Decline In Heart Rate Variability Research Articles

The Pulse of Singapore: Short-Term HRV Norms.

Short-term heart rate variability (HRV) is increasingly used to assess autonomic nervous system activity and found to be useful for monitoring and providing care due to its quick measurement. With evidence of low HRV associated with chronic diseases, mental disorders, and an increased risk of cardiovascular disease, having normative data of HRV across the age spectrum would be useful for monitoring health and well-being of a population. This study examines HRV of healthy Singapore sample, with ages ranging from 10 to 89 years. Short-term HRV of five minutes was measured from 2,143 participants. 974 males and 1,169 females, and overall HRV was found to be 42.4ms (RMSSD) and 52.0 ms (SDNN) with a further breakdown of HRV by age and gender. Overall HRV declined with age and gender, although gender differences dissipated in the 60s age range onwards, with the 50s age range having the sharpest decline in HRV. Short-term HRV norms were similar to Nunan et al.'s (2010) systematic review in various populations and less similar to Choi et al.'s (2020) study on Koreans.

Home-Based Dynamics of Sleepiness-Related Conditions Starting at Biological Evening and Later (Beyond Working).

Shift work requires round-the-clock readiness to perform professional duties, and the workers' performance highly depends on their sleepiness level, which can be underestimated during a shift. Various factors, including the time of day, can influence sleepiness in shift workers. The objective of this study was to explore the dynamics of sleepiness-related conditions assessed through heart rate variability analysis, starting from the biological evening and continuing in vivo (at home), without the need for artificial alertness support. The participants solely performed regular evening household duties. A total of 32 recordings were collected from the Subjective Sleepiness Dynamics Dataset for analysis. At 8:00 p.m. and every 30 min thereafter, the participants completed cyclic sleepiness scales (the KSS and the SSS) until the time they went to bed, while their heart rate was recorded. The results of the study indicated that during the biological evening, high sleepiness is associated with a 'stressed' condition characterized by higher sympathetic activation. Later on, it is associated with a 'drowsy' condition characterized by higher parasympathetic activation and a decline in heart rate variability. Our findings provide evidence that the type of condition experienced during high sleepiness depends on the biological time. This should be taken into account when managing work regimes in shift work and developing alertness detectors.

Neuroimaging Studies of the Neural Correlates of Heart Rate Variability: A Systematic Review.

Direct and indirect links between brain regions and cardiac function have been reported. We performed a systematic literature review to summarize current knowledge regarding the associations of heart rate variability (HRV) and brain region morphology, activity and connectivity involved in autonomic control at rest in healthy subjects. Both positive and negative correlations of cortical thickness and gray matter volumes of brain structures with HRV were observed. The strongest were found for a cluster located within the cingulate cortex. A decline in HRV, as well as cortical thickness with increasing age, especially in the orbitofrontal cortex were noted. When associations of region-specific brain activity with HRV were examined, HRV correlated most strongly with activity in the insula, cingulate cortex, frontal and prefrontal cortices, hippocampus, thalamus, striatum and amygdala. Furthermore, significant correlations, largely positive, between HRV and brain region connectivity (in the amygdala, cingulate cortex and prefrontal cortex) were observed. Notably, right-sided neural structures may be preferentially involved in heart rate and HRV control. However, the evidence for left hemispheric control of cardiac vagal function has also been reported. Our findings provide support for the premise that the brain and the heart are interconnected by both structural and functional networks and indicate complex multi-level interactions. Further studies of brain-heart associations promise to yield insights into their relationship to health and disease.

Cardiac Behavior and Heart Rate Variability in Elderly Hypertensive Individuals during Aerobic Exercise: A Non-Randomized Controlled Study.

