Caffeine effectively counteracts performance impairments during the first two days of chronic sleep restriction in genetically caffeine-sensitive individuals

Abstract

Objectives/Introduction: Caffeine is commonly trusted to counteract the performance impairing effects of sleep loss. However, the knowledge on the day-to-day efficacy of caffeine in preserving optimal performance under conditions of chronic sleep restriction is scarce. We investigated the efficacy of caffeine in individuals who carry the C/C-allele of the adenosine A2A receptor (ADORA c.1976), a genotype known to have a high caffeine-sensitivity. Methods: We examined 71 healthy volunteers aged 20 to 40 years in the lab. After one adaptation and two baseline days with prior 8h time in bed (TIB) each, (1) the control group (CO, n=15, 5 female) had 8h TIB for the following six nights, (2) the restriction group (RG, n=21, 9 female) had five days (E1 to E5) with prior 5h TIB followed by an recovery day (Rec) after 8h TIB, (3) the caffeine group (Caff, n=19, 8 female) had the same schedule as the RG, but received standardized 600 ml coffee (∼300 mg caffeine) per day during E1 to E4 and 400 ml coffee (∼200 mg caffeine) on E5, (4) the decaff group (Decaff, n=16, 7 female) underwent the same schedule as the Caff, but consumed decaffeinated coffee. The Caff and Decaff participants carried the caffeine-sensitive genotype. Mixed ANOVAs with Bonferroni adjusted α<0.016 compared the impairment in participants’ mean daytime (at 2h, 5h, 11h, and 15h awake) speed (1/reaction time) as difference to baseline on a 10-min Psychomotor Vigilance Task. Results: Speed in the RG was impaired compared to the CO at E1 to E5 (p< 0.009), but not at Rec (p=0.103). In the Caff speed was faster than in the Decaff at E1 (p=0.014) and faster than in the RG at E1 and E2 (p< 0.002), but slower than in the CO at E3 to Rec (p< 0.014). At 11h awake, speed in the Decaff was faster than in the RG at E1 and E2, but slower than in the CO at E3 to E5 (p< 0.006). Conclusions: Under chronic sleep restriction, ∼300 mg caffeine per day kept performance at rested levels for two days. Decaffeinated coffee also seemed to be beneficial. The use of caffeine delayed recovery.