Plain English Summary
Background and study aims
Melatonin is a hormone produced by the brain that controls sleeping patterns. Levels peak at around 4am, and when night shift workers attempt to sleep in the daytime when melatonin levels are low, a ‘mismatch’ between melatonin levels and timing of sleep occurs. It takes several days to adapt. A ‘transcriptome’ is a collection of RNA molecules produced by a particular cell or tissue. The transcriptome can vary with the external environment, and changes in the transcriptome can tell us a lot about gene activity. Recent studies have shown that when there is a mismatch between melatonin production and sleep patterns, there are changes in the transcriptome. Night shift working has been associated with adverse health effects, which might be related to transcriptome changes. Poorer performance and alertness has been reported in night shift workers and this continues until the timing of melatonin production has changed to match sleeping patterns. Administration of melatonin has been used previously in ‘jet lag’, which is a similar situation to that of night shift workers. However, it is unknown whether taking a dose of melatonin affects transcriptome changes or if it helps sleeping patterns and work performance to recover quicker. Melatonin has an excellent safety profile and may be used as a new treatment to improve sleep patterns, improve performance and possibly correct the adverse health effects of night shift working. The aim of this study is to determine the effects of giving doses of melatonin in medical staff working night shifts, and to assess whether melatonin given before sleep time is able to improve sleep, improve alertness and affect transcriptome changes.
Who can participate?
Doctor and nurses working two series of night shifts at least 4 weeks apart
What does the study involve?
Each participant is studied twice - during one series of night shifts they take melatonin and during the other series of night shifts they take a placebo (dummy drug). The order in which they take melatonin or placebo is decided randomly. They complete questionnaires about their normal sleeping habits, their sleeping patterns during the night shift and how sleepy they feel. Participants' alertness is assessed using a computer reaction test and blood samples are taken to measure transcriptome changes. Participants also wear a wristband monitor during sleep periods to obtain data on their sleeping patterns and restlessness.
What are the possible benefits and risks of participating?
The study will tell us whether melatonin might help people undertaking night shifts adapt more quickly to a new sleeping pattern and whether taking melatonin affects the transcriptome changes which have been previously described, which may improve adverse health outcomes.
Where is the study run from?
University of Aberdeen/NHS Grampian (UK)
When is the study starting and how long is it expected to run for?
April 2016 to March 2018
Who is funding the study?
Chief Scientist Office
Who is the main contact?
Prof Helen Galley
Prof Helen Galley
Institute of Medical Sciences
Melatonin In Doctors and nurses working NIGHTshifts (MIDNIGHT): a randomised double-blind placebo-controlled crossover pilot study
The aim of this pilot study is to determine the effects of exogenous melatonin administration compared with placebo in medical staff working night shifts on the intensive care unit.
North of Scotland research ethics committee 2, 17/02/2016
Randomised double-blind placebo-controlled crossover pilot study
Primary study design
Secondary study design
Randomised cross over trial
Quality of life
Patient information sheet
Not available in web format, please use the contact details below to request a patient information sheet
Doctors and nurses working nightshifts
Subjects will take 6mg Circadin (slow release melatonin) or a matching placebo on three consecutive days during night shift working on two separate series of night shifts at least 4 weeks apart.
Primary outcome measure
The primary endpoint is successful completion of the trial, defined as recruitment, randomisation and protocol completion of 25 individuals i.e., both arms of the crossover design.
Secondary outcome measures
1. Determination of drop out, non completion and retention rate (end of trial)
2. Differential gene expression (blood samples on Day 1 before shift, and end of shifts series on Day 4)
3. Differential gene expression between placebo and active arms (blood samples Day 4 after each shift series)
4. Serum interleukin-6 and tumour necrosis factor alpha levels (blood samples on Day 1, and end of shifts series on Day 4)
5. Serum IL-6 and TNFalpha levels after placebo and active arms (blood samples Day 4 after each shift series)
6. Serum melatonin and 6-hydroxymelatonin sulphate levels at each time point (blood samples on Day 1 before shift, and end of each shift for shift series)
7. Verran and Snyder-Halpern sleep scale, Epworth sleepiness scale, data from wristband activity monitor (VSH before each shift, ESS before, during and after each shift. Activity monitoring during each sleep period)
8. Psychomotor vigilance task, double digit addition test (PVT and DDAT before and after each shift)
9. Usual sleep habits and owl-lark questionnaires (before randomisation)
10. Questionnaire about trial (trial end)
11. Focus group about trial (trial end - requires additional consent)
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Either sex
3. Not taking regular medicine
4. No health complaints
5. Doctor or nurse working two series of night shifts at least 4 weeks apart
Target number of participants
Participant exclusion criteria
1. Pregnant or trying to get pregnant
3. Use of sedatives, hypnotics, herbal remedies, sleeping pills
4. Taking medication except oral contraceptives
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
University of Aberdeen/NHS Grampian
Research Governance Office Foresterhill House Annexe Foresterhill
Chief Scientist Office
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Not provided at time of registration.
Intention to publish date
Participant level data
Not expected to be available
Basic results (scientific)
See additional file (ISRCTN15529655_BasicResults_12Mar2019)