Effects of caffeine on alertness

Abstract

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.

Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed

“…Tolerance to the alertness enhancing effects of caffeine develops quickly, 45 and the practice of using high doses of caffeine to improve alertness is becoming increasingly common among both adults and adolescents. 46,47 However, the risks of caffeine use in terms of sleep disturbance are underestimated by both the general population and physicians.…”

Caffeine, Mental Health, and Psychiatric Disorders

“…Caffeine has been repeatedly shown to attenuate performance impairments due to decreases in arousal induced by sleep loss, fatigue, working at night, or by sedative drugs [89][90][91][92][93]. Furthermore, caffeine can remove the impaired performance and negative mood associated with the common cold [94] and attenuate memory impairment induced by scopolamine in humans [95].…”

Comparing the benefits of caffeine, naps and placebo on verbal, motor and perceptual memory

“…A number of studies have examined the benefits of daytime caffeine consumption in nonexperimentally sleep-deprived individuals (Loke et al 1985;Lieberman et al 1987;Zwyghuizen-Doorenbos et al 1990;Nehlig et al 1992;Dimpfel et al 1993;Spriet 1995;Lorist et al 1996;Kaplan et al 1997;Brice et al 2002;Lorist et al 2003;Cysneiros et al 2007). The performance tasks used in these studies measure reaction time and motor speed, speed of information processing, vigilance and attention, immediate and delayed verbal memory, as well as mood and alertness (for review see (Nehlig et al 1992;Lorist et al 2003).…”

“…The performance tasks used in these studies measure reaction time and motor speed, speed of information processing, vigilance and attention, immediate and delayed verbal memory, as well as mood and alertness (for review see (Nehlig et al 1992;Lorist et al 2003). Generally, caffeine enhances mood and alertness (Lieberman et al 1987;Kaplan et al 1997), vigilance and attention (Lieberman et al 1987;Zwyghuizen-Doorenbos et al 1990), speed of information processing (Kaplan et al 1997;Cysneiros et al 2007), reaction time and motor speed (Lieberman et al 1987;Zwyghuizen-Doorenbos et al 1990; Kaplan et al 1997;Cysneiros et al 2007). One study found 200 and 300 mg of caffeine benefited visual vigilance, choice reaction time, repeated acquisition, and self-reported fatigue and sleepiness, but did not improve marksmanship, a task that requires fine motor coordination and steadiness .…”