Clocks at Work - Introducing chronotype measures to epidemiological shift work research

• Applicant: Dr. Céline Vetter
• Subject Area: Epidemiology and Medical Biometry/Statistics
• Term: from 2013 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 251870514

With shift work having been identified as a risk factor for a range of diseases, such as cardio-vascular disease, sleep and metabolic disorders as well as several forms of cancer, the need improve the assessment of shift work exposure is increasingly vital. Even though the exact mechanisms underlying this increased risk remain to be elucidated, circadian disruption has been suggested to play a central role in the etiology of these pathologies. Yet, one observes a wide distribution of the individual phase of entrainment or chronotype (commonly referred to as "larks" and "owls") within a population, which also translates into a chronotype-dependent variability in timing of behavior, physiology and gene expression. Circadian disruption associated to a work schedule can consequently only be sensibly estimated when taking into account chronotype. Recent epidemiological studies on shift work and cancer have used rather coarse circadian phenotyping, suggesting a moderating effect of chronotype, but also showing an imprecision of the estimates. It follows the necessity of a more reliable tool for assessing chronotype, which would in turn allow a deeper insight into the role of circadian disruption and the aforementioned diseases. The proposed project aims at developing a questionnaire that quantifies a shift worker s chronotype, independent of the shift schedule, and suitable for large-scale epidemiological studies. First, this project will 1) identify a shift-independent chronotype parameter amongst an extensive and available data base of questionnaire-based variables, 2) evaluate the quality of this parameter by the gold standard of circadian phenotyping, namely actigraphy, and 3) validate the chronotype amongst a sample of participants of the Nurses Health Studies 2 cohort, one of the largest epidemiological cohorts worldwide, using established methods, such as actigraphy, sleep logs and urinary melatonin expression, as phase markers for chronotype. Secondly, I will introduce the newly developed questionnaire to the currently being recruited Nurses Health Studies 3 cohort questionnaire pool. This will allow the first systematic chronotyping of a large-scale cohort study (N= 100.000). In the long term, this project will foster the understanding of the role of individual, and work schedule dependent, circadian disruption in the etiology of chronic diseases, and potentially offers a tool for the development of prevention strategies.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professorin Dr. Eva Schernhammer