Coffee & Health
Neurodegenerative disorders

What’s the relationship between coffee, sleep, and alertness?

July 21, 2016

European experts discuss why coffee may affect some people’s sleep but not others’  

The Institute for Scientific Information on Coffee (ISIC) has today published an expert report examining the relationship between coffee, sleep, and alertness, featuring input from independent European specialists. The report is accompanied by an infographic on coffee and sleep, which outlines a normal sleep cycle, how coffee may be used to increase alertness levels, and why coffee may affect some people’s sleep in varying degrees (or not at all).

Main conclusions:

  • The commonest cause of excessive sleepiness in otherwise healthy people is ‘voluntary sleep deprivation’. This is when people do not allow themselves enough sleep, and can often be a result of modern lifestyle factors such as an ‘always-on’ work culture; or smartphone use in bed.
  • Caffeine’s effect on sleep varies widely between individuals, hence some people may find that consuming coffee has little to no effect on their sleep; while others will notice a significant difference. Factors affecting individual variability include: age, gender, genetic make-up, and metabolic processes1,2.
  • There is no ‘one size fits all’ definition of how many hours’ sleep people need per night. While a rough estimate for adults would be 7-8 hours’ sleep per night, there is wide variation within the population. However, the experts noted that many individuals may not realise that routinely getting only 5 hours’ sleep a night is not enough for most people.
  • The main effect of caffeine consumption is an increase in alertness3.This effect can help in low arousal situations, such as those seen in cases of sleep deprivation and fatigue (e.g. people who work in shifts, or are suffering from jet lag4,5).
  • The consumption of caffeine can prolong the time taken to fall asleep, reduce total sleep time and worsen perceived sleep quality6,1.

The experts suggested ways in which healthcare professionals can help people who are particularly sensitive to the stimulating effects of caffeine manage their sleep, such as keeping track of caffeine intake from all sources during the day (for example, recognising that caffeine is also found in tea, cola and energy drinks, and chocolate).

The experts were:

  • Dr Renata Riha, Consultant in Sleep and Respiratory Medicine at the Royal Infirmary, Edinburgh and Honorary Reader at the University of Edinburgh.
  • Dr Elena Philippou, Assistant Professor in Nutrition-Dietetics at the University of Nicosia, Cyprus, and Visiting Lecturer at King’s College London.
  • Additional commentary was provided by Professor Hans-Peter Landolt, co-head of the Clinical Research Priority Program (CRPP) Sleep and Health, University of Zürich.

The experts discussed the science surrounding coffee, caffeine and sleep; looking at why a good night’s sleep is important, how people typically take advantage of coffee’s alertness-boosting properties, and the factors that help determine why caffeine may affect some people’s sleep but not others’.

Overall, moderate consumption of coffee – typically 3-5 cups per day based on the European Food Safety Authority’s review of caffeine safety7 – has been associated with a range of desirable physiological effects in scientific literature and can fit within a healthy, balanced diet and active lifestyle8.


  • To access the roundtable report, please click here.
  • To access to sleep infographic, please click here.

Additional resources:

  • To watch an animated video explaining coffee’s effect on the brain, please click here.
  • Further information on coffee consumption and mental performance can be found here.


  1. Clark I. and Landolt H.P. (2016) Coffee, Caffeine, and Sleep. Sleep Med Rev, 1016/j.smrv.2016.01.006, published online ahead of print.
  2. Byrne E.M. et al. (2012) A genome-wide association study of caffeine related sleep disturbance: confirmation of a role for a common variant in the adenosine receptor. Sleep, 35(7):967-75.
  3. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) (2011) Scientific Opinion on the substantiation of health claims related to caffeine and increased fat oxidation leading to a reduction in body fat mass (ID 735, 1484), increased energy expenditure leading to a reduction in body weight (ID 1487), increased alertness (ID 736, 1101, 1187, 1485, 1491, 2063, 2103) and increased attention (ID 736, 1485, 1491, 2375) pursuant to Article 13(1) of Regulation (EC) No 1924/20061. EFSA Journal, 9(4):2054.
  4. Ker K. et al. (2010) Caffeine for the prevention of injuries and errors in shift workers. Cochrane Database Syst Rev, (5):CD008508.
  5. Arendt J. (2009) Managing jet lag: Some of the problems and possible new solutions. Sleep Med Rev, 13:249-56.
  6. Roehrs T. et al. (2008) Caffeine: sleep and daytime sleepiness. Sleep Med Rev, 12:153-62.
  7. EFSA (2015) Scientific Opinion on the Safety of Caffeine. EFSA Journal, 13(5):4102.
  8. ISIC, ‘Coffee as part of a healthy diet and lifestyle’. Available at

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