Slawik, H. | bioRxiv Science

bioRxiv2020

The impact of daily caffeine intake on nighttime sleep: signs of overnight withdrawal?

Acute caffeine intake can delay sleep initiation and reduce sleep intensity, particularly when consumed in the evening. However, it is not clear whether these sleep disturbances disappear when caffeine is continuously consumed during daytime, which is common for most coffee drinkers. To address this question, we investigated the sleep of twenty male young habitual caffeine consumers during a double-blind, randomized, crossover study including three 10-day conditions: caffeine (3 x 150 mg caffeine daily), withdrawal (3 x 150 mg caffeine for eight days, then switch to placebo), and placebo (3 x placebo daily). After nine days of continuous treatment, electroencephalographically (EEG)-derived sleep structure and intensity were recorded during a scheduled 8-h nighttime sleep episode starting 8 (caffeine condition) and 15 h (withdrawal condition) after the last caffeine intake. Upon scheduled wake up time, subjective sleep quality and caffeine withdrawal symptoms were assessed. Unexpectedly, neither polysomnography-derived total sleep time, sleep latency, sleep architecture, nor subjective sleep quality differed among placebo, caffeine, and withdrawal conditions. Nevertheless, EEG power density in the sigma frequencies (12-16 Hz) during non-rapid eye movement (NREM) sleep was reduced in both caffeine and withdrawal conditions when compared to placebo. These results indicate that daily caffeine intake in the morning and afternoon hours does not strongly impair nighttime sleep structure or subjective sleep quality in healthy good sleepers who regularly consume caffeine. The reduced EEG power density in the sigma range might represent early signs of overnight withdrawal from the continuous presence of the stimulant during the day. Statement of SignificanceCaffeine consumption is highly prevalent worldwide and has been repeatedly shown to acutely disrupt sleep, particularly when consumed after several days of abstinence or close to bedtime. However, commonly, caffeine is consumed daily and during daytime. Our well-controlled laboratory study revealed that this common pattern of intake affects nighttime sleep differently: While slow-wave sleep duration or slow-wave activity were rather similar compared to placebo, caffeine intake surprisingly reduced EEG power density in the sigma frequencies. In the light of earlier studies, this might present early signs of caffeine withdrawal which occurs due to overnight caffeine abstinence. The present findings provide novel insights into the impact of daily presence and nightly abstinence of caffeine on nighttime sleep in regular consumers.

neuroscience↗

bioRxiv2020

Wide awake at bedtime? The effects of caffeine on sleep and circadian timing in teenagers - a randomized crossover trial

BackgroundAdolescents frequently consume caffeine with unknown consequences on sleep and circadian rhythms. In adults, the evidence indicates that caffeine acutely reduces homeostatic sleep pressure and delays the circadian timing system. ObjectiveHere, we investigated the acute effects of caffeine intake on the developing sleep-wake regulatory system of teenagers. DesignIn a double-blind randomized crossover laboratory study, 18 teenagers (16.1 {+/-} 1 years old, pubertal development scale [PDS]: 2.76 {+/-} 0.35) ingested 80 mg caffeine (vs placebo) four hours prior to bedtime. Until bedtime, participants regularly filled in the Karolinska Sleepiness Scale and gave saliva samples to measure melatonin secretion. During nighttime, we quantified homeostatic sleep need by the electroencephalographically derived amount of slow wave sleep duration (SWS). After sleep, participants rated sleep quality by the Leeds Sleep Evaluation Questionnaire. ResultsWhile participants felt less sleepy after caffeine vs. placebo (P=0.038), their ratings of sleep quality were not strongly affected by the treatment. However, objectively, SWS was on average reduced by [~]20 min after caffeine vs. placebo (P=0.026). This caffeine-induced reduction was more pronounced in those individuals with more SWS under placebo (regression: P=0.042; standardized beta=0.622, P=0.011), even if controlling for habitual caffeine intake or pubertal stage (PDS). In melatonin onsets we observed both delays and advances in response to caffeine. This variance could partly be explained by differences in relative dose (i.e., mg caffeine/kg of bodyweight): the higher the relative dose, the more likely were delays (regression: P=0.01; standardized beta=0.592, P=0.01). ConclusionsIn teenagers, evening caffeine intake of already 80 mg (i.e. [~]8fl oz of common energy drinks) is sufficient to promote alertness at the costs of subsequent sleep. These costs might be more pronounced in adolescents with a higher need for SWS. Moreover, caffeine might disturb the circadian timing system, consequently hampering the balanced interplay of sleep-wake regulatory components. Sources of SupportMarie-Heim-Voegtlin Grant of the Swiss National Science Foundation (SNSF) PMPDP1_171364

neuroscience↗