|Year : 2017 | Volume
| Issue : 3 | Page : 595-599
|Effects of bright light shock on sleepiness and adaptation among night workers of a hospital in Iran
Alireza Khammar1, Maryam Moghimian2, Mohammad Hossein Ebrahimi3, Milad Abbasi4, Mohammad Mehdi Baneshi5, Ahmad Reza Yari6, Mahsa Hami7, Mohsen Poursadeghiyan8
1 Department of Occupational Health Engineering, School of Health, Zabol University of Medical Sciences, Zabol, Iran
2 Department of Physiology, School of Medicine, Gonabad University of Medical Sciences, Gonabad, Iran
3 Occupational and Environmental Health Research Center, Shahroud University of Medical Sciences, Shahroud, Iran
4 Research Center for Environmental Determinants of Health (RCEDH), Kermanshah University of Medical Sciences, Kermanshah; Students' Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran
5 Social Determinants of Health Research Center, Yasuj University of Medical Sciences, Yasuj, Iran
6 Research Center for Environmental Pollutants, Qom University of Medical Sciences, Qom, Iran
7 Master of Economic Development and Planning, University of Firoozkooh Branch, Islamic Azad University, Firoozkooh, Iran
8 Department of Ergonomics, School of Rehabilitation, Pediatric Neurorehabilitation Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
Click here for correspondence address and email
|Date of Web Publication||21-Aug-2017|
| Abstract|| |
Background: Night work has many harmful effects on health, efficiency, and industrial safety of workers. Night workers often complained of sleepiness, decrease of performance, and sleep disorder due to the lack of circadian influence that fully encourages night orientation. Objective: This research was conducted in an industrial environment and it accessed the effects of bright-light (BL) exposure on sleepiness during night work. Materials and Methods: This is an interventional study with a cross-over design. A total of 140 night workers with an experience of >1 year at a hospital participated voluntarily in this study. The night workers were divided into two groups, and both groups were exposed to either BL (3000-3500 lux) or normal light (NL) (400 lux) during break times at night work for two consecutive nights. Results: The 15-minute breaks were initiated at 22:00 (before starting work), 24:00, 2:00, and 4:00 h. The range of sleepiness was assessed by the Karolinska Sleepiness Scale (KSS) at 23:00, 1:00, 3:00, and 5:00 h. We used SPSS16 software for data analysis. The results obtained using the paired t-test analysis (P < 0.000) demonstrated that there were significant differences in the rate of sleepiness between the two groups (case and control). Conclusion: The findings of the present study have also demonstrated the feasibility and benefits of photic stimulation in industrial settings which increased the adaptation to night work.
Keywords: Circadian rhythms, shift work, sleepiness
|How to cite this article:|
Khammar A, Moghimian M, Ebrahimi MH, Abbasi M, Baneshi MM, Yari AR, Hami M, Poursadeghiyan M. Effects of bright light shock on sleepiness and adaptation among night workers of a hospital in Iran. Ann Trop Med Public Health 2017;10:595-9
|How to cite this URL:|
Khammar A, Moghimian M, Ebrahimi MH, Abbasi M, Baneshi MM, Yari AR, Hami M, Poursadeghiyan M. Effects of bright light shock on sleepiness and adaptation among night workers of a hospital in Iran. Ann Trop Med Public Health [serial online] 2017 [cited 2019 Sep 23];10:595-9. Available from: http://www.atmph.org/text.asp?2017/10/3/595/213117
| Introduction|| |
Shift workers play central roles in many critical aspects of modern life, including medical care, power generation, the military and law enforcement agents, and important commercial sectors, such as manufacturing and public transportation.,,,,, An estimated 15- 30% of the workforce in industrialized countries operates outside standard daytime hours.,,
Shift work is associated with a number of negative health consequences, the most prominent of which is disturbed sleep. Night work typically leads to sleepiness and reduced performance; it also increases the number of accidents and health problems.,,,, The notable the effects of shift work are the result of the circadian interference such as sleep during the daylight hours and circadian suppression of the metabolism at night., Circadian rhythm has effect on sleep-wake to breath rate and vital capacity and other factor in performance of workers.,
Safety is a primary concern of both employees and their employers in most shift-oriented workplace, especially in nuclear power plants or chemical industries., Several factors can be attributed to the lack of adjustment to shift work. The light exposure in many night workers receive on their way home after work has been proposed as major factor in preventing adaptation of the circadian rhythm. among most night workers. Circadian rhythms are generated by a central pacemaker, the suprachiasmatic nucleus (SCN) in the anterior hypothalamus, and are synchronized to the external environment.,, This pacemaker is regulated by light and does not depend on the timing of sleep/wake cycle., The effect of light depends on the timing of exposure relative to the nadir of the endogenous body temperature rhythm which is usually located 1-2 h before the habitual time of waking up. Pre-exposure of light to nadir triggers a phase delay, whereas the exposure after the nadir induces an advance phase.
