Differences In Autonomic Function Research Articles

Sex differences in autonomic functions and cognitive performance during cold-air exposure and cold-water partial immersion.

This study investigated the differences between males and females in autonomic functions and cognitive performance during cold-air exposure and cold-water partial-immersion compared to a room temperature-air environment. Although several studies have investigated the effects of cold-air or cold-water exposures on autonomic function and cognitive performance, biological sex differences are often under-researched. Twenty-two males and nineteen females participated in the current study. Subjects completed a battery of cognitive tasks based upon those used within the Defense Automated Neurobehavioral Assessment (DANA), consisting of five subtasks that assess simple and procedural reaction time, spatial manipulation, attention, and immediate memory. In total, subjects took the battery within a 15-minute period across 30-minute intervals throughout the duration of environmental exposure. Across three separate days, subjects were exposed to three different environmental conditions: room temperature air (23°C), cold air (10°C), and cold water (15°C; in which subjects were immersed up to their necks). Room temperature and cold-air conditions consisted of five sessions (about 2.5h), and the cold-water condition consisted of three sessions (about 1.5h). During each experimental condition, physiological data were collected to assess autonomic function, including electrodermal activity (EDA) data and heart rate variability (HRV) derived from electrocardiogram signals. Females showed slower reaction time in spatial manipulation tasks, immediate memory, and attention during cold-air exposures compared to room temperature air, whereas the performance of males were similar or better during cold-air exposures compared to room temperature air. Cold-water immersion affected the immediate memory performance of males. Both males and females exhibited smaller EDA amplitudes during cold-air and cold-water conditions compared to room temperature air. For HRV, only male subjects exhibited significantly greater values in low-frequency and very-low-frequency components during cold air exposure compared to the normal condition. Sex introduces important differences in cognitive performance and autonomic functions during exposure to cold-air and cold-water. Therefore, sex should be considered when assessing the autonomic nervous system in cold environments and when establishing optimal thermal clothing for performance in operational environments. Our findings can assist with determination of operational clothing, temperature in operating environment, and personnel deployment to operational sites, particularly in settings involving both males and females.

Relationship between baroreflex sensitivity and orthostatic blood pressure increases in humans

Background: Orthostatic hypertension (OHT) is characterized by an increase in blood pressure (BP) upon standing. Although not a common condition, it is not considered rare. Autonomic dysfunction has been speculated to be a potential cause of OHT as the baroreflex is essential for maintaining homeostasis. However, the exact mechanism responsible for OHT remains unclear. Additionally, the definition of OHT varied among prior reports, and diagnostic criteria have not been firmly established. Thus, this study aims to assess differences in autonomic function in the supine and standing positions in individuals with and without elevated BP upon standing. Hypothesis: Individuals with elevated BP upon standing will have lower cardiovagal baroreflex sensitivity (CBRS) than individuals without elevated BP upon standing. Methods: This study included 90 healthy volunteers (39 ± 14 years; 21 men and 69 women). Brachial BP was measured with a cuff on an upper arm. Beat-by-beat BP with a Finometer and heart rate (HR) with ECG were measured during 10 minutes of supine rest and 10 minutes of standing. Spontaneous CBRS was calculated from the relationship between systolic BP (SBP) and R-R intervals using the sequence method. Heart rate variability (HRV) indices were also calculated. Results: Subjects were sorted into four groups based on the change in brachial SBP upon standing: Control (-5 < ΔSBP < 10 mmHg, n = 53), Mild (10 ≤ ΔSBP < 15 mmHg, n = 22), Moderate (15 ≤ ΔSBP < 20 mmHg, n = 8), and Severe (ΔSBP ≥ 20 mmHg, n = 7). There were no significant differences in age, body mass index, or sex ratio among groups (all P > 0.05). Supine CBRS was significantly lower in the Severe group than in the Control group (9.8 ± 4.1 vs. 16.9 ± 9.0 ms/mmHg, P = 0.003) and the other two groups (all P < 0.05). Additionally, ΔSBP was negatively correlated with supine CBRS in subjects with ΔSBP ≥ 10 mmHg (R = -0.39, P = 0.02, n = 37). Supine high-frequency (HF) power of HRV, an index of vagal activity, was also significantly lower in the Severe group than in the Control group (493 ± 503 vs. 1561 ± 2277 ms2, P = 0.006). Standing induced significant decreases in CBRS and HF power in all groups (all P < 0.05). During standing, CBRS remained significantly lower in the Severe group than in the Control group (P = 0.045), but no other significant differences were observed in CBRS or HRV indices between the groups. Discussion and Conclusion: OHT is associated with adverse cardiovascular events. Our data show that supine baroreflex sensitivity and vagal tone are lower in individuals with higher (ΔSBP ≥ 20 mmHg) elevated BP upon standing. Additionally, a negative relationship was observed between CBRS and elevated SBP (ΔSBP ≥ 10 mmHg) upon standing. These findings suggest that altered or impaired autonomic function may contribute to OHT. In addition, the data support the recent consensus definition of clinical OHT (ΔSBP ≥ 20 mmHg). Further studies are warranted to examine the mechanisms in more detail. This study was supported by NIH R01 HL144781 and R01 HL141198. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Heart rate variability and its association with symptoms of orthostatic hypotension in spinal cord injury

