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PubMed2001

Presence of a pet dog and human cardiovascular responses to mild mental stress.

The mechanisms underlying the possible cardiovascular benefits of pet ownership have not been established. Using a randomized design, the effect of a friendly dog on cardiovascular and autonomic responses to acute, mild mental stress was investigated. Seventy-two subjects (aged 40 +/- 14 y; mean +/- SD) participated. Rest was alternated with mental stress during four 10-minute periods. An unknown dog was randomly selected to be present during the first or the second half of the study. Blood pressure (BP) and heart rate (HR) were monitored continuously and cardiac autonomic function assessed using spectral analysis of heart period. Heart period variability data were expressed as the ratio of 0.1 Hz to respiratory or high frequency variation (LF/HF). Whereas mental stress significantly increased BP and HR in the absence of the dog (from 125/71 +/- 3/2 to 133/75 +/- 3/2 mm Hg; p <0.001), the presence of the dog had no effect on these variables. Heart period LF/HF ratio was lowest in dog owners in the presence of the dog (dog present 2.8 +/- 0.3 versus dog absent 3.4 +/- 0.4; p <0.001) and in non-dog owners in the absence of the dog (dog present 3.4 +/- 0.4 versus dog absent 2.8 +/- 0.3; p <0.001). In conclusion, a friendly but unfamiliar dog does not influence BP or HR either at rest or during mild mental stress. Cardiac autonomic profile was most favorable in the presence of the dog for dog owners and in the absence of the dog for non-owners.

Adult↗
PubMed2006

Cardiac autonomic hypofunction in preschool children with short nocturnal sleep.

Preschool children with sleep deficit may suffer from autonomic symptoms or hypotension. Heart rate variability, reflecting cardiac parasympathetic and sympathetic activities, and blood pressure were assessed to clarify the effects of nocturnal sleep duration on cardiac autonomic function in 134 preschool children aged 5 and 6 years. Parents reported their children's typical bedtimes and wake times for weekdays. In the children, the mean nocturnal sleep duration (+/- standard deviation) was 575 +/- 42 min. The parasympathetic and sympathetic activities and systolic blood pressure (SBP) were significantly lower in the 80 children with short sleep (nocturnal sleep duration < 10 hrs) than in the 54 children with long sleep (> or = 10 hrs). Only the SBP was positively correlated with nocturnal sleep duration in the children (p < 0.001); also, short nocturnal sleep duration was significantly related to hypotension (SBP < 100 mmHg), as judged by multiple logistic regression analysis. Among the children, inverse correlations were seen between the parasympathetic activity and SBP and between the sympathetic activity and diastolic blood pressure (p < 0.05). These findings indicate that shortening of nocturnal sleep is associated with cardiac autonomic hypofunction and low SBP in preschool children. We suggest that sleep duration is an important predictor for autonomic development in childhood.

Autonomic Nervous System↗
PubMed2006

Genetic variation in the renin-angiotensin system and autonomic nervous system function in young healthy Japanese subjects.

CONTEXT: The renin-angiotensin system (RAS) interacts with the autonomic nervous system (ANS) in the regulation of blood pressure and cardiovascular function. Several genetic polymorphisms in the RAS have been identified and have been implicated as a cause of hypertension and cardiovascular disease. OBJECTIVE: The aim of the present study was to evaluate the relation between genetic polymorphisms of the RAS (M235T of AGT gene, insertion/deletion of ACE gene, A1166C of AT1R gene, and A1675G of AT2R gene) and ANS function. SUBJECTS: One hundred forty-nine young healthy Japanese males were genotyped for each RAS polymorphism. MAIN OUTCOME MEASURES: ANS function was evaluated by power spectral analysis of heart rate variability (HRV) during supine rest and in a standing position. RESULTS: In a supine position, subjects homozygous for the AGT 235T allele had a higher HRV sympathetic index than 235M allele carriers, whereas the orthostatic change in this index was relatively blunted in AGT 235TT carriers. In the analysis of gene-gene interaction, these effects of the AGT 235T homozygotes on HRV sympathetic index were more apparent in the presence of the ACE D allele. Meanwhile, the AT1R 1166C allele was significantly associated with higher HRV low-frequency power and sympathetic index in a standing position. These data suggest that the AGT M235T polymorphism is associated with sympathetic predominance at rest, and AT1R 1166C allele carriers have potentially increased sympathetic response. CONCLUSIONS: Cardiac autonomic function can be modulated by genetic variation in the RAS even in young and healthy states.

