• Journal of Preventive Medicine and Public Health
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• v.37 no.2
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• pp.182-189
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• 2004

Objectives : The objective of this study is to compare the circadian patterns of heart rate variability assessed by 24-hour ambulatory electrocardiographic (ECG) recordings during day shift and night shift among the workers in the 5 days-concecutive-12-hour shift in an automobile factory in Korea. Methods : The study population consisted 300 workers, who were randomly selected among the 8700 total workers in one car factory. To analyse circadian variation, the 24-hour ECG recordings (Marquette) were measured during day shift (08:00-20:00 h) and night shift (20:00-08:00 h). Analysis was performed for all time and frequency domain measures of HRV. 233 workers completed taking 24-hour ECG recordings. Results : This study shows that the 24 hourcircadian variation mainly follows work/sleep cycle rather than day/night cycle among shift workers. This study also shows that among the night shift, the circadian variation between work and sleep cycle decreased compared to the work/sleep cycle among day shift workers. All time and frequency domain parameters (except LF/HF ratio) show significantly different between work and sleep in the day shift and night shift. Conclusion : These changes in heart rate variability circadian rhythms reflect significant reductions in cardiac parasympathetic activity with the most marked reduction in normal vagal activity among the shift workers. Especially, it suggests the circadian rhytm has blunted among the night workers. The quantification of the circadian variation in HRV can be a surrogates of workers' potential health risk, as well as suggests possible mechanisms through which the shift works compromise workers' health.

• Journal of Korean Biological Nursing Science
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• v.19 no.3
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• pp.198-205
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• 2017

Purpose: The purpose of this study was to identify sleep patterns, alertness, and fatigue of shift nurses according to circadian types. Methods: The researchers' enrolled 17 nurses doing shift work in a tertiary hospital. To evaluate circadian types, a morningness-eveningness questionnaire (MEQ) was administered. Sleep patterns were examined using an actigraph for 14 days. To assess alertness and fatigue, Visual Analogue Scale (VAS) was used. The data were analyzed using ANOVA and Kruskal-Wallis test with a SPSS 21.0 program. Results: The researchers found that 17.6% of participants reported morning type, 47.1% neither type, and 35.3% evening type. Mean total sleep time (TST) was 6.8 h, mean sleep efficacy was 82%, level of alertness was 6.54, and level of fatigue was 5.49, regardless of the type of shift work. Evening type nurses had higher variation in TST and alertness, according to the shift patterns than other circadian type nurses. Evening type nurses also had higher fatigue levels than other circadian type nurses. Conclusion: Sleep, alertness, and fatigue were related with circadian types. These results suggest that circadian rhythm management in shift work nurses, particularly in evening type nurses is urgently needed to improve sleep patterns, alertness, and to decrease the level of fatigue.

• Proceedings of the KOSOMBE Conference
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• v.1991 no.11
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• pp.113-118
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• 1991

Hypertension is a medical problem with no permanent cure. Extended hypertension can cause various cardio vascular diseases, cerebral vascular diseases, and circulatory system trouble. Medical treatment at present does not consider circadian variation of blood pressure in patients ; therefore, the problem of over-reduction of blood pressure through drugs sometimes occurs. This paper presents a prediction model of circadian variation or moon blood pressure employing the endocrine grand and the autonomic nervous system.

• Journal of Veterinary Clinics
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• v.15 no.1
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• pp.1-7
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• 1998

The present study was performed to evaluate circadian rhythm of blood nortisol concentration and change of blood cortisol concentration by various stress type in domestic cats. The ELISA kit for cortisol measurement was evaluated on the effective assay range, day to day variation, within-run variation and accuracy. The results were 1-1,000 ng/ ml, 0.7-5.9%, 0.9-4.5% and 98%, respectively. The circadian rhythm of serum cortisol concentration is presented in cats. Change of serum cortisol concentration was also examined with several stressors, stimulation with hamster as a prey, beep electronic sounds, vehicle transportation and unfamiliar environment. Unfamiliar environment showed most remarkable change in serum cortisol level.

• The Journal of Korean Medicine
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• v.28 no.4
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• pp.8-12
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• 2007

Objectives : This study aimed to investigate the circadian variation in stroke types, ischemic stroke subtypes, and Sasang constitutions. Methods : 295 patients with acute stroke within 14 days onset were included, who were admitted to Kyunghee Oriental Medical Center from October 2005 to May 2007. The stroke onset time was subdivided into four groups of 6-hour intervals in a day. Stroke types, ischemic stroke subtypes, and Sasang constitutions in four groups were examined. Results : Most ischemic stroke occurred between 6:01-12:00 hours (30.2%). For ischemic stroke subtypes, the peak period of small-vessel occlusion was between 6:01-12:00 hours (33.2%), large-artery atherosclerosis was most common between 12:01-18:00 hours (39.5%), and cardiac embolism was most frequent between 18:01-24:00 hours (50%). In terms of Sasang constitution, Soyeumin and Taeyeumin were most common between 6:01-12:00 hours (36.4% versus 41.5%, respectively), but the peak time of Soyangin was between 12:01-18:00 hours (35.2%). Conclusion :Most ischemic stroke events occurred in the mid-to-late morning hours in the present study and there was a circadian variation of onset in ischemic stroke subtypes and Sasang constitution.

