Babkoff 2002

Methods	Design: Randomised cross‐over trial (4 periods) Setting: USA
Participants	N=12, healthy males and females, aged 19‐36 years Simulated night shift from 17.30 to 10.00
Interventions	Dim light (20‐50 lux) + placebo Bright light (3000 lux) + placebo Dim light (20‐50 lux) + caffeine (200mg tablets, No Doz®) Bright light (3000 lux) + caffeine (200mg tablets, No Doz®) Placebo and caffeine capsules were identical in appearance. Light exposure between 01.30‐02.30, caffeine/placebo administered at 01.40. Each experimental condition separated by at least one week.
Outcomes	Performance measures ‐ reaction time, spatial discrimination, letter cancellation task, logical reasoning, team performance task, air traffic‐control task.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk	Report states that the "order of the four experimental conditions was randomized across the groups of three participants each over the 4 test weeks". Author correspondence confirmed that sequence was generated with use of a table of random numbers.
Allocation concealment?	Low risk	Correspondence with author ‐ the pharmacy had control of randomisation.
Blinding? All outcomes	Low risk	Investigators and participants could not be blinded to the bright/dim light conditions, however were blind to the caffeine/placebo conditions. Review authors judge that the outcome and the outcome measurement are not likely to be influenced by lack of blinding.
Incomplete outcome data addressed? All outcomes	Unclear risk	Report states that "of the 12 participants who began the experiment, 11 successfully completed the 4 wk of testing" and "one subject chose to terminate his participation after the first week". 11 were included in the analyses.
Free of selective reporting?	High risk	Outcome data for the team performance task and air traffic‐control task are not reported.
Free of other bias?	Low risk	The study appears to be free of other sources of bias.