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International Coffee Day: Drinking coffee before bed does not affect quality of sleep, study finds

That late night-latte won’t rob you of a deep slumber

Sarah Young
Tuesday 01 October 2019 08:50 BST

Drinking coffee or tea just before bed does not affect quality of sleep, a new study has found.

US researchers from Florida Atlantic University and Harvard Medical School monitored 785 people for a total of 5,164 days and nights, recording how much caffeine, alcohol and nicotine they consumed.

The team then compared their consumption to results from sleep diaries and wrist sensors which recorded the participants’ sleep duration, sleep efficiency and how quickly they woke up after drifting off.

The study found that while nicotine and alcohol did disrupt sleep – with a pre-bed cigarette taking 42 minutes off total duration of sleep for insomniacs (a person who is regularly unable to sleep) – caffeine seemed to have no effect.

Writing in the journal Sleep, Dr Christine Spadola, of Florida Atlantic University, said that up until now relatively few studies have thoroughly investigated the association between evening substance use and sleep parameters.

“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 Spadola said.

“A night with use of nicotine and/or alcohol within four hours of bedtime demonstrated worse sleep continuity than a night without.

“We did not observe an association between ingestion of caffeine within four hours of bed with any of the sleep parameters.”

The scientists added that the findings were “a surprise” to the team but that it was in line with previous evidence on the effect of caffeine on sleep.

Nicotine was the substance most strongly associated with sleep disruption among participants with insomnia.

On average, the data showed that nightly nicotine use was associated with an average 42.47-minute reduction in sleep duration.

Speaking previously to The Independent, sleep expert Dr Neil Stanley supported the study’s findings, claiming that the idea that drinking coffee before bed will keep you awake at night is a myth.

“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,” Dr Stanley said.

“For some people the effects caused by caffeine are much lower and [it] may not have any effects at all.

“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.”

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Earlier this year, a separate study suggested that drinking as little as two cups of coffee a day could increase life expectancy by up to two years.

The research, published in the European Journal of Epidemiology, found that moderate coffee consumption, such as two to four cups a day, “was associated with reduced all-cause and cause-specific mortality, compared to no coffee consumption”.

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