Investigating the effect of different light intensities in work environments on Circadian rhythm using animal model

P Yekzamani; A Ashtarinezhad; J Aboulghasemi; B Masruri; M Arabian; I Alimohammadi

doi:10.18502/tkj.v14i1.9851

P Yekzamani Department of occupational health engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
A Ashtarinezhad Department of occupational health engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
J Aboulghasemi Department of Biostatistic, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
B Masruri Department of occupational health engineering, School of Public Health, University of Tarbiat Modaress, Tehran, Iran
M Arabian Rajaie Cardiovascular Medical and Research centre, Iran University of Medical Sciences, Tehran, Iran
I Alimohammadi Department of occupational health engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran

DOI: https://doi.org/10.18502/tkj.v14i1.9851

Keywords: artificial light, cortisol, melatonin, circadian rhythms, work environment

Abstract

Introduction: light intensity and duration are physical factors that affect hormone secretion and circadian rhythms. This study aimed to determine the effects of various light intensities on serum melatonin and cortisol levels.

Materials and methods: This experimental study was carried out on 32 male rats: Group 1 as the control group, received a brightness of 150 lux, and groups 2, 3, and 4 as the exposure groups received light intensities of 300, 5000, and 8000 lux for 14 days, respectively. To evaluate hormone levels, blood samples were taken on before and after 7 and 14 days of exposure. Then cortisol and melatonin levels were determined by ELISA. Data were analyzed using SPSS.

Results: The results showed that cortisol levels after seven days of exposure in the groups exposed to the light intensity of 300, 5000, and 8000 lux increased significantly compared to the control group, and after 14 days, the level of cortisol in the groups. Exposure to a light intensity of 5000 and 8000 lux increased significantly compared to the control. Also, melatonin levels in the group of rats exposed to the light intensity of 5000 lux and 8000 lux after 7 and 14 days of exposure compared to the control significantly decreased.

Conclusion: Increased light intensity is associated with increased melatonin suppression and cortisol levels. It is suggested that more studies be done to prove the effect of different light intensities on changes in the levels of these hormones at varying hours of the day.