| Home | << 1 >> |
|
Chang, A. - M., Scheer, F. A. J. L., Czeisler, C. A., & Aeschbach, D. (2013). Direct effects of light on alertness, vigilance, and the waking electroencephalogram in humans depend on prior light history. Sleep, 36(8), 1239–1246.
Abstract: STUDY OBJECTIVES: Light can induce an acute alerting response in humans; however, it is unknown whether the magnitude of this response is simply a function of the absolute illuminance of the light itself, or whether it depends on illuminance history preceding the stimulus. Here, we compared the effects of illuminance history on the alerting response to a subsequent light stimulus. DESIGN: A randomized, crossover design was used to compare the effect of two illuminance histories (1 lux vs. 90 lux) on the alerting response to a 6.5-h 90-lux light stimulus during the biological night. SETTING: Intensive Physiologic Monitoring Unit, Brigham and Women's Hospital, Boston, MA. PARTICIPANTS: Fourteen healthy young adults (6 F; 23.5 +/- 2.9 years). INTERVENTIONS: Participants were administered two 6.5-h light exposures (LE) of 90 lux during the biological night. For 3 days prior to each LE, participants were exposed to either 1 lux or 90 lux during the wake episode. MEASUREMENTS AND RESULTS: The alerting response to light was assessed using subjective sleepiness ratings, lapses of attention, and reaction times as measured with an auditory psychomotor vigilance task, as well as power density in the delta/theta range of the waking EEG. The alerting response to light was greater and lasted longer when the LE followed exposure to 1 lux compared to 90 lux light. CONCLUSION: The magnitude and duration of the alerting effect of light at night depends on the illuminance history and appears to be subject to sensitization and adaptation.
Keywords: Arousal/*radiation effects; Attention/radiation effects; Cross-Over Studies; *Electroencephalography; Female; Humans; *Light; Male; Melatonin/blood/physiology; Psychomotor Performance/radiation effects; Reaction Time; Wakefulness/*radiation effects; Young Adult; Light history; alertness and performance; light exposure
|
|
Figueiro, M. G., Sahin, L., Wood, B., & Plitnick, B. (2015). Light at Night and Measures of Alertness and Performance: Implications for Shift Workers. Biol Res Nurs, .
Abstract: Rotating-shift workers, particularly those working at night, are likely to experience sleepiness, decreased productivity, and impaired safety while on the job. Light at night has been shown to have acute alerting effects, reduce sleepiness, and improve performance. However, light at night can also suppress melatonin and induce circadian disruption, both of which have been linked to increased health risks. Previous studies have shown that long-wavelength (red) light exposure increases objective and subjective measures of alertness at night, without suppressing nocturnal melatonin. This study investigated whether exposure to red light at night would not only increase measures of alertness but also improve performance. It was hypothesized that exposure to both red (630 nm) and white (2,568 K) lights would improve performance but that only white light would significantly affect melatonin levels. Seventeen individuals participated in a 3-week, within-subjects, nighttime laboratory study. Compared to remaining in dim light, participants had significantly faster reaction times in the GO/NOGO test after exposure to both red light and white light. Compared to dim light exposure, power in the alpha and alpha-theta regions was significantly decreased after exposure to red light. Melatonin levels were significantly suppressed by white light only. Results show that not only can red light improve measures of alertness, but it can also improve certain types of performance at night without affecting melatonin levels. These findings could have significant practical applications for nurses; red light could help nurses working rotating shifts maintain nighttime alertness, without suppressing melatonin or changing their circadian phase.
Keywords: Human Health; GO/NOGO test; alertness; melatonin; red light; shift work
|
|
Martin, J. S., Laberge, L., Sasseville, A., Berube, M., Alain, S., Lavoie, J., et al. (2021). Timely use of in-car dim blue light and blue blockers in the morning does not improve circadian adaptation of fast rotating shift workers. Chronobiol Int, in press.