High blood pressure is an important public health problem due to its high prevalence, the difficulty to control it, and its high contribution to morbidity. A series of changes may be linked to the aging process, compromising cardiac conduction, and reducing cardiovascular baroreceptor function. Advancing age promotes a decline in heart rate variability and this decrease can increase the probability of cardiovascular disease. The aim of this study was to analyze the autonomic modulation of heart rate in hypertensive elderly individuals during and after a session of aerobic exercise, and to compare it with elderly individuals without cardiovascular or metabolic disease. Our study was a non-randomized controlled study with hypertensive elderly (HBP group) and elderly without cardiovascular and/or metabolic diseases (control group). Data on blood pressure and heart rate variability (HRV) were collected before, during, and after 30 min of aerobic physical exercise on a treadmill. There was a reduction in HF (ms2) and SD1 (ms) in the 5 min of recovery for the elderly in the control group. The elderly in the control group also had greater RMSSD and SD1 30 min post-exercise when compared to the initial mins of recovery. We concluded that there was no difference in autonomic modulation and global heart rate variability between elderly individuals without cardiovascular and metabolic diseases and hypertensive individuals after a bout of aerobic exercise. Elderly individuals without metabolic diseases showed a decrease in parasympathetic modulation and global variability between the time of rest and 5 min of recovery. However, up to 30 min of post-exercise recovery, they restored parasympathetic activity.

News and Views

Menopause refers to a non-pathological condition, wherein there is cessation of menstruation for atleast one year.The age of natural menopause in india is 46.2 ± 4.9 years.[1] Research studies show that in urban cities like pondicherry, more than one‑third of the postmenopausal women are having a poor quality of life.[2] There is impaired urogenital, vasomotor and cognitive symptoms, caused due to decreased estrogen levels in the body. This estrogen deficient state puts post-menopausal women at a higher risk of cardiovascular events.[3] Also, sympathovagal imbalance is observed in post-menopausal women with  increased sympathetic activity and reduced parasympathetic activity which adds to the cardiovascular risk.[4] Heart rate variability is a sensitive measure of sympathovagal imbalance.[4] It is found that there is a decline in heart rate variability in post menopausal women.[5] Recent study shows that postmenopausal state also offers higher risk of developing metabolic syndrome with an increased level of insulin resistance.[6] This can also be indicated by deranged lipid profile in them, such as higher triglyceride and total cholestrol.[7] With a myriad of symptoms to deal with, there are fewer treatment alternatives for post-menopausal women.

Autonomic aging \u2013 A dataset to quantify changes of cardiovascular autonomic function during healthy aging

Autonomic regulation of blood pressure and cardiac rhythm progressively declines with increasing age. Impaired cardiovascular control promotes a variety of age-related cardio-vascular conditions. This study aims to provide a database of high-resolution biological signals to describe the effect of healthy aging on cardiovascular regulation. Electrocardiogram and continuous non-invasive blood pressure signals were recorded simultaneously at rest in 1,121 healthy volunteers. With this database, we provide raw signals as well as basic demographic information such as gender and body mass index. To demonstrate validity of the acquired data, we present the well-known decline of heart rate variability with increasing age in this database.

Can Physical Exercise Attenuate Heart Rate Variability Decline Produced By Cancer?

As cancer therapies have evolved, survival rates have increased, yet side-effects still exist. Cardiotoxicity and neurotoxicity have negative effects on the autonomic nervous system and create cardiovascular dysfunction. Heart rate variability (HRV), a marker of autonomic modulation, negatively decreases with cancer, and is associated with fatigue, depression, and mortality. Exercise appears to attenuate the decline in HRV. PURPOSE: This review analyzes the effects of exercise programs on HRV of cancer patients and survivors. METHODS: PRISMA guidelines were followed by searching Web of Science articles and PubMed databases. The quality of the articles was assessed by PEDro scale. Statistical procedures used Revman 5.3. RESULTS: Six studies fulfilled the inclusion/exclusion criteria and included 272 participants, 30 to 75 years old. Exercise programs had a mean length of 10.4 wks, a frequency of 3.1 d/wk, and a mean duration of 78 min/session. In the time domain HRV measures, exercise increased in Standard deviation of NN intervals (p < 0.00001; MD = 12.79 ms [95% CI = 9.03 to 16.55]) and decreased Root mean square of successive RR interval differences (p = 0.002; MD = 13.08 ms [95% CI = 4.90 to 21.27]) compared to controls. Frequency domain data reveal that significant differences between control and exercise groups could be reached in low-frequency (absolute power: p < 0.0001; SMD = 0.97 [95% CI = 0.61 to 1.34]; relative power: p = 0.04; MD = -7.70 [95%CI = -15.4 to -0.36]) high-frequency (absolute power: p = 0.001, SMD = 1.49 [95% CI = 0.32 to 2.66]; relative power: p = 0.04, MD = 8.00 nu [95% CI = 0.20 to 15.80]) and HF/LF ratio (p = 0.007; MD = -0.32 [95% CI = -0.55 to -0.09). CONCLUSIONS: Exercise programs can lead to positive effects on HRV of cancer patients and survivors, with more positive changes realized with resistance and endurance workouts. However, the overall small sample size studying exercise and HRV in cancer patients warrants further study to confirm these results.

