Caffeine Consumption Within Six Hours Of Bedtime May Disrupt Sleep

Consumption of caffeine, even six hours before bedtime, can have significant, disruptive effects on sleep. The study, from the American Academy of Sleep Medicine, was published in the Journal of Clinical Sleep Medicine.

“Sleep specialists have always suspected that caffeine can disrupt sleep long after it is consumed,” said American Academy of Sleep Medicine President M. Safwan Badr, MD. “This study provides objective evidence supporting the general recommendation that avoiding caffeine in the late afternoon and at night is beneficial for sleep.”

The researchers found that 400 mg of caffeine (about 2-3 cups of coffee) taken at bedtime, or three to six hours before bedtime, significantly impacts sleep. Objectively measured total sleep time was reduced by more than an hour even when the caffeine was consumed six hours before going to bed. Subjective reports, however, suggest that the study participants were unaware of this sleep disturbance.

“Drinking a big cup of coffee on the way home from work can lead to negative effects on sleep just as if someone were to consume caffeine closer to bedtime,” said Christopher Drake, PhD, investigator at the Henry Ford Sleep Disorders and Research Center and associate professor of psychiatry and behavioral neurosciences at Wayne State University.

People tend to be less likely to detect the disruptive effects of caffeine on sleep when taken in the afternoon,” noted Drake, who is also on the board of directors of the Sleep Research Society.

The researchers recruited 12 healthy normal sleepers, as determined by a physical examination and clinical interview. Subjects were instructed to maintain their normal sleep schedule, but were given three pills a day for four days to be taken at six, three and zero hours before scheduled bedtime. Two of the pills were placebos, and one was 400 mg of caffeine. On one of the four days, all three of the participants’ pills were a placebo. The researchers measured sleep disturbance subjectively using a standard sleep diary and objectively using an in-home sleep monitor.

This is the first study to investigate the effects of a given dose of caffeine taken at different times before sleep. The findings suggest that, in order to allow healthy sleep, individuals should avoid caffeine after 5pm.