Adolescent↗
PubMed2000

Impairment of heart rate variability during paclitaxel therapy.

BACKGROUND: Paclitaxel, which has been reported to be effective in treating metastatic breast carcinoma and advanced ovarian carcinoma, has been associated with cardiac side effects. Therefore, the effect of paclitaxel on cardiovascular autonomic regulation was studied. METHODS: Twenty-four-hour ambulatory electrocardiogram measurements were recorded twice from 14 women with breast or ovarian carcinoma: once before paclitaxel treatment and once on the day after the second chemotherapy course. Heart rate variability (HRV) was assessed with spectral analysis. For the frequency domain analysis, HRV was assessed in the very low (0.005-0.040 hertz [Hz]), low (0.040-0.150 Hz), and high frequency (0.150-0.400 Hz) spectral components. RESULTS: The ratio between low frequency and high frequency HRV decreased (daytime values of 2.7% [standard deviation (SD) 1.6] vs. 1.7% [SD 0.91; P = 0.0098) after 2 courses of paclitaxel. The circadian fluctuation of HRV also decreased in all studied frequency components. CONCLUSIONS: The observed changes in spectral characteristics suggest that autonomic modulation of the heart rate is impaired after paclitaxel therapy. However, from these data it is not clear whether the observed changes are permanent or whether autonomic cardiac function returns to normal some time after treatment. Further studies are needed to examine whether these indices based on HRV can be used to detect those patients at risk for cardiac side effects during chemotherapy.

Adult↗
PubMed2001

Influence of free radicals on cardiovascular risk due to occupational exposure to mercury.

This study was designed to investigate the relation between occupational exposure to mercury and cardiovascular risk, as well as free radicals. The study subjects included 30 male workers exposed to mercury from a fluorescent lamp plant in Alexandria after exclusion of 12 workers with conditions that may bias the results. A matched control group of 20 male subjects were selected from a food industrial plant. The participants were subjected to interview, clinical examination, electrocardiography and R-R deep breathing variability test as a measure of cardiac autonomic function. Spot urine and venous blood samples were collected to measure mercury levels. Free radicals related markers were measured in serum namely lipid peroxide, superoxide dismutase (SOD) activity, catalase activity and glutathione S-transferase. Results showed significant longer electrocardiographic Q-Tc interval, which is corrected to heart rate, in exposed workers than in controls (p=0.002). The R-R deep breathing variability indices were significantly increased among exposed workers in comparison to controls (maximal variation (MV) ratio, p=0.024 & MV rate, p=0.019). The mercury levels in both urine and blood of exposed workers were significantly higher than controls (p<0.0001), with mean levels exceeding the permissible limits. Free radicals related markers revealed significant higher level of lipid peroxide, as well as significant lower levels of SOD activity, catalase activity and glutathione S-transferase among exposed workers than among controls (p<0.0001 for all). Independent relations were observed between Q-Tc and lipid peroxide, and between MV rate and SOD and catalase activities among exposed workers after adjustment for the confounders by multivariate regression analyses. These findings may suspect a cardiac autonomic dysfunction probably related to free radicals in mercury exposed workers. Also, it may through light on some preventive implications.

Adult↗
PubMed1994

Autonomic neurotoxicity of alcohol assessed by heart rate variability.

Measurement of heart rate variability (CVR-R) provides a promising approach for evaluation of the autonomic nervous function. Specifically, high- and low-frequency component coefficients of variation of the CVR-R (C-CVHF and C-CVLF), computed from component spectral powers by autoregressive spectral and component analyses, are inferred to reflect parasympathetic and sympathetic activities, respectively. To assess the acute and chronic effects of alcohol on parasympathetic and sympathetic activities, ECGs in the supine posture were obtained in 11 male healthy volunteers, and in 23 male patients with severe alcoholic dependency together with the same number of age-matched healthy men. Significant changes in the CVR-R and heart rate were found 1 h after ethanol intake in the volunteers; also, the 1-h alteration in heart rate after intake was inversely correlated with that in the C-CVHF. The CVR-R, C-CVHF and C-CVLF were significantly depressed in the alcoholics compared to the matched controls. In the alcoholics, the age-adjusted correlation coefficients between not only the CVR-R but also C-CVHF and heart rate were negatively significant. These data suggest that acute and habitual intake of alcohol affects cardiac autonomic functions including sympathetic and parasympathetic activities; and, increase of heart rate in relation to alcohol, at least in alcoholics, seems to occur through reducing the parasympathetic activity.

