Coffee may not be the enemy of sleep that it is often made out to be. In a large Swedish study of middle-aged adults, habitual coffee drinking showed little meaningful relationship with self-reported sleep quality or daytime sleepiness, although some statistically significant associations did emerge.
Published in PLOS One, the cross-sectional study examined coffee habits and sleep-related measures among 25,381 adults ages 50 to 64 from the Swedish Cardiopulmonary Bioimage Study.
The authors concluded that habitual coffee consumption showed a “very low association” with sleep patterns, while the broader correlation with perceived sleepiness was described as “negligible.”
“According to our analyses, different degrees of coffee consumption, confirmed by statistical association with previously reported genetic variants, showed very low association with estimated patterns of sleep habits or perceived daytime sleepiness,” the authors wrote.
The finding pushes back against the simpler assumption that more coffee automatically means worse sleep. But the study doesn’t exactly let coffee off the hook, either.
Participants reported how often they drank coffee, along with a series of sleep-related factors including sleep duration, sleep quality, difficulty falling asleep, waking during the night, waking too early, reflux after bedtime and loud snoring. They also completed the Epworth Sleepiness Scale, a common tool used to assess daytime sleepiness.
Some of the results were counterintuitive. Higher coffee intake was associated with slightly better self-reported sleep quality, less difficulty falling asleep, less waking too early and lower reflux frequency at bedtime. At the same time, higher coffee consumption was also associated with a higher frequency of loud snoring.
Yet the authors repeatedly stressed that these effects were minor in practical terms. On most of the sleep measures, the gap between heavier and lighter coffee drinkers was about 2%, and the biggest gap the researchers found was 7.7%.
The study adds to a mountain of research on coffee and sleep associations. One recent study found that caffeine may make certain parts of the brain more active and less restful during sleep. Researchers have also suggested that coffee can help a sleep-deprived brain get by in the moment, even if it can’t help sleep-deprived brains with complex tasks.
The new study was led by researchers from Linköping University and multiple other universities in Sweden and Denmark. The authors declared no competing interests.
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