Study: Drinking coffee before bed doesn't affect sleep quality

Study published in Sleep says drinking coffee before bed is OK 

Go ahead, drink that last cup of coffee with dessert. According to a new study from the Harvard Medical School and Florida Atlantic University, having a late-night cup of coffee won't affect the quality of your sleep. 

Two cups of coffee sitting on a tray on a bed with two blue pillows
Photo: The Sleep Judge

Researchers arrived at this conclusion after studying 785 people for a total of 5,164 days and nights, and their findings were published in Sleep. The researchers looked at how much caffeine, alcohol, and nicotine people consumed and then studied their sleep habits with wrist sensors and sleep diaries. 

They recorded sleep duration, sleep efficiency, and how quickly people woke up after falling asleep. 

The results, the researchers said, were surprising: Alcohol and nicotine negatively affected sleep, and caffeine seemed to have no effect. 

"This study represents one of the largest longitudinal examinations of the associations of evening use of alcohol, caffeine, and nicotine with objectively measured sleep outcomes," Dr. Christine Spadola of FAU said. "We did not observe an association between ingestion of caffeine within four hours of bed with any of the sleep parameters."

However, some doctors noted that everyone responds different to caffeine — so if you're sensitive to caffeine, it's best to not drink coffee before bed. 

"Some people are very sensitive to the effects of caffeine and for these people it’s important to avoid drinking beverages containing caffeine too close to bedtime – but there is no golden rule about this, just listen to your body," Sleep expert Dr. Neil Stanley said in an interview. "If you have been drinking two strong black cups of coffee every evening for the past 40 years and you have just developed a sleeping problem, then it is almost certainly not the coffee."

Related: If you're sensitive to caffeine, genetics might be to blame

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