Adult↗
PubMed2006

Association between reduced heart rate variability and cognitive impairment in older disabled women in the community: Women's Health and Aging Study I.

OBJECTIVES: To examine the independent association between heart rate variability (HRV), a marker of cardiac autonomic function, and cognitive impairment. DESIGN: Cross-sectional analysis of baseline data from Women's Health and Aging Study I. SETTING: Urban community in Baltimore, Maryland. PARTICIPANTS: A subset of 311 physically disabled, community-dwelling women aged 65 and older whose HRV data were obtained. MEASUREMENTS: Reduced HRV was defined as the lowest quartile of each of several HRV measures exploring time and frequency domains and compared with the remaining three quartiles. Cognitive impairment was defined as a Mini-Mental State Examination score less than 24. Multiple logistic regression was used to model the independent relationship between reduced HRV and prevalent cognitive impairment. RESULTS: The age-, education-, and race-adjusted prevalence of cognitive impairment was higher in those with reduced HRV than in those with nonreduced HRV. After adjusting for relevant demographic and clinical characteristics, participants with reduced HRV were significantly more likely than those with nonreduced HRV to have cognitive impairment; these findings were consistent across different HRV indices. In particular, reduced high-frequency power, indicative of decreased parasympathetic activity, was associated with 6.7 times greater odds of cognitive impairment (95% confidence interval = 2.27-20.0). CONCLUSION: Cardiac autonomic dysfunction, particularly decreased parasympathetic activity, was independently associated with cognitive impairment in older disabled women in the community. This finding may improve understanding of the pathophysiological basis of cognitive impairment. The potential role of HRV as a cause or consequence of cognitive impairment needs to be elucidated in future studies.

Aged↗
PubMed1981

Cardiac autonomic dysfunction in patients with diabetic retinopathy.

Cardiac autonomic function was assessed by an on-line microcomputer technique in 67 patients with diabetic retinopathy. Sixteen patients had a resting tachycardia (92 beats/min or greater). R-R interval variations were abnormally low in 29 patients at rest, in 35 during deep breathing and in four in response to a Valsalva manoeuvre. The severity of retinopathy correlated significantly with the degree of autonomic dysfunction assessed by the interval variations at rest (p less than 0.05), during deep breathing (p less than 0.01), and with the Valsalva manoeuvre (p less than 0.01). The results emphasise the important association between diabetic retinopathy and cardiac autonomic dysfunction.

Adult↗
PubMed2003

Heart rate variability and endogenous sex hormones during the menstrual cycle in young women.

To our knowledge, the relationship between all four endogenous female sex hormones and resting cardiac autonomic function has not been studied. The aim of the current study was to examine the association between the normal endogenous levels of oestrogen (17beta-oestradiol), progesterone, luteinising hormone and follicle-stimulating hormone and heart rate variability (HRV) during the menstrual cycle in young eumenorrheic women. Ten healthy, young, female subjects volunteered for this study. HRV and endogenous hormone levels were recorded at three phases of the menstrual cycle: menses (day 3.8 +/- 0.5), ovulation (day 15.8 +/- 0.7) and luteal (day 22.1 +/- 0.4) to ensure HRV recordings at times of low (menses) and high (ovulation and luteal) hormonal influence. Heart rate recordings were obtained from supine resting subjects and analysed on a Holter analysis system. Total power (TP, 0-1.0 Hz), low frequency (LF, 0.041-0.15 Hz), high frequency (HF, 0.15-0.80 Hz) and LF/HF components of HRV were examined. Despite a significantly greater HR at ovulation and normal cyclic variations in all endogenous sex hormone levels, no measure of HRV was significantly different between menstrual cycle phases. Significant correlations between oestrogen levels and absolute measures of HRV at ovulation were identified. The results of the current study demonstrated that the normal cyclic variations in endogenous sex hormone levels during the menstrual cycle were not significantly associated with changes in cardiac autonomic control as measured by HRV. Significant correlation between peak oestrogen levels and HRV measures at ovulation provided further support for the reported cardioprotective effects of oestrogen in healthy females.

Adult↗
PubMed2005

Effects of air pollution on heart rate variability: the VA normative aging study.