The proposal of bright light as a countermeasure to physiological maladaptation to shifted sleep/wake schedules was based on some previous laboratory studies.,,, Doses of bright light administered at the beginning of the shift period ranged from 6 h of very bright light (5000-12,000 lux) to more moderate bright light (1230-2000 lux) in short or intermittent time.,,, Field research on the population of night-shift workers supports the effectiveness of bright light treatment during the night-shift despite some reported negative results., A recent study regarding the operators in a truck production plant in Sweden showed the useful effect of bright light on reducing sleepiness and melatonin levels during night shifts and no detrimental effects during off-days. Similar observations were reported for oil workers on rotating shifts. Indeed, permanent night nurses who presented adaptive phase delays also tended to expose themselves to light more during the night (and evening) and less during the day than nonadapted nurses. Some field studies do not support the use of bright lights for shift workers. In a study using a short (120 min) bright light (BL) for night workers on an oil platform, it was concluded that adaptation to night work was not significantly enhanced by the exposure. Instead, the normal indoor light appeared sufficient for rapid adaptation as the workers were isolated from the outdoor light. There are no known moderate and minimum light intensities and duration of exposure that are necessary for the production of phase shifts. Low intensities may also cause a phase shift in the rhythm, but higher intensities appear to push the shift rhythm faster.
The present study evaluated if short (15 min) BL exposure during regular breaks would decrease sleepiness during the night shift.
| Materials and Methods|| |
The participants of our study were medical staff of a hospital in Iran. A total of 140 participants completed the study out of 167 men who work in the night shift. Participants were asked to sign the consent form to confirm that they understood the goals, risks, and potential benefits of the study and their right to withdraw from the study at any time. The study was approved by the Ethical Committee of the Tehran University. Seven night workers had to be excluded in the final analysis because of personal reasons.
The participants had to work for 2 days on a 12-h day shift (18:00 h to 6:00 h), 2 days off work, and 2 days on a 12-h morning shift (6:00 h to 18:00 h), and then the schedule was repeated. The night workers were allowed to enjoy four ~15-min short breaks at night. The participants were randomized to one of two sequences: BL exposure during the first two night shifts followed by normal light (NL) exposure during the next two night shifts, and vice versa. After the 4 days washout, baseline sleepiness was assessed using the Karolinska Sleepiness Scale
Out of two similar rooms, one was modified and BLs were installed in it for use during breaks. Up-light armature was used to install fluorescent tubes in the ceiling and this gave an indirect white light with a mean luminance level of 350 candela m2, generated by full-spectrum light tubes with temperatures of 5000 k. In order to increase luminance, an off-white floor was installed and white textiles were used to cover the walls of the room. This generated a mean exposure of 3000-3500 lux at the eye level (with an 80° gaze angle) for a person sitting down. During their break times, night workers were directed to move to the light room. In the NL condition, night workers went to the room with normal illumination (400 lux). The Karolinska Sleepiness Scale (KSS) was used to obtain ratings of sleepiness. The KSS is an eight-point verbally anchored scale. The participants rated sleepiness with KSS every 2 h during the night shift (at 23:00, 1:00, 3:00, and 5:00 h). The BL or NL exposure initiated at 22:00 (before starting to work), 24:00, 2:00, and 4:00 h.
The approval of University of Social Welfare and Rehabilitation Sciences was obtained for conducting the study. All participants were presented about the objectives of the study, and their informed consent was obtained.
