Iran Occupational Health Journal
سلامت كار ايران
ioh
Medical Sciences
http://ioh.iums.ac.ir
136
journal136
1735-5133
2228-7493
10.61186/ioh
fa
jalali
1399
2
1
gregorian
2020
5
1
17
1
online
1
fulltext
fa
اثرات غیر بینایی دمای رنگ منابع روشنایی بر قدرت سیگنال های مغزی، خواب آلودگی و عملکرد عصبی رفتاری
Non-visual effects of the light source “correlated color temperature” on electroencephalographic spectral power, sleepiness and neurobehavioral performance
نور و روشنایی
Illumination
Full Text
Full Text
<strong>چکیده</strong>:<br>
<strong>زمینه و هدف</strong>: خستگی و خواب آلودگی (کاهش سطح هوشیاری) علاوه بر تاثیر منفی بر عملکرد و کیفیت کار، به عنوان یکی از علل اصلی خطاهای انسانی و حوادث در محیط های کاری شناخته می شوند. شواهد تجربی اخیر نشان داده است که روشنایی علاوه بر تسهیل فرایند دید، می تواند بر عملکردهای فیزیولوژیکی، روانی و عصبی رفتاری انسان تأثیر بگذارد که به عنوان اثرات غیر بینایی روشنایی شناخته می شوند. برخی از مطالعات نشان داده است که نور آبی تک رنگ یا روشنایی سفید غنی شده از نور آبی (روشنایی با دمای رنگ بالا) می تواند باعث افزایش سطح هوشیاری، بهبود خلق و خوی و عملکرد شود. گرچه شواهد اخیر نشان داده که نور تک رنگ قرمز یا روشنایی سفید اشباع شده از نور قرمز (روشنایی با دمای رنگ پایین)، نیز توانایی القاء چنین اثرات مثبتی را داشته است. سوالی که مطرح است کدامیک از این وضعیت های روشنایی (روشنایی با دمای رنگ بالا یا روشنایی با دمای رنگ پایین) تاثیر قوی تری بر سطح هوشیاری و عملکرد عصبی رفتاری دارند. این مطالعه با هدف بررسی تاثیر مواجهه با روشنایی سفید با دمای رنگ پایین (<span dir="LTR">LWL</span>، 2700کلوین)، روشنایی سفید با دمای رنگ بالا (<span dir="LTR">HWL</span>،12000کلوین)، روشنایی سفید با دمای رنگ استاندارد (4000 کلوین،<span dir="LTR">SWL</span> ) و روشنایی خیلی کم (کنترل-<span dir="LTR">DL</span>) بر قدرت سیگنال های مغزی (شاخص عینی سطح هوشیاری) خواب آلودگی، خلق وخوی و عملکرد عصبی رفتاری (عملکرد شناختی) در زمان صبح انجام شده است.<br>
<strong>روش بررسی</strong>: در این مطالعه، بیست داوطلب سالم در مواجهه با وضعیت های روشنایی به مدت 140 دقیقه قرار گرفتند. داده هایی شامل الکتروانسفالوگرافی (سیگنال های مغزی الفا، الفا-تتا، بتا و تتا)، شاخص هوشیاری ذهنی(خواب آلودگی)، شاخص خلق و خوی، آزمون های عملکرد شناختی (برای سنجش توجه پیوسته، حافظه کاری، ظرفیت مهاری و توجه انتخابی) و ارزیابی ذهنی افراد شرکت کننده نسبت به وضعیت های روشنایی، جمع آوری گردید.<br>
<strong>یافتهها:</strong> نتایج مطالعه نشان داد که در مقایسه با وضعیت <span dir="LTR">DL</span>، وضعیت های روشنایی<span dir="LTR">LWL</span> و <span dir="LTR">HWL</span>، قدرت سیگنال های آلفا، آلفا تتا، خواب آلودگی و میانگین زمان عکس العمل در آزمون های عملکرد شناختی توجه پیوسته، حافظه کاری، توجه انتخابی و ظرفیت مهاری را به صورت معنی داری کاهش داده اند. با وجود تاثیر مثبت هر دو وضعیت روشنایی<span dir="LTR">HWL</span> (12000 کلوین) و <span dir="LTR">LWL</span> (2700 کلوین) بر سطح هوشیاری و عملکرد شناختی در مقایسه با وضعیت <span dir="LTR">SWL</span> (4000 کلوین)، اما این تاثیر به حد معنی داری از نظر آماری نرسید. همچنین نتایج مطالعه نشان داد که تفاوت معنی داری میان وضعیت های روشنایی مورد مطالعه در مورد قدرت سیگنال های مغزی بتا و تتا وجود نداشته است. همچنین شرکت کنندگان در وضعیت روشنایی<span dir="LTR">LWL</span>، در مقایسه با سایر وضعیت های روشنایی به صورت معنی داری (009/0><span dir="LTR">p</span>) ، وضعیت خلق و خوی بهتری گزارش کرده اند.<br>
<strong>نتیجه گیری</strong>: با جمع بندی یافته های مطالعه، می توان نتیجه گرفت که علاوه بر ترجیح نسبی وضعیت <span dir="LTR">LWL</span> توسط شرکت کنندگان، این وضعیت روشنایی، اثر قابل توجهی در بهبود وضعیت خلق و خوی افراد شرکت کننده داشته است. لذا طراحی و استفاده از مداخلات روشنایی با استفاده از منابع روشنایی دمای رنگ پایین می تواند به عنوان یک رویکرد کمکی در کنار سایر راهکارها برای کاهش خستگی، خواب آلودگی و بهبود عملکرد و وضعیت خلق و خوی کارکنان در ساعت های کاری صبح سودمند باشد. گرچه مطالعات بیشتری برای تعیین پارامترهای بهینه مداخلات روشنایی مورد نیاز می باشد.<br>