Reduced heart rate variability (HRV), a marker of poor cardiac autonomic function, has been associated with air pollution, especially fine particulate matter [< 2.5 microm in aerodynamic diameter (PM2.5)]. We examined the relationship between HRV [standard deviation of normal-to-normal intervals (SDNN), power in high frequency (HF) and low frequency (LF), and LF:HF ratio] and ambient air pollutants in 497 men from the Normative Aging Study in greater Boston, Massachusetts, seen between November 2000 and October 2003. We examined 4-hr, 24-hr, and 48-hr moving averages of air pollution (PM2.5, particle number concentration, black carbon, ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide). Controlling for potential confounders, HF decreased 20.8% [95% confidence interval (CI), 4.6-34.2%] and LF:HF ratio increased 18.6% (95% CI, 4.1-35.2%) per SD (8 microg/m3) increase in 48-hr PM2.5. LF was reduced by 11.5% (95% CI, 0.4-21.3%) per SD (13 ppb) increment in 4-hr O3. The associations between HRV and PM2.5 and O3 were stronger in people with ischemic heart disease (IHD) and hypertension. The associations observed between SDNN and LF and PM2.5 were stronger in people with diabetes. People using calcium-channel blockers and beta-blockers had lower associations between O3 and PM2.5 with LF. No effect modification by other cardiac medications was found. Exposures to PM2.5 and O3 are associated with decreased HRV, and history of IHD, hypertension, and diabetes may confer susceptibility to autonomic dysfunction by air pollution.

Adrenergic beta-Antagonists↗
PubMed1991

Circadian variation and influence of risk factors on heart rate variability in healthy subjects.

Quantification of variations in instantaneous heart rate (HR) can be used to evaluate cardiac autonomic function. A 24-hour standard deviation of all normal RR intervals less than 50 ms in survivors of myocardial infarction has been shown to be an independent marker of adverse prognosis. Twenty-four-hour HR variability in 140 healthy subjects aged 40 to 77 years was determined as (1) standard deviation, and (2) percentage of successive RR interval differences greater than 6%--an index of parasympathetic activity. The 24-hour standard deviation varied between 68 and 261 ms (median 139). Range for index of parasympathetic activity was 0.1 to 29.6% (median 4.4). Twenty percent of the interindividual variation in HR variability was explained by impact of risk factors. Standard deviation was uninfluenced by age, whereas parasympathetic activity decreased by increasing age. High physical training level was independently associated with significantly higher standard deviation (and parasympathetic activity) values during both day and night. Hourly figures of standard deviation decreased during the night, whereas parasympathetic activity increased and peaked early morning. Standard deviation values as low as those reported in high-risk patients were not observed, but comparable low values for, and lack of diurnal variation in, parasympathetic activity were seen in healthy subjects also. In conclusion, risk factors and, in particular, the physical training level have impact on 24-hour HR variability in healthy subjects. This may prove valuable for modification of cardiac autonomic activity in patients.

Adult↗
PubMed1998

Abnormal vasovagal reaction, autonomic function, and heart rate variability in patients with paroxysmal atrial fibrillation.

The aim of this study was to evaluate the cardiovascular autonomic function and vasovagal reaction in patients with paroxysmal atrial fibrillation without significant structural heart disease. Twenty-eight patients with paroxysmal atrial fibrillation (9 patients were categorized to have autonomic-mediated atrial fibrillation while atrial fibrillation in other patients was nonautonomic mediated) and 19 normal control subjects were recruited. Cardiovascular autonomic function tests included measuring heart rate response to standing, deep breathing, Valsalva maneuver, baroreflex sensitivity, 24-hour heart rate variability, and also head-up tilt test. Compared with normal subjects, no significant autonomic dysfunction was found in patients with autonomic-mediated and nonautonomic-mediated atrial fibrillation. All subjects had negative baseline tilt test. With isoproterenol provocation, six patients developed atrial fibrillation. Four of 9 patients and 3 of 19 patients with autonomic mediated and nonautonomic mediated atrial fibrillation had a positive tilt test respectively, while none occurred in the controls. A significant percentage (32%) of patients with paroxysmal atrial fibrillation had episodes of atrial fibrillation provoked by changes in autonomic tone, although there was no underlying abnormal cardiac autonomic function nor sympathetic-parasympathetic imbalance. A heightened susceptibility to vasovagal cardiovascular response may have important implications on the occurrence and symptomatology of patients with paroxysmal atrial fibrillation.

Adult↗
PubMed2001

Heart rate variability and its determinants in patients with severe or mild essential hypertension.

