuals, providing evidence for a prominent role of the vagus nerve in the modulation of the energy expenditure of the human organism. Furthermore, this relation can be observed in short term recordings of HRV of 5 minutes in length.

Ethnic Differences in Resting Heart Rate Variability : A Systematic Review and Meta-Analysis

Background Ethnic disparities in cardiovascular morbidity and mortality are widely documented in the literature. Recently, research has shown that decreased parasympathetic cardiac modulation is associated with the established and emerging risk factors for cardiovascular disease (CVD) and stroke. In consideration of the disproportionate CVD risk and disease profile of African Americans (AAs), it is plausible that decreased cardiac parasympathetic functioning may partially explain these disparities. In the present systematic review and meta-analysis, we assess the available evidence for a reliable ethnic difference in tonic vagally mediated heart rate variability (HRV), an indicator of parasympathetic cardiac modulation. Methods A systematic literature search was conducted yielding studies comparing tonic HRV in AAs and European Americans. Adjusted standardized effect sizes (Hedges g) were calculated using a mixed-effects model, with restricted maximum likelihood estimation for 17 studies containing appropriate measures of vagally mediated HRV. Results Meta-analysis results suggest that AAs have greater HRV than do European Americans (Hedges g = 0.93, 95% confidence interval = 0.25–1.62), even after consideration of several covariates including health status, medication use, and subgroup stratification by sex and age. Conclusions These findings suggest that decreased vagally mediated HRV is not likely to account for the persistent health disparities experienced by AAs with respect to CVD risk and burden. These disparities underscore the need for continued research addressing socioethnic cardiovascular differences and the biobehavioral mechanisms involved.

Investigating the associations of self-rated health: heart rate variability is more strongly associated than inflammatory and other frequently used biomarkers in a cross sectional occupational sample.

The present study aimed to investigate the possible mechanisms linking a single–item measure of global self-rated health (SRH) with morbidity by comparing the association strengths between SRH with markers of autonomic nervous system (ANS) function, inflammation, blood glucose and blood lipids. Cross–sectional comprehensive health–check data of 3947 working adults (age 42±11) was used to calculate logistic regressions, partial correlations and compare correlation strength using Olkins Z. Adjusted logistic regression models showed a negative association between SRH (higher values indicating worse health) and measures of heart rate variability (HRV). Glycemic markers were positively associated with poor SRH. No adjusted association was found with inflammatory markers, BP or lipids. In both unadjusted and adjusted linear models Pearson’s correlation strength was significantly higher between SRH with HRV measures compared to SRH with other biomarkers. This is the first study investigating the association of ANS function and SRH. We showed that a global measure of SRH is associated with HRV, and that all measures of ANS function were significantly more strongly associated with SRH than any other biomarker. The current study supports the hypothesis that the extent of brain–body communication, as indexed by HRV, is associated with self-rated health.

Lower heart rate variability predicts increased level of C-reactive protein 4 years later in healthy, nonsmoking adults.

Inflammation and vagally mediated heart rate variability (vmHRV) have been implicated in a number of conditions including diabetes and cardiovascular disease. Consistent with the inflammatory reflex termed the ‘cholinergic anti‐inflammatory pathway’, numerous cross‐sectional studies have demonstrated negative associations between vmHRV and inflammatory markers such as C‐reactive protein (CRP). The only prospective study, however, showed the opposite: higher CRP at baseline predicted higher high‐frequency heart rate variability (HF‐HRV) at follow‐up. Thus, additional studies are needed to examine the prospective association between vmHRV and CRP.

A careful look at ECG sampling frequency and R-peak interpolation on short-term measures of heart rate variability

As the literature on heart rate variability (HRV) continues to burgeon, so too do the challenges faced with comparing results across studies conducted under different recording conditions and analysis options. Two important methodological considerations are (1) what sampling frequency (SF) to use when digitizing the electrocardiogram (ECG), and (2) whether to interpolate an ECG to enhance the accuracy of R-peak detection. Although specific recommendations have been offered on both points, the evidence used to support them can be seen to possess a number of methodological limitations. The present study takes a new and careful look at how SF influences 24 widely used time- and frequency-domain measures of HRV through the use of a Monte Carlo-based analysis of false positive rates (FPRs) associated with two-sample tests on independent sets of healthy subjects. HRV values from the first sample were calculated at 1000 Hz, and HRV values from the second sample were calculated at progressively lower SFs (and either with or without R-peak interpolation). When R-peak interpolation was applied prior to HRV calculation, FPRs for all HRV measures remained very close to 0.05 (i.e. the theoretically expected value), even when the second sample had an SF well below 100 Hz. Without R-peak interpolation, all HRV measures held their expected FPR down to 125 Hz (and far lower, in the case of some measures). These results provide concrete insights into the statistical validity of comparing datasets obtained at (potentially) very different SFs; comparisons which are particularly relevant for the domains of meta-analysis and mobile health.

Short-term effects of espresso coffee on heart rate variability and blood pressure in habitual and non-habitual coffee consumers – A randomized crossover study

Objective: Coffee is one of the most widely consumed beverages worldwide. Aim of this study was to investigate short-term effects of espresso coffee on heart rate variability (HRV), a marker of vagal activity, in healthy habitual and non-habitual coffee consumers. Methods: Seventy-seven healthy subjects (38 habitual and 39 non-habitual coffee consumers, 74% women, mean age 26.97 ± 6.88 years) took part in three laboratory sessions in a randomized order. In condition 1, subjects consumed espresso; in condition 2, subjects consumed decaffeinated espresso; and in condition 3, subjects consumed warm water. HRV and blood pressure were assessed at rest before and after ingestion of the respective beverage. Results: HRV was significantly increased after consumption of caffeinated espresso, decaffeinated espresso, or water, indicating increased vagal activity in the course of the experiments. In the habitual coffee consumers, the increase in vagally mediated HRV was significantly lower after consumption of decaffeinated espresso compared to caffeinated espresso. Increases of systolic blood pressure were only found in the non-habitual consumers. Conclusion: We found no evidence for specific short-term effects of caffeinated espresso on vagal activity in healthy subjects. Instead, consumption of decaffeinated espresso inhibited vagal activity in habitual consumers. This may be explained by an attempt of the organism to establish a sympathovagal equilibrium comparable to that after caffeine consumption. In the absence of caffeine-induced sympathetic activation, this may have been achieved by relative vagal withdrawal.