The goal of this intervention study is to test behavioral interventions in night shift workers. The main question it aims to answer is:

• Can personalized sleep or nutrition intervention strategies help against the negative health effects of night shift work?

Participants will be followed before and after the intervention. Participants will wear smart devices, do a alertness/performance test and complete questionnaires. Blood samples will be collected.

Researchers will compare the intervention groups to the control group (which receives no intervention) to see if the sleep and nutrition interventions affected the health of night shift workers.

Rationale: Night work interferes with the timing of daily activities and disturbs the circadian rhythms of multiple physiological processes in the human body. This is associated with detrimental health effects, such as disturbances in sleep (shorter, less consolidated sleep) and insulin regulation (due to altered eating behaviour). Night shift work is prevalent and difficult to limit in many job types, yet there is currently limited evidence on effective interventions to prevent the health consequence of shift work in a real life context. Therefore more research on tools for the prevention of negative health effects is warranted.

Objective: The current study aims to investigate two types of preventive interventions in night shift workers: a personalised sleep intervention and a personalised nutritional intervention. It will assess the effects of the two interventions on sleep and on (continuous) glucose patterns.

Study design: A non-blinded controlled intervention study, consisting of a run-in period with baseline levels, an intervention of ~ 3 months including measurements at the start of the intervention, a post-intervention measurement and a follow up after 12 months. Study population: The study population consists of employees who work at least 4 night shifts a month on average, with at least 1 year prior experience with shift work. Employees are aged 18-60 years and without a diagnosis of major disease. Each arm of the study will include 25 participants. There are three study arms: control group (no advice), personalised sleep intervention, and personalised nutritional intervention.

Intervention: Participants in the sleep intervention receive advice on: sleep hygiene/environment, sleep timing, naps, and exposure to light. These advices will be tailored to the personal situation of the participant, as measured during the run-in period. Participants in the nutritional intervention receive personalised advice on the distribution of calories and nutrients over 24 hrs, and on specific food products based on the outcomes of the continuous glucose measurements (CGM) during the run-in period. The guidelines will include room for personal dietary preferences. The control group is asked to carry on with their normal sleep and nutritional habits.

Main study parameters/endpoints: The primary outcomes are the quality and quantity of sleep and stability and levels of (continuous) glucose patterns. Secondary outcomes include a set of relevant clinical biomarkers (of metabolic health, epigenetic DNA methylation profiles in blood, and stress markers in hair, and anthropometrics), and alertness during night shifts. For the nutritional intervention, metabolic flexibility and inflammatory resilience will be measured with the mixed-meal challenge test (PhenFlex) test. The outcomes will be compared, pre- and post-intervention.

Inclusion Criteria:

• Age 18 to 60 years.
• Work at least 4 night shifts a month on average.
• Shift workers, working rotating shifts (morning, evening and night shifts) or working predominantly night shifts. Night shift defined as work at least 1 hours between 0:00- and 6:00.
• Work at least 2 night shifts in a row
• Work ≥ 20 work hours per week.
• Having a shift duration of 6 h-12 h.
• History of ≥ 1 year of working rotating shift work or night shifts prior to the study.

Exclusion Criteria:

• Taking medication that the investigator believes would interfere with the objectives of the study. For example, sleep medication, medication that interferes with glucose homeostasis, and/or anti-inflammatory drugs.
• Pregnant or have a wish to become pregnant during the study period.
• Planned surgery during the entire study period Alcohol consumption > 21 units/week
• Severe psychiatric disease and/or any mental or physical disability that will hinder participation in the interventions
• Severe cardiovascular disease, to the discretion of the study doctor
• Having a chronic inflammatory disease, including asthma, rheumatic fever, irritable bowel disease, chronic obstructive pulmonary disease.
• Other bowel diseases, including Chron's disease and Colitis Ulcerosa.
• A disease or condition with higher bleeding risk (/risk of hemorrhage), under which a blood sample may lead to complications.
• Participation in any clinical trial including blood sampling and/or administration of substances up to 90 days before Day 01 of this study
• Recent blood donation (<1 month prior to the start of the study)