How cardiac autonomic nervous control is related to the severity of essential hypertension in patients receiving long-term antihypertensive therapy is not well known. The aim of this study was to examine heart rate variability (HRV), a non-invasive measure of cardiac autonomic function, in patients with long-term and medically treated mild and severe essential hypertension and healthy control subjects, and to assess the clinical determinants of HRV in these patients. Thirty-four patients with severe essential hypertension (SEHT) and 29 with mild essential hypertension (MEHT) as well as healthy age- and sex-matched control subjects were studied. HRV was assessed from 10 min ECG-recordings during paced (0.2 Hz) breathing at rest and expressed as time and frequency domain measures. In the SEHT group time (SDNN, RMSSD) and frequency domain measures (total power, low-frequency (LF) power and high-frequency (HF) power of HRV in absolute units, and LF and HF power of HRV in normalized units) of HRV were significantly lower when compared with those of the control group. The MEHT and control groups did not differ from each other with respect to time or frequency domain measures of HRV. Comparison between the hypertensive groups showed that SDNN, total power, LF power and HF power were lower in the SEHT group compared with the MEHT group (P<0.05 for all). Among hypertensive patients RR-interval, age, gender, systolic finger blood pressure and diastolic office blood pressure as well as 24-h blood pressure were significant determinants of HRV. In conclusion, we found that the severity of chronic essential hypertension seems to be related to the severity of impairment of cardiac autonomic control.

Adult↗
PubMed1998

Altered autonomic cardiac control in hypertrophic cardiomyopathy. Role of outflow tract obstruction and myocardial hypertrophy.

AIM: The goal of this study was to investigate the role of left ventricular outflow tract obstruction and myocardial hypertrophy on autonomic cardiac function in patients with hypertrophic cardiomyopathy. METHODS AND RESULTS: The sympatho-vagal function was evaluated by spectral analysis of heart rate variability in 28 patients with hypertrophic obstructive cardiomyopathy, 22 patients with hypertrophic non-obstructive cardiomyopathy, 12 with systemic hypertension and left ventricular hypertrophy and 28 healthy subjects. Left ventricular out-flow tract pressure gradient in patients with hypertrophic cardiomyopathy was evaluated by echo-Doppler methods and the quantitative assessment of left ventricular hypertrophy was based on an echocardiographic index. At rest, patients with hypertrophic non-obstructive cardiomyopathy showed normal spectral patterns, while in patients with hypertrophic obstructive cardiomyopathy and in patients with systemic hypertension we observed, respectively, a significant reduction and increase in the low frequency component relative to the control (P < 0.05). During tilt, the physiological increases in the low frequency component and in the low to high frequency ratio were markedly blunted, or even reverted, only in patients with hypertrophic obstructive cardiomyopathy. In these patients, the heart rate increase during tilt was delayed in comparison to the other groups. Finally, in the hypertrophic obstructive cardiomyopathy group, the impairment of sympathetic activation (lack of increase in the low frequency component during tilt) was significantly correlated to the echocardiographic index of left ventricular hypertrophy (r = -0.800, P < 0.001) rather than to the left ventricular outflow tract pressure gradient (r = 0.295, P: ns). CONCLUSION: Among patients with hypertrophic cardiomyopathy, only those with outflow tract obstruction show spectral signs of altered autonomic cardiac control. Within this group, the autonomic dysfunction appears to be correlated to myocardial hypertrophy rather than to left ventricular outflow tract obstruction.

Adult↗
PubMed1998

Decreased heart-period variability in patients with panic disorder: a study of Holter ECG records.

This study investigated cardiac autonomic function in patients with panic disorder and normal controls using Holter ECG records. A decrease in ultra-low frequency power (< 0.0033 Hz) is known to be associated with an increased risk for cardiovascular mortality in humans. Twenty-four-hour ECG was recorded in 29 patients with panic disorder and 23 normal controls using Holter records. Data for 20 h and also 20000 s of awake and 20000 s of sleep periods were analyzed using spectral analysis to quantify absolute and relative heart-period variability in ultra low (ULF: < 0.0033 Hz), very low (VLF: 0.0033-0.04 Hz), low (LF: 0.04-0.15 Hz) and high (HF: 0.15-0.5 Hz) frequency bands. The patients with panic disorder had significantly lower total and absolute ULF power, which was more pronounced during sleep. The patients also had significantly lower relative ULF power and significantly higher relative LF power during sleep. There was a significant increase of relative LF power from awake to sleep period only in the patient group. The decrease in total and ULF power may increase the risk of mortality and sudden arrhythmic death in patients with panic disorder if they experience a cardiac event. The higher relative LF power during sleep also suggests a possible higher sympathetic drive in the patients during sleep.

Adult↗
PubMed2005

Heart rate turbulence: a new predictor for risk of sudden cardiac death.

