Variability in 24-h and visit-to-visit blood pressure (BP) has been reported to be predictive of adverse cardiovascular outcomes. Although recent studies have used beat-to-beat blood pressure variability (BPV) as a predictor of cardiovascular risk, the reliability of beat-to-beat BPV remains equivocal. The purpose of this study was to examine the intraindividual reliability of BPV and to compare that reliability to more widely documented heart rate variability (HRV) in young healthy adults. Continuous heart rate (HR, electrocardiogram), beat-to-beat blood pressure (BP, finger plethysmography), and respiratory rate (pneumobelt) were recorded during 10 min of rest in 77 participants [38 males and 39 females; age: 23 ± 5 yr; body mass index (BMI): 25 ± 4 kg·m-2] on two occasions separated by ≥2 days (25 ± 19 days; 2-98 days). Reliabilities of beat-to-beat BPV, HRV (time- and frequency-domain), and additional cardiovascular (heart rate, blood pressure) assessments were quantified as relative and absolute reliability using the intraclass correlation coefficient (ICC) and the coefficient of variation (CoV), respectively. Beat-to-beat BPV demonstrated moderate relative and good absolute reliability (10-min duration: ICC = 0.601-0.684, CoV = 14%-16%). In contrast, relative reliability of time-domain HRV was good-to-excellent, whereas absolute reliability was poor-to-good (10-min duration: ICC = 0.844-0.904, CoV = 13%-34%). Frequency-domain HRV demonstrated moderate to excellent relative reliability and poor absolute reliability (10-min duration: ICC = 0.626-0.903, CoV = 34%-37%). In summary, the rigor and reliability of continuous BPV and HRV are different when parsed out by relative versus absolute reliability, with relative reliability being stronger with HRV and absolute reliability being stronger with BPV. These findings suggest both caution and specificity when using continuous BPV or HRV for cardiovascular disease (CVD) risk-stratification purposes.NEW & NOTEWORTHY Beat-to-beat blood pressure variability (BPV) has gained attention as a noninvasive predictor of cardiovascular disease. However, the reliability of BPV has not been adequately characterized. We investigated the intraindividual reliability of beat-to-beat BPV and compared that reliability to more traditional heart rate variability (HRV). BPV demonstrated higher absolute, but lower relative, reliability compared with HRV. These findings suggest a need for caution and specific reporting when using continuous BPV or HRV for cardiovascular risk-stratification purposes.

Chronic musculoskeletal pain (CMP) involves autonomic dysregulation quantifiable with heart rate variability (HRV), but findings are heterogeneous and the influence of HRV protocols and clinical characteristics remain unclear. This study aimed to quantify autonomic imbalance in CMP and identify methodological and clinical moderators of between-study heterogeneity. A systematic review, meta-analysis, and multilevel meta-regression following PRISMA was conducted. Electronic databases were searched for studies comparing resting-state HRV between adults with CMP and healthy controls. Effect sizes (Hedges g) were pooled with random-effects models. Individual HRV indices were meta-analyzed and then aggregated into functional domains (vagal, global, sympathovagal balance) for multilevel meta-regression including recording duration, pain condition, posture, and sex distribution as moderators. Twenty-six studies (3641 participants: 1207 CMP, 2434 controls) were included. Patients showed reduced vagal indices and global variability and higher sympathovagal balance across time, frequency, and nonlinear domains. Domain-aggregated effects indicated impaired vagal modulation (g = -0.52, 95% CI -0.67 to -0.37), reduced global variability, and elevated sympathovagal balance, with substantial heterogeneity. Multilevel meta-regression identified a significant recording duration × condition interaction (β = 0.154, P < 0.001): in fibromyalgia, longer recordings were associated with greater vagal impairment (β = -0.078, P < 0.001), whereas regional pain conditions were adequately characterized by shorter protocols. CMP is characterized by consistent HRV reductions, most prominently vagal withdrawal. Heterogeneity across studies reflects condition-specific autonomic phenotypes: fibromyalgia shows systemic dysregulation detectable with extended recordings, whereas regional pain conditions display more localized HRV alterations. Protocol standardization must be condition-tailored rather than universal.

Sleep bruxism as a potential modifier of autonomic function and heart rate variability in patients with obstructive sleep apnea.

Respiratory heart rate variability: Insights into mechanisms, measurements and interpretations.

Alpha1 adrenergic receptors integrate across multiple separable heart rate variability metrics during alcohol drinking.