<strong>Background and aims:</strong> Fatigue and sleepiness (decreased alertness), in addition to a negative impact on performance and quality of work, are considered as one of the leading causes of human error and accidents in work environments. There is much evidence indicating that physical factors in the workplace could affect fatigue, vitality, motivation, and productivity of individuals. A physical environment suitable for activity is formed by various factors, among which light is known as an essential element. Recent photobiological advances and recognition of intrinsically photosensitive retinal ganglion cells (ipRGCs) have shown that in addition to improving eyesight, light can affect the circadian and homeostatic regulations and melatonin suppression in human. Furthermore, light can have acute effects on the physiological, psychological, neurobehavioral, and neuroendocrine responses, such as improvement in the alertness and neurobehavioral performance, which are known as the non-visual or non-imaging forming effects (NIF) of light. However, the possible roles of these potential effects in the improvement of human safety and efficiency have not been thoroughly investigated.<br>
Some studies have shown that monochromatic blue light or blue-enriched white light (high correlated color temperature white light or high CCT) can enhance levels of alertness, and improve mood and cognitive function. Although recent evidence has indicated that monochromatic red light or red saturated white light (low correlated color temperature white light or low CCT) has also been able to induce such positive effects. There is still an open question left unanswered: “which of these lighting conditions (high CCT vs. low CCT) has a stronger effect on the alertness level and neurobehavioral function?” Therefore, the present study tested this hypothesis in a simulated office workplace environment with the recommended illumination level of 500 lx on the desk for daytime office work environments during the morning hours.<br>
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<strong> Methods</strong><strong>:</strong> In this study, 20 healthy paid volunteers (male; mean ± SD age, 27.6 ± 3.6 years) were selected and followed the experimental protocol. All participants were interviewed about the quality of sleep, lifestyle habits, and general health. The inclusion criteria were: not having any mental or physical health problem, having a good sleep quality according to the Persian version of Pittsburgh Sleep Quality Index (PSQI score<5 ), being neither extreme early nor extreme chronotype, having a regular sleep-wake state (bedtimes 22:00 to 24:00 p.m. and wake up between 07:00 and 08:00 a.m.), not smoking, not traveling to a different time zone or experiencing shift-work during three months prior the experiment, no history of eye diseases, and having a normal color blindness as evaluated by the Ishihara test. To control the effect of potential differences in the levels of alertness due to circadian variations and sleep pressure between the light conditions, the participants completed a sleep/wake log, starting one week prior to the beginning of the study. In addition, they were asked to keep a regular sleep/wake state during the study. The participants were also asked not to drink caffeine and/or alcohol about 12 h before the experiment. The aim of the study was described for all participants and they signed an informed consent before the commencement of the study. In addition, the protocol of the study was confirmed by the university ethics committee.<br>
The present study had a repeated-measures design, and the participants were exposed to four light conditions for 140 minutes in a counterbalanced order with a one-week interval. The light conditions were dim light (DL, <5 lx, control), and a 500 lx light intensity on the desk level for high CCT white light (HWL, nominal CCT= 12000 K), low CCT white light (LWL, nominal CCT= 2700 K), and standard white light (SWL, nominal CCT= 4000 K).The study was performed in an air-conditioned room with an area of 19 m<sup>2</sup>. The room’s windows were closed with light-blocking curtains to restrict the penetration of daylight into the experimental setting. Electroencephalogram (EEG) activity (5–7 Hz: theta, 5-9: alpha-theta, 8–12 Hz: alpha, and 13–30 Hz: beta), subjective sleepiness (Karolinska Sleepiness Scale, KSS), subjective mood (Visual Analogue Mood Scale, VAMS), cognitive performance tests (sustained attention, working memory, selective attention task, and inhibitory capacity) and subjective evaluation and beliefs of the participants about the light conditions were measured. The data were analyzed using the MATLAB software package (ver. R2012a, Math-Works, USA) and version 20.0 of the SPSS software (IBM, Armonk, NY, USA). Repeated-measures analysis of