Acute caffeine intake can attenuate homeostatic sleep pressure and worsen sleep quality. Caffeine intake—particularly in high doses and close to bedtime—may also affect circadian-regulated rapid eye movement (REM) sleep promotion, an important determinant of subjective sleep quality. However, it is not known whether such changes persist under chronic caffeine consumption during daytime. Twenty male caffeine consumers (26.4 ± 4 years old, habitual caffeine intake 478.1 ± 102.8 mg/day) participated in a double-blind crossover study. Each volunteer completed a caffeine (3 × 150 mg caffeine daily for 10 days), a withdrawal (3 × 150 mg caffeine for 8 days then placebo), and a placebo condition. After 10 days of controlled intake and a fixed sleep-wake cycle, we recorded electroencephalography for 8 h starting 5 h after habitual bedtime (i.e., start on average at 04:22 h which is around the peak of circadian REM sleep promotion). A 60-min evening nap preceded each sleep episode and reduced high sleep pressure levels. While total sleep time and sleep architecture did not significantly differ between the three conditions, REM sleep latency was longer after daily caffeine intake compared with both placebo and withdrawal. Moreover, the accumulation of REM sleep proportion was delayed, and volunteers reported more difficulties with awakening after sleep and feeling more tired upon wake-up in the caffeine condition compared with placebo. Our data indicate that besides acute intake, also regular daytime caffeine intake affects REM sleep regulation in men, such that it delays circadian REM sleep promotion when compared with placebo. Moreover, the observed caffeine-induced deterioration in the quality of awakening may suggest a potential motive to reinstate caffeine intake after sleep.

急性咖啡因摄入会减弱稳态睡眠压力并恶化睡眠质量。咖啡因摄入量——尤其是高剂量和接近就寝时间——也可能影响昼夜节律调节的快速眼动 (REM) 睡眠促进，这是主观睡眠质量的重要决定因素。然而，尚不清楚这种变化是否在白天长期摄入咖啡因的情况下持续存在。20 名男性咖啡因消费者（26.4 ± 4 岁，习惯性咖啡因摄入量为 478.1 ± 102.8 毫克/天）参与了一项双盲交叉研究。每位志愿者完成了一次咖啡因（每天 3 × 150 毫克咖啡因，持续 10 天）、戒断（3 × 150 毫克咖啡因，持续 8 天，然后是安慰剂）和安慰剂条件。经过 10 天的控制摄入量和固定的睡眠-觉醒周期后，我们从习惯性就寝时间后 5 小时开始记录了 8 小时的脑电图（即，平均在 04:22 h 开始，大约是昼夜节律 REM 睡眠促进的高峰期）。在每次睡眠发作之前进行 60 分钟的晚间小睡，可降低高睡眠压力水平。虽然三种情况的总睡眠时间和睡眠结构没有显着差异，但与安慰剂和戒断相比，每天摄入咖啡因后 REM 睡眠潜伏期更长。此外，REM 睡眠比例的积累被延迟，与安慰剂相比，志愿者报告在咖啡因条件下睡后醒来更困难，醒来时感觉更疲倦。我们的数据表明，除了急性摄入外，白天定期摄入咖啡因也会影响男性的 REM 睡眠调节，因此与安慰剂相比，它会延迟昼夜节律的 REM 睡眠促进。而且，