Prognostic significance of impaired baroreflex sensitivity assessed from Phase IV of the Valsalva maneuver in a population-based sample of middle-aged subjects

Lower hemoglobin levels associate with higher baroreflex sensitivity and heart rate variability

The aim of this study was to cross-sectionally examine whether hemoglobin (Hb) levels within the normal variation associate with heart rate variability (HRV) measures and baroreflex sensitivity (BRS). The study population included 733 Finnish subjects of the OPERA cohort (aged 41-59 yr, 53% males, 51.7% treated for hypertension) of whom HRV was measured from a standardized 45-min period and whose Hb levels were within the Finnish reference intervals. The low Hb tertile (mean Hb, 135 g/L) had an overall healthier metabolic profile compared with the high Hb tertile (mean Hb, 152 g/L). BRS was higher in the low Hb tertile compared with the high Hb tertile (P < 0.05). R-R interval (RRi) and standard deviation (SD) of the RRi (SDNN)index were the longest in the low Hb tertile regardless of posture. Of the spectral components of HRV, HF power was the highest in the low Hb tertile regardless of posture (P < 0.05). In a stepwise logistic regression model, BRS associated negatively with Hb levels after adjusting for covariates (B = -0.160 [-0.285; -0.035]). Similar associations were observed for SDNNindex when lying down (B = -0.105 [-0.207; -0.003]) and walking (B = -0.154 [-0.224; -0.083]). For HF power negative associations with Hb levels were observed when lying down (B = -0.110 [-0.180; -0.040]), sitting (B = -0.150 [-0.221; -0.079]), and in total analysis (B = -0.124 [-0.196; -0.053]). Overall, lower Hb levels associated independently with healthier cardiac autonomic function.NEW & NOTEWORTHY Heart rate variability (HRV) and baroreflex sensitivity (BRS), which can be measured noninvasively, can predict cardiac and metabolic diseases. Our findings show that within normal variation subjects with lower hemoglobin (Hb) levels have an overall healthier HRV profile and increased cardiac parasympathetic activity in middle age, independent of age, sex, smoking status, and key metabolic covariates. These findings support our previous findings that Hb levels can be used in assessing long-term risks for cardiometabolic diseases.

A systematic review of the effects of transcutaneous auricular vagus nerve stimulation on baroreflex sensitivity and heart rate variability in healthy subjects

PURPOSE

This systematic review aimed to evaluate the effect of transcutaneous auricular vagus nerve stimulation on heart rate variability and baroreflex sensitivity in healthy populations.

METHOD

PubMed, Scopus, the Cochrane Library, Embase, and Web of Science were systematically searched for controlled trials that examined the effects of transcutaneous auricular vagus nerve stimulation on heart rate variability parameters and baroreflex sensitivity in apparently healthy individuals. Two independent researchers screened the search results, extracted the data, and evaluated the quality of the included studies.

RESULTS

From 2458 screened studies, 21 were included. Compared with baseline measures or the comparison group, significant changes in the standard deviation of NN intervals, the root mean square of successive RR intervals, the proportion of consecutive RR intervals that differ by more than 50 ms, high-frequency power, low-frequency to high-frequency ratio, and low-frequency power were found in 86%, 75%, 69%, 47%, 36%, and 25% of the studies evaluating the effects of transcutaneous auricular vagus nerve stimulation on these indices, respectively. Baroreflex sensitivity was evaluated in six studies, of which a significant change was detected in only one. Some studies have shown that the worse the basic autonomic function, the better the response to transcutaneous auricular vagus nerve stimulation.

CONCLUSION

The results were mixed, which may be mainly attributable to the heterogeneity of the study designs and stimulation delivery dosages. Thus, future studies with comparable designs are required to determine the optimal stimulation parameters and clarify the significance of autonomic indices as a reliable marker of neuromodulation responsiveness.

Baroreflex sensitivity derived from the Valsalva manoeuvre: A physiological protective factor for anxiety induced by breathing CO2-enriched air

This study aimed to determine the capacity of baroreflex sensitivity, derived from the Valsalva manoeuvre (BRS_v), to predict state anxiety induced by a biological stressor (CO₂ inhalation). Healthy adults (n = 50) breathed 7.5 % CO₂-enriched air for 8 min, preceded and followed by breathing medical air for 5 min. State anxiety was evaluated with a visual analogue scale. Anxiety sensitivity (Anxiety Sensitivity Index-3; ASI-3) and trait anxiety (Trait form of the State-Trait Anxiety Inventory; STAI_T) served as cognitive-affective predictors. BRS_v was adopted as a physiological predictor. Multiple regression analysis revealed that BRS_v predicted lower anxiety during CO₂ exposure, and attenuated the effect of ASI-3 in increasing anxiety. No significant effects were found for STAI_T. This is the first study to identify baroreflex sensitivity as a strong protective physiological factor for anxiety beyond the effect of anxiety sensitivity.

Age-associated reductions in cardiovagal baroreflex sensitivity are exaggerated in middle-aged and older men with low testosterone

Aging is associated with reductions in cardiovagal baroreflex sensitivity (cBRS), which increases cardiovascular disease risk. Preclinical data indicate that low testosterone reduces cBRS. We determined whether low testosterone is associated with reduced cBRS in healthy men.

METHODS

Twenty-six men categorized as young (N=6; age=31±4 years; testosterone=535±60 ng/dL), middle-aged/older with normal (N=10; aged 56±3 years; testosterone=493±85 ng/dL), or low (N=10; age=57±6 years; testosterone=262±31 ng/dL) testosterone underwent recordings of beat-by-beat blood pressure and R-R interval during rest and two Valsalva maneuvers, and measures of carotid artery compliance. IL-6, CRP, oxidized LDL cholesterol and TAS were measured.

