0200 The Effectiveness Of Caffeine Gum In Reducing Sleep Inertia Following A 30min Nighttime Nap Opportunity: Preliminary Results

Many shiftworkers take short naps on nightshift to reduce the detrimental effects of sleep loss. However, sleep inertia resulting from napping can have deleterious effects on performance. Caffeine may be a useful countermeasure for sleep inertia. This study examined the effectiveness of 200mg caffeine gum in reducing sleep inertia following a 30min nighttime nap opportunity at 0200h. N=5 subjects (3F, M=22.2±SD3.8y) took part in a 2-day laboratory study, with a randomised double-blind, placebo-controlled crossover design following one-week abstaining from caffeine consumption. The study involved one simulated nightshift with a 30min nap opportunity at 0200h. Immediately after waking from the nap, subjects were administered caffeinated gum or placebo gum. Subjects undertook a 3min psychomotor vigilance task (PVT) at 10min pre-nap (0150h) and 5, 15, 25 and 35min post-wakeup. Subjects returned one-week later to undertake the alternate caffeine/placebo condition. Linear mixed model ANOVA assessed differences in PVT lapses (response times >355msec) between caffeine and placebo conditions post-nap. Planned contrasts were conducted to assess differences in each post-nap PVT trial (5,15,25,35min) compared to pre-nap (0150h). There was a significant main effect of condition (F1,37=23.06, p<0.001), with fewer lapses post-nap in the caffeine condition (M=11.9, SE=4.4) compared to placebo (M=18.7, SE=4.5 lapses), but no significant effect of trial or condition*trial interaction. Planned contrasts revealed that compared to pre-nap, there were significantly more lapses at 25- and 35min (p<0.05) post-nap in the placebo condition, but no differences in the caffeine condition (p>0.05). Following a 30min nap opportunity at 0200h, 200mg of caffeinated gum attenuated performance decrements that were apparent from 25- to 35min post-wakeup in the placebo condition. Caffeine gum may be an effective countermeasure for mitigating performance deficits on nightshift, and appears to take 15-25min to take effect. Future analyses should investigate whether the alerting effects of caffeine gum also protect against performance deficits following longer and/or later nap opportunities, and whether any benefits last towards the end of the nightshift. University of South Australia