The alerting effects of caffeine were assessed using a standard physiological measure of daytime sleepiness/alertness, the Multiple Sleep Latency Test (MSLT). Healthy young men (n=24) were randomly assigned to receive caffeine 250 mg or placebo administered double blind, at 0900 and 1300 hours on each of 2 days. On the 3rd day both groups received placebo to test for conditioning to the alerting effects of caffeine. Each day sleep latency was measured at 1000, 1200, 1400, and 1600 hours and performance (divided attention at 1030 hours and auditory vigilance at 1430 hours) was assessed. Caffeine increased sleep latency (i.e., improved alertness) and auditory vigilance performance compared to placebo. Tolerance to the effects of caffeine on sleep latency developed over the four administrations. On the conditioning test (day 3) the group receiving caffeine the previous two days was more alert and performed better than the placebo group.
Key wordsMultiple sleep latency test Caffeine Alertness Tolerance Conditioning
Unable to display preview. Download preview PDF.
- Carskadon MA, Dement WC, Mitler MM, Roth T, Westbrook PR, Keenan S (1986) Guidelines for the Multiple Sleep Latency Test (MSLT). A standard measure of sleepiness. Sleep 9:518–524Google Scholar
- Clubley W, Bye CE, Henson TA, Peck AW, Riddington CJ (1979) Effects of caffeine and cyuclizine alone and in combination on human performance, subjective effects and EEG activity. Br J Clin Pharmacol 7:157–163Google Scholar
- Levine B, Moyles T, Roehrs T, Fortier J, Roth T (1986) Actigraphic monitoring and polygraphic recording in determination of sleep and wake. Sleep Res 15:247Google Scholar
- Pavlov IP (1927) Conditioned reflexes. Oxford University Press, LondonGoogle Scholar
- Rechtschaffen A, Kales A (1968) A manual of standardized terminology techniques and scoring system for sleep stages of human subjects. National Institutes of Health Publications 204, Government Printing Office, Washington DCGoogle Scholar