caffeine at night

New research finds that drinking caffeine at night can actually shift your body’s internal clock


Your internal clock, or circadian rhythm, is responsible for regulating several physiological processes, including sleep-wakefulness timing. External factors can influence your circadian clock, resulting in shifts of circadian timing. Some of the known influencers of circadian timing include light, physical activity, and certain drugs.

A new research study has investigated whether caffeine can affect circadian timing via melatonin signalling. The researchers compared consumption of caffeine in the evening, 3 hours before bedtime, compared with exposure to bright light before bedtime, which is known to delay the circadian clock. The researchers found that caffeine intake 3 hours prior to bedtime delayed the circadian clock by approximately 40 minutes compared with the control group. Exposure to the bright light delayed circadian clock timing by approximately 85 minutes, while a combination of caffeine and bright light delayed timing by approximately 105 minutes when compared to the control group.

The researchers then conducted experiments in human cells to determine the mechanisms that may be involved in this caffeine-induced shift in circadian timing. The researchers found that the shift in timing is mediated through the adenosine receptor which adjusts cAMP signalling. This signalling pathway is a central mediator of the circadian clock within cells.

Overall the researchers report that caffeine is able to shift the phase of the circadian clock in humans, via adenosine and cAMP signalling pathways. They suggest that the results of this study are important in terms of treating certain sleep-wake disorders. By strategically timing the intake of caffeine, it can be used as a tool to adjust circadian timing. Such adjustment also has the potential to be used to help in adjusting circadian clock timing in response to jet lag when traveling internationally.


Burke, TM, Markwald, RR, McHill, AW, Chinoy, ED, Snider, JA, Bessman, SC, Jung, CM, O’Neill, JS, Wright, KP. “Effects of caffeine on the human circadian clock in vivo and in vitro” Science Translational Medicine  16 Sep 2015: Vol. 7, Issue 305, pp. 305





Written by Deborah Tallarigo, PhD

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