Initial acceleration and a subsequent deceleration of sinus rhythm following a ventricular ectopic beat with a compensatory pause has been termed heart rate turbulence (HRT). The changes in sinus rhythm are thought to be mediated by a baroreflex response to the lower stroke volume of the ectopic beat. HRT is vagally mediated and abolished by atropine, whereas beta-blockers have no effect. HRT has been shown to be an independent and powerful predictor of mortality after myocardial infarction. In patients on beta-blockers, it scores better than left ventricular ejection fraction (LVEF) in its predictive value. Two common measures of HRT are turbulence onset and turbulence slope. When both these measures are abnormal, it is as powerful a predictor of mortality as LVEF. HRT correlates with other indices of cardiac autonomic functions like baroreflex sensitivity and heart rate variability. A composite autonomic index including all these three has been shown to be a powerful predictor of mortality. In patients undergoing direct percutaneous intervention for myocardial infarction, HRT improves in those attaining successful reperfusion. Abnormal values for HRT have been noted in patients with dilated cardiomyopathy and Chagas disease. Diabetic and elderly individuals are more likely to have blunted HRT. HRT cannot be measured in patients lacking ventricular ectopic beats and in patients presenting with atrial fibrillation.

Arrhythmias, Cardiac↗
PubMed2005

Dose-response relationship of endurance training for autonomic circulatory control in healthy seniors.

Aging results in marked abnormalities of cardiovascular regulation. Regular exercise can improve many of these age-related abnormalities. However, it remains unclear how much exercise is optimal to achieve this improvement or whether the elderly can ever improve autonomic control by exercise training to a degree similar to that observed in healthy young individuals. Ten healthy sedentary seniors [71 +/- 3 (SD) yr] trained for 12 mo; training involved progressive increases in volume and intensity. Static hemodynamics were measured, and R-wave-R-wave interval (RRI), beat-to-beat blood pressure (BP) variability, and transfer function gain between systolic BP and RRI were calculated at baseline and every 3 mo during training. Data were compared with those obtained in 12 Masters athletes (68 +/- 3 yr) and 11 healthy sedentary young individuals (29 +/- 6 yr) at baseline. Additionally, the adaptation of these variables after completion of identical training loads was compared between the seniors and the young. Indexes of RRI variability and baroreflex gain were decreased in the sedentary seniors but preserved in the Masters athletes compared with the young at baseline. With training in the seniors, baroreflex gain and resting BP showed a peak adaptation after moderate doses of training following 3-6 mo. Indexes of RRI variability continued to improve with increasing doses of training and increased to the same magnitude as the young at baseline after heavy doses of training for 12 mo; however, baroreflex gain never achieved values equivalent to the young at baseline, even after a year of training. The magnitude of the adaptation of these variables to identical training loads was similar (no interaction effects of age x training) between the seniors and the young. Thus RRI variability in seniors improves with increasing "dose" of exercise over 1 yr of training. In contrast, more moderate doses of training for 3-6 mo may optimally improve baroreflex sensitivity, associated with a modest hypotensive effect; however, higher doses of training do not lead to greater enhancement of these changes. Seniors retain a similar degree of "trainability" as young subjects for cardiac autonomic function to dynamic exercise.

Adaptation, Physiological↗
PubMed1996

Autonomic activity assessed by heart rate spectral analysis varies with fat distribution in obese women.

Obesity in humans has been associated with altered autonomic nervous system activity. The objective of this study was to examine the relationship between autonomic function and body fat distribution in 16 obese, postmenopausal women using power spectrum analysis of heart rate variability. Using this technique, a low frequency peak (0.04-0.12 Hz) reflecting mixed sympathetic and parasympathetic activity, and a high frequency peak (0.22-0.28 Hz) reflecting parasympathetic activity, were identified from 5-minute consecutive heart rate data (both supine and standing). Autonomic activity in upper body (UBO) vs. lower body obesity (LBO)(by waist-to-hip ratio) and subcutaneous vs. visceral obesity (by CT scan) was evaluated. Power spectrum data were log transformed to normalize the data. The results showed that standing, low-frequency power (reflecting sympathetic activity) and supine, high-frequency power (reflecting parasympathetic activity) were significantly greater in UBO than in LBO, and in visceral compared to subcutaneous obesity. Women with combined UBO and visceral obesity had significantly higher cardiac sympathetic and parasympathetic activity than any other subgroup. We conclude that cardiac autonomic function as assessed by heart rate spectral analysis varies in women depending on their regional body fat distribution.

Adipose Tissue↗