Effects Of Acute Caffeine Ingestion Following A Period Of Sleep Loss On Cognitive And Physical Performance: A Systematic Review And Meta-analysis

Abstract

PURPOSE: This systematic review and meta-analysis examined the impact of acute caffeine consumption on cognitive and physical performance in sleep deprived/restricted individuals. METHODS: Electronic databases were searched for studies measuring cognitive and/or physical performance following sleep restriction (≤6h sleep within 24h) or deprivation (≥24h wakefulness) under control (placebo) and intervention (caffeine) conditions. Studies were included if performance was assessed within 6h of caffeine consumption. Individual effect estimates (EEs) were calculated as Hedges’ g for independent groups. Random effects meta-analyses were performed to determine intervention efficacy. Statistical significance was attained if the 95% CI did not include zero. Multiple meta-regression analysis was conducted to determine effects of caffeine dose and period of wakefulness on the magnitude of the effect. RESULTS: 36 publications providing 250 EEs were included. Caffeine improved performance on reaction time tasks (12 EEs; g=1.11; 95% CI: 0.75-1.47) and both response time (44 EEs; g=0.86; 95% CI: 0.53-0.83) and accuracy (27 EEs; g=0.68; 95% CI: 0.48-0.88) on attention tasks. The magnitude of the effect increased as caffeine dose increased, but was not influenced by the period of wakefulness for either task. Caffeine improved executive function (38 EEs; g=0.35; 95% CI: 0.15-0.55) and the magnitude of the effect increased as caffeine dose increased (p=0.007) and period of wakefulness decreased (p=0.021). Caffeine also improved response time (20 EEs; g=1.95; 95% CI: 1.39-2.52) and accuracy (34 EEs; g=0.43; 95% CI: 0.30-0.55) on information processing tasks, but neither caffeine dose (p=0.785) nor period of wakefulness (p=0.373) influenced the magnitude of the effect. No other performance outcomes were appropriate for meta-analysis. However, studies typically indicated a benefit of caffeine on memory (25 EEs), crystallized intelligence (11 EEs) and physical (39 EEs) performance. CONCLUSION: Caffeine is an effective counter-measure to the cognitive and physical impairments associated with sleep loss.