The overall goal of this project is to study the efficacy of blue-enriched solid state polychromatic light for acutely enhancing alertness and cognitive performance in healthy men and women. The purpose of this work is to develop in-flight and ground-based lighting countermeasures for enhancing alertness in astronauts and NASA ground crew.
This is the final year of this directed research project. This year's aims were reduced due to an unexpected funding reduction. The reduced aims were:
1) Continue the three-day inpatient study of narrowband blue solid state light on alertness and cognitive performance: (a). complete neurocognitive and melatonin data analysis (b). initiate analysis of polysomnography data, completing as much as possible with remaining funds.
2) Complete a pilot study on testing the effect of light emitting surface size on melatonin suppression. (a). finish running subjects through the test conditions (b). complete blood assays and data analysis.
3) Write a report on the results on items 1 and 2 above.
Two studies have been previously completed for this project using two prototype 122 cm x 122 cm solid-state blue light (peak wavelength 469 nm) exposure systems. A melatonin suppression study has resulted in a peer-reviewed manuscript published in the Journal of Applied Physiology (West et al., 2011). The second study was a three-day inpatient study on the effects of narrowband blue light from light emitting diodes (LEDs) on alertness and cognitive performance.
Per the first aim above, plasma melatonin, alertness, and neurocognitive performance measures have been analyzed. Polysomnographic data from Karolinska Drowsiness Tests (KDTs) was analyzed from 8 of the 22 subjects. Further KDT analysis was not feasible due to the unexpected funding cut. Two presentations were made at international meetings describing the protocol and the preliminary analysis of the melatonin data set (Hanifin et al., 2010a, 2010b). The completed melatonin, alertness, and neurobehavioral data sets are now being written up as a chapter in a doctoral thesis (Hanifin, unpublished) and subsequently are likely to be published as a peer-review manuscript. Importantly, the experimental 122 cm x 122 cm LED light panels we have used in the first two studies for this project are too large to be flight-worthy, although they could be used for lighting countermeasures for ground crew.
This year's second aim was concerned with testing the consequences of reducing the size of the light-emitting surface to a more flight-worthy size. This pilot study used the acute melatonin suppression response as its dependent variable for quantifying how different size light-emitting surfaces influence this neuroendocrine response. A pilot study protocol was designed and approved by the Jefferson Institutional Review Board (IRB). Two new exposure systems were designed, constructed, and equipped with blue-enriched broad-bandwidth LEDs (6,500 K) for this study. Of note, this blue-enriched LED light source is similar to one of the LED sources being specified for the Solid-State Light Assembly (SSLA) that is being proposed for replacing the current fluorescent General Luminaire Assemblies (GLA) onboard the International Space Station. Eight healthy male and female subjects were recruited, screened, and enrolled in an experiment that employed a within-subjects design. Subjects were seated comfortably with their head resting in an ophthalmologic head holder facing the light source at a distance of 90 cm. The volunteers' pupils were freely reactive during the light exposure that was given between 2:00 and 3:30 AM. Subjects were exposed to a 122 cm x 122 cm exposure area or a much smaller 3.81 cm x 3.81 cm exposure area at an equal surface irradiance and a dark control exposure (with at least one week between each exposure). The volunteers have completed all 24 study nights and their plasma samples have been quantified for plasma melatonin content. The resultant data support the hypothesis that light source size is a critical factor in the design of SSLA lighting that can be used to serve as an in-flight countermeasure for circadian disruption and sleep during long duration space exploration. A follow up study testing a range of light emitting surface sizes including the surface size of the SSLA (approximately 11 cm x 54 cm) was planned but not initiated due to the unexpected funding cut. The ultimate goal from this work is to develop a lighting countermeasure that enhances alertness and cognitive performance in ground crew members and astronauts.
This year's results ultimately will impact the NASA Human Integration Design Handbook and the Space Flight Human Systems Standard, NASA-STD-3001, that provide guidance for supporting crew health, habitability, environment, and human factors in human space flight. Our progress addresses NASA Human Research Program Integrated Risk Plan (2011) risk area 22 (Sleep 5, 9, and 10) Critical Risk areas. These areas concern countermeasures that will optimally mitigate health, performance and safety problems due to circadian, neuroendocrine, and neurobehavioral disruption, for flight, surface, and ground crews.