Continuous heart rate variability and electroencephalography monitoring in severe acute brain injury: a preliminary study.

BackgroundDecreases in heart rate variability have been shown to be associated with poor outcomes in severe acute brain injury. However, it is unknown whether the changes in heart rate variability precede neurological deterioration in such patients. We explored the changes in heart rate variability measured by electrocardiography in patients who had neurological deterioration following severe acute brain injury, and examined the relationship between heart rate variability and electroencephalography parameters.MethodsRetrospective analysis of 25 patients who manifested neurological deterioration after severe acute brain injury and underwent simultaneous electroencephalography plus electrocardiography monitoring.ResultsEighteen electroencephalography channels and one simultaneously recorded electrocardiography channel were segmented into epochs of 120-second duration and processed to compute 10 heart rate variability parameters and three quantitative electroencephalography parameters. Raw electroencephalography of the epochs was also assessed by standardized visual interpretation and categorized based on their background abnormalities and ictalinterictal continuum patterns. The heart rate variability and electroencephalography parameters showed consistent changes in the 2-day period before neurological deterioration commenced. Remarkably, the suppression ratio and background abnormality of the electroencephalography parameters had significant reverse correlations with all heart rate variability parameters.ConclusionsWe observed a significantly progressive decline in heart rate variability from the day before the neurological deterioration events in patients with severe acute brain injury were first observed.

Heart Rate Variability in a Patient with Coronavirus Disease 2019

This case study investigates the heart rate (HR) and heart rate variability (HRV) in a patient with coronavirus disease 2019 (COVID-19). We report the case of a 58-year old male who contracted COVID-19. During his disease, 24-hour Holter electrocardiography (ECG) was performed continuously. For comparison, his 24-hour Holter ECGs from the previous 10 years were available. In this patient, COVID-19 was associated with a decrease in HR and a paradoxical decline in HRV. An abrupt decline in HRV and a decrease in HR may signal the onset of COVID-19 before common symptoms such as dry cough or fever appear. In addition, HRV and HR measurements may help to evaluate the course of the disease.

An Algorithm to Predict Life-Threatening Complications using Heart Rate Variability and the Circadian Heart Rate Difference with a Special Interest on Covid-19, Sudep Children with Congenital Heart Disease and Obesity

Corona virus disease (COVID-19) has been declared as a pandemic by the WHO with a global mortality rate of about 3.4%. More recently the neuroinvasive potential of SARS-CoV2 was emphasized as a potential cause for respiratory failure. Such pathophysiology has been investigated in sudden unexplained death in epilepsy (SUDEP) including functional neuroimaging that demonstrates alterations to networks involved in central autonomic and respiratory control located in the brainstem. For risk stratification in these patients, one method may be heart rate and heart rate variability (HRV) monitoring. Method: For a better understanding, we compare HRV monitoring in two cases; 1.) Twenty Holter ECGs of a boy with generalized tonic-clonic seizures up to his dead at the age of 10.5 years with special interest on an acute respiratory failure at the age of 5.4 years. 2.) Thirty one Holter ECGs of a 58-year old pediatric cardiologist who survived an infection with COVID-19. During his disease 24-hour Holter electrocardiography (ECG) was performed continuously over 10 days. Moreover, 24-hour Holter ECGs from the last 10 years were available. The derived algorithm that depends on the global heart rate variability and circadian heart rate difference was proofed in 151 healthy children, 26 children with a fatal outcome or transplantation, 151 patients with operated congenital heart disease, 130 obese children and healthy adult data from literature. Results: In both cases we observe a decline of the global heart rate variability SDNN together with a loss of the circadian heart rate difference. The derived algorithm differentiate healthy children from children with a fatal outcome. The algorithm identify 7.3% of 151 patients with operated congenital heart disease and 5.4% of children with obesity as candidates for COVID-19 complications. Conclusions: A sudden decline of HRV together with a loss of the circadian heart rate difference may indicate a life-threatening complication in critical illness.

