You’ve likely heard that drinking coffee before bed hinders sleep, but new research shows that other lifestyle habits may affect quality rest, too.
A recent U.S. study on evening use of alcohol, caffeine and nicotine found that drinking and smoking within four hours of bedtime were associated with “increased sleep fragmentation.” This includes negative effects on sleep duration, sleep efficiency and wake after sleep onset.
Caffeine, on the other hand, wasn’t found to significantly impact sleep patterns.
“These findings support the importance of sleep health recommendations that promote the restriction of evening alcohol and nicotine use to improve sleep continuity,” the study’s authors wrote in health journal Sleep.
Led by a professor out of Florida Atlantic University (FAU), researchers tracked the habits of 785 African-American adults for over 5,000 days with wrist sensors and sleep diaries. Data showed that people who used nicotine and alcohol before bed “demonstrated worse sleep continuity than a night without these substances,” FAU said in a statement.
This was true even after controlling for factors like age, gender, level of education, having work the next day, depressive symptoms such as anxiety and stress.
Nicotine was the substance most strongly associated with sleep disruption, researchers found. For participants with insomnia, “nightly nicotine use was associated with an average 42.47-minute reduction in sleep duration.”
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Alcohol is also known to affect sleep quality. Previous research found that booze before bedtime may affect sleep, and the U.S. National Institute on Alcohol Abuse and Alcoholism says alcohol “has extensive effects on sleep and daytime sleepiness” and can cause sleep disturbance in healthy adults.
(A recent global report also found that no amount of alcohol is safe for our health.)
When it comes to caffeine, it’s important to note that the study’s researchers were not able to measure individual variations in caffeine sensitivity and tolerance. This means that coffee may affect some people more than others.
A standard cup of brewed coffee has around 130 milligrams of caffeine in it, and Health Canada advises healthy adults not to consume more than 400 milligrams (about three cups) a day.
Dr. Ahmed El-Sohemy, a professor in the department of nutritional sciences at the University of Toronto, previously told Global News that “50 per cent of the population… is a ‘slow’ metabolizer of caffeine,” meaning many folks may want to limit their intake to no more than two cups of coffee a day.
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