RESULTS

Middle-aged/older men had lower cBRS compared to young men (17.0±6.5 ms/mmHg; p=0.028); middle-age/older men with low testosterone had lower cBRS (5.5±3.2 ms/mmHg; p=0.039) compared to age-matched men with normal testosterone (10.7±4.0 ms/mmHg). No differences existed among groups during Phase II of the Valsalva maneuver; middle-aged/older men with low testosterone had reduced cBRS (4.7±2.6 ms/mmHg) compared to both young (12.8±2.8ms/mmHg; p<0.001) and middle-aged/older men with normal testosterone (8.6±4.4ms/mmHg; p=0.046) during Phase IV of the Valsalva maneuver. There were no differences in oxidized LDL, (p=0.882) or TAS across groups (p=0.633). IL-6 was significantly higher in middle-aged/older men with low testosterone compared to the other groups (p<0.05 for all) and inversely correlated with cBRS (r=-0.594, p=0.007). Middle-aged/older men had reduced carotid artery compliance compared to young, regardless of testosterone status (p<0.001).

CONCLUSIONS

These observations indicate that low testosterone in middle-aged/older men may contribute to a reduction in cBRS; increased inflammation may also contribute to a reduction in cBRS.

Effects of the number of sit-stand maneuver repetitions on baroreflex sensitivity and cardiovascular risk assessments

Sit-stand maneuvers (SSM) have increasingly been used for baroreflex sensitivity (BRS) measurement in physiological research, but it remains unknown as to how many SSM need to be performed to measure BRS and assess its relation with cardiovascular disease (CVD) risk. Therefore, this study aimed to determine 1) the effect of the number of SSM repetitions on BRS and 2) the association between BRS and CVD risk factors. Data were collected from 174 individuals during 5 minutes of spontaneous rest and 5 minutes of repeated SSM at 0.05 Hz (i.e., 15 cycles of 10-second sit and 10-second stand). During SSM, BRS was calculated from the incremental cycles of 3, 6, 9, 12, and 15 SSM using transfer function analysis of heart rate (HR) and systolic blood pressure (SBP). General CVD risk factors, carotid arterial stiffness, and cardiorespiratory fitness were measured. In result, HR and SBP increased during SSM (p<0.05). The BRS remained at a similar level during the resting and SSM conditions, while the coherence function reached its peak after 3 cycles of SSM. BRS with ≥6 cycles of SSM was strongly correlated with age (r=-0.721 to -0.740), carotid distensibility (r=0.625 to 0.629), and cardiorespiratory fitness (r=0.333 to 0.351) (all p<0.001). Multiple regression analysis demonstrated that BRS with ≥6 cycles of SSM explained >60% of the variance in CVD risk factors. Therefore, our findings suggest that repeated SSM significantly strengthens the association between BRS and CVD risk factors. Particularly, BRS with ≥6 cycles of SSM is strongly associated with CVD risk.

Valsalva-derived Measures and Phenylephrine Test in Patients With Heart Failure With Reduced Ejection Fraction Receiving Comprehensive Neurohormonal Blockade Drug Therapy: A 5-year Event-free Survival Analysis

BACKGROUND

To assess the relationships between Valsalva- and phenylephrine test-derived measures and outcome in patients with heart failure with reduced ejection fraction (HFrEF) receiving comprehensive neurohormonal blockade pharmacotherapy.

METHODS AND RESULTS

Data from 56 patients with HFrEF (mean left ventricle ejection fraction of 32 ± 6%) subjected to Valsalva and phenylephrine tests were analyzed retrospectively. Baroreflex-related (Valsalva-ratio and blood pressure-RR interval slope from phase IV) and non-baroreflex-related measures (systolic blood pressure rise in phase IV [ΔSBP_{PHASE_IV}], and pulse amplitude ratio [PAR]) were calculated from Valsalva. Short-term outcomes (HF-related hospitalization, implantable cardioverter-defibrillator shock or all-cause death within 24 months from examination) and long-term outcomes (implantable cardioverter-defibrillator shock or all-cause death within 60 months) were analyzed. The end point occurred in 16 and 18 patients, for the short- and long-term outcomes, respectively. A low ΔSBP_{PHASE_IV} identified patients at risk in the long term, as evidenced by a low vs high ΔSBP_{PHASE_IV} comparison (square-wave response patients assigned to low ΔSBP_{PHASE_IV} group, P = .002), and Cox model (hazard ratio 0.91, 95% confidence interval 0.86-0.96, P < .001), and tended to identify patients at risk in the short term outcome (hazard ratio 0.95, 95% confidence interval 0.91-1.00, P = .055). There was a tendency toward a higher event-free survival in the low PAR group (low vs high PAR; hazard ratio 0.44, 95% CI 0.17-1.18, P = .104).

CONCLUSIONS

Non-baroreflex-related measures obtained from Valsalva-namely, ΔSBP_{PHASE_IV} and PAR-might carry prognostic value in patients with HFrEF receiving neurohormonal blockade pharmacotherapy.