Abstract 316: Influence of Aging and Na Channels on Sinus Rhythm and Heart Rate Variability

Heart rate variability (HRV) is an index of cardiovascular health and reflects the ability of the heart to adjust sinus rhythm in response to autonomic regulation, a process affected by age. Importantly, Na channels have emerged as key components of discharge and conduction of the sino-atrial node, but whether altered Na channels affect HRV remains to be established. Thus, we studied effects of aging and altered Na channels on heart rate and HRV using wild type (WT) mice and mice with phosphomimetic mutation of Na channel Nav1.5 at Ser571 (S571E mice). Electrocardiograms (ECG) were obtained in male conscious mice at ~4, ~12, ~18, and ~24 months of age (n=13-51). The mean RR interval of the ECG was similar in WT mice at ~4, ~12, and ~18 months (83±4, 81±2, 83±2 ms, respectively), but increased at ~24 months (85±5 ms). In contrast, mean RR interval in S571E mice was maximal at ~4 months (86±6 ms) and progressively decreased at ~12 (83±9 ms), ~18 (79±2 ms), and ~24 months (80±3 ms). Standard deviation of RR intervals (SDRR), an indicator of RR variability, was maximal in WT at ~4 months (3.8±1.6 ms) and was reduced at ~12, ~18, and ~24 months (2.1±0.9, 2.4±1, and 2.6±1.2 ms). Similarly, SDRR was maximal in S571 at ~4 (5.1±2.6 ms) and ~12 months (4.3±1.5 ms), and decreased at ~18 and ~24 months of age (2.6±1.0 and 3.1±1.1 ms). Standard deviation of instantaneous (SD1) and long-term (SD2) RR interval variability, indicative of parasympathetic and sympathetic influence, respectively, were derived from Poincaré plots of RR i and RR i+1 intervals. Overall, SD1 was preserved for the two groups of aging mice, whereas SD2 was maximal at ~4 months and decreased at ~18 and ~24 months. In the presence of complete autonomic block (propranolol and atropine), RR interval increased in young (~4 months, +10%) and old (~24 months, +16%) WT mice. Similarly, autonomic block increased RR interval in young (~4 months, +12%) and old (~24 months, +14%) S571E, but it abrogated RR interval differences between young and old. For the two genotypes, autonomic block reduced SDRR and SD2 exclusively in young animals, abolishing age-related differences in HRV. Overall, these data suggest that Na + channel function conditions heart rate and its age-related adaptations, but does not interfere with the decline of HRV occurring with age.

Can decreased heart rate variability be a marker of autonomic dysfunction, metabolic syndrome and diabetes?

