title: Klokwerk + study protocol: An observational study to the effects of night-shift work on body weight and infection susceptibility and the mechanisms underlying these health effects.
abstract: Night-shift work may cause severe disturbances in the worker's circadian rhythm, which has been associated with the onset of health problems and diseases. As a substantial part of the workforce is exposed to night-shift work, harmful aspects of night-shift work should not be overlooked. The aim of the Klokwerk + study is to study the effects of night-shift work on body weight and infection susceptibility and the mechanisms underlying these health effects. First, we will study the relation between night-shift work exposure and body weight and between night-shift work exposure and infection susceptibility. Second, we will examine the mechanisms linking night-shift work exposure to body weight and infection susceptibility, with a specific focus on sleep, physical activity, diet, light exposure, vitamin D level, and immunological factors. Lastly, we will focus on the identification of biomarkers for chronic circadian disturbance associated with night-shift work.
  
  
  
  The design of this study is a prospective observational cohort study consisting of 1,960 health care workers aged 18-65 years. The study population will consist of a group of night-shift workers and an equally sized group of non-night-shift workers. During the study, there will be two measurement periods. As one of the main outcomes of this study is infection susceptibility, the measurement periods will take place at approximately the first (September/October) (T0) and the last month (April/May) (T1, after 6 months) of the flu season. The measurements will consist of questionnaires, anthropometric measurements, a smartphone application to determine infection susceptibility, food diaries, actigraphy, light sensors, and blood sample analyses.
  
  
  
  The Klokwerk + study will contribute to the current need for high-quality data on the health effects of night-shift work and its underlying behavioral and physiological mechanisms. The findings can be the starting point for the development of interventions that prevent negative health effects caused by night-shift work. In addition, the identification of biomarkers indicative of loss of homeostasis due to circadian disturbance may be an important asset in monitoring the effects of such interventions.
authors.affiliation: Center for Nutrition, Prevention and Health Services, National Institute for Public Health and the Environment, P.O. Box 1, 3720 BA, Bilthoven, The Netherlands.|Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center Amsterdam, Amsterdam, The Netherlands.
authors.forename: Bette
authors.initials: B
authors.lastname: Loef
authors.affiliation: Center for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Debbie
authors.initials: D
authors.lastname: van Baarle
authors.affiliation: Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center Amsterdam, Amsterdam, The Netherlands.
authors.forename: Allard J
authors.initials: AJ
authors.lastname: van der Beek
authors.affiliation: Center for Health Protection, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Linda W
authors.initials: LW
authors.lastname: van Kerkhof
authors.affiliation: Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Daniëlla
authors.initials: D
authors.lastname: van de Langenberg
authors.affiliation: Center for Nutrition, Prevention and Health Services, National Institute for Public Health and the Environment, P.O. Box 1, 3720 BA, Bilthoven, The Netherlands. karin.proper@rivm.nl.|Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center Amsterdam, Amsterdam, The Netherlands. karin.proper@rivm.nl.
authors.forename: Karin I
authors.initials: KI
authors.lastname: Proper
mesh_terms: D000293:Adolescent; D000328:Adult; D001835:Body Weight; D002940:Circadian Rhythm / Q000502:physiology*; D004198:Disease Susceptibility; D015444:Exercise; D006282:Health Personnel; D006801:Humans; D007239:Infections / Q000209:etiology*; D007251:Influenza, Human; D008027:Light; D008550:Melatonin; D008875:Middle Aged; D011446:Prospective Studies; D012107:Research Design; D012621:Seasons; D012890:Sleep / Q000502:physiology*; D020178:Sleep Disorders, Circadian Rhythm / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D014937:Work; D014940:Work Schedule Tolerance / Q000502:physiology*; D055815:Young Adult
chemical_list: D008550:Melatonin
keywords: Body weight; Diet; Immunological factors; Infection susceptibility; Light exposure; Night–shift work; Physical activity; Sleep; Vitamin D