1. Olah, Andras RN, MSN
  2. Betlehem, Jozsef RN, MSN, PhD
  3. Muller, Agnes MSc
  4. Jozsa, Rita MD, PhD

Article Content

We read the excellent review from Owens,1 where the author summarized the most important factors, consequences, and prevention opportunities of sleep loss and fatigue in healthcare professionals. We would like to highlight the further opportunities and limits of examinations concerning the effects of shift work and the important role of using the animal experimental model processed by our research group.


In the last decades, more and more research teams have focused on the examination of the health status of shift workers. A number of studies point out that there is a close relationship between shift work and mood disorders and/or psychosomatic diseases. The most frequent is the development of sleep abnormalities and indisposition,2 but certain studies discovered a relationship between sleeploss and gastrointestinal disorders, diseases of the heart-circulatory system, malignant tumors, the disorders of melatonin secretion caused by night work, and the increased risk of breast cancer development.3 Other researchers have reported elongated menstrual cycle caused by work stress and shortened menstrual cycle caused by rotating shift order. A higher risk of premature birth in case of shift work is also reported.4,5


We agree with the statement of the author that strategies unique to the healthcare professions must continue to be developed and tested, but it is technically easier and most effective to set up such groups in animal experimental models (suitable for modeling of different work schedules) where it is possible to determine the changes in the rhythms by following the rhythm parameters in long-term MESOR (midline estimating statistic of rhythm), amplitude (the extent of the higher and lower results alteration in cycles), and acrophase (the highest result within the period). Besides the changes in hormonal and other parameters among animal experimental model circumstances, the changes in the general state of health could be well analyzed and conclusions concerning humans could be made.6


We think it is important to emphasize that apart from the number of the daily working hours it is also important to examine how long the 8 to 12 hours shift repeats in the case of shift work in different parts of a day before the change is coming. Beside these factors the number and the ratio of working and rest days following each other contribute significantly to the adaptation or disorder of circadian rhythms.


Our research group worked out an animal experimental model of examining the long-term ultradian and infradian rhythms. The difficulties in examining the rhythm parameters are that at least 6 samplings are needed every 4 hours during 24 hours and staying awake during the nights in case of several weeks' observation is technically difficult to carry out. Making use of this animal experiment, the sampling could be successful with keeping the animals in 2 opposite lighting regimens, which means the whole daily profile could be covered during office hours (3 times a day, in every 4 hours) sampling without sampling during the night. After the adaptation of the animals to the opposite lighting regimens (1-month synchronization) we discovered 180[degrees] (12 hours) displacement of animals kept in daylight (eg, sampling at 8 AM from animals kept in daylight, the sample from animals kept in dark and light is like we sampled at 8 PM.7-9


In our opinion it is important not only to examine what kind of effects could occur in relation to the entire health status in shift work but also to examine the different kinds of shifts. All these are important because the continuous night or day work during the 8 or 12 hours' long shift indicates quite different risk factors. Besides this, in what order the working and rest days follow each other in case of continuous night work could also have a significant effect because depending on this the adaptation of the biological rhythms with new connections and then the regulation or complete overturn could also occur.


Of course these questions could be answered within the frame of long-range follow-up studies, however, these human studies are difficult because of different factors, such as the unsystematic shifts caused by labor shortage, overtime, and colleagues working in different profile units, the limited possibility of setting up methodologically suitable samples, unavoidable disturbing factors raised from the other effects on the sample as well as the problems connected to the implementation of examining certain parameters with repeated-and often invasive intervention-sampling.


Andras Olah, RN, MSN


Senior Lecturer, Institute of Nursing and Patient Care, Faculty of Health Sciences, University of Pecs, Hungary


Jozsef Betlehem, RN, MSN, PhD


Associate Professor, Institute of Nursing and Patient Care, Faculty of Health Sciences, University of Pecs, Hungary


Agnes Muller, MSc


Assistant Lecturer, Institute of Public Health, Recreation, and Health Promotion, Faculty of Health Sciences, University of Pecs, Hungary


Rita Jozsa, MD, PhD


Associate Professor, Department of Anatomy, Medical School, University of Pecs, Hungary




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