Epidemiological studies show an emergence of diet- and lifestyle-related diseases; Cardio-metabolic diseases (CMD) and neuropsychiatric diseases (classified as non-communicable diseases or chronic diseases). Diet and lifestyle factors can cause adverse effects on autonomic function resulting in decreased heart rate variability (HRV). Low HRV is a risk factor for CMDs. There is a need to find out new methods of early diagnosis for prevention and treatment of these problems because the neurohormonal dysfunction could be the earliest manifestation. It is possible that HRV could be a marker for the early diagnosis of these problems, because it is characterised with increased sympathetic and reduced parasympathetic activity. Several studies indicate that increased unhealthy diet, mental stress, sedentary lifestyle, tobacco, insomnia and alcoholism may be associated with neurohormonal dysfunction, which may cause decline in HRV. Majority of the chronic diseases (e.g., diabetes, hypertension, heart attack, neuropsychiatric disease and cancer) are associated with decreased HRV. The studies also indicate that solar and geomagnetic activities may influence circadian clock and hypothalamus resulting in the oxidative stress and inflammation with alteration in HRV. It is possible that reduced HRV will correlate with various stages of autonomic dysfunction, associated with chronic diseases. Simple methods need to be developed to measure HRV for early diagnosis of neurohormonal dysfunction, which may be important for early management. This review aims to find out available evidence on the role of HRV in the early diagnosis of chronic disease (with specific focus on Type 2 diabetes) and the factors affecting HRV.

Heart rate variability as a marker of healthy ageing

BackgroundWith population ageing a significant concern, modifiable factors contributing to healthy ageing must be identified. Autonomic responding reflected by heart rate variability (HRV) has well-established links to general health and wellbeing in younger populations; but has yet to be explored in older individuals. MethodsForty-five healthy participants (49–82 years old) completed questionnaires about sleep and physical and psychological health. Autonomic activity was measured during rest and whilst completing a computerised battery of cognitive tasks. Participants then wore an ambulatory heart rate monitor overnight, and recorded their sleep and physical activity for one week. HRV parameters reflecting cardiac vagal tone were derived from electrocardiograph recordings. ResultsAge and resting HRV were not related; however a positive association was identified between higher HRV in the 2 h prior to sleep and older age. Higher resting HRV, older age, and better sleep quality significantly predicted psychological wellbeing; and fewer somatic and physical health symptoms and older age predicted better average sleep quality ratings. Older age and poorer general health were significant predictors of cognitive performance deficits. ConclusionThese findings suggest that an age-related decline in HRV is not inevitable. Longitudinal designs exploring within-individual changes in cardiac vagal tone are required to better understand the factors contributing to healthy ageing.

A Thermoneutral Environment Abolishes Age‐Associated Reduction in Heart Rate Variability in Mice

BackgroundCurrent dogma suggests sympathetic tone is the dominant regulator of rodent heart function at standard laboratory ambient temperature (LTA). Recent studies have shown, however, the high surface area to body mass ratio of rodents forces them to use non‐shivering thermogenesis driven by sympathetic stimulation of brown fat to maintain proper thermoregulation at LTA, raising heart rate (HR). When mice are studied at their thermoneutral ambient temperature (NTA) there is a decrease in HR and a formidable vagal component to HR regulation is revealed. HR regulation can be described by heart rate variability (HRV), a group of parameters which quantify the variation of beat‐to‐beat intervals. Additionally, HRV becomes reduced in advanced age due to reduced parasympathetic input.ObjectiveTo unravel the impact of autonomic input on age‐associated changes in HR and HRV over a range of ambient temperatures.MethodsHR was measured in young (3 mo) and aged (30 mo) male C57/BL6 telemetry‐implanted mice via in‐vivo ECG after a 3‐day acclimation period at 20ºC. Another ECG was recorded after a 3‐day acclimation period at 30ºC. HRV was evaluated in both time and frequency domains extrapolated from ECG recordings. Data was analyzed using linear mixed effects models. The double interaction term (temperature and age) in the models was used to evaluate the effect of temperature on HR and HRV by age group while correcting biases stemming from repeated measurements and uneven group sizes.ResultsChanging the ambient temperature altered mean HR of both age groups and several HRV indices in the aged mice. Mean HR of young mice was 595 ± 23 beats per minute (bpm) at 20ºC and decreased to 367 ± 14 bpm at 30ºC (p &lt; 0.0001). Mean HR of aged mice was 622 ± 9.0 bpm at 20ºC and decreased to 323 ± 23 bpm at 30ºC (p &lt; 0.0001) (Figure 1). Coefficient of variance (CV), an indicator of overall time‐domain HRV, was significantly reduced in old mice (2.24 ± 0.3 %) than in young mice (6.96 ± 1.5 %). This difference disappeared at 30ºC because the CV of the aged mice significantly increased to 6.57 ± 0.9 % (p &lt; 0.0001) (Figure 2). Detrended fluctuation analysis (DFA), a measure of correlation within a time series, was significantly lower in the old mice at 30 C (0.81 ± 0.06) than 20ºC (1.1 ± 0.04) (p &lt; 0.008) (Figure 3). The changes in CV and DFA suggest a restoration in complexity in the old mice at 30ºC. Aged mice also showed a significant increase in the high frequency power spectral density compared at 30ºC (175.4 ± 33.2 Hz) compared to 20ºC (20.79 ± 1.72), indicating increased parasympathetic tone at NTA (p &lt; 0.0001) (Figure 4).ConclusionRodents are studied in cold‐stressed conditions at LTA and increased sympathetic stimulation distorts the correct view of autonomic balance. An age‐associated decline in HRV observed at LTA was ameliorated when mice were studied at their NTA. Thus, a true elucidation of autonomic neurotransmitter modulation of cardiovascular function alterations in advanced age require mammals to be at their NTA.Support or Funding InformationFunded by the National Institute of Health/National Institute on Aging Intramural Research Program.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

