Short-term heart rate variability and factors modifying the risk of coronary artery disease in a population sample

Associations between affective factors and high-frequency heart rate variability in primary care patients with depression

OBJECTIVE

Depression is a risk factor for cardiovascular disease (CVD), and subgroups of people with depression may be at particularly elevated CVD risk. Lower high-frequency heart rate variability (HF HRV), which reflects diminished parasympathetic activation, is a candidate mechanism underlying the depression-CVD relationship and predicts cardiovascular events. Few studies have examined whether certain depression subgroups - such as those with co-occurring affective factors - exhibit lower HF HRV. The present study sought to assess associations between co-occurring affective factors and HF HRV in people with depression.

METHODS

Utilizing baseline data from the 216 primary care patients with depression in the eIMPACT trial, we examined cross-sectional associations of depression's co-occurring affective factors (i.e., anxiety symptoms, hostility/anger, and trait positive affect) with HF HRV. HF HRV estimates were derived by spectral analysis from electrocardiographic data obtained during a supine rest period.

RESULTS

Individual regression models adjusted for demographics and depressive symptoms revealed that anxiety symptoms (standardized regression coefficient β = -0.24, p = .002) were negatively associated with HF HRV; however, hostility/anger (β = 0.02, p = .78) and trait positive affect (β = -0.05, p = .49) were not. In a model further adjusted for hypercholesterolemia, hypertension, diabetes, body mass index, current smoking, CVD prevention medication use, and antidepressant medication use, anxiety symptoms remained negatively associated with HF HRV (β = -0.19, p = .02).

CONCLUSION

Our findings suggest that, in adults with depression, those with comorbid anxiety symptoms have lower HF HRV than those without. Co-occurring anxiety may indicate a depression subgroup at elevated CVD risk on account of diminished parasympathetic activation.

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.

Effects of Acute Partial Sleep Deprivation and High-Intensity Interval Exercise on Postprandial Network Interactions

Introduction: High-intensity interval exercise (HIIE) is deemed effective for cardiovascular and autonomic nervous system (ANS) health-related benefits, while ANS disturbance increases the risk for cardiovascular disease (CVD). Postprandial lipemia and acute-partial sleep deprivation (APSD) are considered as CVD risk factors due to their respective changes in ANS. Exercising in the morning hours after APSD and have a high-fat breakfast afterwards may alter the interactions of the cardiovascular, autonomic regulation, and postprandial lipemic systems threatening individuals' health. This study examined postprandial network interactions between autonomic regulation through heart rate variability (HRV) and lipemia via low-density lipoprotein (LDL) cholesterol in response to APSD and HIIE. Methods: Fifteen apparently healthy and habitually good sleepers (age 31 ± 5.2 SD yrs) completed an acute bout of an isocaloric HIIE (in form of 3:2 work-to-rest ratio at 90 and 40% of VO2 reserve) after both a reference sleep (RSX) and 3-3.5 h of acute-partial sleep deprivation (SSX) conditions. HRV time and frequency domains and LDL were evaluated in six and seven time points surrounding sleep and exercise, respectively. To identify postprandial network interactions, we constructed one correlation analysis and one physiological network for each experimental condition. To quantify the interactions within the physiological networks, we also computed the number of links (i.e., number of significant correlations). Results: We observed an irruption of negative links (i.e., negative correlations) between HRV and LDL in the SSX physiological network compared to RSX. Discussion: We recognize that a correlation analysis does not constitute a true network analysis due to the absence of analysis of a time series of the original examined physiological variables. Nonetheless, the presence of negative links in SSX reflected the impact of sleep deprivation on the autonomic regulation and lipemia and, thus, revealed the inability of HIIE to remain cardioprotective under APSD. These findings underlie the need to further investigate the effects of APSD and HIIE on the interactions among physiological systems.

Associations between the rs5498 (A > G) and rs281432 (C > G) polymorphisms of the ICAM1 gene and atherosclerotic cardiovascular disease risk, including hypercholesterolemia

Background

Atherosclerotic cardiovascular disease (ASCVD) originates from complex risk factors, including age, gender, dyslipidemia, obesity, race, genetic and genetic variation. ICAM1 gene polymorphisms are a significant risk factor for ASCVD. However, the impact of the rs5498 and rs281432 polymorphisms on the prevalence of hypercholesterolemia (HCL) has not been reported. Therefore, we determine the relationships between single nucleotide polymorphisms (SNPs), including rs5498 and rs281432 on Intercellular adhesion molecule 1 gene (ICAM1) and ASCVD susceptibility in patients with HCL.

Methods

The clinical characteristics of 278 participants were assessed, and classified to groups having HCL and without HCL. ICAM1 SNPs genotyping was performed by DNA sequencing, and ICAM1 expression was measured using real-time PCR.

Results

Positive dominant model rs5498 participants had twice the risk of HCL (95% confidence interval (CI): [1.24-3.23], P = 0.005). The frequency of the G allele in rs5498 was 1.69 times higher in participants with HCL than in controls (95% CI [1.15-2.47], P = 0.007). Participants with the rs5498 AG or GG variants and high ICAM1 mRNA expression (≥3.12) had 2.49 times the risk (95% CI [1.42-4.38], P = 0.001), and those with a high LDL-C concentration (≥3.36 mmol/L) had 2.09 times the risk (95% CI [1.19-3.66], P = 0.010) of developing ASCVD compared with those with low ICAM1 mRNA and LDL-C levels. Interestingly, participants carrying the rs5498 AG or GG variants who had tachycardia (resting heart rates (RHRs) >100 beats/min) had a 5.02-times higher risk than those with a lower RHR (95% CI [1.35-18.63], P = 0.016).

Conclusions

It may consider the G allele in ICAM1 rs5498 is associated with a higher risk of ASCVD in Thai people with HCL, and is also positively associated with ICAM1 mRNA expression, LDL-C concentration, and RHR.

The effect of age on the heart rate variability of healthy subjects

In this work we study the characteristics of heart rate variability (HRV) as a function of age and gender. Our analysis covers a wider age range than that studied so far. It includes results previously reported in the literature and reveals behaviours not reported before. We can establish basic scale relationships in different HRV measurements. The mean value of the RR intervals shows a power-law behaviour independent of gender. Magnitudes such as the standard deviation or pNN50 show abrupt changes at around the age of 12 years, and above that age they show gender dependence, which mainly affects short-time (or high frequency) scales. We present a unified analysis for the calculation of the non-linear α and β parameters. Both parameters depend on age; they increase in the extremes of life and reach a minimum at around one year of age. These gender-independent changes occur at low frequencies and in scale ranges that depend on age. The results obtained in this work are discussed in terms of the effects of basal metabolic rate, hormonal regulation, and neuronal activity on heart rate variability. This work finally discusses how these findings influence the interpretation of HRV measurements from records of different lengths.