Context/objective To assess differences in autonomic function using heart rate variability (HRV) parameters between people with and without orthostatic hypotension (OH), and to determine symptoms of OH in people with spinal cord injury (SCI). Methods R-R interval and blood pressure (BP) data were recorded using Finometer PRO® in both the supine position and at a 60-degree tilt using a tilt table, each lasting for 6 minutes. R-R interval data were processed using the Kubios HRV analysis software to convert R-R interval into time and frequency domains for further analysis. Results Compared to the non-OH group, the SCI group with OH exhibited lower values for root mean square of the successive differences (RMSSD) and standard deviation of normal-to-normal interval (SDNN), along with an elevated heart rate during tilt-up. Participants with OH symptoms had a lower average heart rate in the supine and 60-degree positions compared to asymptomatic participants. Logistic regression analysis indicated that SDNN in the supine position correlated with the presence of OH, and that the mean heart rate in the 60-degree position was related to the presence of symptoms. Conclusions Differences in HRV parameters were observed in people with SCI and OH, suggesting a reduced parasympathetic activity in the supine position, likely as a response to maintain homeostasis in BP regulation. Despite the presence or absence of OH symptoms, there was no difference in HRV parameters. This finding suggests that autonomic function may not be the primary determinant of these symptoms, with other factors likely being more influential.

Head Trauma not Associated with Long Term Effects on Autonomic Function

Contact-sports can elicit concussions, which impacts autonomic function, as well as elicit repetitive head trauma, where autonomic function has not yet been assessed. Purpose To determine if differences in autonomic function exist among three groups (CTRL: healthy non-contact-sport participant; RHT: repetitive head trauma contact-sport participant; CONC: previous concussion). Methods Forty men (16) and women (24), aged 18-37 (22±3), participated. Participants were grouped based on their sport and concussion history (CTRL, RHT, CONC). The participant was outfitted with equipment to evaluate heart rate, blood pressure, and cerebral-artery blood flow velocity (CBFv), as the participant performed three stimuli: deep breathing, Valsalva maneuver, and a 70° head-up tilt test. All group comparisons were analyzed using a one-way ANOVA; all data are presented as means ± standard deviation. Results The groups did not differ in respiratory sinus arrhythmia (CTRL: 22±6bpm, RHT: 21±8bpm, CONC: 19±7bpm; p=0.471), Valsalva ratio (CTRL: 2.19±0.39, RHT: 2.09±0.37, CONC: 2.00±0.47; p=0.519), CBFv (CTRL: 47.74±25.28cm/s, RHT: 40.99±10.93cm/s, CONC: 43.97±17.55cm/s; p=0.657), or tilt time (CTRL: 806.09±368.37sec, RHT: 943.07±339.54sec, CONC: 978.40±387.98sec; p=0.479). However, CONC (113.24±11.64mmHg) had a significantly higher mean systolic blood pressure during the tilt test than CTRL (102.66±7.79mmHg; p=0.026), while RHT (107.9±9.0mmHg) was not significantly different than CTRL (p=0.39) or CONC (p=0.319). Conclusion Concussions do not seem to have lasting effects on autonomic function. Overwhelmingly, dysautonomia is not present during chronic recovery from concussions or in individuals with RHT from contact-sports.