Roles of cardiovascular autonomic regulation and sleep patterns in high blood pressure induced by mild cold exposure in rats

Increased blood pressure (BP) caused by exposure to cold temperatures can partially explain the increased incidence of cardiovascular events in winter. However, the physiological mechanisms involved in cold-induced high BP are not well established. Many studies have focused on physiological responses to severe cold exposure. In this study, we aimed to perform a comprehensive analysis of cardiovascular autonomic function and sleep patterns in rats during exposure to mild cold, a condition relevant to humans in subtropical areas, to clarify the physiological mechanisms underlying mild cold-induced hypertension. BP, electroencephalography, electromyography, electrocardiography, and core body temperature were continuously recorded in normotensive Wistar-Kyoto rats over 24 h. All rats were housed in thermoregulated chambers at ambient temperatures of 23, 18, and 15 °C in a randomized crossover design. These 24-h physiological recordings either with or without sleep scoring showed that compared with the control temperature of 23 °C, the lower ambient temperatures of 18 and 15 °C not only increased BP, vascular sympathetic activity, and heart rate but also decreased overall autonomic activity, parasympathetic activity, and baroreflex sensitivity in rats. In addition, cold exposure reduced the delta power percentage and increased the incidence of interruptions during sleep. Moreover, a correlation analysis revealed that all of these cold-induced autonomic dysregulation and sleep problems were associated with elevation of BP. In conclusion, mild cold exposure elicits autonomic dysregulation and poor sleep quality, causing BP elevation, which may have critical implications for cold-related cardiovascular events.

Whole Milk and Full-Fat Dairy Products and Hypertensive Risks

Lifestyle modifications in the form of diet and exercise are generally a first-line approach to reduce hypertensive risk and overall cardiovascular disease (CVD) risk. Accumulating research evidence has revealed that consumption of non- and low-fat dairy products incorporated into the routine diet is an effective means to reduce elevated blood pressure and improve vascular functions. However, the idea of incorporating whole-fat or full-fat dairy products in the normal routine diet as a strategy to reduce CVD risk has been met with controversy. The aim of this review is to review both sides of the argument surrounding saturated fat intake and CVD risk from the standpoint of dairy intake. Throughout the review, we examined observational studies on relationships between CVD risk and dairy consumption, dietary intervention studies using non-fat and whole-fat dairy, and mechanistic studies investigating physiological mechanisms of saturated fat intake that may help to explain increases in cardiovascular disease risk. Currently available data have demonstrated that whole-fat dairy is unlikely to augment hypertensive risk when added to the normal routine diet but may negatively impact CVD risk. In conclusion, whole-fat dairy may not be a recommended alternative to non- or low-fat dairy products as a means to reduce hypertensive or overall CVD risk.

Epidemiological evidence of increased waist circumference, but not body mass index, associated with impaired baroreflex sensitivity

Although an inverse relationship between body mass index (BMI) and baroreflex sensitivity (BRS) was found, the effect of waist circumference (WC) on BRS is still inconclusive. The contradictory results of previous studies may be related to the heterogeneity and relatively small sample size of the subjects examined. The aim of this population-based study was to investigate whether the influence of increased WC is more detrimental to BRS than BMI. A total of 760 community dwellers were recruited and they were classified into Q1 (n = 189), Q2 (n = 183), Q3 (n = 192) and Q4 (n = 196) groups, based on WC quartiles. Spontaneous BRS was determined by spectral α coefficient method. Valsalva ratio was the longest RR interval after release of Valsalva maneuver divided by the shortest RR interval during maneuver. Cardiac autonomic function was calculated by power spectrum of heart rate in low and high frequency (LF, 0.04-0.15 Hz; HF, 0.15-0.40 Hz), and LF/HF ratio in supine position for five minutes. There were significant differences in spontaneous BRS and Valsalva ratio among different WC groups. In multivariate analysis, obesity was inversely associated with spontaneous BRS and Valsalva ratio. However, these inverse relationships became insignificant after further adjustment for WC quartiles. In contrast, Q4 vs. Q1, Q3 vs. Q1 and Q2 vs. Q1 of WC were inversely related to spontaneous BRS. Q4 vs. Q1 and Q3 vs. Q1 of WC were negatively associated with the Valsalva ratio. In conclusion, increased and even high-normal WC had a stronger adverse effect on BRS than BMI, independent of cardio-metabolic risk factors.

Are 15-Year Trajectories of Low Back Pain and Sciatica Associated With Cardiovascular Autonomic Function in the General Population?: The Northern Finland Birth Cohort 1966 Study

STUDY DESIGN

A population-based cohort study.

OBJECTIVE

The aim of this study was to examine whether 15-year trajectories of low back pain (LBP) and sciatica are associated with cardiovascular autonomic function in a large general population sample.

SUMMARY OF BACKGROUND DATA

Previous studies using mainly small patient samples have suggested that LBP and sciatica are associated with abnormal cardiovascular autonomic function, namely altered heart rate variability (HRV) and baroreflex sensitivity (BRS). We examined this association in a large general population sample.

METHODS

The data collections of the Northern Finland Birth Cohort 1966 consisted of pain questionnaires at 31 and 46 years (history of LBP, sciatica, and other musculoskeletal pains during the previous year; yes/no for each) and measurements of HRV and BRS at 46 years (heart rate, HR; root mean square of successive differences in beat-to-beat intervals, rMSSD; low-frequency systolic blood pressure variability, SBPV; cross-spectral BRS, BRS; each while seated and standing). The data collections also comprised several confounders. Trajectories for LBP, sciatica, and both together ("no pain," "decreasing," "increasing," "long-term pain") were constructed and general linear models were used to perform comparisons between trajectories (for HR/rMSSD, n = 3398; for SBPV/BRS, n = 1667).

