Condition category
Not Applicable
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status

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

Trial website

Contact information



Primary contact

Prof Helen Galley


Contact details

Institute of Medical Sciences
AB25 2ZB
United Kingdom

Additional identifiers

EudraCT number

2015-004106-42 number

Protocol/serial number


Study information

Scientific title

Melatonin In Doctors and nurses working NIGHTshifts (MIDNIGHT): a randomised double-blind placebo-controlled crossover pilot study



Study hypothesis

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

Ethics approval

North of Scotland research ethics committee 2, 17/02/2016

Study design

Randomised double-blind placebo-controlled crossover pilot study

Primary study design


Secondary study design

Randomised cross over trial

Trial setting


Trial type

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.

Intervention type



Phase II

Drug names

Circadin (melatonin)

Primary outcome measures

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


Participant inclusion criteria

1. Either sex
2. Non-smokers
3. Not taking regular medicine
4. No health complaints
5. Doctor or nurse working two series of night shifts at least 4 weeks apart

Participant type

Health professional

Age group




Target number of participants


Participant exclusion criteria

1. Pregnant or trying to get pregnant
2. Breastfeeding
3. Use of sedatives, hypnotics, herbal remedies, sleeping pills
4. Taking medication except oral contraceptives

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

University of Aberdeen/NHS Grampian
Research Governance Office Foresterhill House Annexe Foresterhill
AB25 2ZB
United Kingdom

Sponsor information


University of Aberdeen/NHS Grampian (UK)

Sponsor details

Research Governance Office
Foresterhill House Annexe
AB25 2ZB
United Kingdom

Sponsor type




Funder type


Funder name

Chief Scientist Office

Alternative name(s)


Funding Body Type

government organisation

Funding Body Subtype

government non-federal


United Kingdom

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

Results - basic reporting

Publication summary

Publication citations

Additional files

Editorial Notes