Sleep Dysregulation and Daytime Electrodermal Patterns in Children With Autism: A Descriptive Study

Sleep deficiency influences emotion and behavior regulation but the mechanisms of influence are poorly understood. Emotion, behavioral, and sleep theories highlight differences in autonomic function as a potential pathway of influence and research in typical populations draw links between sleep deficiency and autonomic dysregulation (e.g., elevated reactivity within the sympathetic nervous system). In populations at elevated risk for sleep deficiency/problems (i.e., individuals with autism), greater variability in sleep and autonomic/arousal profiles may be particularly informative. Using electrodermal activity (EDA) as an indicator of sympathetic nervous system activation, this descriptive pilot study aimed to document daytime EDA patterns in children with autism and to explore their relations with sleep dysregulation/deficiency. EDA and sleep were measured using ankle and wrist worn sensors in 13 children (Meanage 6.11 years). EDA indices included nonspecific skin conductance responses (NSSCR) and tonic skin conductance levels (SCL). Descriptively, children in the dysregulated sleep group had fewer NSSCRs and lower SCL in the afternoon. This blunted physiological arousal profile/pattern is consistent with previous research, but this is the first study to explore how sleep may be linked. Notably, this pattern may not reflect sleep but an overall dysregulation profile which in this sample included: dysregulated sleep, a blunted afternoon arousal profile, and elevated ASD symptom severity. Replication with larger, more diverse samples is needed to disentangle the complex relations among sleep, arousal, and ASD behavioral features. However, this study represents an important first step in documenting extended daytime arousal patterns.

68 Autonomic Impairment and its Manifestations in Patients with Delirium

Abstract Background Delirium is common among unwell older adults. Despite this the pathophysiology remains poorly understood. We hypothesised that autonomic dysfunction may be associated with the development of delirium. Methods 35 participants completed a case-control study. Delirium was assessed using DSM-IV and DRS-R98. Autonomic function was assessed with Head-Up Tilt testing (HUT), baroreflex sensitivity (BRS) testing using Baroreflex Effectiveness Index (BEI), 24-hour blood pressure variability (BPV), nocturnal blood pressure dipping status and 24-hour heart rate variability (HRV). A subgroup analysis of those without pre-existing cognitive impairment (CI) was completed. Results During tilting the delirium group (DG) had a median decrease of 1mmHg (IQR 38.5) in systolic blood pressure (SBP) compared to a median decrease of 17.5mmHg (IQR 20.75) in the control group (CG) (p=0.04). Increased delirium severity correlated with a reduction in the decrease in SBP (rs= -0.42, p=0.03). In those without CI, BRS testing during HUT showed that increases in blood pressure were not followed by an appropriate reduction in heart rate with a mean BEI of 36.87% (SD 22.26) in the DG and 56.03% (SD 23.04) in the CG (p=0.05). Nocturnal dipping differed during subgroup analysis. 58.3% (7) of DG were reverse dippers, 33.3% (4) were non-dippers and 8.3% (1) had a normal dipping pattern. In CG 57.1% (4) were non-dippers, 14.3% (1) had a normal dipping pattern and 28.6% (2) were extreme dippers (p=0.01). BPV was measured by average real variability (ARV). In those without CI mean ARV was 13.81 (SD 5.98) in the CG and 9.69 (SD 2.75) in the DG (p=0.05). No difference was detected in HRV. Conclusion We identified differences in autonomic function between the DG and CG. This is the first study to look at several components of autonomic function in delirium and thus can provide insights into physiological abnormalities present during, or contributing to delirium.

Sex Differences in Autonomic Function Following Aerobic Exercise

Heart rate variability (HRV), blood pressure variability (BPV) and baroreceptor sensitivity (BRS) provides insight into cardiovascular regulation in different physiological settings. Pre-menopausal females have been shown to exhibit a cardioprotective autonomic profile compared to males following maximal exercise, but it is unknown if there are sex differences in autonomic recovery following submaximal aerobic exercise. PURPOSE: To determine the effects of sex on autonomic function at rest and following an acute bout of submaximal aerobic exercise. METHODS: Forty-three (males n=22, age = 22 ± 1 yrs, BMI = 25.9 ± 0.7 kg/m2; females n=21, age = 22 ± 1 yrs, BMI = 23.7 ± 0.5 kg/m2) healthy, normotensive participants completed a 45-min moderate intensity aerobic exercise session. Beat-to-beat BP was recorded using finger plethysmography for 5 min prior to exercise (REST), at 30 min (P30), 60 min (P60) and 90 min (P90) following exercise. Frequency domain measurements of HRV and BRV were calculated. The low frequency power of BPV (BPV_LF) was used as an estimation of sympathetic vasomotor tone and the ratio of low- (LF) and high-frequency (HF) bands in HRV (LF/HF) has been used to quantify the degree of sympathovagal balance. BRS was estimated by the alpha coefficient method (Alpha_LF). Repeated measures analysis of variance (ANOVA) (2 x 4; sex x time-point) was performed. RESULTS: Data were presented in Table 1 as mean ± standard error. CONCLUSION: Forty-five min of submaximal aerobic exercise results in sustained disturbance of cardiovascular homeostasis as manifested by elevated sympathovagal balance and increased cardiovagal baroreceptor sensitivity 90 min after exercise. In addition, young, healthy women exhibited lower sympathetic tone at rest and during recovery from aerobic exercise compared to age-matched males.Table 1: Autonomic function variables at rest and 30,60, and 90 mins following aerobic exercise