The statistical analysis was done using SPSS software version 16. Having confirmed the normality from the Kolmogorov-Smirnov test, we conducted parametric tests. Using the paired t-test, we compared sleepiness among the two conditions (sleepiness with BL condition, and sleepiness with NL condition). Statistical significance was considered at P < 0.05.
| Results|| |
Out of 167 voluntary participants, 140 successfully completed the study; participants were divided into two groups of 70 people each. In both conditions, the night workers took at least four breaks at work. The average breaks had a means length of 15+/-1 minute. There were no significant differences between conditions regarding the timing of breaks or their frequencies.
All the participants were male with a mean age of 30.36 years (range 21-45 years).
The KSS was completed at 23:00, 1:00, 3:00, and 5:00 h. Then, the amount of sleepiness peaks rose at 5:00 h followed by 3:00 h. This increase in sleepiness was consistent over the 4 days of study. [Figure 1], [Figure 2], [Figure 3], [Figure 4] show the comparison of sleepiness score among BL and NL treatment.
[Figure 1], [Figure 2], [Figure 3], [Figure 4] display and compare the sleepiness score for the BL and NL conditions
In [Table 1], significant differences were detected between BL and NL conditions. This difference is found by comparing both groups at these times: time 1-time 3; time 1-time 4; time 2-time 3; and time 2-time 4. Furthermore for the sleepiness variable, significant differences were detected between NL and BL in the two groups (time 1-time 2) and (time 3-time 4) (P < 0.05, both comparisons), whereas the expected difference between time 1 and time 2 in group 2 (to be in the control condition). Furthermore, the sleepiness score at second night BL was significantly less than that of sleepiness score at first night BL (P < 0.05). In [Table 2], showed the treatment effect, carry over effect and wash out period.
|Table 1: Comparison differences in rate of sleepiness between two groups in four nights of study|
Click here to view
|Table 2: Treatment effect #9;carry over effect, period effect in this study|
Click here to view
| Discussion|| |
This research has shown how effective the exposure to BL was when levels of sleepiness in shift workers were decreased during their break periods. The results of the present study were consistent with those of a similar study conducted in Sweden where exposure to two 20-min periods of bright light during the night had significantly reduced subjective sleepiness (measured using the KSS questionnaire ,,,, or measured using the SSS questionnaire.).
The findings of the present study also revealed reduced levels of sleepiness during the second night of intervention as compared to both the first night and the baseline which can be attributed to the adaptation to shift work as a result of the exposure to BLs. There was consistency in this decrease in sleepiness during consecutive nights as compared to results from other similar studies that have shown an increase in adaptation to the night shift due to exposure to BLs during five consecutive nights of the night shift work but disappeared during the weekend.
It is noteworthy to say that in spite of the short period of exposure to BL with four 15-min breaks, significant differences were found. In our study, there was no real placebo and we classify this as one of our limitations. This is because the participants in the study had ample knowledge of the study procedure. This might have affected the results.
The present study showed the positive effects of utilizing bright lights during work on decreasing levels of sleepiness and this supports the use of light stimulants on adaptation to night shifts.
It is economical to give industrial work places rooms furnished with BLs instead of supplying the entire workplaces with BLs. More so, previous studies showed no disruptive effects of post-exposure to bright lights. These are capable of having important applications regarding the safety and productivity of the workplace and the workers as well. However, the moderate dose, intensity, and timing of BL exposure have not yet been determined and there is need to verify them before utilization of BL stimulants at industrial work places.
| Conclusion|| |
Short-term bright light could be an effective treatment for decreasing sleepiness and adaptation to the shift work. We suggested that the intervention must be continued and examining the prevalence of various sleep disorders in future study must be done before and after the intervention.
The authors gratefully acknowledge the cooperation of the study participants and their managers. They thank the volunteers and people involved in data collection. The authors express their deep appreciation towards help contributed in any manner to this study, and a special thanks is extended to Professor Hossein Kakoei, wishing him eternal peace.
Financial support and sponsorship
This study was supported by grant No 9352 in University of Social Welfare & Rehabilitation Sciences.
Conflicts of interest
There are no conflicts of interest.
| References|| |
Nurminen T. Shift work and reproductive health. Scan J Work Environment Health 1998;24:28-34.
