PURPOSE: Patients with insulin-dependent diabetes mellitus (IDDM) are especially susceptible to microangiopathic complications such as nephropathy, retinopathy, and neuropathy. Microangiopathic changes are also the most important findings in histopathologic studies of the inner ear and central nervous systems in diabetic subjects. No previous studies have measured acoustic-reflex latencies (ARL) or amplitudes (ARA) in patients with IDDM. ARL and ARA reflect the function of the acoustic-reflex arch. Furthermore, possible changes in the tympanic membrane, ossicular chain, and stapedius muscle may affect the shape of acoustic-reflex. SUBJECTS AND METHODS: Acoustic-reflex thresholds, latencies, and amplitudes were studied in 53 patients with IDDM and 42 randomly selected nondiabetic control subjects, aged between 20 and 40 years, using the Madsen Model ZO 73 Impedance Bridge (Madsen Electronics, Copenhagen, Denmark). Subjects with an abnormal tympanic membrane, conductive hearing loss, and known cause for hearing impairment eg, noise damage, were excluded from the study. RESULTS: There were no differences between control and diabetic subjects in the contralateral acoustic-reflex thresholds. In contrast, patients with IDDM had longer ARLs and decreased ARAs compared with those of control subjects. ARA amplitude had linear correlation with the amplitude of tympanogram, whereas ARL had no linear correlation with auditory brainstem latencies in the same study subjects. Acoustic-reflex responses in insulin-dependent diabetic patients were not associated with the duration of diabetes, metabolic control, microangiopathy, or neuropathy. CONCLUSIONS: Prolonged ARLs and decreased ARAs in patients with insulin-dependent diabetes are probably caused more by the stiff middle ear system than disturbances in the brainstem.
BACKGROUND. Prospective epidemiological studies indicate that elevated heart rate may carry increased risk for coronary heart disease. Little is known about the relation between heart rate and serum lipid and lipoprotein concentrations in the general population. METHODS AND RESULTS. We assessed anthropometric and life-style determinants of heart rate and examined the association between heart rate and serum lipid and lipoprotein concentrations in a cross-sectional study of 9,719 men and 9,433 women 12-59 years old. Stratified and multivariate analyses were used to detect possible modification of effect and to control for confounding variables. Heart rate was positively associated with male sex and smoking, decreased with body height and physical activity, and showed a U-shaped relation to body mass index. In both sexes, there was a significant progressive increase in age-adjusted levels of total cholesterol, non-high density lipoprotein (HDL) cholesterol, and triglycerides and a decrease in HDL cholesterol with heart rate. Men with heart rate greater than 89 beats per minute had 14.5% higher non-HDL cholesterol and 36.3% higher triglyceride levels than men with heart rate less than 60 beats per minute. The corresponding differences in women were 12.5% and 22.2%. The associations remained significant when anthropometric and life-style factors were controlled for. The slopes relating total and non-HDL cholesterol level to heart rate were steeper with advancing age. CONCLUSIONS. Increases in heart rate correlate with higher levels of atherogenic serum lipid fractions in the general population. Alterations in aortic impedance and/or autonomic influences may underlie these associations.
In spite of recent advances in secondary prevention, sudden cardiac death has remained a major public health problem as the majority of fatalities occur in subjects without a history of severe heart disease. Abrupt rupture of a vulnerable plaque resulting in thrombotic occlusion of a coronary artery is a common cause of sudden death in this population. Coronary occlusion does not, however, invariably lead to sudden death but may cause acute myocardial infarction or exacerbation of chest pain. Extensive studies in experimental animals and increasing clinical evidence indicate that autonomic nervous activity has a significant role in modifying the clinical outcome. Sympathetic hyperactivity favours the genesis of life-threatening ventricular tachyarrhythmias while vagal activation exerts an antifibrillatory effect. Strong afferent stimuli from the ischaemic myocardium impair arterial baroreflex and may lead to dangerous haemodynamic instability. Studies with a human angioplasty model have shown that there is wide interindividual variation in the type and severity of autonomic reactions during the early phase of abrupt coronary occlusion, a critical period for out-of-hospital cardiac arrest. The site of the occlusion is not a significant determinant of the reactions, whereas the severity of a coronary stenosis, adaptation or ischaemic preconditioning, beta-blockade and gender seem to affect the autonomic reactions and occurrence of complex ventricular arrhythmias. Clinical and angiographic factors are, however, poor predictors of autonomic reactions in an individual patient. Recent studies have documented a hereditary component for autonomic function, and genetic factors may also modify the clinical manifestations of acute coronary occlusion.
INTRODUCTION: Cold habituation could affect sympatho-vagal balance, which modulates cold stress responses. The study examined cardiovascular autonomic function at the sinus node level during controlled breathing and while undertaking isometric exercise during whole-body cold exposure before and after cold acclimation. METHODS: There were 10 male subjects who were exposed to control (25 degrees C) and cold (10 degrees C) environments for 2 h on 10 successive days in a laboratory. Time and frequency domain heart rate variability (HRV) in terms of root mean square of successive differences in RR intervals, total, high, and low frequency power were determined from controlled breathing at the beginning and end of cold acclimation. Heart rate and blood pressure during an isometric handgrip test (30% MVC for 3 min) were recorded at the beginning and end of cold acclimation. Catecholamines (NE and E), mean skin (Tsk), and rectal temperatures (Trect) were measured. RESULTS: Acute cold exposure increased total (36%), low (16%), and high frequency power (25%) and RMSSD (34%). Cold acclimation resulted in higher Tsk (0.6 degrees C) and lower NE (24%) response in cold. The cold-induced elevation in high frequency power became significant after cold acclimation, while other HRV parameters remained unchanged. A smaller increase in heart rate and blood pressure occurred at 10 degrees C during the handgrip test after cold acclimation. DISCUSSION: Cold exposure increased sympathetic activity, which was blunted after cold acclimation. Parasympathetic activity showed a minor increase in cold, which was enhanced after cold acclimation. In conclusion, cold habituation lowers sympathetic activation and causes a shift toward increased parasympathetic activity.