Assessment of the Impact of Alcohol Consumption Patterns on Heart Rate Variability by Machine Learning in Healthy Young Adults

Background and Objectives: Autonomic nervous system (ANS) dysfunction is present in early stages of alcohol abuse and increases the likelihood of cardiovascular events. Given the nonlinear pattern of dynamic interaction between sympathetic nervous system (SNS) and para sympathetic nervous system (PNS) and the complex relationship with lifestyle factors, machine learning (ML) algorithms are best suited for analyzing alcohol impact over heart rate variability (HRV), because they allow the analysis of complex interactions between multiple variables. This study aimed to characterize autonomic nervous system dysfunction by analysis of HRV correlated with cardiovascular risk factors in young individuals by using machine learning. Materials and Methods: Total of 142 young adults (28.4 ± 4.34 years) agreed to participate in the study. Alcohol intake and drinking patterns were assessed by the AUDIT (Alcohol Use Disorders Identification Test) questionnaire and the YAI (Yearly Alcohol Intake) index. A short 5-min HRV evaluation was performed. Post-hoc analysis and machine learning algorithms were used to assess the impact of alcohol intake on HRV. Results: Binge drinkers presented slight modification in the frequency domain. Heavy drinkers had significantly lower time-domain values: standard deviation of RR intervals (SDNN) and root mean square of the successive differences (RMSSD), compared to casual and binge drinkers. High frequency (HF) values were significantly lower in heavy drinkers (p = 0.002). The higher low-to-high frequency ratio (LF/HF) that we found in heavy drinkers was interpreted as parasympathetic inhibition. Gradient boosting machine learner regression showed that age and alcohol consumption had the biggest scaled impact on the analyzed HRV parameters, followed by smoking, anxiety, depression, and body mass index. Gender and physical activity had the lowest impact on HRV. Conclusions: In healthy young adults, high alcohol intake has a negative impact on HRV in both time and frequency-domains. In parameters like HRV, where a multitude of risk factors can influence measurements, artificial intelligence algorithms seem to be a viable alternative for correct assessment.

Cigarette smoke exposure causes systemic and autonomic cardiocirculatory changes in rats depending on the daily exposure dose

AIMS

To evaluate the systemic changes and autonomic cardiocirculatory control of awaken rats chronically exposed to the cigarette smoke (CS) of 1 or 2 cigarettes/day.

MAIN METHODS

Rats were exposed to clean air (control) or cigarette smoke of 1 (CS1) or 2 (CS2) cigarettes/animal/day for 30 days. Then, arterial pressure (AP) and heart rate (HR) were recorded in conscious rats to assess spontaneous baroreflex sensitivity and HR and AP variabilities. Evoked baroreflex and cardiac autonomic tone were evaluated by vasoactive drugs and autonomic blockers, respectively. In another group, ventilatory and cardiovascular parameters were recorded under hypoxia and hypercapnia stimulus. At the end of protocols, heart, lung, kidneys and liver were collected for histological analysis.

KEY FINDINGS

Rats exposed to CS showed morphological changes, being more evident in the CS2 group. Also, less weight gain and cardiac hypertrophy were prominent in CS2 rats. Basal AP and HR, spontaneous baroreflex sensitivity and cardiovascular variabilities were similar among groups. CS exposure progressively blunted the bradycardia response to phenylephrine (-2.2 ± 0.1 vs. -1.7 ± 0.2 vs. -1.5 ± 0.2) while the tachycardia response to sodium nitroprusside was slightly increased compared to control. Vagal tone was not affected by CS, but CS2 rats exhibited higher sympathetic tone (-25 ± 4 vs. -28 ± 4 vs. -56 ± 9) and lower intrinsic HR (411 ± 4 vs. 420 ± 8 vs. 390 ± 6). Exposure to CS of 2 cigarettes also exacerbated the reflex cardiovascular and ventilatory responses to hypoxia and hypercapnia.

SIGNIFICANCE

CS exposure for 30 days promoted systemic changes and autonomic cardiocirculatory dysfunction in rats depending on the daily exposure dose.

Snacking on Whole Almonds for Six Weeks Increases Heart Rate Variability during Mental Stress in Healthy Adults: A Randomized Controlled Trial

Cardiac autonomic regulation can be indirectly measured by heart rate variability (HRV). Low HRV, which can be induced by mental stress, is a predictor of risk of sudden cardiac death. Few studies have investigated cause-and-effect relationships between diet and HRV. Nut consumption is associated with CVD risk reduction, but the impact on HRV, particularly in response to stress, is unclear. Men and women (30–70 y) with above average risk of developing CVD were randomly assigned in a 6-week randomized, controlled, parallel arm trial to consume either whole almond or isocaloric control snacks (20% of daily estimated energy requirement). Control snacks contained the average nutrient profile of UK snacks. Five-minute periods of supine heart rate (HR) and HRV were measured at resting and during mental stress (Stroop color-word test) at baseline and six weeks. High frequency (HF) power, which reflects parasympathetic regulation of HR, was increased following almonds during the mental stress task relative to control (mean difference between groups 124 ms2; 95% CI 11, 237; p = 0.031, n = 105), but other indices were unaffected. Snacking on whole almonds instead of typical snacks may reduce risk of CVD partly by ameliorating the suppression of HRV during periods of mental stress.

Assessment of Ultra-Short Heart Variability Indices Derived by Smartphone Accelerometers for Stress Detection

Body acceleration due to heartbeat-induced reaction forces can be measured as mobile phone accelerometer (m-ACC) signals. Our aim was to test the feasibility of using m-ACC to detect changes induced by stress by ultra-short heart rate variability (USV) indices (standard deviation of normal-to-normal interval—SDNN and root mean square of successive differences—RMSSD). Sixteen healthy volunteers were recruited; m-ACC was recorded while in supine position, during spontaneous breathing at rest conditions (REST) and during one minute of mental stress (MS) induced by arithmetic serial subtraction task, simultaneous with conventional electrocardiogram (ECG). Beat occurrences were extracted from both ECG and m-ACC and used to compute USV indices using 60, 30 and 10 s durations, both for REST and MS. A feasibility of 93.8% in the beat-to-beat m-ACC heart rate series extraction was reached. In both ECG and m-ACC series, compared to REST, in MS the mean beat duration was reduced by 15% and RMSSD decreased by 38%. These results show that short term recordings (up to 10 s) of cardiac activity using smartphone’s accelerometers are able to capture the decrease in parasympathetic tone, in agreement with the induced stimulus.

Effects of smoking status, history and intensity on heart rate variability in the general population: The CHRIS study

Background

Heart rate variability (HRV) reflects the autonomous nervous system modulation on heart rate and is associated with several pathologies, including cardiac mortality. While mechanistic studies show that smoking is associated with lower HRV, population-based studies present conflicting results.

Methods

We assessed the mutual effects of active smoking status, cumulative smoking history, and current smoking intensity, on HRV among 4751 adults from the Cooperative Health Research In South Tyrol (CHRIS) study. The HRV metrics standard deviation of normal-to-normal (NN) inter-beat intervals (SDNN), square root of the mean squared differences of consecutive NN intervals (RMSSD), total power (TP), low (LF) and high frequency (HF) power, and their ratio (LF/HF), were derived from 20-minute electrocardiograms. Smoking status, pack-years (PY), and tobacco grams/day from standardized questionnaires were the main exposures. We fitted linear mixed models to account for relatedness, non-linearity, and moderating effects, and including fractional polynomials.

