Effect of Working Hours on Cardiovascular-Autonomic Nervous Functions in Engineers in an Electronics Manufacturing Company.
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A field survey of 147 engineers (23-49 years) in an electronics manufacturing company was conducted to investigate the effect of working hours on cardiovascular-autonomic nervous functions (urinary catecholamines, heart rate variability and blood pressure). The subjects were divided into 3 groups by age: 23-29 (n = 49), 30-39 (n = 74) and 40-49 (n = 24) year groups. Subjects in each age group were further divided into shorter (SWH) and longer (LWH) working hour subgroups according to the median of weekly working hours. In the 30-39 year group, urinary noradrenaline in the afternoon for LWH was significantly lower than that for SWH and a similar tendency was found in the LF/HF ratio of heart rate variability at rest. Because these two autonomic nervous indices are related to sympathetic nervous activity, the findings suggested that sympathetic nervous activity for LWH was lower than that for SWH in the 30-39 year group. Furthermore, there were significant relationships both between long working hours and short sleeping hours, and between short sleeping hours and high complaint rates of "drowsiness and dullness" in the morning in this age group. Summarizing these results, it appeared that long working hours might lower sympathetic nervous activity due to chronic sleep deprivation.Keywords:
Sympathetic nervous system
Sympathetic activity
The autonomic nervous system regulates the heart rate through its sympathetic and para-sympathetic nervous system to maintain body visceral homeostasis. The sympathetic tone enhances the heart rate whereas the para-sympathetic tone inhibits this rise. The continuous variation of heart rate in synchronism with visceral systems is termed as heart rate variability. This heart rate variability is higher in normal and healthy conditions, whereas it is reduced in case of cardiac abnormalities. The present study is regarding heart rate variability in non-yogic practitioners and yogic practitioners. The spectral parameters were evaluated in two groups, where one group is having forty two normal and healthy male subjects who are non-yogic practitioners, and the other group is also having forty two normal and healthy male subjects who are experienced yoga practitioners. The subjects in both groups are in the age group of 18-48 years. The power in low frequency (LF) has been observed to be higher in non-yogic practitioners as compared to those of yogic practitioners. Moreover, the heart rate variability in yogic practitioners has shown to be higher than the subjects who do not practise yoga.
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A low-frequency to a high-frequency component ratio (LF/HF) in heart rate variability (HRV) may not accurately reflect sympathetic nervous activity during exercise. Thus, a valid HRV-based index of sympathetic nervous activity is needed. Therefore, the heart rate to LF ratio (Heart rate/LF) was evaluated as sympathetic nervous activity index which is reflected by catecholamine levels during incremental exercise. In this study, 15 healthy adults performed an incremental exercise test using a cycle ergometer. HRV was derived from electrocardiography and HRV components related to the autonomic nervous system were obtained using frequency analysis. Heart rate/LF was calculated using the heart rate and LF component produced by HRV analysis. Catecholamine, blood lactate levels and respiratory gas were also measured throughout the exercise test. While LF/HF did not increase with increasing exercise intensity, Heart rate/LF non-linearly increased during the incremental exercise test, as did noradrenaline and blood lactate. Interestingly, Heart rate/LF values were positively correlated with noradrenaline (ρ = 0.788, p < 0.05) and blood lactate (ρ = 0.802, p < 0.05) levels and carbon dioxide production (ρ = 0.903, p < 0.05) from at rest through the exercise stages. Heart rate/LF reflects sympathetic nervous activity and metabolic responses during incremental cycling exercise and has potential as an HRV index of sympathetic nervous activity during exercise.Trial registration: UMIN Japan identifier: UMIN000039639.