RESULTS

In the crude models, LBP and sciatica were associated with higher HR, lower rMSSD, higher SBPV, and lower BRS, but these associations were mostly attenuated by adjustments. Regarding both LBP and sciatica, only the "increasing" trajectory was associated with two of the eight outcomes (standing SBPV, seated BRS) after adjustments. Regarding LBP, the "increasing" trajectory was associated with three (standing SBPV, seated BRS, standing BRS), the "long-term pain" trajectory with one (standing BRS), and the "decreasing" trajectory with one outcome (seated SBPV) after adjustments. Sciatica showed no association with the outcomes after adjustments.

CONCLUSION

We conclude that the 15-year trajectories of LBP and sciatica do not have a consistent independent association with cardiovascular autonomic function among the general population.

LEVEL OF EVIDENCE

3.

Adverse childhood experiences (ACEs) and cardiovascular development from childhood to early adulthood: study protocol of the Niagara Longitudinal Heart Study

INTRODUCTION

Recent reviews have found substantial links between a toxic childhood environment including child abuse and severe household dysfunction and adult cardiovascular disease (CVD). Collectively referred to as adverse childhood experiences (ACEs), this toxic environment is prevalent among children, with recent Canadian estimates of child abuse at 27%-32%, and severe household dysfunction at 49%. Based on these prevalence rates, the potential effect of ACEs on CVD is more significant than previously thought. Yet, how ACEs amplify the risk for later CVD remains unclear. Lifestyle risk factors only partially account for this connection, instead directing attention to the interaction between psychosocial factors and physiological mechanisms such as inflammation. The Niagara Longitudinal Heart Study (NLHS) examines how ACEs influence cardiovascular health (CVH) from childhood to early adulthood. Integrating the stress process and biological embedding models, this study examines how psychosocial and physiological factors in addition to lifestyle factors explain the relationship between ACEs and CVH.

METHODS

This follow-up study combines three baseline studies from 2007 to 2012 that collected CVH measures including child blood pressure, heart rate, left ventricular structure and function, arterial stiffness indices and baroreflex sensitivity on 564 children. Baseline data also include anthropometric, biological, lifestyle, behavioural, and psychosocial measures that varied across primary studies. Now over 18 years of age, we will recruit and retest as many participants from the baseline studies as possible collecting data on ACEs, CVH, anthropometric, lifestyle and psychosocial measures as well as blood, saliva and hair for physiological biostress markers.

ETHICS AND DISSEMINATION

Ethics approval has been received for the NLHS follow-up. Written consent to participate in the follow-up study is obtained from each participant. Results testing all proposed hypotheses will be submitted for publication in peer-reviewed journals.

Childhood growth patterns and cardiovascular autonomic modulation in midlife: Northern Finland 1966 Birth Cohort Study

OBJECTIVES

To test the hypothesis that age and body mass index (BMI) at BMI peak during infancy and at BMI rebound in childhood are related to cardiovascular autonomic modulation in adulthood.

METHODS

At the age of 46 years, a sample (n = 5861) of the participants of the Northern Finland Birth Cohort 1966 took part in follow-up examinations. Heart rate variability (HRV), baroreflex sensitivity (BRS) and low-frequency oscillations of systolic blood pressure (LF_SBP) were measured during sympathetic stimulus by standing. BMI at various ages was calculated from frequent anthropometric measurements collected from child welfare clinical records. BRS and LF_SBP were available for 1243 participants with BMI peak data and 1524 participants with BMI rebound data, and HRV for 2137 participants with BMI peak data and 2688 participants with BMI rebound data.

RESULTS

Age at BMI rebound had a significant inverse association with LF_SBP (beta = -0.071, p = 0.006) after all adjustments (p < 0.001) and was also directly associated with BRS (beta = 0.082, p = 0.001) independently of birth and maternal factors (p = 0.023). BMI at BMI peak and at BMI rebound was inversely associated with high-frequency component of HRV (HF) (beta = -0.045, p = 0.036 for BMI at peak; beta = -0.043, p = 0.024 for BMI at rebound) and directly associated with the ratio of low- and high-frequency components of HRV (LF/HF ratio) (beta = 0.084, p = < 0.001 for BMI at peak; beta = 0.069, p < 0.001 for BMI at rebound). These associations remained significant after all adjustments (p < 0.05 for all).

CONCLUSIONS

This novel study shows that younger age at BMI rebound and higher BMI at BMI peak and at BMI rebound are associated with higher levels in markers suggestive of augmented sympathetic and reduced vagal cardiovascular modulation in midlife.

Musculoskeletal pains and cardiovascular autonomic function in the general Northern Finnish population

BACKGROUND

Heart rate variability (HRV) and baroreflex sensitivity (BRS) measurements provide means for the objective assessment of cardiovascular autonomic function. As previous studies have associated chronic pain with abnormal autonomic function, we aimed to characterize the relationship between the number of musculoskeletal pain sites (NPS), pain intensity, and cardiovascular autonomic function among the population-based Northern Finland Birth Cohort 1966.

METHODS

At the age of 46, cohort members self-reported their musculoskeletal pains (enabling the determination of NPS [0-8] and pain intensity [Numerical Rating Scale, NRS, 0-10]) and underwent clinical assessments of cardiovascular autonomic function in seated and standing positions (HRV variables: heart rate [HR] and root mean square of successive differences in beat-to-beat intervals [rMSSD] for the entire cohort; BRS variables: low-frequency systolic blood pressure variability [SBPV] and cross-spectral baroreflex sensitivity [BRS] for those attending the examination in Oulu, Finland). Extensive confounder data were also collected (body mass index, physical activity, smoking, Hopkins Symptom Checklist-25, comorbidities, and medications). The full samples included 4186 and 2031 individuals (HRV and BRS samples, respectively). Three subanalyses focused on individuals with intense and frequent pain, individuals with symptoms of depression and anxiety, and the relationship between pain intensity and autonomic parameters.

