What is the role of caffeine in sleep alterations?

Updated: Jun 14, 2018
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

Answer

Every exposure to caffeine can produce cerebral stimulant effects. This is especially true in the areas that control locomotor activity (eg, caudate nucleus) and structures involved in the sleep-wake cycle (eg, locus ceruleus, raphe nuclei, and reticular formation). In humans, sleep seems to be the physiologic function most sensitive to the effects of caffeine. Generally, more than 200 mg of caffeine is required to affect sleep significantly. Caffeine has been shown to prolong sleep latency and shorten total sleep duration while preserving the dream phases.

Whether observed differences in sensitivity to the effects of coffee on sleep can be attributed to tolerance has not been positively established. Some studies suggest that these differences might reflect varying individual sensitivity to caffeine, possibly related to differing rates of caffeine metabolism. Indeed, poor sleepers are reported to metabolize caffeine at a lower rate. The variability in response from one night to the next also should be taken into account.

Nevertheless, there is some evidence that tolerance to caffeine-related sleep disturbances may develop, in that heavy coffee drinkers appear to be less sensitive to such disturbances than light coffee drinkers are. In addition, tolerance to sleep latency and quality of caffeine has been shown to develop over a period of days; however, the tolerance is not complete, and the sleep efficiency remains below 90% of the baseline value after 7 days of caffeine treatment.

The evidence for development of tolerance to some of the effects linked to regular consumption of coffee comes primary from animal data. The data from human studies are less conclusive. This may be the result of individual differences in susceptibility and tolerance to caffeine-induced effects. Moreover, mechanisms of tolerance may be overwhelmed by the nonlinear accumulation of caffeine and its primary metabolites in the human body when caffeine metabolism is saturated under multiple-dosing conditions.


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