Abstract: Circadian adaptation to night work usually does not occur in naturalistic conditions, largely due to exposure to low levels of light during the night and light in the morning on the way home. This leads to circadian misalignment, which has documented deleterious effects on sleep and functioning during waking hours. Chronic circadian misalignment is also being increasingly associated with long-term health comorbidities. As the circadian system is mostly sensitive to short wavelengths (i.e., blue light) and less sensitive to long wavelengths (i.e., red light), shaping light exposure in a “wavelength-wise” manner has been proposed to promote partial adaptation to night shifts, and, therefore, alleviate circadian rhythms disruption. This report presents results from two cross-over designed studies that aimed to investigate the effects of three different light conditions on circadian phase, sleepiness, and alertness of police patrol officers on a rotating shift schedule. The first study took place during summer (n = 15) and the second study (n = 25) during winter/early spring. In both studies, all participants went through three conditions composed of four consecutive night shifts: 1) in-car dim blue light exposure during the night shift and wearing of blue-blocking glasses (BBG) in the morning after 05:00 h; 2) in-car red light exposure during the night shift and wearing of BBG in the morning after 05:00 h; 3) a control condition with no intervention. To assess circadian phase position, salivary melatonin was collected hourly the night before and the night after each condition. Sleep was monitored by wrist actigraphy. Also, a 10-min Psychomotor Vigilance-Task was administered at the beginning and end of each night shift and the Karolinska Sleepiness Scale was completed every 2 h during each night shift. In the summer study, no difference was found in alertness and sleepiness between conditions. Participants though exhibited greater ( approximately 3 h) phase delay after four consecutive night shifts in the control condition (in which morning light exposure was expected to prevent phase delay) than after the blue and red conditions ( approximately 2 h) (in which wearing BBG were expected to promote phase delay). In the second study performed during the winter/early spring, a comparable approximately 2 h phase delay was found in each of the three conditions, with no difference in alertness and sleepiness between conditions. In conclusion, participants in both studies exhibited modest phase delay across the four night shifts, even during the control conditions. Still, re-entrainment was not fast enough to produce partial circadian adaptation after four night shifts. A greater number of consecutive night shifts may be necessary to produce enough circadian alignment to elicit benefits on sleepiness and alertness in workers driving a motorized vehicle during night shifts. In-car dim blue light exposure combined with the wearing of BBG in the morning did not show the expected benefits on circadian adaptation, sleepiness, and alertness in our studies. Higher levels of light may be warranted when implementing light intervention in a motorized vehicle setting.
|
|
Savarese, M., & Di Perri, M. C. (2019). Excessive sleepiness in shift work disorder: a narrative review of the last 5 years. Sleep Breath, , 1–14.
Abstract: INTRODUCTION: Shift work sleep disorder (SWSD), also known as shift work disorder (SWD), is a circadian rhythm sleep disorder characterized by insomnia and/or excessive sleepiness, associated with a recurring work schedule that overlaps the usual time designated for sleeping. PURPOSE: This article aims to provide a narrative review of the pharmacological trials conducted on SWD in the last 5 years, to better address safety and health issues inherent to this disorder. METHODS: An electronic literature search was conducted using PubMed. All eligible randomized controlled trials (RCTs) and cross-over RCTs with employees undertaking shift work (including night shifts) were considered, yielding three articles. RESULTS: All three studies showed the efficacy of armodafinil in improving subjective and objective sleepiness, clinical conditions, and global functioning regardless of shift duration. Both performance and driving simulator performance tests administered during the night shift bore better results following armodafinil administration than after placebo. However, armodafinil only reduced subjective disability in individuals working more than 9 h; furthermore, even after armodafinil, alertness was reduced but not normalized. CONCLUSION: These studies underscore the importance of preventing and/or minimizing disturbances due to shift work. This may be achieved through various strategies, such as the employer's commitment to adopt ergonomic criteria in shift design and to implement work-environment interventions like controlled bright light. Health personnel is of pivotal importance to detect potential factors of intolerance to shift work or early symptoms of SWD. Additional and improved studies are needed to further evaluate the effectiveness and safety of both pharmacological and non-pharmacological interventions.
|