We read the excellent review from Owens1 in which the author summarized the most important factors, consequences, and prevention opportunities in the background of sleep loss and fatigue among healthcare professionals. We would like to highlight further opportunities and limits 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 have pointed out that there is a close relation 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 gastrointestinal disorders, diseases of the heart-circulatory system and malignant tumors, the disorders of melatonin secretion caused by night work, and the increased risk of breast cancer development, respectively.3 Other researchers reported elongated menstrual cycle caused by work stress, and shortened menstrual cycle caused by rotating shift order, but a higher risk of premature birth in shift work is also known.4,5
We agree with the author that strategies unique to the healthcare professions must continue to be developed and tested, but it is technically easier and more effective to set up animal experimental models such as groups (suitable for modeling of different work schedules), where it is possible to determine the changes in the rhythms 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 could be made about humans.6
Although we think it is important to examine the number of the daily working hours more attention should be paid on how many times the 8- to 12-hour shift repeats in a week and in which sequence (night or morning shift). Besides 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 because of the difficulties of human trials for examining the ultradian and infradian rhythms in the long term. The difficulties in examining the rhythm parameters are that the arrangement for at least 6 sampling times are needed during the 24 hours. Staying awake during the nights in case of several weeks' observation are technically difficult. Making use of animal experiments, allows sampling to be made successful with keeping the animals in 2 opposite lighting regimens, which means that the whole daily profile could be covered during office hours (3 times a day, in every 4 hours), 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 dark-light (DL) (eg sampling at 8 AM from animals kept in light-dark (LD), the sample from animals kept in DL is like that we sampled at 8 PM.7-9
In our opinion it is also critical not only to examine what health effects could occur in shift work but to examine the different kinds of shifts. All these are important, because the continuous night or daily work, and the 8- or 12-hour-long shift, indicate different risk factors.
Beyond these factors, it might have a significant effect on the health status in what order the working and rest days follow each other in case of continuous night-work because it can result disturbances in the adaptation of biological rhythms.
Of course, these questions could be answered within the frame of long-range follow-up studies, but human studies are difficult because of different factors, such as the unsystematic shifts caused by labor shortages, overtime, working in different profile units, the limited possibility of setting up methodologically suitable sampling, unavoidable disturbing factors raised from the other effects on the sample, as well the problems connected to the implementation of examining certain parameters with repeated-and often invasive intervention-sampling.
Andras Olah, MNS, RN
Institute of Nursing and Patient Care, Faculty of Health Sciences, University of Pecs, Hungary
Agnes Muller, MSc
Institute of Public Health, Recreation and Health Promotion, Faculty of Health Sciences, University of Pecs, Hungary
Jozsef Betlehem, MNS, PhD, RN
Institute of Nursing and Patient Care, Faculty of Health Sciences, University of Pecs, Hungary
Rita Jozsa, MD, PhD
Department of Anatomy, Medical School, University of Pecs, Hungary
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