Gender Variations in Electrodermal Activity among Medical Students in Response to Cold Pressor Test

Objectives
 To evaluate & compare the electrodermal activity(EDA) among males and females in response to cold pressor test. Thus know the differences in autonomic functions in males & females.
 Materials & Method
 In this experimental study Galvanic skin response(GSR) was the parameter measured for EDA. The sample size of our study was 70 MBBS students (35 males & 35 females)
 Cold pressor test was performed by immersing hand in cold water (temp 4°C to 6°C) &changes in electrodermal activity(GSR) was recorded by using Biochart (version 1.0) device in our research lab.
 Results
 There was a significant increase in GSR after immersion of hand in cold water both in males and females. The baseline GSR value, GSR after immersion in cold water & the recovery GSR value were significantly higher in males compared to females.
 Conclusion
 There is substantial evidence of gender difference in the functioning of the autonomic system, including specific effects of both male & female sex hormones. As a generalisation, at least in humans there is a preponderance of sympathetic mediated responses in males and of parasympathetic in females.
 Our data show that EDA(GSR) is such a simple and non invasive method that can be used reliably to measure the autonomic nervous system functions i.e., the sympathetic over activity during cold induced acute pain.

Sex Differences in Autonomic Response to Hand Grip Exercise Among Individuals with Intellectual Disability

Individuals with an intellectual disability (ID) are at increased risk for cardiovascular disease (CVD), which may be attributed to autonomic dysfunction. Sex differences in autonomic function are apparent in the general population but have not been investigated in persons with ID, and may help to further explain the high prevalence of CVD. Heart rate variability (HRV) is a non‐invasive measure for autonomic modulation and using a sympatho‐excitatory stimulus such as isometric handgrip (HG) exercise, may reveal altered autonomic function not observed at rest.PURPOSETo assess sex differences in cardiac autonomic function in individuals with and without ID using an isometric handgrip (HG) exercise test.METHODSHRV was assessed in 18 individuals with ID (Male: 9; 28±6yrs, 33±11.1kg/m2) and 23 without ID (Male: 13; 30±9.0yrs, 26±3.8kg/m2) in response to isometric HG exercise at 30% of maximal voluntary contraction. Heart rate was continuously recorded via ECG and the last 2 minutes of quiet rest and HG exercise were analyzed. HRV was analyzed in both the time (root mean square of successive differences (RMSSD) and percentage of RR intervals differing by <50ms (PNN50)) and frequency domains (low and high frequency (LF, HF), and LF/HF ratio). A change score was calculated from HG exercise ‐ baseline.RESULTSThere were no differences between controls and ID. However, males in both groups demonstrated a blunted response to HG exercise in RMSSD, pNN50, and LF (p<0.05) compared to females.CONCLUSIONMales in both groups appear to have a suppressed vagal withdrawal to HG when compared to the females. Future research should investigate autonomic regulation in sex‐specific groups with and without ID in a larger sample size. Control ID ANOVA Male Female Male Female Group Sex Group*Sex Time‐Domain RMSSD (ms2) −8±9 −21±24 −0±14 −12±12 0.05 0.00 0.35 pNN50 (%) −6±8 −13± 17 −4± 13 −9± 12 0.26 0.02 0.25 Frequency‐Domain LF (ms2) −337± 1098 −1401± 1638 125± 1038 −245±361 0.56 0.00 0.29 HF (ms2)¥ −211±254 −350±428 −118±510 −221±277 0.27 0.10 0.27 LF/HF Ratio§ 6± 1 6± 1 6±0 6± 1 0.64 0.65 0.39 Data presented as mean change ± standard deviation. Control= M (n=13), F (n=9); ID= M (n=9), F (n=9) Log‐transformed for the case of non‐normal data This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Gender-based differences in cardiovascular autonomic function tests among deaf children

