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Caffeine consumption at night delays circadian clock by 40 minutes

Drinking the amount of caffeine found in a double espresso or a comparable amount 3 hours prior to going to bed results in a 40 minute phase delay in an individual’s biological clock, according to recently published data.

“This is the first study to show that caffeine, the mostly widely used psychoactive drug in the world, has an influence on the human circadian clock. It also provides new and exciting insights into the effects of caffeine on human physiology,” Kenneth Wright, Jr., PhD, professor in the department of integrative physiology at the University of Colorado, Boulder, said in a press release.

Wright and colleagues conducted a double-blind, placebo controlled, 49-day long within-subject study (n = 5 individuals) to assess the effects of caffeine consumption on human circadian timing.

Results demonstrated that a phase delay of the melatonin rhythms by approximately 40 minutes was seen when participants consumed caffeine amounts equivalent to that of a double espresso 3 hours prior to habitual bedtime. The researchers noted that this delay was equivalent to half the delay caused by 3 hours of evening bright light prior to habitual bedtime.

According to the researchers, the study findings may be of benefit for different sleep disorders, as well as those who are traveling across time zones.

“The findings that caffeine influences human circadian physiology may have implications for the pathophysiology and perhaps treatment of some circadian sleep-wake disorders. … Properly timed caffeine use may also be of benefit with respect to shifting circadian timing, potentially assisting with circadian adaptation to large phase delays required when flying across many time zones westward, as well as sustaining wakefulness until bedtime in the new time zone,” Wright and colleagues wrote. – by Casey Hower

Disclosures: Wright reports receiving consulting fees from the NIH, Northwestern American Waterways Project, Takeda Pharmaceuticals, Torvec Inc., and Zeo, Inc. Please see full study for a list of all authors’ relevant financial disclosures.