Postural orthostatic tachycardia syndrome (POTS) is associated with autonomic dysregulation, but ambulatory markers that capture autonomic phenotype remain incompletely defined.To compare Holter-derived heart rate variability (HRV) metrics between adolescents with POTS and healthy controls and to derive candidate discriminatory thresholds.Retrospective case-control analysis of an existing Holter dataset (POTS n = 19, controls n = 44). Heart rate variability was processed in Kubios HRV Premium. Between-group comparisons used Welch's t-test with Benjamini-Hochberg false discovery rate adjustment. Nonparametric sensitivity analyses yielded similar results. Discrimination was assessed using receiver operating characteristic analysis; optimal thresholds were defined by the Youden index. An exploratory penalized logistic regression model (L1 regularization) was fit with standardized candidate HRV predictors and internal cross-validation.Among 19 POTS patients and 44 control subjects, POTS demonstrated lower time- and frequency-based HRV, higher rate-related and sympathetic composite indices, and lower parasympathetic composite measures. The strongest univariate discriminator was PNSi (Parasympathetic Nervous System index; AUROC 0.874; threshold ≤ -1.10; sensitivity 77.8%; specificity 88.6%). Other high-performing discriminators included SNSi, mean RR, mean heart rate, and SDNNi.Holter-derived HRV metrics demonstrate a reproducible pattern consistent with reduced parasympathetic modulation and relative sympathetic predominance in POTS. Several variables yield candidate discriminatory thresholds that may support physiologic phenotyping and warrant validation in independent cohorts.

Methylphenidate is a first-line psychostimulant widely prescribed for the treatment of attention-deficit/hyperactivity disorder (ADHD). Although its therapeutic efficacy is well established, concerns remain regarding its potential effects on cardiovascular regulation, particularly on autonomic nervous system balance. To evaluate the effect of methylphenidate on heart rate variability (HRV) in ADHD children and adolescents. Our review included children and adolescents diagnosed with ADHD, studies wherein the intervention group should receive short- or long-term methylphenidate treatment, studies that evaluated participants under conventional treatment except methylphenidate, single or double-blind, non-blind randomized or non-randomized control studies. No significant changes were observed in time- and frequency-domain HRV indices, with all outcomes presenting very low certainty of evidence. Our results indicate that methylphenidate does not significantly affect resting heart rate HRV in ADHD children and adolescents. The very low certainty of this review's evidence level and high risk of bias warrant further studies to provide stronger scientific and statistical evidence.

Workplace stress is one of the main sources of stress for adults, although physiological and cognitive factors may impact each person's stress response. Numerous studies have shown heart rate, heart rate variability, neural activity, and cognitive performance are affected by stress. Additionally, visual and auditory stimuli in one's environment have been shown to affect individuals' reaction to stressful events. To our knowledge, few studies have examined how each of these physiological and cognitive measures relate to one's perception of stress, the ability to recover from stress, and what environmental factors may help with stress recovery. Here, 80 healthy adults performed a laboratory-controlled stress induction task where they experienced and recovered from an acute psychological stressor (Trier Social Stress Test, TSST, using verbal math skills and a public presentation that was videotaped). Throughout the assessment, heart rate, heart rate variability, and neural activity were measured using wearable devices to assess changes before, during, and after the stressor. Additionally, participants were assessed their perceived stress levels at specific times throughout the assessment. After the psychological stressor, participants were randomly assigned to one of four recovery conditions within a multisensory relaxation room: Control (C), Auditory Only (A), VisualOnly (V), or Combined Auditory and Visual (AV). During the stressor, anxiety, heart rate, and beta EEG power increased and high-frequency power and heart rate variability decreased, confirming participants reactivity to the stressor (P < 0.01 for all vs. baseline). Only the V and AV conditions led to notable reductions in anxiety (15 and 17%, respectively) vs. the C condition, but these did not reach statistical significance. There was no difference between V and AV, suggesting a stronger impact of V. We observed no differences between conditions during recovery for HR and HRV. Overall, these findings suggest the visual features of the relaxation room impacted self-reported anxiety, however physiological and neurological effects did not demonstrate a statistically meaningful response.

