Drinking coffee at this time of day reduces sleep by an hour
The study, published in the Journal of Clinical Sleep Medicine, is the first of its kind to examine in-depth how consuming caffeine at various hours before bedtime affects sleep.
Lead author Christopher Drake, associate professor of psychiatry and behavioral neurosciences at Wayne State University in Detroit, says that a single cup of coffee in the afternoon can interfere with sleep just as much as a cup of coffee after dinner or later in the evening would.
Drake therefore advises people who want a good night’s sleep to avoid consuming any caffeine for at least 6 hours before bedtime.
The study involved 12 healthy participants who, generally speaking, slept normally. During the study, the participants were asked to adhere to their normal sleep schedules. Each participant was also given 3 pills per day for a period of 4 days. They were instructed to take one of the pills at 6 hours prior to bedtime, another pill at 3 hours before bedtime, and the other pill at bedtime.
Of the three different pills, one had caffeine in an amount equivalent to 2 to 3 cups of coffee. The other two identical-looking pills were placebos – and on one of the 4 days of the study, the 3 pills the participants took (unbeknownst to them) were placebos.
The researchers then measured the quality of their sleep two different ways:
- Objectively, using a sleep monitor; and:
- Subjectively, using diaries kept by the participants with their perceptions of how they slept.
Objectively speaking, the researchers found that when the participants consumed caffeine anywhere from 3 to 6 hours before going to bed, their sleep was significantly disrupted and reduced by at least one hour.
However, from a subjective standpoint, the participants’ self-reports from their diaries revealed that they did not perceive any disturbance in their sleep.
Prof. Drake says this may be due to people having a tendency not to notice the negative effects that caffeine can have on sleep when consumed in the afternoon.
Although sleep specialists have long believed that caffeine can interfere with sleep hours after it’s consumed, Dr. M. Safwan Badr, president of the American Academy of Sleep Medicine, points out that this study is the first to show objective evidence in support of the long-held belief that late day caffeine consumption is disruptive to sleep.
SOURCE: Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed; Christopher Drake, Timothy Roehrs, John Shambroom, and Thomas Roth; Journal of Clinical Sleep Medicine, Volume 09 Number 11, 15 November 2013; DOI: 10.5664/jcsm.3170;