variance (ANOVA) was conducted, and where necessary, the Greenhouse–Geisser correction was applied. A 4 (light conditions) × 6 time intervals ANOVA was performed for the EEG activity measures (alpha, theta, beta, and alpha-theta) and CPT data. For the subjective sleepiness and mood, a 4 (light conditions) × 3 time intervals ANOVA was performed. Also, a 4 (light conditions) ANOVA was performed using each cognitive performance (GO/NO-GO, 2-Back, and divided attention) outcome measures. A 3 (light conditions) ANOVA was performed using each subjective evaluation and belief measures about the light conditions. The Bonferroni-adjusted post-hoc tests were applied to multiple comparisons (P<0.05).<br>
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<strong>Results:</strong> The means±standard error (SE) of the normalized alpha power was 1.083±0.018 for HWL, 1.147±0.021 for SWL, 1.069±0.021 for LWL, and 1.225±0.027 for DL condition. The Bonferroni-adjusted post-hoc tests indicated a significantly lower power under HWL (P=0.012) and LWL (P=0.006) compared to DL condition. The other comparisons revealed no significant differences. The means±SE of the normalized alpha-theta power was 1.009±0.012 for LWL, 1.053±0.014 for SWL, 1.024±0.016 for HWL, and 1.106±0.017 for DL condition. Post-hoc tests showed a significantly lower alpha-theta power under LWL (P<0.001) and HWL (P=0.033) compared to DL condition. The other comparisons indicated no significant differences. No significant main effect of the light conditions and interaction between them and the time intervals in the normalized beta and theta powers were observed.<br>
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The means±SE of the normalized subjective sleepiness were 1.129± 0.045 for LWL, 1.25±0.057 for SWL, 1.127±0.052 for HWL, and 1.499±0.074 for DL condition. Post-hoc tests showed that HWL (P=0.002) and LWL (P=0.001) conditions significantly decreased the sleepiness compared to the DL condition. The other comparisons revealed no significant differences. Furthermore, the present study results indicated that the means±SE of the normalized mood scores were 1.048±0.013 for SWL, 1.066±0.011 for HWL, 0.942±0.014 for DL, and 1.158±0.02 for LWL condition. Post-hoc tests indicated that the participants had significantly better mood under the LWL (P<0.001), SWL (P=0.001), and HWL (P<0.001) conditions compared to the DL condition. Furthermore, the LWL enhanced the participants' mood state as compared to the SWL (P<0.001) and HWL (P=0.009) conditions.<br>
The means±SE of the normalized mean reaction time for continuous performance test (CPT) were 0.998±0.011 for SWL, 0.977±0.011 for HWL, 1.066±0.017 for DL, and 0.985±0.011 for LWL condition. The post‐hoc with Bonferroni‐adjusted pairwise comparison revealed a significantly lower mean reaction time under HWL (P<0.001), LWL (P=0.009), and SWL (P=0.026) conditions compared to the DL condition. Furthermore, the means±SE of the normalized mean reaction time for GO/NO-GO task were 305.13±13.959 ms for HWL, 308.91±13.78 ms for SWL, 304.64±14.11 ms for LWL, and 327.49±17.7 ms for DL condition. Post-hoc tests indicated a significantly lower mean reaction time under LWL (P=0.033) and HWL (P=0.034) conditions compared to DL condition. The means±SE of the normalized mean reaction time for 2–Back task were 394.24±32.22 ms for SWL, 387.92±31.64 ms for HWL, 398.62±31.81 ms for DL, and 384.16±30.66 ms for LWL condition. Post-hoc tests revealed a significantly lower reaction time under LWL (P=0.001) and HWL (P=0.027) conditions compared to DL condition. The means±SE of the normalized mean reaction time for selective attention task were 4.16.25±10.262 ms for SWL, 415.95±10.292 ms for HWL, 408.05±10.75 ms for LWL, and 437.75±9.618 ms for DL condition. Post-hoc tests showed a significantly lower reaction time under LWL (P=0.001), HWL (P=0.027), and SWL (P=0.02) conditions compared to DL condition. The Bonferroni-adjusted post-hoc tests did not show any significant differences between HWL, LWL, and SWL light conditions in the CPT, GO/NO-GO, selective attention, and 2–Back tasks.<br>