Chronic heart failure (CHF) is a condition affecting millions worldwide, characterized by the heart's reduced ability to pump blood efficiently. Conventional diagnostics, such as imaging and ECG assessments, can be time-consuming and expensive, often identifying CHF only after significant progression. Early detection is crucial for improving treatment options and reducing healthcare costs. Heart rate variability (HRV), which measures the variation in time intervals between heartbeats, is emerging as a non-invasive and cost-effective biomarker for CHF detection. HRV reflects the autonomic nervous system's regulatory functions, often impaired in CHF patients. This study aims to assess advanced HRV measures for earlier CHF detection. The research involved examining CHF patients (N = 934, Age 65 ± 12) compared to healthy controls (N = 274, Age 43 ± 17). Data was sourced from Physionet and the Telemetric and Holter ECG Warehouse, with RR interval (RRI) data extracted from 24-h Holter recordings. The study utilized dynamical detrended fluctuation analysis (DDFA), which considers changes in RRI correlations over time and scale, resulting in scaling exponent α(t,s). This was further aggregated into scale and heart rate (HR)-dependent forms, α(HR,s), classified using XGBoost ensemble method with 10-fold nested cross-validation. The classifier achieved 97% sensitivity and 90% specificity for distinguishing between CHF and control groups. Sensitivity and specificity remained consistent across subgroup analyses based on beta blocker medication and NYHA class. This method demonstrated high classification accuracy, suggesting potential utility for early CHF detection, independent of CHF severity.

To investigate the effects of a 13-week Pilates Method (PM) program, combining mat and apparatus-based exercises, on ambulatory blood pressure (BP), autonomic reflex regulation, and endothelial function in women with hypertension receiving pharmacological treatment. Twenty-eight women with hypertension (39-59 years) were randomized to a control group (CG, n = 14) or a Pilates group (PG, n = 14). The PG completed supervised PM sessions twice weekly, while the CG maintained usual care. Outcomes included ambulatory BP monitoring (24-h, daytime, and nighttime), heart rate variability (HRV), autonomic reflex tests (Valsalva ratio, deep breathing, HR and BP response to standing, and isometric handgrip), flow-mediated dilation (FMD), and circulating nitric oxide (NO) and nitric oxide synthase (NOS). Analyses were adjusted for baseline body weight. Significant Group × Time interactions were observed for all ambulatory BP parameters (all P ≤ 0.022, η2p = 0.19-0.31), with greater reductions in PG (e.g., 24-h SBP -10.3 mmHg, P = 0.009). Among autonomic reflex tests, only the deep breathing test demonstrated a significant interaction (P < 0.001, η2p = 0.61), whereas HRV indices did not change. FMD showed no time or interaction effects. NO decreased in the CG (P = 0.002) but remained stable in the PG, while NOS decreased in the PG (P < 0.001). A 13-week PM program was associated with reductions in ambulatory BP and enhanced autonomic reflex responsiveness in women with hypertension. PM appears to be a feasible and safe low-to-moderate-intensity adjunct to pharmacological treatment, with favorable hemodynamic effects.

Clinical significance of fragmented QRS in isolated hypertension: Associations with ventricular arrhythmia burden and autonomic dysfunction.

This study compared a novel relative-to-body-mass FATmax test (RFT; 0.15 W/kg/4 min from 0.45 W/kg) with a traditional absolute power FATmax test (AFT; 10 W/3min15sec from 30 W) in postmenopausal females. The aim was to determine whether the RFT protocol would improve fat oxidation kinetics during exercise, in females with lower maximal fat oxidation (MFO). It was hypothesized that the longer duration and the lower workload increments would result in higher fat oxidation values than AFT. Seventeen active postmenopausal females (69.2 ± 5.1 years) performed both protocols in a randomized order and were divided into above (H-MFO) or below (L-MFO) 0.3 g/min MFO. Groups were equal in age and body composition. Overall, time to MFO was delayed during the RFT protocol (765 ± 621 vs. 401 ± 262 s) without MFO differences. Both groups displayed longer time to MFO in RFT, whilst significantly only for L-MFO (420 ± 280 s vs. 317 ± 232). Although no statistical differences, moderate effect sizes were observed in the L-MFO group during RFT for both MFO (0.22 ± 0.04 vs. 0.19 ± 0.06 g/min, d = 0.65) and VO2 (12.8 ± 3.8 vs. 15.4 ± 5.5 mL/min/kg, d = -0.53). RFT may improve the determination of substrate oxidation kinetics in postmenopausal females with reduced fat oxidation capacity, while facilitating complementary analyses requiring longer recordings and stability (efficiency and Heart Rate Variability).

The cardiovascular conundrum in Non-Hispanic Black emerging adults: multiethnic differences in its association with emotion regulation strategies and socioeconomic status.

A well-powered test of task difficulty effects on cardiovascular indicators of mental effort.

Psychosomatic medicine, consultation-liaison psychiatry, and integrated care in Taiwan: Snapshot 2026.