RESULTS

Linear regression models showed varying associations between NPS, pain intensity, and cardiovascular autonomic parameters. However, after all adjustments NPS was only associated with one outcome among women (BRS, standing: beta = - 0.015, p = 0.048) and two among men (HR, seated: beta = - 0.902, p = 0.003; HR, standing: beta = - 0.843, p = 0.014). Pain intensity was not associated with any outcome after full adjustments. Significant sex*pain interactions were found in the data.

CONCLUSIONS

Our data suggest that musculoskeletal pain has, at most, a limited independent association with cardiovascular autonomic function. Future studies should carefully account for the potential confounders and sex interactions that this study revealed.

Associations of fitness and physical activity with orthostatic responses of heart rate and blood pressure at midlife

Cardiorespiratory fitness (CRF) and physical activity (PA) are associated with autonomic function, but their associations to orthostatic autonomic responses are unclear in epidemiological setting. We hypothesized that higher CRF and PA would associate with higher immediate vagal responses and lower incidence of adverse findings during orthostatic test. At age of 46, 787 men and 938 women without cardiorespiratory diseases and diabetes underwent an orthostatic test (3-minutes sitting, 3-minutes standing) with recording of RR intervals (RRi) and blood pressure (BP) by finger plethysmography. Acute responses of RRi (30:15 ratio) and BP were calculated. CRF was measured by a submaximal step test and daily amount of moderate-to-vigorous PA (MVPA) for 2 weeks by wrist-worn accelerometer. Lifelong PA was based on questionnaires at ages of 14, 31, and 46. High CRF was significantly associated with higher RRi 30:15 ratio (adjusted standardized β = 0.17, P < 0.001) and milder acute decrease of systolic BP while standing (β = 0.10, P = 0.001), while MVPA was not (β = 0.04 for RRi 30:15 ratio and β = 0.05 for systolic BP acute response). High lifelong PA was significantly associated with higher RRi 30:15 ratio (β = 0.08, P = 0.002) but not with acute systolic BP response. Those in the lowest tertile of CRF had 9.2-fold risk (P = 0.002) of having postural orthostatic tachycardia syndrome compared to more fit. Cardiorespiratory fitness and lifelong physical activity, but not current physical activity, were independently associated with higher cardiac vagal response to orthostasis. The present results underscore the importance fitness and lifelong physical activity in prevention of abnormal autonomic function and related cardiovascular risk.

Altered baroreflex sensitivity in young women with a family history of hypertension

A positive family history of hypertension (+FH) is a risk factor for the future development of hypertension. Hypertension is associated with reductions in baroreflex sensitivity (BRS). Therefore, we hypothesized that young women with a +FH [ n = 12, 22 ± 1 yr, body mass index (BMI) 21 ± 1 kg/m², mean arterial pressure (MAP) 79 ± 1 mmHg] would have lower BRS compared with young women without a family history of hypertension (-FH) ( n = 13, 22 ± 1 yr, BMI 21 ± 1 kg/m², MAP 77 ± 2 mmHg, all P > 0.05 between groups). Continuous measurements of muscle sympathetic nerve activity, blood pressure, and electrocardiogram derived R-R interval were recorded at rest and during a Valsalva maneuver. Both cardiovagal BRS and vascular sympathetic BRS were assessed. Resting cardiovagal BRS was reduced in the +FH women (all sequences: -FH 32.3 ± 3.7 vs. +FH 20.2 ± 2.9 ms/mmHg, P = 0.02). Cardiovagal BRS during phase IV (-FH 16.5 ± 2.7 vs. +FH 7.6 ± 1.3 ms/mmHg, P < 0.01) but not phase II (-FH 5.5 ± 0.9 vs. +FH 5.0 ± 0.8 ms/mmHg, P = 0.67) of the Valsalva maneuver was also lower in the +FH women. Vascular sympathetic BRS at rest (-FH -2.38 ± 0.7 vs. +FH -2.33 ± 0.3 bursts· min^-1·mmHg^-1, P = 0.58) and during the Valsalva (-FH -0.74 ± 0.23 vs. +FH -0.66 ± 0.18 bursts·15 s^-1·mmHg^-1, P = 0.79) were not different between groups. These data suggest that healthy young women with a positive family history of hypertension have reduced cardiovagal BRS. This may be one mechanism contributing to the increased incidence of hypertension in this population later in life. NEW & NOTEWORTHY Having a family history of hypertension increases the risk of developing future hypertension. Reductions in baroreflex function have been demonstrated in hypertension and are an important marker for future cardiovascular disease. We show that young women with a family history of hypertension have lower cardiovagal baroreflex sensitivity. This alteration in autonomic function may be one mechanism contributing to the future incidence of hypertension in this patient population.

Fitness, Fatness, Physical Activity, and Autonomic Function in Midlife

PURPOSE

Although low cardiorespiratory fitness (CRF), physical inactivity, and obesity are associated with impaired autonomic function, they are also extensively interrelated. The present study aimed to assess the extent to which they contribute to autonomic function independently of each other.