Results

Past smokers had higher HRV levels than never smokers, independently of PY. The association of HRV with current smoking became apparent when accounting for the interaction between smoking status and PY. In current smokers, but not in past smokers, we observed HRV reductions between 2.0% (SDNN) and 4.9% (TP) every 5 PY increase. Furthermore, current smokers were characterized by dose-response reductions of 9.8% (SDNN), 8.9% (RMSSD), 20.1% (TP), 17.7% (LF), and 19.1% (HF), respectively, every 10 grams/day of smoked tobacco, independently of common cardiometabolic conditions and HRV-modifying drugs. The LF/HF ratio was not associated with smoking status, history, or intensity.

Conclusions

Smoking cessation was associated with higher HRV levels. In current smokers, heavier smoking intensity appears gradually detrimental on HRV, corroborating previous evidence. By affecting both the sympathetic and parasympathetic nervous system indexes, but not the LF/HF balance, smoking intensity seems to exert a systemic dysautonomic effect.

Acute Effects of Instructed and Self-Created Variable Rope Skipping on EEG Brain Activity and Heart Rate Variability

The influence of physical activity on brain and heart activity dependent on type and intensity of exercise is meanwhile widely accepted. Mainly cyclic exercises with longer duration formed the basis for showing the influence on either central nervous system or on heart metabolism. Effects of the variability of movement sequences on brain and heart have been studied only sparsely so far. This study investigated effects of three different motor learning approaches combined with a single bout of rope skipping exercises on the spontaneous electroencephalographic (EEG) brain activity, heart rate variability (HRV) and the rate of perceived exertion (RPE). Participants performed repetitive learning (RL) and two extremely variable rope skipping schedules according to the differential learning approach. Thereby one bout was characterized by instructed variable learning (DLi) and the other by self-created variable learning (DLc) in randomized order each on three consecutive days. The results show higher RPE after DLi and DLc than after RL. HRV analysis demonstrates significant changes in pre-post exercise comparison in all training approaches. No statistically significant differences between training schedules were identified. Slightly greater changes in HRV parameters were observed in both DL approaches indicating a higher activation of the sympathetic nervous system. EEG data reveals higher parietal alpha1 and temporal alpha2 power in RL compared to both DL schedules immediately post exercise. During the recovery of up to 30 min, RL shows higher temporal and occipital theta, temporal, parietal and occipital alpha, temporal and occipital beta and frontal beta3 power. In conclusion, already a single bout of 3 min of rope skipping can lead to brain states that are associated with being advantageous for cognitive learning. Combined with additional, cognitively demanding tasks in form of the DL approach, it seems to lead to an overload of the mental capacity, at least on the short term. Further research should fathom the reciprocal influence of cardiac and central-nervous strain in greater detail.

A unifying conceptual framework of factors associated to cardiac vagal control

Cardiac vagal control (CVC) reflects the activity of the vagus nerve regulating cardiac functioning. CVC can be inferred via heart rate variability measurement, and it has been positively associated to a broad range of cognitive, emotional, social, and health outcomes. It could then be considered as an indicator for effective self-regulation, and given this role, one should understand the factors increasing and decreasing CVC. The aim of this paper is to review the broad range of factors influencing CVC, and to provide a unifying conceptual framework to integrate comprehensively those factors. The structure of the unifying conceptual framework is based on the theory of ecological rationality, while its functional aspects are based on the neurovisceral integration model. The structure of this framework distinguishes two broad areas of associations: person and environment, as this reflects adequately the role played by CVC regarding adaptation. The added value of this framework lies at different levels: theoretically, it allows integrating findings from a variety of scientific disciplines and refining the predictions of the neurovisceral integration model; methodologically, it helps identifying factors that increase and decrease CVC; and lastly at the applied level, it can play an important role for society regarding health policies and for the individual to empower one's flourishing.

Heart rate variability in alcohol use: A review

BACKGROUND

Prior studies have shown that resting heart rate variability (HRV) is reduced in those with alcohol use disorders (AUD). However, HRV following an acute stressful stimulus (reactive HRV), and the relationship between resting or reactive HRV and drinking, craving and relapse in AUD have received less attention.

METHODS

Studies using HRV in relationship to acute or chronic alcohol consumption were included in this review. Manuscripts that related to alcohol in the context of cardiovascular disease were excluded.

RESULTS

Thirty-three articles were included and findings are presented in healthy social drinkers, moderate/heavy drinkers without AUD and individuals with AUD. Results on resting and reactive HRV were presented separately. Acute alcohol reduced resting HRV in healthy subjects but healthy controls had higher resting HRV then AUD subjects and moderate/heavy drinkers (in some studies). Resting HRV improved in AUD subjects only after at least 4 months of abstinence. AUD subjects had higher reactive HRV scores when compared to controls. In AUD subjects increased reactivity was related to more craving, faster relapse and more negative mood. Reactive HRV showed slower improvement with abstinence in AUD subjects.

CONCLUSIONS

Chronic, heavy alcohol has a negative effect on the autonomic nervous system and may be a sensitive biomarker of craving and relapse.

The Association of Cigarette Smoking With High-Frequency Heart Rate Variability: An Ecological Momentary Assessment Study

OBJECTIVE

Evidence from both laboratory and observational studies suggests that acute and chronic smoking leads to reduced high-frequency heart rate variability (HF-HRV), a measure of cardiac vagal regulation. We used ecological momentary assessment (EMA) to study the effect of smoking on concurrent HF-HRV in a trial measuring the effects of hostility reduction and compared 24-hour HF-HRV in smokers and nonsmokers.

METHOD

Ambulatory electrocardiogram data were collected before randomization from 149 healthy individuals with high hostility levels (20-45 years, body mass index ≤ 32 kg/m) and paired with concurrent EMA ratings of smoking and physical position during waking hours. A multilevel mixed model was estimated associating ln(HF-HRV) from smoking status (between-person factor) and person-centered momentary smoking (within-person factor, treated as a random effect), adjusting for momentary physical position, medication use, and consumption of alcohol and caffeine.

RESULTS

Thirty-five smokers and 114 nonsmokers provided both EMA and HF-HRV data. Within smokers, ln HF-HRV was reduced by 0.31 millisecond (p = .04) when participants reported having recently smoked cigarettes, compared with when they had not. The 24-hour HF-HRV was significantly lower in smokers (M [SD] = 5.24 [0.14] milliseconds) than nonsmokers (5.63 ± 0.07 milliseconds, p = .01).

CONCLUSIONS

In healthy smokers with high hostility levels used as their own controls during daily living, smoking acutely reduced HF-HRV. HF-HRV was also reduced in smokers as compared with nonsmokers. Although limited by a small sample of individuals with high hostility levels, these findings nonetheless provide additional evidence that cardiac vagal regulation is lowered by cigarette smoking, which may be one of the numerous pathophysiological effects of smoking.

Influence of Smoking Consumption and Nicotine Dependence Degree in Cardiac Autonomic Modulation

Background

Smoking consumption alters cardiac autonomic function.

Objective

Assess the influence of the intensity of smoking and the nicotine dependence degree in cardiac autonomic modulation evaluated through index of heart rate variability (HRV).