This study investigated the acute effects of two structured breathwork methods on autonomic recovery following maximal exertion. A randomized control trial was conducted with 62 cadets (44 males and 18 females) assigned to three distinct groups: box breathing (BB), cyclic sighing (CS), or spontaneous breathing control. Participants performed a graded exercise test to assess maximal oxygen consumption (VO 2 ). High-frequency heart rate variability (HF-HRV) and heart rate recovery (HRR) were collected to evaluate autonomic recovery and parasympathetic reactivation. HF-HRV was analyzed at three time points: baseline (Pre), 1-3-min postexercise recovery (Post1), and 4-6-min postexercise (Post2). HRR was measured at 1- and 3-min intervals, analyzing reductions from peak heart rate captured at VO 2max . All analyses were evaluated using a 3 (group) × 3 (time) mixed-design repeated-measures analysis of variance. All groups were comparable in age, weight, height, and body mass index (21 ± 3 yr; 77.4 ± 15.4 kg; 173.1 ± 9.0 cm; 25.7 ± 4.0 kg·m -2 , respectively). HF-HRV revealed significant main effects for time ( F(2,118) = 465.01, P < 0.001, η 2 =0.89), group ( F(2,59) = 8.20, P < 0.001, η 2 =0.22), and time × group interaction ( F(4,118) = 3.54, P = 0.009, η 2 =0.21). Both the CS and BB groups had greater increases in HF-HRV from Post1 to Post2 when compared to spontaneous breathing ( P = 0.001). HRR improved across all participants from 1- to 3-min postexercise with n group level differences ( F(1,59) = 33.51, P < 0.001, η 2 =0.36). Structured breathwork following maximal exertion significantly accelerated parasympathetic reactivation as reflected by HF-HRV. Both BB and CS offer a simple field-ready intervention aimed to enhance operational readiness for tactical populations through enhancing acute physiological recovery.

Cardiac activity is associated with changes in microstates of the electroencephalogram in healthy adults: A resting state study.

In-hand breeding involving restraint methods is likely the most common practice in the horse breeding industry worldwide. However, welfare issues that arise from such management have not been investigated in detail. (1) To investigate whether the mares show increased stress responses during in-hand breeding using (a) a lip twitch and (b) hobbles. (2) To evaluate if the use of restraint methods influences the mare's expression of oestrous behaviour. Intra-individual cross-over design. Six Franches-Montagnes stallions and 10 warmblood mares were used in these experiments. Each mare underwent standardised teasing and breeding sessions with and without one of the two restraint methods (morning and afternoon) on the day before ovulation. Salivary cortisol concentrations, continuous heart rate (HR) and heart rate variability (HRV) before, during and after the teasing and breeding sessions were measured as objective stress indicators. An ethogram was established to evaluate the behaviour during breeding. Using the lip twitch increased cortisol concentrations (with twitch from 0.77 ± 0.07 to 1.20 ± 0.07 ng/mL vs. without twitch from 0.73 ± 0.07 ng/mL to 0.99 ± 0.07 ng/mL; p = 0.04), and the hobbles could not be applied to 2 out of the 10 mares in our study, as they did not tolerate this restraint method. The sample contained a small number of mares. Using a lip twitch in mares during in-hand breeding is accompanied by a slight degree of stress, while hobbles are tolerated very well or not at all by the mares.

Physical restraint of horses for veterinary procedures is necessary to allow completion of tasks effectively and without injury to patient or personnel. To compare physiological effects and behavioural responses to four commonly used restraint techniques for upper respiratory tract (URT) endoscopy in unsedated horses. Blocked and randomised interventional study. Twelve university owned teaching horses were blocked into groups of four and randomly allocated to one of four restraint methods (nose twitch, ear hold, Stableizer® and nil restraint) for URT endoscopy. Horse response to restraint and endoscopy was evaluated subjectively and by objective measures of procedural efficacy (duration and head movement), time domain indices of heart rate variability (HRV), saliva cortisol and plasma β-endorphin concentrations. Horses demonstrated strong individual differences for procedure tolerance and preferred method of restraint, but there were no differences observed in outcome measures related to procedural efficacy or neuroendocrine response associated with restraint type. Repetition of experimental procedures was associated with a progressive decrease in mean (95% CI) minimum heart rate from 34.2 (31.7-36.7) to 30.1 (28.0-32.2) bpm (p < 0.001), and increased HRV measures related to parasympathetic dominance. Cortisol was greatest on Day 2 (1.5, 1.1-2.5 nmol/L; median, 95% CI), compared with Day 1 (0.8, 0.5-1.6 nmol/L; p = 0.02). Convenience sample of horses familiar with most study interventions; intervention was minimally invasive and of short duration. Study findings did not support current recommendations to prioritise one type of restraint over other available techniques.

Autonomic dysfunction in fibromyalgia syndrome: the role of small fiber damage.