Advocates of the “coffee nap” drink a cup of coffee before they have a short sleep, as a way to boost energy levels. Find out the science behind the trend here.

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A “Coffee nap” – drinking coffee before a short nap of 15-20 minutes – is thought to increase energy because of its effect on adenosine, a hormone which promotes sleep.

Caffeine and adenosine have similar structures, so caffeine can act as an imposter and block the actions of adenosine, replacing tiredness with feelings of alertness and arousal1.

Caffeine is absorbed into the body about 45 minutes after ingestion, increasing alertness once it has been digested. Drinking coffee before a nap may boost energy because levels of adenosine fall as we sleep, resulting in a lower level of the hormone for caffeine to compete with in the brain. This enhances the effect of caffeine by increasing the availability of receptors for caffeine in the brain2. Find out more about the effect of caffeine on adenosine receptors here.

It is worth noting that sleep in humans can be affected by caffeine. There is an association between a daily intake of caffeine, reduced sleep quality and increased daytime tiredness3. Research also suggests that there is a genetic variability in the metabolism of caffeine, and several genes have been identified that affect an individual’s sensitivity to caffeine4,5, so some individuals are likely to be more sensitive to the effects of caffeine than others.

A small study has shown a significant reduction in driving incidents in those who consumed 200mg caffeine and had a 30 minute nap, compared with no caffeine or no nap6. However, further research is required to draw more detailed conclusions. As there is individual variability in the response to caffeine consumption, coffee naps are something that may suit some individuals and not others.

References

  1. Fredholm B.B. et al. (1999) Actions of caffeine in the brain with special reference to factors that contribute to its widespread use. Pharmacol Rev, 51:83-133.
  2. Bjorness T.E., Greene R.W. (2009) Adenosine and Sleep. Curr Neuroharmacol, 7(3):238-245.
  3. Clark I. and Landolt H.P. (2016) Coffee, Caffeine, and Sleep. Sleep Med Rev, 31:70-78.
  4. Retey J.V. et al. (2007) A genetic variation in the adenosine A2A receptor gene (ADORA2A) contributes to individual sensitivity to caffeine effects on sleep. Clin Pharmacol Ther, 81:692–8.
  5. Cornelis M.C. et al. (2007) Genetic polymorphism of the adenosine A2A receptor is associated with habitual caffeine consumption. Am J Clin Nutr, 86:240–4.
  6. Reyner L.A., Horne, J.A. (1997) Suppression of sleepiness in drivers: combination of caffeine with a short nap. Psychopharmacol, 34(6):721-5.

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