The participants believed that there was no significant difference between the light conditions (SWL, LWL, and HWL) according to the subjective appraisals of light, including brightness, distribution, activating, adequacy amount, and color. Also, the participants reported that the light conditions did not significantly improve their performance. In contrast, the volunteers stated that the LWL (P=0.006) condition was more effective in improving their mood status compared to the SWL condition. Also, about the pleasantness of light, the participants preferred the LWL (P=0.037) over the HWL condition.<br>
<br>
<strong>Conclusion:</strong> Under natural conditions (healthy participants and with regular sleep-wake cycle), both the low and high CCT lights (500 lx at the desk) improved alertness and performance compared to the DL condition during the morning hours. In contrast, compared to the SWL, no significant improvement in alertness and cognitive performance during inhibitory capacity, working memory, selective attention, and sustained attention tasks was observed<span dir="RTL">.</span> Briefly, it can be concluded that in addition to the relative preferences of the LWL (2700 K) light condition by the participants, it has had a significant impact on improving the mood of the participants. Hence, the designing and application of lighting interventions by using low correlated color temperature lighting sources can be beneficial for reducing fatigue and sleepiness and improving performance and mood during the morning hours although more studies are required to determine the optimal parameters for lighting interventions.<br>
<br>
دمای رنگ, الکتروانسفالوگرام, روشنایی, هوشیاری, عملکرد
Keywords: correlated color temperature, electroencephalogram, light, alertness, performance
499
519
http://ioh.iums.ac.ir/browse.php?a_code=A-10-1503-2&slc_lang=fa&sid=1
Taleb
Askaripoor
طالب
عسکری پور
askaripoor@semums.ac.ir
13600319475328460038116
13600319475328460038116
No
Assistant Professor, Research Center for Health Sciences and Technologies, Semnan University of Medical Sciences, Semnan, Iran.
دانشگاه علوم پزشکی سمنان
Majid
Motamedzade
مجید
معتمد زاده
motamedzade@yahoo.com
13600319475328460038117
13600319475328460038117
Yes
Corresponding author: Professor, Department of Ergonomics, School of Public Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran
دانشگاه علوم پزشکی همدان-دانشکده بهداشت
Rostam
Golmohammadi
رستم
گلمحمدی
golmohamadi@umsha.ac.ir
13600319475328460038118
13600319475328460038118
No
Professor, Center of Excellence for Occupational Health, School of Public Health and Research Center for Health Sciences, Hamadan University of Medical Science, Hamadan, Iran
دانشگاه علوم پزشکی همدان-دانشکده بهداشت
Mohammad Babamiri
Babamiri
محمد
بابامیری
mohammad.babamiri@gmail.com
13600319475328460038119
13600319475328460038119
No
Assistant Professor, Department of Ergonomics, School of Public Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran.
دانشگاه علوم پزشکی همدان-دانشکده بهداشت
Maryam
Farhadian
مریم
فرهادیان
maryam_farhadian80@yahoo.com
13600319475328460038120
13600319475328460038120
No
Assistant Professor, Department of Biostatistics, School of Public Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran.
دانشگاه علوم پزشکی همدان-دانشکده بهداشت
Mohammad Ebrahim
Ghaffari
محمد ابراهیم
غفاری
m.gh19@yahoo.com
13600319475328460038121
13600319475328460038121
No
Ph.D. Candidate in Biostatistics, Dental Sciences Research Center, Faculty of Dentistry, Guilan University of Medical Sciences, Rasht, Iran
دانشگاه علوم پزشکی گیلان-دانشکده دندان پزشکی
Mehdi
Samavati
مهدی
سماواتی
mdsamavati@gmail.com
13600319475328460038122
13600319475328460038122
No
Ph.D. in Biomedical Engineering, Department of Medical Physics & Biomedical Engineering & Research Center for Biomedical Technologies and Robotics (RCBTR), Tehran University of Medical Sciences, Tehran, Iran
دانشگاه علوم پزشکی تهران-مرکز تحقیقات فن آوری های بیومدیکال و رباتیک،
Elahe
Kazemi
الهه
کاظمی
kazemie187@yahoo.com
13600319475328460038123
13600319475328460038123
No
MSc in occupational health and safety engineering, Research Center for Health Sciences and Technologies, Semnan University of Medical Sciences, Semnan, Iran.
دانشگاه علوم پزشکی سمنان-دانشکده بهداشت
Hamed
Aghaei
حامد
آقایی
hamedaghaeih@gmail.com
13600319475328460038124
13600319475328460038124
No
Assistant Professor, Department of Occupational Health Engineering, Faculty of Health, Arak University of Medical Sciences, Arak, Iran
دانشگاه علوم پزشکی اراک-دانشکده بهداشت