AGE-RELATED CHANGES IN HEART RATE VARIABILITY AND THEIR RELATION WITH LEUCOCYTE TELOMERE LENGTH

Aim. To assess the relation of age-depended changes in heart rate variability (HRV) with telomere length. With the age, even with no cardiovascular diseases (CVD), there is a decline of HRV which is an indicator of vegetative system condition. The probable mechanism for age-related decrease in HRV might be cellular ageing. One of the markers of cellular ageing is telomere length regarded as a marker of biological age. Material and methods . Totally, 229 persons of age 23-91 y.o. included, with no clinical signs of cardiovascular diseases. All participants underwent the HRV analysis by the data of Holter ECG monitoring and of short ECG recordings supine and upright position by 5 minutes. Telomere length was assessed in leucocytes on genomic desoxyribonucleic acid (DNA) with plymeraze chain reaction real time. The participants were selected to two groups: <60 y.o. and ≥60 y.o. Comparative analysis was done, of the parameters studied, in two age groups, correlational analysis of telomere length with HRV, linear regression analysis and multiple regression. Results. In the group of the older, telomere length was higher than in the younger — 9,90±0,47 units vs 9,65±0,43 units (p<0,001) with close correlation of telomere length with the age (r=-0,32, p<0,05). By the data of linear regression, telomere length is closely related with the mean value of standard deviations of all selected RR intervals for every 5 minutes of 24-hour recording (SDANN), with the power of high-frequency spectrum (HF), relation of lowerand high-frequency waves (L/H) (β=0,36, p=0,006; β=0,39, p=0,004; β=-0,32, р=0,02, resp.). In older persons, in the group of shorter telomeres there were significantly lower values of mean standard deviations for all selected R-R-intervals (SDNN) (111 (94; 126) ms vs 122 (112; 122) ms), mean-square differences between the duratons of the next sinus intervals RR (RMSSD) R-R (RMSSD) — 16 (11; 22) ms vs 22 (17; 25) ms), power of the very low frequency spectrum components (VLF) — 1176 (718; 1453) ms2 vs 1476 (850; 1763) ms2) by the data from Holter ECG, than in the group of longer telomeres (p<0,05). Differences by the shorter recordings supine and upright were not significant. Conclusion. Telomere length is related to the age-relevant HRV changes. Telomere length might be an early predictor of the ageassociated weakening of autonomous regulation of heart functioning and reflect real biological age of vegetative nervous system irrelevant to other cardiovascular risk factors.

