Bjorvatn 2007.

Methods	Trial design: Cross‐over RCT Country: Bergen, Norway Work settings: Oil rig on the North Sea Shift system: Two weeks on a 12‐hour shift, first week on night shift (18:30 to 06:30) and the second week on day shift (06:30 to 18:30). On the "swing" day workers ended night shift at 04:00 and started day work at 10:00. After three to four weeks off, the schedule was repeated. Randomisation procedure: One of the authors scheduled the exposure Recruitment: All people working night shift at oil rig (N = 109) Follow‐up: April 2002 to April 2003 Washout period: Three to four weeks off work
Participants
Interventions	Trial intervention: Melatonin 3 mg Comparison intervention: Placebo Treatment frequency and duration: Melatonin 3 mg for four days during night shifts and four days of the second week during the day period one hour before bedtime Control: Identical placebo Part of a three‐armed trial, other arm intervention bright light 10,000 lux for 30 minutes (Bjorvatn reported in another review)
Outcomes	Sleep length, sleep onset and quality while off work: Total sleep time (actigraphy, diary); sleep onset latency (actigraphy and diary); sleep quality (diary) Cognitive performance, sleepiness and fatigue at work: Sleepiness (KSS)
Notes	Ethics: The Regional National Committee for Research Ethics and the Norwegian Medicines Agency
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"The workers were given melatonin and bright light in a randomised, double‐blind, placebo‐controlled crossover design", " the exposure was scheduled individually by one of the authors" (P. 205).
Allocation concealment (selection bias)	Low risk	"The code was broken after all of the data had been collected and entered into worksheets so that any bias would be reduced." (P. 205).
Blinding of participants All outcomes	Low risk	"The placebo and melatonin capsules were identical in size and colour, and the two treatments were administered blind, both for the participants and for everyone else involved in the study" (P. 205) (bright light arm of the trial was not blinded).
Blinding of care providers	Unclear risk	See above (exposure was scheduled by one of the authors).
Blinding of outcome assessment (detection bias) All outcomes	Low risk	See above.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Number randomised: Screened 109, included 38, followed‐up 17. Lost to follow‐up: Discontinued 22.
Outcome measured with validated instrument All outcomes	Low risk	Sleep length, sleep onset and quality while off work: Total sleep time (actigraphy, diary); sleep onset latency (actigraphy and diary); sleep quality (diary). Cognitive performance, sleepiness and fatigue at work: Sleepiness (KSS).
Selective reporting (reporting bias)	Low risk	No indication of selective reporting (discontinuation in the trial was a problem).
Other bias	Low risk	Balance in baseline characteristics: Cross‐over design, good balance in baseline characteristics. Balance in interventions: High proportion of discontinuation (> 50%) Funding public/private: No data.