Background: Deafness is a social stigma and also due to various reasons, studies show deaf individuals have altered autonomic functions. In our study, we tried to look for gender differences in autonomic functions in deaf population. Aims and Objectives: Our aim is to study the autonomic function tests among the male and female deaf children. Materials and Methods: After obtaining ethical clearance, we conducted a cross-sectional study among deaf children with a sample size of 60 subjects, of which 30 were male and 30 were female. Cardiovascular autonomic function tests such as systolic blood pressure (SBP) response to immediate standing, BP response to cold pressor test, heart rate (HR) response to immediate standing expressed as 30:15 ratio, and HR response to deep breathing were performed and compared among the two groups. Statistical analysis was done using the Statistical Package for the Social Sciences Software version: 22 and results are expressed in percentage and proportions. Results: The mean of SBP on immediate standing (108.93, P = 0.026) and difference of mean BP from supine to standing among male cases (5.13, P = 0.050) is significantly higher than female cases. The mean of 30:15 HR ratio on immediate standing from supine position among female cases (1.32) was significantly higher than male cases (1.25). Conclusion: Deaf individuals apart from having altered autonomic functions revealed from various studies also provide us with statistically significant results that there is a gender-based difference in the autonomic functions mostly accountable to difference in the baroreceptor sensitivity among males and females.

Progressive multiple sclerosis patients have a higher burden of autonomic dysfunction compared to relapsing remitting phenotype

ObjectiveTo determine autonomic dysfunction (AD) differences in patients with relapsing remitting multiple sclerosis (pwRRMS) and progressive MS (pwPMS). MethodsComposite autonomic scoring scale (CASS) and heart rate variability (HRV) were performed in 40 pwRRMS and 30 pwPMS. ResultspwPMS had a significantly higher sudomotor index and total CASS score compared to pwRRMS (p < 0.001 and p < 0.001, respectively). Disease duration positively correlated with sudomotor index and total CASS (rs = 0.409, p < 0.001 and rs = 0.472, p < 0.001, respectively), while the Expanded Disability Status Scale (EDSS) positively correlated with sudomotor index and total CASS (rs = 0.411, p < 0.001 and rs = 0.402, p = 0.001, respectively) in all patients. Type of multiple sclerosis (pwRRMS or pwPMS) corrected for age, sex and disease duration, was a statistically significant predictor of CASS value (B = 1.215, p = 0.019). Compared to pwRRMS, pwPMS had a significantly lower standard deviation of NN intervals (SDNN), low frequency (LF), and high frequency (HF), during both the supine and tilt-up phases (all p-values <0.006). pwPMS had a significantly lower LF/HF (p = 0.008) during tilt-up. ConclusionThere is a significant difference in autonomic function in pwRRMS and pwPMS; with pwPMS having a higher burden of AD, which is particularly evident for sweating dysfunction. SignificanceFurther research is needed to establish whether parasympathetic and sudomotor dysfunction may serve as markers of progressive MS.

Neonatal autonomic function after pregnancy complications and early cardiovascular development

BackgroundHeart rate variability (HRV) has emerged as a predictor of later cardiac risk. This study tested whether pregnancy complications that may have long-term offspring cardiac sequelae are associated with differences in HRV at birth, and whether these HRV differences identify abnormal cardiovascular development in the postnatal period.MethodsNinety-eight sleeping neonates had 5-min electrocardiogram recordings at birth. Standard time and frequency domain parameters were calculated and related to cardiovascular measures at birth and 3 months of age.ResultsIncreasing prematurity, but not maternal hypertension or growth restriction, was associated with decreased HRV at birth, as demonstrated by a lower root mean square of the difference between adjacent NN intervals (rMSSD) and low (LF) and high-frequency power (HF), with decreasing gestational age (p < 0.001, p = 0.009 and p = 0.007, respectively). We also demonstrated a relative imbalance between sympathetic and parasympathetic tone, compared to the term infants. However, differences in autonomic function did not predict cardiovascular measures at either time point.ConclusionsAltered cardiac autonomic function at birth relates to prematurity rather than other pregnancy complications and does not predict cardiovascular developmental patterns during the first 3 months post birth. Long-term studies will be needed to understand the relevance to cardiovascular risk.

Altered Autonomic Functions and Distressed Personality Traits in Male Adolescents with Internet Gaming Addiction.

Internet gaming addiction (IGA) has been associated with many negative health outcomes, especially for youth; however, few studies have examined the physiological parameters and personality features related to this addiction. This study aimed to identify differences in autonomic functions and distressed (type D) personality traits among Korean adolescent males with and without IGA. In a cross-sectional study, 68 adolescent males were recruited in a Korean city using convenience and snowball sampling methods. For each subject, heart rate variability (HRV) parameters were measured as autonomic functions and questionnaires were used to identify IGA and type D personality traits. Data were analyzed using descriptive analyses, t tests, χ2 tests, and Pearson's correlation. Most HRV parameters significantly differed between the IGA and non-IGA groups (all p < 0.05). Type D personality total and subscale scores, including those for negative affectivity (NA) and social inhibition, were significantly higher in the IGA group (all p < 0.001). Of the 68 subjects, 46 were classified as having type D personality, with nearly twice as many in the IGA group as in the non-IGA group (p = 0.002). Type D personality total scores negatively correlated with the logarithmic value of total power and low frequency among the HRV parameters (both p < 0.05). Results showed that excessive Internet gaming was related to alterations in autonomic functions and distressed personality traits in male adolescents. These findings provide further understanding of the IGA phenomenon and highlight the need for interventions that address male adolescents with IGA.