Methods

83 smokers, of both genders, between 50 and 70 years of age and with normal lung function were divided according to the intensity of smoking consumption (moderate and severe) and the nicotine dependency degree (mild, moderate and severe). The indexes of HRV were analyzed in rest condition, in linear methods in the time domain (TD), the frequency domain (FD) and through the Poincaré plot. For the comparison of smoking consumption, unpaired t test or Mann-Whitney was employed. For the analysis between the nicotine dependency degrees, we used the One-way ANOVA test, followed by Tukey's post test or Kruskal-Wallis followed by Dunn's test. The significance level was p < 0,05.

Results

Differences were only found when compared to the different intensities of smoking consumption in the indexes in the FD. LFun (62.89 ± 15.24 vs 75.45 ± 10.28), which corresponds to low frequency spectrum component in normalized units; HFun (37.11 ± 15.24 vs 24.55 ± 10.28), which corresponds to high frequency spectrum component in normalized units and in the LF/HF ratio (2.21 ± 1.47 vs 4.07 ± 2.94). However, in the evaluation of nicotine dependency, significant differences were not observed (p > 0.05).

Conclusion

Only the intensity of smoking consumption had an influence over the cardiac autonomic modulation of the assessed tobacco smokers. Tobacco smokers with severe intensity of smoking consumption presented a lower autonomic modulation than those with moderate intensity.

Arterial Compliance and Autonomic Functions in Adult Male Smokers

INTRODUCTION

Smoking is known to augment sympathetic activity and may lead to increased arterial stiffness. Several studies have reported association of increased sympathetic activity and arterial stiffness to cardiovascular risks among smokers. Pulse Wave Velocity (PWV) of peripheral arteries, instead of aorta can be used as a non-invasive indicator of arterial stiffness.

AIM

To measure non-invasively, the autonomic functions and peripheral arterial stiffness in smokers, and to find out whether the aforementioned factors are modified by the level of physical activity in these smokers.

MATERIALS AND METHODS

This cross-sectional analytical study was conducted in the Department of Physiology, HIMS, Dehradun, over a period of 12 months (2013-2014) on 100 adult males (20-40 years); 50 smokers and 50 non-smokers. The parameters analysed include relevant anthropometric and cardiovascular parameters, Pulse Wave Velocity (PWV), sustained Hand Grip Test (HGT) and Heart Rate Variability (HRV) domains. Data interpretation and analysis was carried out using SPSS 17.0. Comparison of the above mentioned parameters amongst groups was done with unpaired t-test. The relationship of pack-years & physical activity with vascular functions was assessed by Pearson's correlation. Interaction of various grades of smoking and physical activity with Cardiovascular System (CVS) parameters was assessed by one-way ANOVA.

RESULTS

Smokers had higher values of PWV (5.7±0.5m/s) as compared to non-smokers (4.8±0.4m/s) (p<0.001). ΔDBP during HGT was lower (7±3.18mmHg) among smokers as compared to non-smokers (19.4±3.5mmHg) (p<0.001). Smoking (pack-years) was positively related to PWV (r= .03) but showed a weak negative relationship with change in Diastolic Blood Pressure (ΔDBP) (r= -0.084, p=0.56) showing that, more the frequency of smoking, the more was arterial stiffening and the lesser was the sympathetic response to the HGT. The smokers had significantly higher sympathetic activity; Low Frequency (LF) & Low Frequency: High Frequency ratio (LF: HF) (p<.001) whereas High Frequency (HF) was significantly lower (p<.001) showing a decline in parasympathetic activity.

CONCLUSION

Smokers demonstrated higher peripheral PWV and higher intrinsic sympathetic activity and this increase in intrinsic sympathetic activity may lead to increased arterial stiffness. Interaction of autonomic function and PWV with levels of physical activity and grades of smoking showed no significant differences, suggesting the fact that increased physical activity or reduced smoking may not have any effect on the endothelial dysfunction or CVS morbidity caused by smoking.

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.

Novel application of multi dynamic trend analysis as a sensitive tool for detecting the effects of aging and congestive heart failure on heart rate variability

The complex fluctuations in heart rate variability (HRV) reflect cardiac autonomic modulation and are an indicator of congestive heart failure (CHF). This paper proposes a novel nonlinear approach to HRV investigation, the multi dynamic trend analysis (MDTA) method, based on the empirical mode decomposition algorithm of the Hilbert-Huang transform combined with a variable-sized sliding-window method. Electrocardiographic signal data obtained from the PhysioNet database were used. These data were from subjects with CHF (mean age = 59.4 ± 8.4), an age-matched elderly healthy control group (59.3 ± 10.6), and a healthy young group (30.3 ± 4.8); the HRVs of these subjects were processed using the MDTA method, time domain analysis, and frequency domain analysis. Among all HRV parameters, the MDTA absolute value slope (MDTS) and MDTA deviation (MDTD) exhibited the greatest area under the curve (AUC) of the receiver operating characteristics in distinguishing between the CHF group and the healthy controls (AUC = 1.000) and between the healthy elderly subject group and the young subject group (AUC = 0.834 ± 0.067 for MDTS; 0.837 ± 0.066 for MDTD). The CHF subjects presented with lower MDTA indices than those of the healthy elderly subject group. Furthermore, the healthy elderly subjects exhibited lower MDTA indices than those of the young controls. The MDTA method can adaptively and automatically identify the intrinsic fluctuation on variable temporal and spatial scales when investigating complex fluctuations in the cardiac autonomic regulation effects of aging and CHF.

COMPARAÇÃO DA MODULAÇÃO AUTONÔMICA CARDÍACA DURANTE ESFORÇO DE FUMANTES E NÃO FUMANTES

Introdução O tabagismo é uma das principais causas de morbimortalidade em todo o mundo. Indivíduos fumantes têm risco aumentado de desenvolver disfunção autonômica, a qual pode ser avaliada tanto pela variabilidade da frequência cardíaca (VFC) como pela frequência cardíaca de recuperação (FCRec). A maioria dos estudos envolvendo esta análise é realizada em adultos de idade avançada e na condição de repouso. Objetivos Comparar a atividade autonômica cardíaca em repouso e esforço, em homens jovens, fumantes e não fumantes. Métodos Trinta e dois jovens voluntários, (idade 22,0 ± 2,8 anos) foram distribuídos em dois grupos: o grupo fumante (GF; n=15) e o não fumante (GNF; n=17). Realizou-se o teste de Cooper, com análise da VFC pelo cardiofrequencímetro Polar(r)s810i, em repouso e durante o esforço e FCRec. Resultados No GF, 73% foram classificados com nível de dependência nicotínica "muito baixa" segundo questionário de Fargeström. A classificação de ativos e muito ativos pelo questionário IPAQ correspondeu a mais de 50% da amostra em ambos os grupos. Não se observou diferenças significativas entre os grupos na VFC, tanto no repouso quanto no esforço. Entretanto, em cada grupo, notou-se diferença na maioria dos índices de VFC do repouso para o esforço. No teste de Cooper não foram observadas diferenças significativas na FCmédia, FCpico e de FCRec entre os grupos, mas notou-se uma melhor capacidade funcional no GNF pela distância caminhada (2050,2 ± 300,0 vs. 1780,3 ± 390,4 m, p=0,036). Conclusão O GF apresentou menor capacidade funcional e ativação parassimpática durante o esforço, além de menores índices de VFC durante repouso, o que pode sugerir um comprometimento precoce na modulação autonômica cardíaca.