Sympathetic nervous system
Incremental exercise
Exercise intensity
Physical exercise
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Abstract The autonomic nervous system (ANS) is a principal regulatory system for maintaining homeostasis, adaptability and physiological flexibility of the organism at rest as well as in response to stress. In the aspect of autonomic regulatory inputs on the cardiovascular system, recent research is focused on the study of exaggerated/diminished cardiovascular reactivity in response to mental stress as a risk factor for health complications, e.g. hypertension. Thus, the analysis of biological signals reflecting a physiological shift in sympathovagal balance during stress in the manner of vagal withdrawal associated with sympathetic overactivity is important. The heart rate variability, i.e. “beat-to-beat” oscillations of heart rate around its mean value, reflects mainly complex neurocardiac parasympathetic control. The electrodermal activity could represent “antagonistic” sympathetic activity, the so-called “sympathetic arousal” in response to stress. The detailed study of the physiological parameters under various stressful stimuli and in recovery phase using traditional and novel mathematical analyses could reveal discrete alterations in sympathovagal balance. This article summarizes the importance of heart rate variability and electrodermal activity assessment as the potential noninvasive indices indicating autonomic nervous system activity in response to mental stress.
Sympathetic nervous system
Sympathetic activity
Psychophysiology
Homeostasis
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Sympathetic activity
Sympathetic nervous system
Parasympathetic nervous system
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Backgound The long-term age-related changes in circadian rhythm of heart rate variability (HRV), that is, autonomic nervous activity, remain unknown in elderly people. Methods and Results Holter monitoring was conducted twice at an interval of 15 years in 15 healthy elderly patients (age: 70.0±4.1 years, at first monitoring, female: 10) and assessed the age-related changes in 24-h mean and hourly mean normal sinus R-R interval (mean NN), HRV (high frequency (HF) component, low frequency (LF) component and LF/HF) and the circadian rhythms. As a result, 24-h mean mean NN (0.976±0.115 vs 0.903±0.117 (s), p=0.0019), LF/HF (1.681±0.731 vs 0.962±0.442, p=0.0022), and LF (278.88±176.43 vs 179.19±132.33 (ms2), p=0.0039) significantly decreased 15 years later, although 24-h mean HF (221.20±138.89 vs 310.78±296.73 (ms2), p=0.1102) increased slightly. The hourly mean NN closely correlated with hourly HF and LF/HF throughout circadian rhythms both at first and second monitoring. In the morning hours, amplitude rates of all HRV indices increased significantly 15 years later. Conclusion In elderly people, age-related changes in the 24-h mean heart rate (HR) were conversely dissociated from those of the 24-h mean HRV. However, the close correlation between hourly HR and HRV was preserved, even in very elderly patients. Additionally, the amplitude rates in HRV in the morning increased with age. These age-related changes of HR and HRV might be characteristic of elderly people. (Circ J 2006; 70: 889 - 895)
Heart Rhythm
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In our previous studies, it was shown that blood pressure variability was largely independent from the adrenergic nervous system. In the present work, vagal nervous influence on blood pressure variability was analysed both in dogs and in men. In eight chronically instrumented conscious dogs, striking fluctuations of blood pressure were observed when quietly resting; these fluctuations correlate well with fluctuation of heart rate. Atropine abolished all variations both of heart rate and of pressure. Reflex stimulation of vagal tone by neosynephrine increased variability of both parameters. Thus, in dogs, blood pressure variability is related to variability of heart rate which is largely influenced by vagal tone. The same question was approached in seven male volunteers; blood pressure and heart rate were measured automatically every 2 min, during 1 h, before and after atropine. In control conditions, no correlation between variability of heart rate and of blood pressure was observed. Atropine clearly decreased variability of heart rate and of diastolic blood pressure. These data confirm the animal results; however, the influence of vagal nerves on variability is less pronounced in man than in dogs.