Folkard S, Lombardi DA, Tucker PT. Shift work: safety, sleepiness and sleep. Ind Health 2005;43:20-3.
Costa G. Shift work and occupational medicine: An overview. Occup Med 2003;53:83-8.
Folkard S, Tudker PT. Shift work, safety and productivity. Occup Med 2003;53:95-101.
Knutsson A. Health disorders of shift workers. Occup Med 2003;53:103-8.
Barger LK, Cade BE, Ayas NT. Extended work shifts and the risk of motor vehicle crashes among interns. N Engl J Med 2005;325:125-34.
Yarmohammadi H, Pourmohammadi A, Sohrabi Y, Eskandari S, Poursadeghiyan M, Biglari H, et al
. Work shift and its effect on nurses' health and welfare, The Social Science 2016;11:2337-41.
Shields M. Shift work and health. Health Rep 2002;13:11-33.
Rahmani A, Khadem M, Madreseh E, Aghaei HA, Raei M, Karchani M. Descriptive Study of Occupational Accidents and their Causes among Electricity Distribution Company Workers at an Eight-year Period in Iran. Saf Health Work 2013;4:160-5.
Poursadeghiyan M, Mazloumi A, Saraji GN, Niknezhad A, Akbarzadeh A, Ebrahimi MH. Determination the Levels of Subjective and Observer Rating of Drowsiness and Their Associations with Facial Dynamic Changes. Iranian Journal of Public Health 2017;46:93-102.
Kecklund G, Akerstedt T. Sleepiness in long distance truck driving: An ambulatory EEG study of night driving. Ergonomics 1993;36:1007-17.
Smith L, Folkard S, Poole C. Light treatment for NASA shift workers. Chronabiol Int 1995;12:141-51.
Dinges DF. An overview of sleepiness and accidents. J Sleep Res 1995;4:4-14.
Costa G. The impact of shift and night work on health. Appl Ergonomics 1995;27:9-16.
Jewett E, Kronauer RE, Czeiler CA. Light-induced suppression of endogenous circadian amplitude in humans. Nature 1991;6:217-20.
Biglari H, Ebrahimi MH, Salehi M, Poursadeghiyan M, Ahamadnezhad I, Abbasi M. The Relationship of Occupational Stress to Cardiovascular Disease Risk Factors in Drivers. International Journal of Occupational Medicine and Environmental Health 2016;29:895-901.
Poursadeghyan M, Khandan M, Baneshi MM, Shiri Malekabad E, Khammar A, Armoon B, et al
. A Relation between Subjective Sleepiness and Changes in Breathe and Beat Rates among the Clinical Night Workers, ARYA Atheroscler; 2017. [In Press].
Khammar A, Amjad RN, Moghadasi M, Pishyareh E, Poursadeghian A, Hami M, et al
. Relation between subjective sleepiness and changes in some vital signs among the clinical night workers. Ann Trop Med Public Health 2017. [In press].
Khandan M, Aligol MH, Shamsi M, Poursadeghiyan M, Biglari H, Koohpaei A. Occupational health, safety, and ergonomics challenges and opportunities based on the organizational structure analysis: A case study in the selected manufacturing industries in Qom Province, Iran, 2015. Ann Trop Med Public Health 2017;10:606-611. [Full text]
Abbasi M, Zakerian A, Mehri A, Poursadeghiyan M, Dinarvand N, Akbarzadeh A, et al
. Investigation into effects of work-related quality of life and some related factors on cognitive failures among nurses. Int J Occup Saf Ergon 2017;23:386-92.
Eastman CI, Stewart KT, Mahoney MP. Dark goggles and bright light improve circadian rhythm adaptation to night-shift. Sleep 1994;17:535-43.
22. Moore RY, Eichler VB. Loss of a circadian adrenal corticosterone rhythm following suprachiasmatic lesions in the rat. Brain Res 1972;42:201-6.
Moore RY. Circadian rhythms: Basic neurobiology and clinical applications. Annu Rev Med 1997;48:253-66.
Stephan FK, Zucker I. Circadian rhythms in drinking behavior and loco motor activity of rats arc eliminated by hypothalamic lesions. Proc Natl Acad Sci USA 1972;69:1583-6.
