0290 Caffeine Efficacy Varies as a Function of Individual Vulnerability to Sleep Restriction

Abstract

Abstract Introduction We previously showed that relative to placebo (PL), caffeine (CAF) significantly improved psychomotor vigilance task (PVT) reaction time (RT) during the first 2 days (ACUTE phase), but not during the last 3 days (CHRONIC phase) of sleep restriction (SR) (Doty et al., 2018). However, while individual differences in RT during sleep deprivation have been previously documented, the interaction between CAF and individual vulnerability (VUL) during SR on PVT-RT is not well-known. Methods For statistical analysis, we computed trends in RTs (SLOPE) as follows; baseline, 1st and the 2nd SR days to represent ACUTE phase, and the 2nd, 3rd, 4th and 5th SR days for CHRONIC phase. Participants in each GROUP (CAF or PL) were split into 2 for VUL; high vulnerable (HIGHVUL), and low vulnerable (LOWVUL), depending on the number of minor lapses made during SR. We used 3-way ANOVA model with independent measures (2x2x2; GROUPxVULxPHASE) and a dependent measure (SLOPE). Results We found a main effect of VUL (F=12.69, p<0.001), an interaction between GROUP and PHASE (F=12.95, p<0.001) and an interaction between VUL, GROUP, and PHASE (F=8.04, p<.01). Resolving this 3-way interaction for ACUTE revealed a main effect of VUL (F=9.34, p<.005), a main effect of GROUP (F=5.96, p<.05). Although the interaction between VUL and GROUP failed to achieve significance (F=3.46, p=0.073), only for the LOWVUL, PL participants were significantly higher than CAF, p<0.01)). Resolving the 3-way interaction for CHRONIC revealed a main effect of GROUP (F=8.95, p<0.01), no significant of VUL (F=3.36, p=0.077) and an interaction between VUL and GROUP (F=6.11, p<0.05). Resolving this interaction showed that only for the LOWVUL participants in CAF, the slope was higher than PL (p<.001). Conclusion Performance enhancing effects of caffeine were only evident for low vulnerability participants, and for only the first few days of sleep restriction. At the tested dose level, caffeine did not result in meaningful improvements in performance in highly vulnerable participants during the sleep restriction period. Support Department of Defense Military Operational Medicine Research Program (MOMRP)