Combined caffeine and carbohydrate ingestion: effects on nocturnal sleep and exercise performance in athletes

In athletes, caffeine use is common although its effects on sleep have not been widely studied. This randomised, double-blind, placebo-controlled crossover trial investigated the effects of late-afternoon caffeine and carbohydrate-electrolyte (CEB) co-ingestion on cycling performance and nocturnal sleep. Six male cyclists/triathletes (age 27.5 +/- A 6.9 years) completed an afternoon training session (TS; cycling 80 min; 65 % VO2max) followed by a 5 kJ kg(-1) cycling time trial (TT). Caffeine (split dose 2 x 3 mg kg(-1)) or placebo was administered 1 h prior and 40 min into the TS. A 7.4 % CEB (3 ml kg(-1) every 15 min) was administered during the TS, followed 30 min after by a standardised evening meal. Participants retired at their usual bedtime and indices of sleep duration and quality were monitored via polysomnography. Data: mean +/- A SD. All participants performed better in the caffeine TT (caffeine 19.7 +/- A 3.3; placebo 20.5 +/- A 3.5 min; p = 0.006), while ratings of perceived exertion (caffeine 12.0 +/- A 0.6; placebo 12.9 +/- A 0.7; p = 0.004) and heart rate (caffeine 175 +/- A 6; placebo 167 +/- A 11 bpm; p = 0.085) were lower in the caffeine TS. Caffeine intake induced significant disruptions to a number of sleep indices including increased sleep onset latency (caffeine 51.1 +/- A 34.7; placebo 10.2 +/- A 4.2 min; p = 0.028) and decreased sleep efficiency (caffeine 76.1 +/- A 19.6; placebo 91.5 +/- A 4.2 %; p = 0.028), rapid eye movement sleep (caffeine 62.1 +/- A 19.6; placebo 85.8 +/- A 24.7 min; p = 0.028) and total sleep time (caffeine 391 +/- A 97; placebo 464 +/- A 49 min; p = 0.028). This study supports a performance-enhancing effect of caffeine, although athletes (especially those using caffeine for late-afternoon/evening training and competition) should consider its deleterious effects on sleep.