The Metabolic and Circadian Effects of Shift Work (OPTI-SHIFT)

The Metabolic and Circadian Effects of Shift Work - An Observational Study

In an exploratory observational pilot study, the investigators will focus on the effects of short-term circadian misalignment induced by shift work on multidimensional measurements including glucose excursion, metabolic health, circadian rhythms (measured in vitro and in vivo), sleep/wake cycles and ambient light, eating and activity patterns, well-being and attention.

Study Overview

• Status: Completed
• Conditions: Shift Work Schedule
• Intervention / Treatment: Other: Exposure to shift work

• Study Type: Observational
• Enrollment (Actual): 72

Contacts and Locations

Study Locations

• Switzerland
  • Geneva, Switzerland, 1211
    • Geneva University Hospitals

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 20 years to 50 years (Adult)
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Shift workers

Description

Inclusion Criteria:

• Men and women
• Age 20-50 years
• Working ≥ 80% full-time equivalent over the previous month and during the study
• Working night shifts (i.e. shifts that comprise working hours between 23h and 06h) in rotation with day shifts (i.e. shifts that comprise working hours between 06h and 20h)
• Planned to work at least 3 consecutive night shifts during the study preceded by at least a day off or day shift
• Planned to work at least 3 consecutive day shifts during the study
• Confident use of a smartphone compatible with the study application (iOS, Android) and able to regularly take pictures of consumed food/drinks
• Able to give a fully informed consent and follow the study procedures

Exclusion Criteria:

• Planned or current pregnancy during the study
• Menopausal women
• Major illness or hospitalization over the previous month
• Carries a pacemaker, pump or other medical device that can be disabled by a magnet
• Major mental illness
• Trip to a different time zone (≥ 2-hour time difference) over the previous month or planned during the study
• Enrolled in an interventional clinical trial (potentially interfering with the main outcomes) over the previous month or planned during the study

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Shift workers; Measurements repeated during a series of day shifts and during a series of night shifts	Other: Exposure to shift work; Detailed questionnaire adapted from the Standard Shiftwork Index, measured at inclusion

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in glucose excursion	As measured by Continuous Glucose Monitoring	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in fasting glucose	As measured by clinical chemistry (mmol/L)	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in weight	Body weight (Kg)	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in waist circumference	Waist circumference (cm) assessed with a measuring tape	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in lipid profile	Total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol measured by clinical chemistry (mmol/L)	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in blood hormonal profile	Insulin (mIU/L), thyroid-stimulating hormone (mIU/L), cortisol (nmol/L) measured by clinical chemistry	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in eating duration	Time from the first to last caloric intake over a 24-hour period	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in nutrient intake	Total calorie and macronutrient intake over a 24-hour period	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in systolic and diastolic blood pressure	As measured by blood pressure arm cuff	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in heart rate variability	As measured by wearable sensor	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in physical activity	As measured by actigraphy and the International Physical Activity Questionnaire	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in sleep/wake cycles	As measured by actigraphy	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in sleep quality	As measured by the Pittsburgh Sleep Quality Index (PSQI), score ranges from 0 to 21 points, 0 indicating no difficulty and 21 severe difficulties	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in attention and sleepiness	As measured by the Sustained Attention to Response Test	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in well-being	As measured by the World Health Organization-5 questionnaire (WHO-5), score ranges from 0 to 25, 0 indicating worst possible and 25 best possible	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in mental health outcomes	As measured by the Patient Health Questionnaire-9 (PHQ-9), score ranges from 0 to 27, 0 indicating no depression and 27 severe depression	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in blood metabolomic parameters	As measured by high-throughput mass spectrometry metabolomics, semi-quantitative identification of small metabolites involved in carbohydrate, fat, protein, and steroid metabolism	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in lipid metabolism	As measured by high-throughput mass spectrometry lipidomics	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in the exposure to ambient light	As measured by wearable spectrometer and the light exposure behaviour assessment (LEBA) questionnaire	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months
Difference in the core body temperature	As measured by a wearable skin temperature and heat transfer sensor	Between a series of day shifts and a series night shifts, separated by an interval from 10 days to 3 months

Collaborators and Investigators

• Sponsor: Tinh-Hai Collet, MD
• Investigators: Principal Investigator: Tinh-Hai Collet, MD, Geneva University Hospitals, Geneva

Publications and helpful links

General Publications

• Hartmeyer SL, Phillips NE, Jassil FC, Joris C, Dibner C, Collet TH, Andersen M. Multi-Wearable Approach for Monitoring Diurnal Light Exposure and Body Rhythms in Nightshift Workers. Acta Physiol (Oxf). 2025 Jul;241(7):e70069. doi: 10.1111/apha.70069.

Study record dates

Study Major Dates

• Study Start (Actual): February 1, 2022
• Primary Completion (Actual): August 30, 2024
• Study Completion (Actual): August 30, 2024

Study Registration Dates

• First Submitted: November 18, 2021
• First Submitted That Met QC Criteria: December 15, 2021
• First Posted (Actual): January 5, 2022

Study Record Updates

• Last Update Posted (Estimated): November 18, 2025
• Last Update Submitted That Met QC Criteria: November 14, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Other Study ID Numbers: 2021-01088

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No