BACKGROUND: The impact of the separate and combined effects of a 1-h exposure to bright light (approximately 3000 lx) and a 200-mg dose of caffeine on nocturnal performance was studied during a simulated shift-work schedule beginning 1730 in the evening and ending 1000 the next morning. HYPOTHESIS: Light and caffeine exposure were expected to improve nocturnal fatigue degradation. METHODS: There were 11 subjects tested under 4 treatment conditions: 1) 1 hDim Light-Placebo; 2) 1 h Bright Light-Placebo; 3) 1 h Dim Light-Caffeine; 4) 1 h Bright Light-Caffeine. Exposure to the light occurred between 0130 and 0230 hours. Caffeine or placebo was administered at 0140 hours. RESULTS:Choice Reaction Time (RT) recorded during the four post-treatment sessions were shorter for the Bright Light-Caffeine, Bright Light-Placebo, and Dim Light-Caffeine conditions than for the Dim Light-Placebo condition. During the sessions beginning 0430 and 0830 hours, the shortest RT was recorded for the Bright Light-Caffeine treatment. The largest number of trials without false alarms per session for the working memory task (letter cancellation) was found for the Bright Light-Caffeine condition. Exposure for 1 h to 3000 lx reduced melatonin concentration between 42-47% from 0230 to 0410 hours. A 200-mg dose of caffeine also reduced melatonin levels, although to a lesser degree than 1 h exposure to 3000 lx. CONCLUSION: Although 1 h exposure to bright light at 0130 hours combined with a 200-mg dose of caffeine maintains performance throughout the remainder of the night/early morning, a 1-h exposure to bright light without the caffeine may actually degrade performance.
RCT Entities:
BACKGROUND: The impact of the separate and combined effects of a 1-h exposure to bright light (approximately 3000 lx) and a 200-mg dose of caffeine on nocturnal performance was studied during a simulated shift-work schedule beginning 1730 in the evening and ending 1000 the next morning. HYPOTHESIS: Light and caffeine exposure were expected to improve nocturnal fatigue degradation. METHODS: There were 11 subjects tested under 4 treatment conditions: 1) 1 h Dim Light-Placebo; 2) 1 h Bright Light-Placebo; 3) 1 h Dim Light-Caffeine; 4) 1 h Bright Light-Caffeine. Exposure to the light occurred between 0130 and 0230 hours. Caffeine or placebo was administered at 0140 hours. RESULTS: Choice Reaction Time (RT) recorded during the four post-treatment sessions were shorter for the Bright Light-Caffeine, Bright Light-Placebo, and Dim Light-Caffeine conditions than for the Dim Light-Placebo condition. During the sessions beginning 0430 and 0830 hours, the shortest RT was recorded for the Bright Light-Caffeine treatment. The largest number of trials without false alarms per session for the working memory task (letter cancellation) was found for the Bright Light-Caffeine condition. Exposure for 1 h to 3000 lx reduced melatonin concentration between 42-47% from 0230 to 0410 hours. A 200-mg dose of caffeine also reduced melatonin levels, although to a lesser degree than 1 h exposure to 3000 lx. CONCLUSION: Although 1 h exposure to bright light at 0130 hours combined with a 200-mg dose of caffeine maintains performance throughout the remainder of the night/early morning, a 1-h exposure to bright light without the caffeine may actually degrade performance.
Authors: Tracy E Slanger; J Valérie Gross; Andreas Pinger; Peter Morfeld; Miriam Bellinger; Anna-Lena Duhme; Rosalinde Amancay Reichardt Ortega; Giovanni Costa; Tim R Driscoll; Russell G Foster; Lin Fritschi; Mikael Sallinen; Juha Liira; Thomas C Erren Journal: Cochrane Database Syst Rev Date: 2016-08-23