MIDNIGHT
Research type
Research Study
Full title
Metabolic Implications of Day and Night-shift working on NHS Healthcare staff (MIDNIGHT study)
IRAS ID
306915
Contact name
J Tomlinson
Contact email
Sponsor organisation
N/A
Duration of Study in the UK
3 years, 0 months, 1 days
Research summary
Research Summary:
Background:
Around 20% of the UK population work night shifts. Night shifts force people to live their lives out-of-sync with the usual 24-hour cycle. This has been linked with a range of diseases including diabetes, weight gain, and non-alcoholic fatty liver disease (NAFLD). NAFLD is a common condition and involves the build-up of fat in the liver. Over time, this can cause liver scarring and eventually liver failure. Studies in large groups of people have shown that night shift working increases the risk of NAFLD, however there are very few studies in real shift workers which look at the ways fat can build up in the liver.Research aims:
We aim to study 15 NHS healthcare workers and see how night shifts effect the way their liver makes, stores and breaks down fat and sugar. We also aim to collect information on sleeping patterns, exercise, and eating habits during day and night shifts.Design and methods:
NHS staff who are scheduled to work both day and night shifts will be included in the study and identical investigations will be performed in each participant after three day shifts and then after three night shifts. Participants will be asked to drink ‘heavy’ water and then undergo a 2-step hyperinsulinaemic clamp with infusions of stable isotope tracers. Samples of blood and breath will then be collected regularly over the next 6 hours. The amount of heavy water and tracer found in blood and breath will allow us to work out how much fat and sugar the liver is making and breaking down. Each participant will also keep food diaries and wear a smart watch for the duration of the study to monitor sleep and exercise.Dissemination:
Understanding the effect of night shifts on NHS workers may help find ways to reduce their risk of diabetes and NAFLD.Summary of Results:
Around one in five people in the UK work night shifts, including many NHS staff. While shift work is essential for healthcare and other services, it disrupts the body's natural 24-hour body clock (circadian rhythm). People who regularly work nights are more likely to develop conditions such as obesity, type 2 diabetes and fatty liver disease, but we still do not fully understand why.
In this study, we investigated how just three consecutive night shifts affect the body's metabolism in healthy NHS healthcare workers. Thirteen doctors and nurses working in busy clinical areas, including the emergency department and intensive care unit, completed detailed metabolic testing after a period of day shifts and again after a period of night shifts. We also measured their sleep, physical activity and eating patterns.
We found that after only three night shifts, the liver became around 44% less responsive to insulin, a hormone that controls blood sugar levels. This change occurred before any measurable changes in muscle or fat tissue and despite participants eating a similar number of calories and maintaining similar levels of physical activity. Participants also slept around 1 hour less per day while working nights.
These findings suggest that the liver is particularly vulnerable to the effects of night shift work and may help explain why long-term shift workers are at increased risk of developing type 2 diabetes and fatty liver disease. Importantly, these harmful changes appear to occur very quickly, after only a few nights of shift work.
By understanding how shift work affects metabolism, this research will help develop practical strategies to reduce these health risks. These could include improving sleep, changing the timing of meals, or using light exposure to help reset the body's internal clock. Ultimately, our goal is to improve the long-term health of the millions of people whose jobs require them to work through the night.
REC name
West Midlands - Black Country Research Ethics Committee
REC reference
22/WM/0049
Date of REC Opinion
11 Mar 2022
REC opinion
Further Information Favourable Opinion