Czeiler CA, Allen IS, Strogatz SI-I. Bright light resets the human circadian pacemaker independent of the timing of the sleep-wake cycle. Science 1989;233:667-71.
Czeiler CA, DIJK DJ. Use of bright light to treat maladaptation to night shift work and circadian rhythm sleep disorders. J Sleep Res 1995;4:70-3.
DIJK DJ, Boulos Z, Eastman Lewy AJ. Light treatment for sleep disorders: Consensus report. II. Basic properties of circadian physiology and sleep regulation. J Biol Rhythms 1995;10:113-25.
Deacon S, Arendt J. Adaptation to phase shifts: II. Effects of melatonin and conflicting light treatment. Physiol Behav 1995;59:675-82.
Horowitz TS, Cade BE, Wolfe JM. Efficacy of bright light and sleep/darkness scheduling in alleviating circadian maladaptation to night work. Am J Physiol 2001;281:384-91.
Dawson D, Lack L, Morris M. Phase resetting of human circadian pacemaker with use of single pulse of bright light. Chronobiol Int 1993;10:94-120.
Czeiler CA, Johnson MP, Duffy JF, Brown EN. Exposure to bright light and darkness to treat physiologic maladaptation to night work. N Engl J Med 1990;322:1253-9.
Burgess HJ, Sharkey KM, Eastman Cl. Bright light, dark and melatonin can prompt circadian adaptation in night shift workers. Sleep Med Rev 2002;6:407-20.
Dawson D, Encel N, Lushington K. Improving adaptation to simulated night shirt: Timed exposure to bright light versus daytime melatonin administration. Sleep 1995;18:11-21.
Mitchell PI, Hoese EK, Liu L, Fogg LF, Eastman CI. Conflicting bright light exposure during night shifts impedes circadian adaptation. J Biol Rhythm 1997;12:5-15.
Baehr EK, Fogg LF, Eastman Cl. Intermittent bright light and exercise to entrain human circadian rhythm to night work. Am J Physiol 1999;277:15981604.
Campbell SS. Effects of timed bright - light exposure on shift - work adaptation in middle-aged subjects. Sleep 1995;18:408-16.
Koller M, Harma M, Laitinen JT, Kundi M, Piegler B. Different patterns of light exposure in relation to melatonin and cortisol rhythms and sleep of night workers. J Pineal Res 1994;16:127-35.
Lowden A, Akerstedt T, Wibom R. Suppression of sleepiness and melatonin by. Bright light exposure during breaks in night work. J Sleep Res 2004;13:37-43.
Barnes RG, Deacon SJ, Forbes MJ, Arendt J. Adaptation of the 6 sulphaloxymelatonin rhythm in shift workers on offshore oil installations during a 2 week, 2-h night shift. Neurosci Lett 1998;241:9-12.
Dumont M, Benhaberou-Burn D, Paquet J. Profile of 24-h light exposure and circadian phase of melatonin secretion in night workers. J Biol Rhythms 2001;16:502-11.
Bjorvatn B, Kecklund G, Akerstedt T. Bright light treatment used for adaptation 10 night work and re-adaptation back to day life. A field study at an oil platform in the North Sea. J. Sleep Res 1999;8:105-12.
Eastman CI, Boulos Z, Terman M, Campbell S, DIJK DJ. Light treatment for sleep disorders: Consensus report.VI. Shift work. J Biol Rhythms 1995;10:157-164.
Boivin DB, Duffy JF, Kronauer RE, Czeiler CA. Does-response relationships for resetting of human circadian clock by light. Nature 1996;379:540-2.
Karchani M, Mazloumi A, NaslSaraji G, Akbarzadeh A, Niknezhad A, Ebrahimi MH, et al.
Association of subjective and interpretive drowsiness with facial dynamic changes in simulator driving. J Res Health Sci 2015;15:250-55.
Karchani M, Kakooei H, Yazdi Z, Zare M. Do bright-light shock exposures during breaks reduce subjective sleepiness in night workers? Sleep Biol Rhythms 2011;9:95-102.
Department of Ergonomics, Pediatric Neurorehabilitation Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]
| Article Access Statistics|
| Viewed||993 |
| Printed||25 |
| Emailed||0 |
| PDF Downloaded||19 |
| Comments ||[Add] |