OS 07-02 DIFFERENCES IN CIRCADIAN BLOOD PRESSURE VARIABILITY PATTERNS BETWEEN JAPANESE AND AMERICAN TREATMENT-RESISTANT HYPERTENSIVE POPULATIONS

Objective: Dynamic changes in 24-hour ambulatory blood pressure (BP) are associated with basal autonomic function and cardiovascular risk. We examined the influence of ethnicity on these parameters by comparing ambulatory BP dynamics in Japanese, African American (AA), and white populations with treatment-resistant hypertension. Design and Method: Both HTN-Japan (N = 41) and SYMPLICITY HTN-3 (N = 384 white and 140 AA) enrolled patients with office systolic BP ≥ 160 mmHg and 24-hour ambulatory systolic BP ≥ 135 mmHg while on ≥3 antihypertensive medications. Indices of circadian variation in ambulatory BP, including morning dynamic surge and maximum dynamic surge, were retrospectively compared after adjusting for differences in baseline demographics. Results: The Japanese and white cohorts were of similar age (58 ± 12 vs 59 ± 11 years) but AA patients were younger (53 ± 10 years, p = 0.016 vs Japanese). All 3 cohorts had similar baseline office systolic BP (180 mmHg in Japanese vs 182 mmHg in AA vs 179 mmHg in white patients, 3-way p = 0.32), but 24-hour ambulatory BP was highest in the Japanese patients (164 mmHg vs 161 mmHg in AA vs 158 mmHg in white patients, 3-way p = 0.014). The Japanese cohort had significantly (p < 0.05) lower body mass index, less obstructive sleep apnea, and less hypercholesterolemia than AA or white patients. Baseline stroke was greatest in the Japanese (17%) compared with AA (15%) or white patients (7%), 3-way p = 0.009. The Japanese cohort had significantly greater average morning, maximum morning, and maximum nighttime systolic BP. Morning dynamic surge parameters were also greater in the Japanese patient population (Figure). These differences persisted after multivariate analysis adjusting for baseline characteristics. Conclusions: Greater circadian variability, including dynamic surge parameters, in Japanese as compared with AA and white patients may indicate differences in the underlying autonomic mechanism of resistant hypertension in these populations. Differences in autonomic function may lead to more specific drug- and device-based therapy strategies based on ethnicity.

Joint hypermobility and autonomic hyperactivity: an autonomic and functional neuroimaging study

BackgroundJoint hypermobility is a common connective tissue variant. Surprisingly, people with this disorder are especially vulnerable to anxiety. Recent imaging studies suggest that non-anxious individuals with hypermobility express structural and functional differences in emotional brain regions. Autonomic dysregulation, typically postural tachycardia, is often found. Our aim was to test the hypothesis that joint hypermobility increases the expression of anxiety through aberrant central autonomic control. MethodsThe study had a 2×2 factorial design (presence or absence of hypermobility×presence or absence of generalised anxiety disorder). Adults with generalised anxiety disorder and healthy controls were prospectively recruited so that half of each group had hypermobility. Autonomic testing was done before measurement by functional MRI of brain responses to emotional stimuli. Between-group analyses tested for differences in autonomic function and patterns of brain activation. Presence of generalised anxiety disorder was assessed with DSM-IV criteria (MINI, MINI International Neuropsychiatric Interview). Anxiety was quantified with the Beck Anxiety Inventory. All neuroimaging findings are presented at a significance threshold of p(FWE corrected)<0·05. All other p values are uncorrected. The study had National Research Ethics Service approval at Brighton and Sussex Medical School. Findings70 adults were recruited (32 with generalised anxiety disorder, of whom 16 had hypermobility; 38 controls of whom 19 had hypermobility). An increase in sympathetic reactivity (proportional change in heart rate on active standing) was observed in individuals with hypermobility (n=35) versus those without hypermobility (n=35) (mean change from baseline 22·4% [SE 2·7] vs 14·2 [2·1], p=0·024) and in those with generalised anxiety disorder (n=32) versus those without anxiety (n=38) (24·0 [2·9] vs 13·9 [1·9], p=0·005), correlating with hypermobility (r=0·34, p=0·024) and anxiety scores (r=0·38, p=0·004). There was an interaction between the effects of hypermobility and anxiety on sympathetic reactivity (p=0·001). Within the brain, individuals with hypermobility showed increased reactivity to emotional stimuli within brain areas implicated in emotional processing and autonomic control, notably amygdala (p[FWE corrected]<0·0001) and insula (p[FWE corrected]<0·0001), where hypermobility interacted with anxiety level. Sympathetic reactivity partly mediated these heightened neural responses. InterpretationThis study shows that joint hypermobility is associated with the expression of anxiety through autonomic hyper-reactivity linked to aberrant engagement of the amygdala and insula. This study is the first, to our knowledge, to provide a mechanistic understanding of the association between joint hypermobility and anxiety; the findings will enhance recognition across medical disciplines of extra-articular features and vulnerabilities of joint hypermobility, offering possibilities for optimum personalised medicine. FundingMedical Research Council.

