Researchers from the University of Washington and the University of California found that a glass of wine after work can help you sleep better. But there’s a catch: you need to have had coffee during the day.
The effect didn’t appear when participants consumed only one of the two beverages that day.
The study also found that people who abstained from both drinks reported the best sleep.
For people who enjoy both coffee and wine, the study may make it easier to justify continuing to indulge.
How the Study Was Conducted
Daytime coffee can make it harder to fall asleep. But the study found that drinking alcohol at night can lengthen sleep, partially offsetting caffeine’s effect. In other words, daytime coffee and evening wine can counterbalance each other’s effects.
Over six weeks, 17 healthy adult men recorded their daily coffee and alcohol intake and rated that night’s sleep on a scale from 0 to 100.
They found each daily cup of coffee (or other caffeinated beverage) reduced nightly sleep by about 10 minutes — roughly an hour a week.
When both coffee and a standard glass of wine were consumed, the net reduction in sleep time was only about five minutes per night — suggesting wine offset roughly half of coffee’s effect.
Because alcohol tends to increase drowsiness, it can partially negate the daytime effects of caffeine.
The researchers also found that each additional dose of alcohol per day (for example, a small glass of wine or half a pint of beer) led to more restless sleep at night, as reported by participants.
When participants also consumed caffeine that same day, their reported sleep quality improved.
The team suggested coffee may help mask daytime drowsiness caused by alcohol’s impact on sleep.
Key Takeaways
Frank Song, the lead researcher from the University of Washington, said, “The interaction effect of alcohol and coffee turned out to be the opposite of what we expected.” He explained that the team observed people drinking coffee and alcohol in an attempt to “balance” their sleep.
Song added, “Indeed, consuming alcohol after coffee may ease the process of falling asleep.” But alcohol suppresses REM sleep early in the night. “Overall,” Song said, “it’s better to avoid alcohol and caffeine.”
The study relied on participants’ self-reports of sleep duration and quality; using sleep trackers could have produced different results. The researchers also didn’t track the timing of coffee and alcohol consumption during the day, so they say more research is needed.
The findings from this study were published in the journal PLOS One.