METHODS

At the age of 46 yr, 1383 men and 1761 women without cardiorespiratory diseases and diabetes underwent assessments of vagally mediated heart rate (HR) variability (root mean square of successive differences in R-R interval (rMMSD)), peak HR during a submaximal step test (CRF), and 60-s HR recovery (HRR). Moderate-to-vigorous physical activity (MVPA; ≥3.5 METs, 2 wk) was measured by wrist-worn accelerometer and body fat percentage (Fat%) by bioimpedance.

RESULTS

In men, CRF and Fat% were significantly associated with higher rMSSD (standardized β = 0.31 and -0.16) and HRR (β = 0.19 and -0.18), whereas higher MVPA was linked with higher HRR (β = 0.13) when including CRF, MVPA, and Fat% in the initial regression. After adjustments for other lifestyle and cardiometabolic factors, CRF remained significantly associated with rMMSD (β = 0.24) and HRR (β = 0.14), as did MVPA with HRR (β = 0.11). In women, CRF was associated with rMSSD (β = 0.23) and HRR (β = 0.15), and MVPA (β = 0.17) and Fat% (β = -0.07) with HRR, when CRF, MVPA, and Fat% were adjusted for each other. After further adjustments, CRF remained a significant determinant of rMSSD (β = 0.20) and HRR (β = 0.13), as did MVPA with HRR (β = 0.15). The final models explained 23% and 21% of variation in rMSSD and HRR in men, and 10% and 12% in women, respectively.

CONCLUSIONS

CRF was a more important determinant of cardiac autonomic function than MVPA and body fat. Furthermore, MVPA but not body fat was independently associated with cardiac autonomic function in both men and women.

Noninvasive beat-to-beat finger arterial pressure monitoring during orthostasis: a comprehensive review of normal and abnormal responses at different ages

Over the past 30 years, noninvasive beat-to-beat blood pressure (BP) monitoring has provided great insight into cardiovascular autonomic regulation during standing. Although traditional sphygmomanometric measurement of BP may be sufficient for detection of sustained orthostatic hypotension, it fails to capture the complexity of the underlying dynamic BP and heart rate responses. With the emerging use of noninvasive beat-to-beat BP monitoring for the assessment of orthostatic BP control in clinical and population studies, various definitions for abnormal orthostatic BP patterns have been used. Here, age-related changes in cardiovascular control in healthy subjects will be reviewed to define the spectrum of the most important abnormal orthostatic BP patterns within the first 180 s of standing. Abnormal orthostatic BP responses can be defined as initial orthostatic hypotension (a transient systolic BP fall of >40 mmHg within 15 s of standing), delayed BP recovery (an inability of systolic BP to recover to a value of >20 mmHg below baseline at 30 s after standing) and sustained orthostatic hypotension (a sustained decline in systolic BP of ≥20 mmHg occurring 60-180 s after standing). In the evaluation of patients with light-headedness, pre(syncope), (unexplained) falls or suspected autonomic dysfunction, it is essential to distinguish between normal cardiovascular autonomic regulation and these abnormal orthostatic BP responses. The prevalence, clinical relevance and underlying pathophysiological mechanisms of these patterns differ significantly across the lifespan. Initial orthostatic hypotension is important for identifying causes of syncope in younger adults, whereas delayed BP recovery and sustained orthostatic hypotension are essential for evaluating the risk of falls in older adults.

Long-term caregiving is associated with impaired cardiovagal baroreflex

OBJECTIVE

Caregiving stress is associated with increased risk of cardiovascular disease (CVD). Inability to adequately regulate blood pressure is a possible underlying mechanism explaining this risk. We examined the relationship between length of caregiving and cardiovagal baroreflex sensitivity (cBRS) to better understand the link between caregiving and CVD risk.

METHODS

A total of 146 elderly individuals (≥55years) participated in this study, of whom 96 were providing in-home care to a spouse with dementia and 50 were healthy controls married to a non-demented spouse (i.e., non-caregivers). Among the caregivers, 56 were short-term caregivers (caring<4years) and 40 were long-term caregivers (caring≥4years). A multiple linear regression model, with contrast codes comparing short and long-term caregivers with non-caregivers was used to understand relationships between chronic caregiving and cBRS.

RESULTS

After controlling for relevant demographic and health characteristics, mean±SE log transformed cBRS for non-caregivers was 0.971±0.029. Relative to non-caregivers, the long-term caregivers had significantly impaired cBRS (0.860±0.033; p=0.013). However, mean cBRS for short-term caregivers did not significant differ from non-caregivers (0.911±0.028; p=0.144).

CONCLUSION

These results suggest that long-term caregiving stress is associated with an impaired cBRS. Accumulation of stress from years of caregiving could result in worse cBRS function, which could be a mechanistic explanation for the correlation between caregiving stress and the increased risk of CVD.

Fingolimod initiation in multiple sclerosis patients is associated with potential beneficial cardiovascular autonomic effects

BACKGROUND

Fingolimod slows heart rate (HR) due to vagomimetic effects and might cause additional cardiovascular autonomic changes. While the time course of HR changes is well described, the extent and course of cardiovascular autonomic changes upon fingolimod initiation has not yet been evaluated. This study, therefore, intended to assess cardiovascular autonomic changes during the first 6 h after fingolimod initiation.

