AVIATION SHIFTWORK: SAFELY TRANSITIONING FROM DAY TO NIGHT FLIGHTS

The study was requested by the Marine Corps Aviation community with a focus on risk mitigation strategies for aviators transitioning from day to night flights. Avoiding the use of stimulants and sedatives to aid in fatigue mitigation, the study instead used a four-hour period of continuous bright light exposure to shift the circadian rhythm. The main goals of this study were to determine if the light intervention protocol successfully shifted the circadian rhythm of our participants, how large of a phase delay shift was possible, and whether the light intervention affected the participants' perceived levels of fatigue. To reach these goals, we examined melatonin secretion levels to determine dim light melatonin onset (DLMO) over the course of three nights. Phase delay shift calculations were computed using differences in DLMO from night to night. Additionally, self-reported scores on the Karolinska Sleepiness Scale (KSS) provided insight into individual perceived levels of fatigue. Results of the study show successful implementation of the light intervention method by an average phase delay shift of 1 hour 20 minutes ± 22 minutes. However, analyzing the KSS scores did not provide statistically significant results. This study can provide a baseline for future fatigue risk mitigation strategies for military aviation. Lieutenant Junior Grade, United States Navy Approved for public release. Distribution is unlimited.