Differences in autonomic functions as related to induced stress between children with and without cerebral palsy while performing a virtual meal-making task

BackgroundEfforts to improve the participation and performance of children with cerebral palsy (CP) are often related to the adaptation of environmental conditions to meet their cognitive and motor abilities. However, the influence of affective stimuli within the environment on emotion and performance, and their ability to improve or impede the children's participation has not been investigated in any systematic way although the emerging evidence suggests that it affects the individuals in many levels. Objectives(1) To measure autonomic responses to affective stimuli during a simulated Meal-Maker task in children with CP in comparison to children who are typically developing, and (2) to examine the interactions between autonomic functions, subjective reports of stress, and task performance among children with and without CP. MethodsFifteen children with CP and 19 typically developing peers (6 to 12 years) participated. After completing behavioral questionnaires (e.g., State and Trait Anxiety Inventories), children prepared meals within a camera tracking virtual Meal-Maker environment. Either a negative, positive, or neutral visual stimulus was displayed, selected from the International Affective Picture System. Children also passively viewed the same pictures while rating their valence and arousal levels. Heart rate (HR) and skin conductance were recorded synchronously with stimulus onset. ResultsSignificant differences in autonomic functions were found between groups, i.e., a higher “low frequency” to “high frequency” (LF:HF) ratio in the children with CP during the meals associated with a negative stimulus (p=0.011). Only children with CP had significant positive correlations between trait anxiety and LF:HF ratio during virtual meal-making associated with positive (p=0.049) and negative stimuli (p=0.003) but not during neutral stimuli. For children with CP the amplitude of skin conductance response during passive picture viewing was significantly higher for negative than for positive stimuli (p=0.017) but there were no significant changes in autonomic responses during virtual Meal-Maker task.Significant correlations between trait anxiety, autonomic activity during the calm state and Meal-Maker performance outcomes were found only for children with CP. ConclusionsIn general, the Meal-Maker virtual environment was shown to be a feasible platform for the investigation of the effect of emotionally loaded stimuli on the balance of autonomic functions in children with and without CP. Anxiety level appears to play a significant role in children with CP and should be considered as a potentially important factor during clinical evaluation and intervention. Further studies are needed to develop additional measurements of emotional responses and to refine the types of affective interference.

Sex differences in autonomic function following maximal exercise.

BackgroundHeart rate variability (HRV), blood pressure variability, (BPV) and heart rate recovery (HRR) are measures that provide insight regarding autonomic function. Maximal exercise can affect autonomic function, and it is unknown if there are sex differences in autonomic recovery following exercise. Therefore, the purpose of this study was to determine sex differences in several measures of autonomic function and the response following maximal exercise.MethodsSeventy-one (31 males and 40 females) healthy, nonsmoking, sedentary normotensive subjects between the ages of 18 and 35 underwent measurements of HRV and BPV at rest and following a maximal exercise bout. HRR was measured at minute one and two following maximal exercise.ResultsMales have significantly greater HRR following maximal exercise at both minute one and two; however, the significance between sexes was eliminated when controlling for VO2 peak. Males had significantly higher resting BPV-low-frequency (LF) values compared to females and did not significantly change following exercise, whereas females had significantly increased BPV-LF values following acute maximal exercise. Although males and females exhibited a significant decrease in both HRV-LF and HRV-high frequency (HF) with exercise, females had significantly higher HRV-HF values following exercise. Males had a significantly higher HRV-LF/HF ratio at rest; however, both males and females significantly increased their HRV-LF/HF ratio following exercise.ConclusionsPre-menopausal females exhibit a cardioprotective autonomic profile compared to age-matched males due to lower resting sympathetic activity and faster vagal reactivation following maximal exercise. Acute maximal exercise is a sufficient autonomic stressor to demonstrate sex differences in the critical post-exercise recovery period.