METHODS

In 21 patients with relapsing-remitting multiple sclerosis (RRMS), we recorded respiration (RESP), electrocardiographic RR interval (RRI), systolic and diastolic blood pressure (BPsys, BPdia) at rest, before and 0.5, 1, 2, 3, 4, 5, and 6 h after fingolimod initiation. We calculated parameters of total autonomic modulation [RRI standard deviation (RRI-SD), RRI coefficient of variation (RRI-CV), RRI-total powers], mainly sympathetic cardiac modulation [RRI low frequency (LF) powers], sympathetic BP modulation (BPsys-LF powers), parasympathetic modulation [square root of the mean squared difference of successive RRIs (RMSSD), RRI high frequency (HF) powers], sympatho-vagal cardiac balance (RRI-LF/HF ratios), and baroreflex sensitivity (BRS). We compared parameters between the eight measurements [analysis of variance (ANOVA) or Friedman test with post-hoc analysis; significance: p < 0.05].

RESULTS

After fingolimod initiation, RESP, BPsys, and BPsys-LF powers remained unchanged while RRIs, RRI-CV, RRI-SD, RRI-total powers, RRI-LF powers, RMSSD, RRI-HF powers, and BRS increased after 1 h and rose to peak values occurring after 5, 1, 2, 2, 1, 4, 4, and 4 h, respectively. After 3 h, BPdia had decreased significantly and was lowest after 5 h. RRI-LF/HF ratios decreased to a nadir after 4 h.

CONCLUSIONS

The increases in parasympathetic and overall cardiac autonomic modulation and in BRS seen with fingolimod initiation are theoretically beneficial for the MS patient's cardiovascular system. However, long-term studies must show whether these effects persist or are attenuated (e.g. due to S1P1 receptor down-regulation upon continued fingolimod therapy).

Association between Birth Characteristics and Cardiovascular Autonomic Function at Mid-Life

Background

Low birth weight is associated with an increased risk of cardiovascular diseases in adulthood. As abnormal cardiac autonomic function is a common feature in cardiovascular diseases, we tested the hypothesis that low birth weight may also be associated with poorer cardiac autonomic function in middle-aged subjects.

Methods

At the age of 46, the subjects of the Northern Finland Birth Cohort 1966 were invited to examinations including questionnaires about health status and life style and measurement of vagally-mediated heart rate variability (rMSSD) from R-R intervals (RRi) and spontaneous baroreflex sensitivity (BRS) in both seated and standing positions. Maternal parameters had been collected in 1965–1966 since the 16^th gestational week and birth variables immediately after delivery. For rMSSD, 1,799 men and 2,279 women without cardiorespiratory diseases and diabetes were included and 902 men and 1,020 women for BRS. The analyses were adjusted for maternal (age, anthropometry, socioeconomics, parity, gestational smoking) and adult variables (life style, anthropometry, blood pressure, glycemic and lipid status) potentially confounding the relationship between birth weight and autonomic function.

Results

In men, birth weight correlated negatively with seated (r = -0.058, p = 0.014) and standing rMSSD (r = -0.090, p<0.001), as well as with standing BRS (r = -0.092, p = 0.006). These observations were verified using relevant birth weight categories (<2,500 g; 2,500–3,999 g; ≥4,000 g). In women, birth weight was positively correlated with seated BRS (r = 0.081, p = 0.010), but none of the other measures of cardiovascular autonomic function. These correlations remained significant after adjustment for potential confounders (p<0.05 for all).

Conclusions

In men, higher birth weight was independently associated with poorer cardiac autonomic function at mid-life. Same association was not observed in women. Our findings suggest that higher, not lower, birth weight in males may contribute to less favourable cardiovascular autonomic regulation and potentially to an elevated cardiovascular risk in later life.

Role of aortic arch vascular mechanics in cardiovagal baroreflex sensitivity

Cardiovagal baroreflex sensitivity (cvBRS) measures the efficiency of the cardiovagal baroreflex to modulate heart rate in response to increases or decreases in systolic blood pressure (SBP). Given that baroreceptors are located in the walls of the carotid sinuses (CS) and aortic arch (AA), the arterial mechanics of these sites are important contributors to cvBRS. However, the relative contribution of CS and AA mechanics to cvBRS remains unclear. This study employed sex differences as a model to test the hypothesis that differences in cvBRS between groups would be explained by the vascular mechanics of the AA but not the CS. Thirty-six young, healthy, normotensive individuals (18 females; 24 ± 2 yr) were recruited. cvBRS was measured using transfer function analysis of the low-frequency region (0.04-0.15 Hz). Ultrasonography was performed at the CS and AA to obtain arterial diameters for the measurement of distensibility. Local pulse pressure (PP) was taken at the CS using a hand-held tonometer, whereas AA PP was estimated using a transfer function of brachial PP. Both cvBRS (25 ± 11 vs. 19 ± 7 ms/mmHg, P = 0.04) and AA distensibility (16.5 ± 6.0 vs. 10.5 ± 3.8 mmHg(-1) × 10(-3), P = 0.02) were greater in females than males. Sex differences in cvBRS were eliminated after controlling for AA distensibility (P = 0.19). There were no sex differences in CS distensibility (5.32 ± 2.3 vs. 4.63 ± 1.3 mmHg(-1) × 10(-3), P = 0.32). The present data demonstrate that AA mechanics are an important contributor to differences in cvBRS.

