The proposed study will provide the ground-based data necessary to inform guidelines for flight testing the new lighting source, in time for the fluorescent light replacement in 2015. The proposal specifically targets lighting countermeasures to address circadian misalignment and performance decrements during a 'slam-shift,' which is a common requirement during Soyuz docking, and to enhance sleep and alertness during both 'slam-shift' and normal operations. Without such data, future recommendations for operational deployment of the Solid State Lighting Assemblies (SSLAs) will be suboptimal.
The Earth-based applications and commercialization potential of these studies are enormous. Electric lighting is ubiquitous and light can be used to improve alertness directly, thereby improving productivity and safety, and ultimately health. Anywhere where electric lighting is used, including schools, colleges, offices, factories, hospitals, care homes, residential homes, and transport and military applications, are potential beneficiaries. The 'slam-shifts' aboard the ISS, and the consequences to sleep, circadian rhythms, performance and health, are very similar to that experienced by many Americans who do shiftwork. The World Health Organization recently designated shiftwork that involves circadian 'desynchrony' as a probable carcinogen and shift-workers also have high rates of night-time accidents and injuries, cardiovascular disease, and diabetes. Similar lighting interventions could be deployed for night shift-workers using the same Dynamic Lighting Schedule (DLS) which would have the benefit of improving productivity and safety while also reducing energy use by using targeted light spectra that only provide the light needed.
This experiment is still in progress. However, preliminary results are available.
Investigators began their recruitment efforts in January 2013 and to date they have screened 94 potential participants; 42 participants were excluded based on study inclusion/exclusion criteria. Four participants are currently enrolled in the screening portion of the study. Twenty-two participants have completed the protocol out of which 18 were studied in the first (advance) arm of Experiment 1. Two participants were admitted but then disempanelled from the study. Investigators expect to complete studies in 36 participants by the end of April 2015. All participants complete an extensive screening procedure lasting about three weeks which includes medical and psychological evaluations to determine eligibility. All participants studied have unremarkable physical, psychological, and ophthalmologic exams, including a negative Ishihara color blindness test. For at least three weeks prior to entering the Intensive Physiological Monitoring Unit at the Brigham and Women's Hospital, participants maintain a self-selected, constant eight hour sleep/rest/dark schedule confirmed with calls to a time- and date-stamped voicemail at bedtime and wake time for three weeks and with actigraphy for at least seven days prior to entering the unit. Participants are asked to refrain from use of any prescription or nonprescription medications, supplements, recreational drugs, caffeine, alcohol, or nicotine. Compliance is verified by urine and blood toxicology during screening and urine toxicology upon entry to the unit. Participants are randomized to either the gradual or slam shift arms of the study on the day of admission. Participants then complete eight days under the inpatient phase of the study which includes four cycles of dynamic light exposure protocols and a 30 hour constant routine protocol. The constant routine minimizes environmental oscillations that may act as time cues. For example, participants remain awake the whole duration in a semi-recumbent posture therefore negating the effects of sleep-wake cycles and postural changes, participants are fed frequent isocaloric snacks at regular intervals instead of daily meals negating the time cues of scheduled meals. This allows studying biologic rhythms under the control of the endogenous clock. The dynamic lighting is generated using the Solid State Lighting Module for Research (SSLM-R), a functional ISS lighting analog, which mimics both the geometry of the light sources aboard the ISS and the light source and spectra that will eventually be deployed.
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