Alteration of Heart Rate Variability in People With Bowel Preparation Before Colonoscopy

In current health examination setting, people frequently undergo heart rate variability (HRV) analysis and colonoscopy on the same day. However, it remains unclear whether the bowel preparation before colonoscopy affects HRV. This study aimed to evaluate the association between HRV and bowel preparation.We conducted a cross-sectional observational study of 1755 people from January 2012 to December 2013 in Taipei, Taiwan. The participants, aged 45 to 65 years, received health examinations that included a physical examination, blood tests, and an HRV analysis. Among these people, 1099 additionally received a colonoscopy on the same day and underwent bowel preparation 1 day before the colonoscopy. The association between HRV and bowel preparation was derived by a multivariable linear regression with adjusted confounding factors.Bowel preparation was associated with a lower standard deviation of the normal-to-normal intervals (SDNN), the root mean square of the successive differences (RMSSD), low-frequency power (LF), and high-frequency power (HF) (all P < 0.0001). After adjusting confounding factors, bowel preparation remained correlated with lower SDNN, RMSSD, LF, and HF (all P < 0.0001). Higher serum phosphorus and lower serum potassium levels were noted in the bowel preparation group (P < 0.0001), and an association between lower HRV and higher serum phosphorus and lower serum potassium levels was only noted in the bowel preparation group.Bowel preparation was significantly associated with lower HRV. The underlying mechanism may be related to an electrolyte imbalance. Cautions may be needed when interpreting HRV reports for people receiving bowel preparations before colonoscopy.

Smoking's effects on respiratory sinus arrhythmia in adolescent smokers

Respiratory sinus arrhythmia (RSA) has emerged as an indicator of how well the body maintains homeostasis and flexibly responds to environmental demands. Previous research has shown that smoking has both acute and chronic effects on RSA in adults. More recent work has focused on adolescent smokers because the natural decrease in RSA over the lifespan might be hastened by smoking at an early age. The goal of the current study, then, was to examine the acute effects of smoking on RSA and mean heart rate (HR) in a group of adolescent smokers. Participants completed two experimental sessions separated by 6-10 weeks, during which resting electrocardiogram (EKG) data were collected before and after smoking or not smoking a single cigarette ad libitum. Results indicate that smoking significantly decreased resting RSA and increased mean HR. In addition, those who smoked their first cigarette earlier in life (i.e., before age 8 or 10) evidenced a greater decrease in RSA during their smoking session relative to those who tried smoking after age 10. Importantly, these findings are largely consistent with the adult literature and suggest that smoking has acute effects on both RSA and HR in adolescence.

Are smoking and passive smoking related with heart rate variability in male adolescents?

Objective

To analyze the relation between smoking and passive smoking with heart rate variability parameters in male adolescents.

Methods

The sample consisted of 1,152 males, aged 14 and 19 years. Data related to smoking and passive smoking were collected using a questionnaire. RR intervals were obtained by a heart rate monitor, on supine position, for 10 minutes. After collecting the RR intervals, time (standard deviation of all RR intervals, root mean square of the squared differences between adjacent normal RR intervals and the percentage of adjacent intervals over 50ms) and frequency domains (low and high frequency and sympathovagal balance) parameters of heart rate variability were obtained.

Results

No significant differences between smoker and nonsmoker adolescents were observed in heart rate variability parameters (p>0.05). Similarly, heart rate variability parameters did not show significant difference between exposed and not exposed to passive smoking (p>0.05).

Conclusion

Cigarette smoking and passive smoking are not related to heart rate variability in adolescence.

Effects of cigarette smoke on Holter ECG recordings in patients with arterial hypertension. Part 2: Parameters of heart rate turbulence

The studies aimed at evaluation of cigarette smoke effect on heart rate turbulence (HRT) in patients with arterial hypertension (AH). 223 consecutive individuals were qualified to the studies. The following groups of patients not suffering from other disease which may affect HRT were distinguished: 1--patients with AH (n=145); 2--patients without AH (n=48). In group 1 the following patient subgroups were studied: A--active smokers (n=42), B--non-smokers exposed to cigarette smoke (n=30), C--non-smokers not exposed to tobacco smoke (n=34), D--former smokers who had quit smoking (n=26). In every participant HRT analysis was conducted. Subgroup A manifested significantly higher values of TO and lower values of TS as compared to analogous values obtained in subgroups B-D. Subgroups B and D were characterized also by significantly higher values of TO and lower values of TS as compared to subgroup C. Active and passive cigarette smoking were found to represent independent risk factors for an abnormal HRT.

CONCLUSION

Both active and passive exposure to tobacco smoke induces causes abnormal HRT in patients with arterial hypertension.

The biphasic effects of moderate alcohol consumption with a meal on ambiance-induced mood and autonomic nervous system balance: a randomized crossover trial

Background

The pre-drinking mood state has been indicated to be an important factor in the mood effects of alcohol. However, for moderate alcohol consumption there are no controlled studies showing this association. Also, the mood effects of consuming alcohol combined with food are largely unknown. The aim of this study was to investigate the effects of moderate alcohol combined with a meal on ambiance-induced mood states. Furthermore effects on autonomic nervous system activity were measured to explore physiological mechanisms that may be involved in changes of mood state.

Methods

In a crossover design 28 women (age 18–45 y, BMI 18.5–27 kg/m²) were randomly allocated to 4 conditions in which they received 3 glasses of sparkling white wine (30 g alcohol) or alcohol-free sparkling white wine while having dinner in a room with either a pleasant or unpleasant created ambiance. Subjects filled out questionnaires (B-BAES, POMS and postprandial wellness questionnaire) at different times. Skin conductance and heart rate variability were measured continuously.

Results

Moderate alcohol consumption increased happiness scores in the unpleasant, but not in the pleasant ambiance. Alcohol consumption increased happiness and stimulation feelings within 1 hour and increased sedative feelings and sleepiness for 2.5 hour. Skin conductance was increased after alcohol within 1 hour and was related to happiness and stimulation scores. Heart rate variability was decreased after alcohol for 2 hours and was related to mental alertness.

Conclusion

Mood inductions and autonomic nervous system parameters may be useful to evaluate mood changes by nutritional interventions. Moderate alcohol consumption elevates happiness scores in an unpleasant ambiance. However, drinking alcohol during a pleasant mood results in an equally positive mood state.

Trial Registration

Clinicaltrials.gov NCT01426022.

