C F Reichert et al, 2020. Wide awake at bedtime? Effects of caffeine on sleep and circadian timing in male adolescents – a randomized crossover trial, Biochemical Pharmacology, published online.Print this page
Adolescents often suffer from short and mistimed sleep. To counteract the resulting daytime sleepiness they frequently consume caffeine. However, caffeine intake may exaggerate sleep problems by disturbing sleep and circadian timing. In a 28-hour double-blind randomized crossover study, we investigated to what extent caffeine disturbs slow-wave sleep (SWS) and delays circadian timing in teenagers. Following a 6-day ambulatory phase of caffeine abstinence and fixed sleep-wake-cycles, 18 male teenagers (14-17 years old) ingested 80 mg caffeine vs. placebo in the laboratory four hours prior to an electro-encephalographically (EEG) monitored night-time sleep episode. Data were analyzed using both frequentist and Bayesian statistics. The analyses suggest that subjective sleepiness is reduced after caffeine compared to placebo. However, we did not observe a substantial influence of the given dose neither on subjective sleep quality nor on SWS, but rather a high inter-individual variability in caffeine-induced SWS changes. Exploratory analyses suggest that particularly those individuals with a higher level of SWS during placebo reduced SWS in response to caffeine. Regarding salivary melatonin onsets, caffeine-induced delays were not evident at group level, and only observed in participants exposed to a higher caffeine dose relative to individual bodyweight (i.e., a dose >1.3mg/kg). Together, the results suggest that 80 mg caffeine are sufficient to induce alertness at a subjective level. However, particularly teenagers with a strong need for deep sleep might pay for these subjective benefits by a loss of SWS during the night. Thus, caffeine-induced sleep-disruptions might change along with the maturation of sleep need.
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