Vagal Tone
Mean blood pressure
Parasympathetic nervous system
Sympathetic nervous system
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Objective To investigate the relationship between circadian rhythm of blood pressure,heart rate variability,and arrhythmia in elderly patients with hypertension.Methods Ambulatory blood pressure monitoring and ambulatory electrocardiography,as well as heart rate variability analysis,were performed in the elderly with and without hypertension.Results Among the elderly with hypertension,the circadian rhythm of blood pressure decreased or disappeared,and the heart rate variability decreased,with significant differences compared with those without hypertension.In addition,there were more cases of arrhythmia in the elderly with hypertension.Conclusion The elderly patients with hypertension have impaired autonomic nervous function;their heart rate variability decreases,and the circadian rhythm of blood pressure decreases or disappears,which are the risk factors for arrhythmia.Heart rate variability measurement and ambulatory blood pressure monitoring should be performed regularly.
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The frequency of adverse cardiovascular events is greater in the morning compared to its 24-hour average. A circadian variation in the regulation of the cardiovascular system could contribute to this increased cardiovascular risk in the morning. Indeed, circadian rhythms have been shown for a wide array of physiological processes. Using an ultradian sleep-wake cycle (USW) procedure, we sought to determine how heart rate (HR) and heart rate variability (HRV) correlate with the well-characterized circadian rhythms of cortisol and melatonin secretion. Specific HRV components, namely the low frequency (LF) power, high frequency (HF) power, and the LF:HF ratio can be used as markers of the autonomic modulation of the heart. Cross-correlation between HRV parameters and hormonal rhythms demonstrated that mean RR interval is significantly phase-advanced relative to salivary cortisol and urinary 6-sulfatoxy-melatonin (UaMt6s). Parasympathetic modulation of the heart (HF power) was phase-advanced relative to cortisol, but was in-phase with UaMt6s levels. Maximal correlation of the sympathovagal balance (the LF:HF ratio) had no significant lag compared to cortisol secretion and UaMt6s excretion. The protective effect of the parasympathetic nervous system at night, combined with the putative risk associated with the sympathetic nervous system peaking in the morning, could be associated with the increased cardiovascular risk observed in the morning hours.
Chronobiology
Cortisol awakening response
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Introduction. Heart rate variability is the leading non-invasive method used for assessing the activity of the autonomic nervous system. Investigation of the changes in the autonomic nervous system activity under the influence of circadian rhythm and daily physical activity can be beneficial to exercise at the best time of the day and at regular time intervals. Furthermore, it can be used to determine the optimal level of total daily physical activity. This study aimed to demonstrate the effects of circadian rhythm and daily physical activity on the autonomic nervous system at rest through short-term measurements of heart rate variability. Material and Methods. Fifteen young healthy adults participated in the study. Heart rate variability was measured on three separate occasions. During these visits, heart rate variability measurements were made in the morning, in the afternoon hours following a physically active day, and in the afternoon hours after a physically inactive day. Results. Our study showed no significant differences in the parameters of heart rate variability measured at different times of the day. A comparison of heart rate variability values after a physically inactive day and heart rate variability values after a physically active day did not show a significant difference in any of the heart rate variability parameters. Conclusion. Short-term measurements of heart rate variability showed no impact of circadian rhythm and daily physical activity on heart rate variability at rest.
Chronobiology
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Sudden cardiac death (SCD) has been reported during and following physical activity. SCD may be due to vagal withdrawal and/or sympathetic dominance associated with the exercise occurring at any time during, immediately following, or up to several days after exercise. Heart rate variability (HRV) describes the influence of the autonomic nervous system on heart rate. We assessed the immediate post-exercise influence of endurance training on HRV in young adults in the morning and also on the same day in the afternoon following the morning exercise session. Linear domain parameter root mean square of successive RR interval differences (RMSSD) showed vagal withdrawal when analysed both immediately after the AM session and also when pre exercise HRV was compared to post exercise HRV during the afternoon (median average change 6.6%). However multiscale Rényi entropy indicated either no change immediately following the exercise for all scaling factors or an increase in HRV complexity of the heart rate. Despite decreased vagal influence, endurance training may be protective for some individuals that retain a higher heart rate complexity as measured by Rényi entropy in the presence of vagal withdrawal.
Vagal Tone
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