Evaluation of autonomic function in obese and non obese adolescents

Reports on autonomic dysfunction associated with obesity in adolescent population are limited and also are conflicting. Therefore in the present study, we have evaluated the difference in autonomic function between the obese and nonobese adolescents. Sixty-five adolescent subjects aged between 17 and 19 years were selected from HAHC Hospital, Jamia Hamdard. Based on their body mass index, these subjects were divided into a nonobese group ( n = 54) and obese group ( n = 11). Autonomic function tests for assessing parasympathetic function (such as heart rate response to immediate standing and standing to lying ratio) and sympathetic function (such as blood pressure response to immediate standing and cold pressor test) were employed. There was no difference in sympathetic and parasympathetic function between the obese and nonobese adolescents. Therefore, the findings of the present study suggest that the autonomic dysfunction was not statistically significant in the studied adolescent population.

Post‐traumatic stress disorder does not affect cerebrovascular reactivity (1068.18)

Post‐traumatic stress disorder (PTSD) is a chronic psychiatric disorder, with symptoms of hyperarousal, which can alter the biological stress response. Our objective was to determine whether possible increased sympathetic tone in veterans with PTSD affected cerebrovascular function due to altered autonomic control. To assess this we measured sympathetic activity from low frequency blood pressure (BP) and heart rate (HR) variability and cerebrovascular function during hyper/hypocapnia using transcranial Doppler in 29 Veterans (10 with PTSD). There was no difference in BP or cerebral flow velocity in the middle (MCA: 51±5 vs 53±3 cm/s) or anterior cerebral artery (ACA: 48±7 vs 49±3 cm/s). Examination of autonomic indicators found no difference in low frequency power in HR or BP variance. Similarly PTSD status did not affect cerebrovascular reactivity for either the MCA (2.2±0.1 vs 2.2±0.1 %/mmHg) or ACA (2.0±0.2 vs 2.3±0.2 %/mmHg). Surprisingly, regardless of PTSD status, all veterans had a blunted response to hypercapnia (MCA: 1.3±0.2; ACA: 1.3±0.2 %/mmHg) compared to hypocapnia (MCA: 2.8±0.2; ACA: 2.7±0.2 %/mmHg). In contrast to our hypothesis, we did not find increased sympathetic activity in PTSD or impaired cerebral blood flow regulation. One explanation for this finding is that our PTSD sample was not of the hyperarousal type. Since we anticipate that hyperarousal is associated with increased sympathetic outflow, if our subjects mainly had dissociative type PTSD, there could be no difference in autonomic function. The finding of impaired vasodilation to CO2 but not vasoconstriction in all Veterans may indicate impaired cerebral vascular function.Grant Funding Source: Supported by NIH R21DC009900 (Serrador) as well as the WRIISC and the Office of VA Public Health

Antidepressants, autonomic function and mortality in patients with coronary heart disease: data from the Heart and Soul Study.

Antidepressants reduce depressive symptoms in patients with coronary heart disease, but they may be associated with increased mortality. This study aimed to examine whether the use of tricyclic antidepressants (TCA) or selective serotonin reuptake inhibitors (SSRI) is associated with mortality in patients with coronary heart disease, and to determine whether this association is mediated by autonomic function. A total of 956 patients with coronary heart disease were followed for a mean duration of 7.2 years. Autonomic function was assessed as heart rate variability, and plasma and 24-h urinary norepinephrine. Of 956 patients, 44 (4.6%) used TCA, 89 (9.3%) used SSRI, and 823 (86.1%) did not use antidepressants. At baseline, TCA users exhibited lower heart rate variability and higher norepinephrine levels compared with SSRI users and antidepressant non-users. At the end of the observational period, 52.3% of the TCA users had died compared with 38.2% in the SSRI group and 37.3% in the control group. The adjusted hazard ratio (HR) for TCA use compared with non-use was 1.74 [95% confidence interval (CI) 1.12-2.69, p = 0.01]. Further adjustment for measures of autonomic function reduced the association between TCA use and mortality (HR = 1.27, 95% CI 0.67-2.43, p = 0.47). SSRI use was not associated with mortality (HR = 1.15, 95% CI 0.81-1.64, p = 0.44). The use of TCA was associated with increased mortality. This association was at least partially mediated by differences in autonomic function. Our findings suggest that TCA should be avoided in patients with coronary heart disease.