Northern European areas are differing in degree of extreme climatic conditions in the Polar and Subpolar latitudes. Formation of the nervous system in adolescents most of all is affected by these adverse climatic factors.
The aim was to study of the autonomic regulation of cardiac activity and brain bioelectric activity in adolescents-inhabitants of the North depending on these autonomic nervous tones.
300 adolescents (male and female) aged 15-16 years living in the Polar (67°40' N) and Subpolar (64°30' N) northern regions of Russia are examined. Assessment of autonomic nervous tone was determined by the heart rate variability (HRV) and blood pressure parameters. After the initial analysis of these indicators, all subjects in both areas were further divided into groups with vagotonic, normotonic and sympathotonic types. Electroencephalogram (EEG) was recorded in the state of quiet wakefulness with closed eyes (16 standard monopolar leads). EEG characteristic were performed on the values of the amplitude and the index in each frequency band. All described changes were statistically significant atp
The responses to cold hand test (blood pressure increase and tachycardia) and to a cold face test (blood pressure increase and bradycardia) were used to study the role of the autonomic nevrous system in cold adaptation in humans. The Eskimos (men, women, children) were shown to have a very weak sympathetic response to cold but the vagal response (bradycardia) was identical to that of white people. A group of mailmen from Quebec city living outdoors approximately 30 h/wk throughout the year was also studied. A significant decline in the cold pressor response and an enhanced bradycardia (cold face test) were observed at the end of the winter. Similarly the fall in skin temperature of the cheek was not as pronounced when the measurements were made in May compared to those made in October. A group of soldiers was also studied before and after an Arctic expedition. It was found that the bradycardia of the cold face test was also more pronounced after sojourning in the cold. These results indicate that repeated exposures to severe cold in men activate some adaptive mechanisms characterized by a diminution of the sympathetic response and a concomitant enhancement of the vagal activation normally observed when the extremities and the face are exposed to cold.
From: Fortuine, Robert et al. 1993. The Health of the Inuit of North America: A Bibliography from the Earliest Times through 1990. University of Alaska Anchorage. Citation number 1033.
PURPOSE: To investigate the effects of training intensity and duration, through a range representative of training in endurance athletes, on acute recovery of autonomic nervous system (ANS) balance after exercise. METHODS: Nine highly trained (HT) male runners (VO2max 72 +/- 5 mL.kg.min(-1), 14 +/- 3 training hours per week) and eight trained (T) male subjects (VO2max 60 +/- 5 mL.kg.min(-1), 7 +/- 1 training hours per week) completed preliminary testing to determine ventilatory thresholds (VT1, VT2) and VO2max. HT performed four intensity-controlled training sessions: 60 min and 120 min below VT1; 60 min with 30 min between VT1 and VT2 (threshold); and 60 min above VT2 (6 x 3 min at 96% VO2max, 2 min of recovery). T also completed the interval session to compare ANS recovery between HT and T. Supine heart rate variability (HRV) was quantified at regular intervals through 4 h of recovery. RESULTS: When HT ran 60 or 120 min below VT1, HRV returned to pretraining values within 5-10 min. However, training at threshold (2.7 +/- 0.4 mM) or above VT2 (7.1 +/- 0.7 mM) induced a significant, but essentially identical, delay of HRV recovery (return to baseline by approximately 30 min). In T, HRV recovery was significantly slower, with HRV returning to baseline by >or=90 min after the same interval session. CONCLUSIONS: In the highly trained endurance athlete, exercise for
We have been studying peculiarities of vegetative provision of mental activity with different level of difficulty. It was revealed that efficiency of mental activity of children from junior school depends on the difficulty of the given visual information and vegetative provision. It was proved that children from junior school had the highest level of mental activity with easiest tasks, but vegetative provision was minimal. When the task became more difficult earning capacity of the brain was down but we saw more expressed change in vegetative provision. In case of the highest level of visual information presentations we saw the lowest level capability of the brain but reducing of vegetative provision. We discussed mechanisms of the links between working ability of the brain and vegetative provision of mental activity of different difficulty level.
Novelty seeking temperament has been associated with higher coronary heart disease risk factors, but the mechanism behind the association is open. Cardiac stress response is a potential candidate.
Cardiac stress reactivity and recovery was studied in 29 healthy subjects (aged 22-37 years) scoring extremely high (n = 16) or extremely low (n = 13) on temperamental dimension of novelty seeking.
Heart rate, respiratory sinus arrhythmia, and pre-ejection period were measured during challenging tasks. Differences in cardiac reactivity and recovery between the novelty seeking groups were examined with repeated-measures and univariate analyses.
The main finding was that stress reactivity did not differ between high and low novelty seeking groups, but high novelty seekers tended to show faster recovery, which is likely to be parasympathetically mediated.
The findings suggest that high novelty seekers may be more stress resilient because they might have faster cardiac recovery after stress. Cardiac stress reactivity seems not to be among the explaining factors for the association between novelty seeking and coronary heart disease risk factors.