Effects of cigarette smoke on Holter ECG recordings in patients with arterial hypertension. Part 1: Time domain parameters of heart rate variability

This report was intended to evaluate the effect of cigarette smoke on heart rate variability (HRV) in patients with arterial hypertension (AH). 223 individuals were qalified to the studies. The following groups of patients not suffering from other disease which may affect HRV were delineated: 1 - patients with AH (n=145); 2 - patients without AH (n=48). In group 1 the following patient groups were studied: A - active smokers (n=42), B - non-smokers exposed to cigarette smoke (n=30), C - non-smokers not exposed to tobacco smoke (n=34), D - former smokers (n=26). A time domain HRV analysis was carried out. Group 1 versus group 2 manifested significantly lower mean values of most parameters in the HRV time domain analysis. Subgroups A, B and D versus subgroup C also exhibited significantly lower mean values of most parameters in the HRV time domain analysis. Active cigarette smoking and passive exposure to tobacco smoke represented independent risk factors for a decreased HRV.

CONCLUSIONS

Active and passive exposure to cigarette smoke decreases HRV in hypertensive patients.

Habitual alcohol consumption is associated with lower cardiovascular stress responses--a novel explanation for the known cardiovascular benefits of alcohol?

In contrast to heavy alcohol consumption, which is harmful, light to moderate drinking has been linked to reduced cardiovascular morbidity and mortality. Effects on lipid status or clotting do not fully explain these benefits. Exaggerated cardiovascular responses to mental stress are detrimental to cardiovascular health. We hypothesized that habitual alcohol consumption might reduce these responses, with potential benefits. Advanced magnetic resonance techniques were used to accurately measure cardiovascular responses to an acute mental stressor (Montreal Imaging Stress Task) in 88 healthy adults (∼1:1 male:female). Salivary cortisol and task performance measures were used to assess endocrine and cognitive responses. Habitual alcohol consumption and confounding factors were assessed by questionnaire. Alcohol consumption was inversely related to responses of heart rate (HR) (r = -0.31, p = 0.01), cardiac output (CO) (r = -0.32, p = 0.01), vascular resistance (r = 0.25, p = 0.04) and mean blood pressure (r = -0.31, p = 0.01) provoked by stress, but not to stroke volume (SV), or arterial compliance changes. However, high alcohol consumers had greater cortisol stress responses, compared to moderate consumers (3.5 versus 0.7 nmol/L, p = 0.04). Cognitive measures did not differ. Findings were not explained by variations in age, sex, social class, ethnicity, physical activity, adrenocortical activity, adiposity, smoking, menstrual phase and chronic stress. Habitual alcohol consumption is associated with reduced cardiac responsiveness during mental stress, which has been linked to lower risk of hypertension and vascular disease. Consistent with established evidence, our findings suggest a mechanism by which moderate alcohol consumption might reduce cardiovascular disease, but not high consumption, where effects such as greater cortisol stress responses may negate any benefits.

Earthing (grounding) the human body reduces blood viscosity-a major factor in cardiovascular disease

OBJECTIVES

Emerging research is revealing that direct physical contact of the human body with the surface of the earth (grounding or earthing) has intriguing effects on human physiology and health, including beneficial effects on various cardiovascular risk factors. This study examined effects of 2 hours of grounding on the electrical charge (zeta potential) on red blood cells (RBCs) and the effects on the extent of RBC clumping.

DESIGN/INTERVENTIONS

SUBJECTS were grounded with conductive patches on the soles of their feet and palms of their hands. Wires connected the patches to a stainless-steel rod inserted in the earth outdoors. Small fingertip pinprick blood samples were placed on microscope slides and an electric field was applied to them. Electrophoretic mobility of the RBCs was determined by measuring terminal velocities of the cells in video recordings taken through a microscope. RBC aggregation was measured by counting the numbers of clustered cells in each sample.

SETTINGS/LOCATION

Each subject sat in a comfortable reclining chair in a soundproof experiment room with the lights dimmed or off.

SUBJECTS

Ten (10) healthy adult subjects were recruited by word-of-mouth.

RESULTS

Earthing or grounding increased zeta potentials in all samples by an average of 2.70 and significantly reduced RBC aggregation.

CONCLUSIONS

Grounding increases the surface charge on RBCs and thereby reduces blood viscosity and clumping. Grounding appears to be one of the simplest and yet most profound interventions for helping reduce cardiovascular risk and cardiovascular events.

Cardiac autonomic function in healthy young smokers

The present study examined the heart rate turbulence (HRT) and heart rate variability (HRV) parameters in healthy young smokers (<40 years) to assess the effects of smoking on cardiac autonomic function. The study included 75 smokers with a history of habitual smoking for at least 1 year (41 males and 34 females; mean age, 29.3 ± 7.3 years) and 30 nonsmokers (hospital staff; 16 males and 14 females; mean age, 29.0 ± 6.1 years). Addiction to smoking was evaluated using the modified Fagerström test for nicotine-dependence index (NDI). HRT, HRV, basic clinical and echocardiographic, and Holter test parameters were compared between groups. No significant differences between the two groups were found in the basic clinical and echocardiographic variables. Turbulence onset (TO) was significantly higher in the smoking group than in the controls, and turbulence slope was significantly lower in the smokers, than in the controls (p < 0.05). Standard deviation of all normal-to-normal (NN) interval index (SDNNI) was the only HRV parameter that was significantly different between the smoking and control groups (p < 0.05). The NDI was positively correlated with the TO (p < 0.05). Smoking impairs the baroregulatory function in healthy young smokers, particularly the HRT parameters and SDNNI. Our findings highlight the importance of complete smoking cessation.

Meditation-induced changes in high-frequency heart rate variability predict smoking outcomes

BACKGROUND

High-frequency heart rate variability (HF-HRV) is a measure of parasympathetic nervous system (PNS) output that has been associated with enhanced self-regulation. Low resting levels of HF-HRV are associated with nicotine dependence and blunted stress-related changes in HF-HRV are associated with decreased ability to resist smoking. Meditation has been shown to increase HF-HRV. However, it is unknown whether tonic levels of HF-HRV or acute changes in HF-HRV during meditation predict treatment responses in addictive behaviors such as smoking cessation.

PURPOSE

To investigate the relationship between HF-HRV and subsequent smoking outcomes.

METHODS

HF-HRV during resting baseline and during mindfulness meditation was measured within two weeks of completing a 4-week smoking cessation intervention in a sample of 31 community participants. Self-report measures of smoking were obtained at a follow up 17-weeks after the initiation of treatment.

RESULTS

Regression analyses indicated that individuals exhibiting acute increases in HF-HRV from resting baseline to meditation smoked fewer cigarettes at follow-up than those who exhibited acute decreases in HF-HRV (b = -4.89, p = 0.008).

CONCLUSION

Acute changes in HF-HRV in response to meditation may be a useful tool to predict smoking cessation treatment response.

Blunted vagal reactivity predicts stress-precipitated tobacco smoking

RATIONALE

Long-term smoking can lead to changes in autonomic function, including decreased vagal tone and altered stress responses. One index of the inability to adapt to stress may be blunted vagal reactivity. Stress is a primary mechanism involved in relapse to smoking, but mechanisms leading to stress-precipitated relapse are not well understood.

OBJECTIVES

Using an experimental paradigm of stress-precipitated smoking behavior, we examined whether autonomic reactivity mediates the relationship between stress and smoking. High-frequency heart rate variability (HF-HRV), a putative measure of vagal tone, and the ratio of low-to-high frequency HRV (LF/HF), a measure of sympathovagal balance, were assessed.

