Naturalistic Effects of Five Days of Bedtime Caffeine Use on Sleep, Next-Day Cognitive Performance, and Mood

Abstract

Background: Disruptive effects of caffeine on sleep have previously been reported, although measures of next-day mood and performance have rarely been included. The present study aims to evaluate the effects of caffeine on sleep and associated next-day effects in a naturalistic field setting. Methods: Nineteen participants (daily caffeine intake 0-141 mg), assessed as good sleepers, took part in a randomized, placebo-controlled, double-blind, 2-week crossover study to assess the effects of bedtime caffeine use (250 mg) on sleep and next-day cognitive performance and mood, which were assessed on a mobile phone in the morning and afternoon. Sleep was assessed objectively (actiwatch) and subjectively (sleep diary). Results: Caffeine's effects on sleep were largely restricted to the first day of administration, with actigraphically measured reduced sleep efficiency, increased activity score and fragmentation index, decreased self-rated sleep quality, and an increased occurrence of participants waking early; only decreased sleep efficiency remained over the week. Effects on next-day performance and mood were evident over the whole week, although despite disrupting sleep, accuracy on a working memory task was higher after caffeine than placebo administration. Conclusions: Caffeine disrupted sleep, although when assessing next-day performance, which may have been affected by the presence of residual caffeine, performance appeared better after caffeine compared to placebo, although this was most likely due to prevention of the effects of overnight withdrawal from caffeine rather than representing a net benefit. Furthermore, partial tolerance developed to the effects of caffeine on sleep.

The role of sleep hygiene in promoting public health: A review of empirical evidence

“…The authors interpreted these changes in between-group differences over the course of just a few days as indicative of tolerance to caffeine's effects. 32 Similarly rapid tolerance to the acute sleep-disrupting effects of caffeine administration has been observed in several other laboratory studies (see review 23 ), yet the role of tolerance in attenuating caffeine's influence on sleep in habitual caffeine consumers remains largely unexplored. Finally, Hindmarch and colleagues 34 utilized a cross-over design to test the impact of tea (37.5 or 75 mg of caffeine) and coffee (75 or 150 mg of caffeine) consumption on nocturnal sleep in 30 habitual caffeine users.…”

“…Another recent randomized, double-blind study compared 5 days of placebo to 5 days of caffeine (250 mg) self-administered 0-60 minutes before bedtime, and measured effects on self-reported and actigraphy-assessed sleep. 32 On the first night, there was significantly greater sleep fragmentation, poorer self-reported sleep quality, and a trend toward lower SE for those in the caffeine condition relative to placebo. Beyond the first night, however, only actigraphy-assessed SE was significantly lower in the caffeine condition.…”

Caffeine intake has no effect on sleep quality in community dwellers living in a rural Ecuadorian village (The Atahualpa Project)

“…However, from the very first study attempting to demonstrate the effects of caffeine intake on sleep quality, it was noticed a widespread individual variability in this relationship [3] . Further studies have shown contradictory results, but most of them have been limited to small numbers of participants, to certain groups of individuals, or under artificial circumstances that might not be representative of the population at large [4] , [5] , [6] , [7] .…”

Alpha Oscillations Prior to Encoding Preferentially Modulate Memory Consolidation during Wake Relative to Sleep

“…Participants completed a paper questionnaire containing questions on age, sex, ethnicity, highest level of education achieved and recent (<24hr) alcohol and caffeine consumption, as caffeine and alcohol are known to influence performance on cognitive tasks (Keenan, Tiplady, Priestley & Rogers, 2014).…”