Hypertension Does Not Alter the Increase in Cardiac Baroreflex Sensitivity Caused by Moderate Cold Exposure

Exposure to cold increases blood pressure and may contribute to higher wintertime cardiovascular morbidity and mortality in hypertensive people, but the mechanisms are not well-established. While hypertension does not alter responses of vagally-mediated heart rate variability to cold, it is not known how hypertension modifies baroreflex sensitivity (BRS) and blood pressure variability during cold exposure. Our study assessed this among untreated hypertensive men during short-term exposure comparable to habitual winter time circumstances in subarctic areas. We conducted a population-based recruitment of 24 untreated hypertensive and 17 men without hypertension (age 55–65 years) who underwent a whole-body cold exposure (−10°C, wind 3 m/s, winter clothes, 15 min, standing). Electrocardiogram and continuous blood pressure were measured to compute spectral powers of systolic blood pressure and heart rate variability at low (0.04–0.15 Hz) and high frequency (0.15–0.4 Hz) and spontaneous BRS at low frequency (LF). Comparable increases in BRS were detected in hypertensive men, from 2.6 (2.0, 4.2) to 3.8 (2.5, 5.1) ms/mmHg [median (interquartile range)], and in control group, from 4.3 (2.7, 5.0) to 4.4 (3.1, 7.1) ms/mmHg. Instead, larger increase (p < 0.05) in LF blood pressure variability was observed in control group; response as median (interquartile range): 8 (2, 14) mmHg², compared with hypertensive group [0 (−13, 20) mmHg²]. Untreated hypertension does not disturb cardiovascular protective mechanisms during moderate cold exposure commonly occurring in everyday life. Blunted response of the estimate of peripheral sympathetic modulation may indicate higher tonic sympathetic activity and decreased sympathetic responsiveness to cold in hypertension.

Valsalva maneuver unveils central baroreflex dysfunction with altered blood pressure control in persons with a history of mild traumatic brain injury

Background

Patients with a history of mild TBI (post-mTBI-patients) have an unexplained increase in long-term mortality which might be related to central autonomic dysregulation (CAD). We investigated whether standardized baroreflex-loading, induced by a Valsalva maneuver (VM), unveils CAD in otherwise healthy post-mTBI-patients.

Methods

In 29 healthy persons (31.3 ± 12.2 years; 9 women) and 25 post-mTBI-patients (35.0 ± 13.2 years, 7 women, 4–98 months post-injury), we monitored respiration (RESP), RR-intervals (RRI) and systolic blood pressure (BP) at rest and during three VMs. At rest, we calculated parameters of total autonomic modulation [RRI-coefficient-of-variation (CV), RRI-standard-deviation (RRI-SD), RRI-total-powers], of sympathetic [RRI-low-frequency-powers (LF), BP-LF-powers] and parasympathetic modulation [square-root-of-mean-squared-differences-of-successive-RRIs (RMSSD), RRI-high-frequency-powers (HF)], the index of sympatho-vagal balance (RRI LF/HF-ratios), and baroreflex sensitivity (BRS). We calculated Valsalva-ratios (VR) and times from lowest to highest RRIs after strain (VR-time) as indices of parasympathetic activation, intervals from highest systolic BP-values after strain-release to the time when systolic BP had fallen by 90 % of the differences between peak-phase-IV-BP and baseline-BP (90 %-BP-normalization-times), and velocities of BP-normalization (90 %-BP-normalization-velocities) as indices of sympathetic withdrawal.

We compared patient- and control-parameters before and during VM (Mann-Whitney-U-tests or t-tests; significance: P < 0.05).

Results

At rest, RRI-CVs, RRI-SDs, RRI-total-powers, RRI-LF-powers, BP-LF-powers, RRI-RMSSDs, RRI-HF-powers, and BRS were lower in patients than controls. During VMs, 90 %-BP-normalization-times were longer, and 90 %-BP-normalization-velocities were lower in patients than controls (P < 0.05).

Conclusions

Reduced autonomic modulation at rest and delayed BP-decrease after VM-induced baroreflex-loading indicate subtle CAD with altered baroreflex adjustment to challenge. More severe autonomic challenge might trigger more prominent cardiovascular dysregulation and thus contribute to increased mortality risk in post-mTBI-patients.

Mild obstructive sleep apnea does not modulate baroreflex sensitivity in adult patients

BACKGROUND

Obstructive sleep apnea (OSA) is a chronic and progressive disease. OSA is associated with increased cardiovascular morbidity and mortality, the risk being more frequently encountered with severe degrees of OSA. Increased sympathetic activation and impaired cardiac autonomic control as reflected by depressed baroreceptor reflex sensitivity (BRS) are possible mechanisms involved in the cardiovascular complications of OSA. However, it is not known at what stage of OSA that changes in BRS appear. The aim of this study was to evaluate BRS in patients with mild OSA.

METHODS

The study population consisted of 81 overweight patients with mild OSA and 46 body weight-matched non-OSA subjects. BRS, apnea-hypopnea index, body mass index, and metabolic parameters were assessed. The phenylephrine test was used to measure BRS.

RESULTS

Patients in the OSA group were slightly but significantly older than the non-OSA population (50.3±9.3 years vs 45.7±11.1 years, P=0.02). Body mass index, percentage body fat, blood pressure, fasting glucose, insulin, and lipid levels did not differ between the OSA patients and non-OSA subjects. Absolute BRS values in patients with mild OSA and non-OSA subjects (9.97±6.70 ms/mmHg vs 10.51±7.16 ms/mmHg, P=0.67) and BRS values proportional to age-related and sex-related reference values (91.4%±22.7% vs 92.2%±21.8%, P=0.84) did not differ from each other. BRS <50% of the sex-specific reference value was found in 6% of patients with mild OSA and in 2% of non-OSA subjects (P=0.29).

CONCLUSION

Patients with mild OSA did not show evidence of disturbed BRS in comparison with weight-matched non-OSA controls.