Caloric restriction may reverse age‐related autonomic decline in humans

Caloric restriction (CR) retards aging in laboratory rodents. No information is available on the effects of long-term CR on physiologic markers of aging and longevity in humans. Heart rate variability (HRV) is a marker for cardiac autonomic functioning. The progressive decline in HRV with aging and the association of higher HRV with better health outcomes are well established. Heart rate variability assessment is a reliable tool by which the effects of CR on autonomic function can be assessed. Time- and frequency-domain analyses compared 24-h HRV in 22 CR individuals aged 35-82 years and 20 age-matched controls eating Western diets (WD). The CR group was significantly leaner than the WD group. Heart rate was significantly lower, and virtually, all HRV values were significantly higher in the CR group than in the WD group (P < 0.002). Heart rate variability in the CR individuals was comparable with published norms for healthy individuals 20 years younger. In addition, when differences in heart rate (HR) and HRV between CR and WD were compared with previously published changes in HRV induced in healthy adults given atenolol, percent differences in each measure were generally similar in direction and magnitude and suggested declines in sympathetic and increases in parasympathetic modulation of HR and increased circadian variability associated with CR. These findings provide evidence that CR has direct systemic effects that counter the expected age-associated changes in autonomic function so that HRV indexes in CR individuals are similar to those of individuals 20 years younger eating WDs.

Interaction between age and aerobic fitness in determining heart rate dynamics

Heart rate variability (HRV) and phase-rectified signal averaging (PRSA) estimates of heart rate dynamics are diminished in older people compared with younger people. However, it is not fully elucidated whether these differences are related to age per se or to the concomitant influence of aerobic fitness. Aerobic fitness (peak oxygen uptake, gas exchange threshold, oxygen uptake kinetics, exercise economy) was assessed in 70 healthy adults (41 male) aged 18–57 years. Participants also underwent a 24 h, ambulatory ECG for the derivation of HRV and PRSA variables. HRV was most sensitive to age and aerobic fitness when measured during the morning period (6 am–12 pm). HRV and PRSA were both diminished with age and were higher in aerobically superior participants. The decline in HRV with age was predominantly attributable to age itself (33%), with aerobic fitness representing an additional modulating factor. The present study also provides tentative evidence that assessment of the influence of aerobic fitness should not rely on O2peak alone. These findings demonstrate that age per se is an important factor in determining HRV. However, given the clinical importance of diminished HRV and the immutable nature of aging, the potential significance of physical activity/training to enhance cardiac regulatory function should not be underestimated.

Varied Walking Dose In Women With Type 2 Diabetes: Heart Rate Variability And Hemorheology Responses

Type 2 diabetes accelerates and exacerbates the age-related decline in heart rate variability (HRV) and impairment of hemorheology. While exercise training is one of the cornerstone therapies for managing type 2 diabetes, little is known about the optimum dose of exercise training for the improvement of HRV and/or hemorheology. PURPOSE: To investigate HRV and hemorheology adaptations to 12 wk of varied-dose treadmill walking in women aged 65-74 yr with type 2 diabetes. METHODS: Fifteen subjects with uncomplicated type 2 diabetes (Age: 69 ± 2 yr; BMI: 30 ± 5 kg·m-2; VO2peak: 20.3 ± 3.1 ml·kg-1·min-1) were randomly allocated into two exercise training groups (Group 1: 2 x 60 min·wk-1 or Group 2: 4 x 30 min·wk-1). The exercise program was 12 wk and the exercise intensity was set and adjusted every 6 wk to equal 100% of each individual’s gas-exchange threshold. Time domain indices of HRV included i. the standard deviation of RR intervals (SDNN) ii. the square root of the mean of squared differences between successive intervals (RMSSD). Frequency domain indices of HRV included: log-transformed low and high frequency (lnLF and lnHF, respectively) power. Red blood cell (RBC) aggregation was measured in plasma and a standard aggregating solution (3% dextran 70 kDa), and RBC deformability was determined via ektacytometry. Dependent variables were measured before (wk -6 and 0), during (wk 6) and after (wk 12) the walking program. RESULTS: Twelve weeks of exercise training significantly improved VO2peak, time to exhaustion, and the gas-exchange threshold (p < 0.05), independent of exercise group. While exercise training did not improve glycemic control, high-density lipoprotein concentration increased by 7.5% for both groups (p = 0.01). Exercise training reduced RBC aggregation in plasma by -6.6% and in dextran-70 by -12.2% (p < 0.05), and improved RBC deformability by 3.4% (p < 0.05) for both groups. No change in HRV was observed for Group 1, whereas SDNN, RMSSD and lnHF power were improved in Group 2 (p < 0.05). CONCLUSIONS: These results suggest that the accumulated weekly exercise duration may be the most important training component for the prescription of exercise in older women with type 2 diabetes. Exercise frequency should be considered, however, when prescribing exercise to improve HRV.