METHODS

Using a within-subjects design, 32 nicotine-dependent, 15-h abstinent smokers (a subgroup from McKee et al. (J Psychopharmacol 25(4):490-502, 2011)) were exposed to individualized script-driven imagery of stressful and relaxing scenarios and assessed on the ability to resist smoking and subsequent ad-lib smoking. HRV was monitored throughout each laboratory session (maximum 60 min following imagery).

RESULTS

As expected, stress and ad-lib smoking additively decreased HF-HRV and increased LF/HF. Blunted stress-induced HF-HRV responses reflecting decreased vagal reactivity were associated with less time to initiate smoking and increased craving relief and reinforcement from smoking. These relationships were specific to HF-HRV following stress as neither baseline HF-HRV, HF-HRV following relaxing imagery, or LF/HF predicted smoking behavior.

CONCLUSIONS

The current findings are the first to experimentally demonstrate that stress-precipitated decreased vagal reactivity predicts the ability to resist smoking. Findings suggest that strategies that normalize vagal reactivity in early abstinent smokers may lead to improved smoking cessation outcomes.

Effects of active and passive tobacco cigarette smoking on heart rate variability

Given the widespread incidence of smoking as well as its deleterious health effects, it is crucial to examine practical and cost effective prognostic markers assessing its health impact. Heart rate variability (HRV) is a straightforward and cost effective technique to foresee health problems of cardiovascular nature and may be used to predict in advance smoking-induced health effects. In this review we evaluate the existing biological evidence regarding the effects of smoking on HRV and their associated cardiovascular consequences. In addition, we summarize fundamental information on the various HRV indicators and their diagnostic significance in relation to heart failure. An in depth analysis of the various HRV indices characterizing changes in the activation of the autonomic nervous system is provided together with a critical evaluation of all evidence published to date on the influence of chronic and acute active and passive smoking on HRV. Overall, the vast majority of published evidence suggests that acute and chronic active and passive smoking generate marked disruptions in the normal autonomic nervous system functioning characterized by increased sympathetic drive and reduced HRV and parasympathetic modulation. The proposed mechanisms that may generate this smoke-induced HRV reduction as well as its clinical implications are thoroughly evaluated.

Association of heart rate variability with the framingham risk score in healthy adults

Background

The aim of this study was to investigate the relationship between heart rate variability (HRV), the Framingham risk score (FRS), and the 10-year risk of coronary heart disease (CHD) development among Korean adults.

Methods

The subjects were 85 healthy Korean adults recruited from a health check-up center. The FRS and 10-year risk of CHD development were calculated.

Results

The FRS in men was inversely correlated with the standard deviation of all normal to normal RR-intervals (SDNN); the root mean square successive difference (RMSSD); the percentage of successive normal cardiac inter-beat intervals greater than 20 ms, 30 ms, and 50 ms (pNN20, pNN30, pNN50); the low frequency (LF); and the high frequency (HF) (P < 0.05). There was no significant relationship between the FRS and HRV in women. Overall, in the receiver operating characteristic (ROC) analysis, the RMSSD, HF, SDNN, LF, LF/HF ratio, and pNN30 predicted an increased 10-year CHD risk. After adjusting for sex and body mass index, those with greater than one standard deviation in the RMSSD, HF, and LF had a 52-59% reduction in their 10-year risk of CHD development ≥ 10%.

Conclusion

This study therefore indicates that the HRV indices, particularly SDNN, RMSSD, pNN30, LF, and HF may be useful parameters for the assessment of CHD risk. Most notably, the usefulness of these HRV measures as indicators for CHD risk evaluation may be greater among men than among women.

Biological mechanisms underlying the relationship between stress and smoking: state of the science and directions for future work

Theories of addiction implicate stress as a crucial mechanism underlying initiation, maintenance, and relapse to cigarette smoking. Examinations of the biological stress systems, including functioning of the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS), have provided additional insights into the relationship between stress and smoking. To date, convergent data suggests that chronic cigarette smoking is associated with alterations in HPA and ANS functioning; however, less is known about the role of HPA and ANS functioning in smoking initiation and relapse following cessation. In order to organize existing findings and stimulate future research, the current paper summarizes the available literature on the roles of HPA axis and ANS functioning in the relationship between stress and cigarette smoking, highlights limitations within the existing literature, and suggests directions for future research to address unanswered questions in the extant literature on the biological mechanisms underlying the relationship between stress and smoking.

Association of health behaviour with heart rate variability: a population-based study

Background

Reduced heart rate variability (HRV), a non-invasive marker of autonomic dysfunction, and an unhealthy lifestyle are associated with an increased morbidity and mortality of cardiovascular diseases (CVD). The autonomic dysfunction is a potential mediator of the association of behavioural risk factors with adverse health outcomes. We studied the association of HRV with behavioural risk factors in an elderly population.

Methods

This analysis was based on the cross-sectional data of 1671 participants (age range, 45-83 years) of the prospective, population-based Cardiovascular Disease, Living and Ageing in Halle (CARLA) Study. Physical activity, smoking habits, alcohol consumption and dietary patterns were assessed in standardized interviews. Time and frequency domain measures of HRV were computed from 5-min segments of highly standardized 20-min electrocardiograms. Their association with behavioural risk factors was determined by linear and non-parametric regression modelling.

Results

There were only weak and inconsistent associations of higher physical activity, moderate consumption of alcohol, and non-smoking with higher time and frequency domain HRV in both sexes, and no association with dietary pattern. Results changed only marginally by excluding subjects with CVD, diabetes mellitus and use of cardioactive medication.

Conclusion

We hypothesized that HRV is associated with behavioural factors and therefore might be a mediator of the effect of behavioural risk factors on CVD, but this hypothesis was not confirmed by our results. These findings support the interpretation that there may be no true causal association of behavioural factors with HRV.

Hypercholesterolemia magnitude increases sympathetic modulation and coagulation in LDLr knockout mice

We investigated the effects of low lipoprotein receptor deficiency in cholesterol blood concentrations, blood pressure, hemostatic factors, and the autonomic nervous system in three groups: control mice fed standard diet (CO, n=9), lipoprotein receptor-deficient mice (LDLr(-/-), n=9) fed standard diet (LDLr-S) or hypercholesterolemic diet (LDLr-H, n=8). Frequency domain analysis of heart rate and blood pressure variability was performed with an autoregressive algorithm. The spectral components were expressed in absolute (s(2) or mmHg(2)) and normalized units. Spontaneous baroreflex sensitivity (BRS) was estimated by alpha index, defined as square root ratio between low frequency power in blood pressure variability and heart rate variability. LDLr/- mice presented a significant increase in the cholesterol blood concentration (mean±SD; mg/dl; LDLr-S=202.01±34.38 and LDLr-H=530.7±75.17) compared to CO (79.2±13.6), p=0.001. The receptor deletion was associated with a heart rate variability reduction (p=0.013). The BRS was reduced (p<0.05) in LDLr-S and LDL-H (mean±SD: 0.96±0.39 and 0.59±0.34, respectively) compared to CO (4.02±1.92). Moreover, hypercholesterolemic diet significantly increased the cardiac sympathetic modulation (0V pattern of symbolic analysis: mean±SD, CO=8.04±4.53; LDLr-S=16.49±4.52 and LDLr-H=21.80±8.24, p=0.006). The 0V pattern was statically correlated to coagulation factor VII (r=0.555, p=0.0208). In LDLr-H, the concentration (interquartile range) of plasmatic fibrinogen and hemostatic factors VII (2.8-3.3) and XII (1.1-1.3) were increased compared to CO (0.9-1.1and 0.9-1.0, respectively) and LDLr-S (0.7-1.0 and 0.8-0.9, respectively) (p<0.004 for FVII and p<0.006 for FXII). Taken together, the results indicate that plasmatic cholesterol magnitude is determinant to increase the coagulation and the sympathetic modulation.

