Effects of caffeine on sleep quality and daytime functioning

Abstract

Caffeine (particularly in the form of coffee) is one of the most widely consumed stimulants in the world, with 90% of American adults consuming caffeine-infused beverages almost daily. While there is substantial evidence that caffeine enhances performance, caffeine withdrawal leads to deficits at both the individual (eg, cognitive, emotional, and behavioral processes) and societal (eg, increases in work accidents) level. Scholars for some time have considered that the supposed psychoactive benefits of caffeine may be the result of the mere reversal of deleterious effects of caffeine withdrawal, rather than a net benefit of caffeine ingestion. In this integrative review, we examine evidence illuminating the relationship between caffeine consumption and subsequent quality and quantity of nighttime rest. Secondly, we consider evidence as to whether performance deficits caused by sleep deprivation linked to caffeine can be reversed by caffeine consumption during the subsequent daytime period. Finally, we consider how these two stages can be reconciled in a single model that enables calculation of the net caffeine effect on daytime functioning. The literature highlights a range of positive impacts of caffeine consumption on both physical and cognitive functioning. There are also a number of factors that complicate any conclusions that can be drawn regarding the potential of caffeine to improve performance. Most critically, performance improvements the next day may simply be a result of the reversal of caffeine withdrawal. Animal studies and well-controlled human studies involving high habitual and low habitual users tend to confirm a “net benefit” for caffeine use. Further research, particularly with (necessarily rare) caffeine-naive populations, is required to elucidate the complexities of the relationship between caffeine, sleep, and daytime functioning. However, the convenience of accessing caffeine compared to ensuring adequate restorative sleep means that caffeine has applied advantages that are likely to see its use as a performance “enhancing” substance persist.

Motivations Influencing Caffeine Consumption Behaviors among College Students in Korea: Associations with Sleep Quality

“…The average sleep duration, which was almost 7 hours, was moderate and the time spent in bed before falling asleep was 23 min, similar to the results from insomniac adults in Korea [35]. Sleep quality may be poor and the caffeinated beverage consumption was correlated with sleep quality, similar to previous studies [18,22,23,36]. However, a study conducted in three European nations showed that caffeine did not cause difficulties in sleep after controlling for some demographics [37].…”

“…In addition, the sensory elements of coffee have a societal impact, inducing mood changes [17]. According to an analysis of previous literature by O'Callahan [18], the positive and negative effects of caffeine coexist.…”

Midday Napping and Successful Aging in Older People Living in the Mediterranean Region: The Epidemiological Mediterranean Islands Study (MEDIS)

“…Alcohol has a soporific effect; as blood alcohol levels decrease, the rate of arousal increases [34]. In addition, caffeine has psychoactive effects, and may reduce total sleep time and sleep quality if consumed later in the day [35]. However, in the present study, it was found that midday napping was associated with higher levels of successful aging among coffee and no-tea drinkers.…”

Caffeine Consumption in Switzerland: Results from the First National Nutrition Survey MenuCH

“…Caffeine is particularly known and sought for its effects on alertness [7] and cognitive performance [7]. However, in some individuals, it can have a negative impact on sleep in a dose-dependent manner if consumed late in the day [2,7,8]. Longer-term effects of caffeine intake on health are more debated.…”