Voluntarily Produced Increases in Heart Rate Variability Modulate Autonomic Effects of Endotoxin Induced Systemic Inflammation: An Exploratory Study

Exposure of healthy people to lipopolysaccharide (LPS; endotoxin) produces a pro-inflammatory response, subjective symptoms, and decreased heart rate variability (HRV). Given the efficacy of HRV biofeedback (BF) for treating asthma, the large autonomic effects of HRV BF, and the link between vagus nerve activity and inflammation, we hypothesized that HRV BF would dampen the acute manifestations of systemic inflammation induced by LPS challenge. Healthy participants age 18-40 were randomly assigned to four-one-hour training sessions of either HRV BF (n = 6) or a control 15/min paced breathing condition (n = 5) prior to acute experimentally induced LPS exposure. Participants were coached to do the procedures for 10 min each at five hourly time points after LPS injection, and then 2 h later. Subjective symptoms, HRV parameters, and plasma cytokine levels were measured at each time point, 2 h afterward, and the following morning. Participants were able to perform the procedures both during four pre-exposure training sessions and while experiencing LPS-induced symptoms. The HRV BF group showed significant attenuation of the LPS-induced decline in HRV for the 6 h following LPS exposure, suggesting that HRV BF decreased autonomic dysfunction produced by LPS-induced inflammation. HRV BF also reduced symptoms of headache and eye sensitivity to light, but did not affect LPS-induced levels of pro-inflammatory cytokines or symptoms of nausea, muscle aches, or feverishness. Further evaluation of HRV BF appears to be warranted among patients with inflammatory conditions.

Acute exposure to elevated PM2.5 generated by traffic and cardiopulmonary health effects in healthy older adults

There are evidences for exposure to vehicular emissions and adverse cardiopulmonary health effects. This study attempted to further explore these effects on elderly. This study monitored personal PM(2.5) concentrations and ambulatory electrocardiograms continuously for 24 h on 1 working day in 3 separate weeks for 11 school crossing guards. Spirometry was also performed before and after the morning shift. The traffic at each work location was video recorded during one of the three morning shifts. The increases in the average personal PM(2.5) concentrations (baseline PM(2.5) was subtracted) of 1.2-87 and 1.1-98 microg/m(3) were observed during the 1-h morning (DeltaPM(2.5-ave-m)) and afternoon shift (DeltaPM(2.5-ave-a)), respectively. Traffic count was not a significant predictor of the DeltaPM(2.5-ave-m) (P=0.78). Mean heart rate variability (HRV), measured as 5-min standard deviation of normal-to-normal (SDNN) beats during the 10-min rest periods, decreased 18-26% (P<0.02) 15 min, 2 and 4 h after the morning shift, but changes in SDNN (DeltaSDNN) were insignificant post-afternoon exposure (-0.3 to -7% with P>0.53). DeltaSDNN were negatively associated with DeltaPM(2.5-ave-m), with the strongest association at 2 h after the morning shift (P<0.01) but insignificant 4 h after the morning exposure. The peak PM(2.5) concentration (DeltaPM(2.5-peak), baseline PM(2.5) was subtracted) was not a significant predictor for DeltaSDNN, and no clear effect of PM(2.5) exposure on heart rate was observed. There was no effect of PM exposure on lung function (P>0.16), either. In conclusion, acute exposure to the PM(2.5) resulting from mobile sources can cause acute decline in HRV in healthy older adults, suggesting one of the biological mechanisms for the adverse cardiovascular health effects associated with traffic-related air pollution. Traffic count may not be an appropriate surrogate measure of acute personal exposure to vehicular emission in traffic congested areas.