Originally Posted by Aileen Reid
Gee I'd like to get home early enough to manage to get tea ready and finish it 3 hours before bed! We manage half an hour, maybe an hour at best. Some people lead a charmed life!
If you had problems sleeping, why would you drink a caffeinated beverage before sleep?
Caffeine and sleep
Every single 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, reticular formation). In humans, sleep seems to be the physiological 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 with preservation of the dream phases of sleep. Whether the difference in the sensitivity to the effects of coffee on sleep can be attributable to tolerance is not clearly established.
According to some studies, this difference could reflect the individual sensitivity to caffeine, possibly related to differences in the rate of caffeine metabolism. Indeed, poor sleepers are reported to metabolize caffeine at a lower rate. Four of the 10 subjects of the study had elimination half-lives exceeding 4.8 hours. The variability in response from one night to the next also should be taken into account. Nevertheless, some evidence exists of tolerance to caffeine-related sleep disturbance, since heavy coffee drinkers appear to be less sensitive to caffeine-induced sleep disturbances than light coffee drinkers. Likewise, tolerance to sleep latency and quality of caffeine has been shown to develop over 2 days of testing in one study and over 7 days in another. However, the tolerance is not complete and the sleep efficiency remains below 90% of the baseline value after 7 days of caffeine treatment.
Thus, tolerance to some of the effects linked to regular consumption of coffee seems to occur, especially in animals. In humans, the data are less conclusive. This may be the result of individual differences in the 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
section taken from
Some sleep Md recommend No caffeine for 6 hours before bed.