Folkard 1993.

Methods	Trial design: Double‐blind randomised cross‐over design Country: Surrey, England Work settings: Surrey Constabulary One complete cycle 28 day system operated by Surrey Constabulary comprise of four rest days, seven nights (22:00 to 06:00), two rest days, seven late shifts (14:00 to 22:00), one rest day and seven early shifts (6:00 to 14:00). For treatment legs the measures were taken for two blocks of 14 days, prior of two successive 28 days cycles of the shift system.
Participants	Inclusion: Number randomised: Screened, randomised, followed‐up 17 volunteer police officers in Surrey Constabulary, all healthy and free from medication, six subject completed all three phases of the trial, seven completed both placebo and melatonin legs, eight completed the baseline recording; the remainder (10) failed to provide sufficiently complete records or their pattern of shift deviated grossly from that scheduled. Lost to follow‐up: Full data were obtained from 7/17 participants (ten lost to follow ‐up) Age mean: Intervention control 29 ± 7 Sex: Intervention male 15/17 control male 15/17
Interventions	Trial intervention: Melatonin 5 mg after six successive night shifts and prior to four normally timed night sleep Comparison intervention:placebo Treatment frequency and duration: once 30 to 60 minutes after night shift, latest at 11 o'clock; Follow‐up: six weeks; four visits and one telephone call during the trial period.
Outcomes	Sleep length, sleep onset and quality while off work: daily sleep diaries (sleep onset, sleep offset, sleep duration, sleep latency, rated sleep quality). Cognitive performance, sleepiness and fatigue at work: mood checklist, work load ratings, rating of alertness, letter search task for memory.
Notes	Ethics: University of Surrey Ethical Committee
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The design was double blind and order of treatments was randomised (P. 316), six subjects completed all three phases of the trial.
Allocation concealment (selection bias)	Unclear risk	No written information.
Blinding of participants All outcomes	Unclear risk	Melatonin (5 mg) in gelatin and placebo (lactose in gelatin) capsules (p.316).
Blinding of care providers	Unclear risk	No written information.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No data.
Incomplete outcome data (attrition bias) All outcomes	High risk	Results are based on N = 7 for placebo and melatonin. Analyses are based on the six recorded day sleeps. The remainder (10) failed to provide sufficiently complete records or their pattern of shift deviated grossly from that scheduled.
Outcome measured with validated instrument All outcomes	Low risk	Sleep length, sleep onset and quality while off work: daily sleep diaries (sleep onset, sleep offset, sleep duration, sleep latency, rated sleep quality). Cognitive performance, sleepiness and fatigue at work: mood checklist, work load ratings, rating of alertness, letter search task for memory.
Selective reporting (reporting bias)	Unclear risk	No data, high attrition bias.
Other bias	Unclear risk	Balance in baseline characteristics: cross‐over design balanced baseline characteristics. Balance in interventions: Discontinuation of trial severely imbalanced trial groups Funding public/private: No data.