Early morning repeat-dose caffeine mitigates driving performance impairments during 50 hours of sleep deprivation

Abstract

Sleep deprivation is a major risk factor in transportation, causing driver fatigue and accidents. Caffeine is commonly chosen to mitigate this risk but its effects depend on dosage and administration regime. Our study investigated early morning, repeat-dose caffeine administration as a countermeasure against driving performance decline during 50 hours of sleep deprivation. Twentyfour healthy young adults (9 females) aged between 18 to 31 years (M = 22.50, SD = 2.90), with normal sleep-wake patterns, participated in a randomised, double-blind placebo-controlled protocol. They were given either caffeinated chewing gum (200 mg/dose) or placebo gum at 0100h, 0300h, 0500h and 0700h and completed fifteen 40-minute drives in a driving simulator (evenly spaced across the 50-hour protocol). Driving performance was assessed with simulation-derived estimates of speed variability, lane deviation and crash count. The caffeine group drove with significantly lower speed variability (t = -6.44, p < 0.0001, Hedges' g = 0.66) and lane deviations (t = -4.74, p < 0.0001, Hedges' g = 0.48) compared to the placebo group who suffered a significantly higher number of crashes (t = 6.45, p < 0.01, Hedges' g = 0.66). The differences emerged at 19 and peaked at 25 hours of continuous wakefulness. These results suggest that early morning, repeat-dose caffeinated chewing gum administration is capable of mitigating driving performance decline under accumulated sleep loss during sustained operations.