The relationship of autonomic imbalance, heart rate variability and cardiovascular disease risk factors

Cardiovascular disease (CVD) is the leading cause of death and disability worldwide. The understanding of the risk factors for CVD may yield important insights into the prevention, etiology, course, and treatment of this major public health concern. Autonomic imbalance, characterized by a hyperactive sympathetic system and a hypoactive parasympathetic system, is associated with various pathological conditions. Over time, excessive energy demands on the system can lead to premature aging and diseases. Therefore, autonomic imbalance may be a final common pathway to increased morbidity and mortality from a host of conditions and diseases, including cardiovascular disease. Heart rate variability (HRV) may be used to assess autonomic imbalances, diseases and mortality. Parasympathetic activity and HRV have been associated with a wide range of conditions including CVD. Here we review the evidence linking HRV to established and emerging modifiable and non-modifiable CVD risk factors such as hypertension, obesity, family history and work stress. Substantial evidence exists to support the notion that decreased HRV precedes the development of a number of risk factors and that lowering risk profiles is associated with increased HRV. We close with a suggestion that a model of autonomic imbalance may provide a unifying framework within which to investigate the impact of risk factors, including psychosocial factors and work stress, on cardiovascular disease.

Cardiac autonomic activity and blood pressure among Nunavik Inuit adults exposed to environmental mercury: a cross-sectional study

BACKGROUND

Mercury is a contaminant that reaches high levels in Nunavik (North of Quebec). It is transformed into methylmercury (MeHg) and accumulated in marine mammals and predator fish, an important part of the traditional Inuit diet. MeHg has been suggested to affect BP in adults and children while the influence on HRV has only been studied in children. We aimed to assess the impact of MeHg levels on HRV and BP in Inuit adults from Nunavik.

METHODS

In the fall of 2004, the <<Qanuippitaa?>> Health Survey was conducted in Nunavik (Quebec, Canada) and information on HRV was collected among 280 adults aged 40 years and older. Indicators of the time and frequency domains of HRV were derived from a 2-hour Holter recording. BP was measured according to the Canadian Coalition for High Blood Pressure technique. Pulse pressure (PP) was the difference between systolic (SBP) and diastolic blood pressure (DBP). Blood mercury concentration was used as exposure biomarker. Statistical analysis was conducted through linear regression and multivariable linear regression was used to control for confounders.

RESULTS

Mercury was negatively correlated with low frequency (LF) (r = -0.18; p = 0.02), the standard deviation of RR intervals (SDNN) (r = -0.14; p = 0.047) and the coefficient of variation of RR intervals (CVRR) (r = -0.18; p = 0.011) while correlations with other HRV parameters did not reach statistical significance. After adjusting for confounders, the association with LF (beta = -0.006; p = 0.93) became non significant. However, the association with SDANN became statistically significant (beta = -0.086; p = 0.026) and CVRR tended to decrease with blood mercury concentrations (beta = -0.057; p = 0.056). Mercury was positively correlated with SBP (r = 0.25; p < 0.0001) and PP (r = 0.33; p < 0.0001). After adjusting for confounders, these associations remained statistically significant (beta SBP = 4.77; p = 0.01 and beta PP = 3.40; p = 0.0036). Moreover, most of the HRV parameters correlated well with BP although SBP the best before adjustment for mercury exposure.

CONCLUSION

The results of this study suggest a deleterious impact of mercury on BP and HRV in adults. SBP and PP increased with blood mercury concentrations while SDANN decreased with blood mercury concentrations.

Non-restrictive heart rate monitoring using an acceleration sensor

Daily long-term monitoring of heart rates is important for health management. An analysis of heart rate variability can facilitate the early discovery of illnesses. In this study, we paid attention to the method of measuring resting heart rate over long term. An acceleration sensor was set inside the down kilt as it opposing to subject's left chest. Mechanical vibration from heart activity is carried to the acceleration sensor through the down quilt. As a result, periodic vibration was measured successfully and this vibration was proved to be in high correlation with the R wave of ECG. The same results were obtained even in case of lying in a left lateral position.

Epidemiological evidence of altered cardiac autonomic function in overweight but not underweight subjects

BACKGROUND

Little is known about the altered cardiac autonomic function (CAF) across different levels of body mass index (BMI), including underweight, normal weight, overweight and obesity. This study provides a thorough analysis to clarify the CAF change in subjects with underweight, overweight and obesity.

METHODS

According to the World Health Organization (WHO) Asia-Pacific BMI cutoffs, a total of 1437 participants were classified as underweight (n=74), normal weight (n=588), overweight (n=313), obesity I (n=390) and obesity II (n=72). CAF was determined by standard deviation of normal-to-normal (SDNN) intervals or RR intervals, power spectrum in low (LF) and high frequency (HF) (LF, 0.04-0.15 Hz; HF, 0.15-0.40 Hz), and LF/HF ratio at supine for 5 min, the ratio between the 30th and the 15th RR interval after standing from the supine position (30/15 ratio) and the average heart-rate change while taking six deep breaths in 1 min (HR(DB)).

RESULTS

There were significant differences in age, gender, socioeconomic status, blood pressure, HOMA insulin resistance index, fasting glucose, cholesterol, triglyceride and high-density lipoprotein (HDL)-C, and the prevalence of hypertension, ischemic/left bundle branch block (LBBB) electrocardiography (EKG) pattern, current smoking and alcohol use among subjects with underweight, normal weight, overweight, obesity I and II. Univariate analysis showed that SDNN, HR(DB), HF power and the square root of the LF/HF ratio differed among these five groups. Multivariate analysis showed that obesity I and II were inverse correlates of HR(DB) and HF power. Overweight, obesity I and II were positively associated with the square root of the LF/HF ratio. No BMI status was related to SDNN, 30/15 ratio or LF power. Underweight was not the independent correlate of any CAF indices.

CONCLUSIONS

The risk for altered CAF is significant in overweight and obese subjects, independent of cardiovascular risk factors. Underweight is not apparently associated with CAF change.

The cardioprotective effects of alcohol consumption: does cardiac autonomic function play a role?

Moderate alcohol consumption has cardioprotective properties and several mechanisms have been proposed. In over 4,000 men and women from the Whitehall II study, mean heart rate variability levels were lowest among those consuming the most alcohol per week, but in multivariate analyses no statistical associations were found. The cardiac autonomic nervous system is unlikely to explain much of the cardioprotective properties of alcohol.