• BMB Reports
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• v.48 no.12
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• pp.677-684
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• 2015

Cardiovascular function is regulated by the rhythmicity of circadian, infradian and ultradian clocks. Specific time scales of different cell types drive their functions: circadian gene regulation at hours scale, activation-inactivation cycles of ion channels at millisecond scales, the heart's beating rate at hundreds of millisecond scales, and low frequency autonomic signaling at cycles of tens of seconds. Heart rate and rhythm are modulated by a hierarchical clock system: autonomic signaling from the brain releases neurotransmitters from the vagus and sympathetic nerves to the heart's pacemaker cells and activate receptors on the cell. These receptors activating ultradian clock functions embedded within pacemaker cells include sarcoplasmic reticulum rhythmic spontaneous Ca²⁺ cycling, rhythmic ion channel current activation and inactivation, and rhythmic oscillatory mitochondria ATP production. Here we summarize the evidence that intrinsic pacemaker cell mechanisms are the end effector of the hierarchical brain-heart circadian clock system.

• Journal of Oral Medicine and Pain
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• v.40 no.3
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• pp.89-95
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• 2015

All living organisms have a biological clock that orchestrates every biological process and function, and this internal clock operates following a circadian rhythm. This biological clock is known to influence various clinical indicators such as blood pressure and body temperature. Also, the fluctuation of signs and symptoms of diseases including pain disorders are affected by circadian rhythm. It has been reported that the pain intensity of various somatic and neuropathic pain disorders show unique pain patterns that depend on the passage of time. The generation of pain patterns could be explained by extrinsic (e.g., physical activity, tactile stimulation, ambient temperature) and also intrinsic factors (neural and neuroendocrine modulation) that are related to the circadian rhythm. It is important to recognize and identify the individual pain pattern in pain therapy to approve treatment outcome. Moreover, chronotherapeutics which considers pain patterns and pharmacokinetics in context of the circadian rhythm could produce greater analgesia in response to medication. However, only a limited number of studies handle the issue of pain patterns according to circadian rhythm and chronotherapeutics in the orofacial region. The present review intends to reflect on the most recent and relevant data concerning the bidirectional relation between pain disorders of the orofacial region and circadian patterns.

• Clinical and Experimental Pediatrics
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• v.52 no.7
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• pp.752-755
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• 2009

It is well known that hemodynamic load is one of the most important determinants of cardiac structure and function. Circadian variations in blood pressure (BP) are usually accompanied by consensual changes in peripheral resistance and/or cardiac output. In recent years, reduction in circadian variations in BP and, in particular, loss of nocturnal decline of BP were observed in hypertensive patients with left ventricular hypertrophy (LVH). The patients with only a slight or no loss of nocturnal decline of BP were considered "non-dippers". Regression of LVH was observed after prolonged antihypertensive therapy. Restoration of the circadian rhythm of BP was also observed. However, the classification of patients into "dippers" and "non-dippers" is arbitrary and poorly standardized and repeatable, and in the recent studies, most hypertensive patients with LVH were "dippers". Therefore, we should be particularly cautious about the conclusions drawn using this index. On the other hand, reduced activity of low-pressure cardiopulmonary baroreceptors and impaired day-to-night modulation of autonomic nervous system activity were observed in patients with only LVH. Therefore, alterations in cardiac structure may impair BP modulation. On the other hand, the reverse can also be trueprimary alterations in BP modulation, through a persistently elevated afterload, can increase cardiac mass. Thus, the interrelationship between cardiac structure and BP modulation is complex. Hence, new and more specific methods of evaluating circadian changes in BP are needed to better clarify the abovementioned reciprocal influences.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.9 no.1
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• pp.113-122
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• 2002

Purpose: The purpose of this study was to identify characteristics of serum ferrum, TIBC and ferritin's circadian rhythm in normal adults and to prepare a standard to determine the examination material extraction time. Method: Nine women and ten men made up the convenience sample for this study they were from the staff of D university hospital and students in D medical School located in K city who met the qualifications for inclusion in the sample. The value of serum ferrum, TIBC and circadian rhythm were calculated as follows : First. each variable's amplitude. the acrophase and average were measured for a 24 hour cycle using the cosinor method, and then each person's rhythm was analyzed. Results: There were significant serum iron circadian rhythm for both men and women (p<.05). For the men, mesor was $105.91{\mu}g/dl$. amplitude was $29.52{\mu}g/dl$, and the acrophase was 9.76 hour. For the women, mesor was $108.17{\mu}g/dl$, amplitude was $28.09{\mu}g/dl$, and the acrophase was 11.42 hour The rhythm change of TIBC was only significant for the women (p<.05), mesor was 383.39mg/dl, amplitude was 60.29mg/dl. and the acrophase was 14.93hour. As for the circadian rhythm of the ferritin, there are no diurnal variation in either sex, men were between 134.0ng/ml and 137.4ng/ml, and women, between 29.1ng/ml and 30.1ng/ml. Conclusion: To help diagnose the boundary line between normal or deficiency in iron, measurement should be carried out at a fixed time in the morning and evening, or a more proper time would be in the afternoon at the time when the width of amplitude is the least.

• Korean Journal of Ichthyology
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• v.22 no.4
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• pp.267-272
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• 2010

Laboratory-reared marbled flounder (Pleuronectes yokohamae) juveniles ($23.2{\pm}0.2mm$ total length; age 89 day) were sampled over a 48-h period to determine any diel patterns in RNA/DNA ratios. RNA/DNA ratios were highest during daytime periods (0800, 1100, 1400, 1700 h) and significantly reduced at night (2000, 2300, 0200, 0500 h). Findings from this study indicate a diel variation in biochemical condition and suggest that special care should be taken in designing sampling plans, including sampling time and data analysis to account for this source of variability.