Quantifying and modeling the impact of mistimed and irregular sleep on health

• Applicant: Dr. Dorothee Fischer
• Subject Area: Public Health, Healthcare Research, Social and Occupational Medicine ; Epidemiology and Medical Biometry/Statistics
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 423917010

The human circadian clock regulates virtually all bodily processes, ranging from gene expression and release of hormones to cognition and sleep. Circadian rhythms are evolutionarily adaptive because they allow synchronization of behaviors to the daily light-dark cycle. Today, however, circadian rhythms are challenged by modern lifestyles where electrical lighting allows us to stay active around the clock (e.g., night work in brightly lit facilities or use of electronic devices after sunset). The resulting conflict between biological drives and societal demands affects sleep-wake behavior, e.g., very early or late working times that end sleep prematurely or delay sleep onset, and thus result in sleep loss. While the detrimental effects of short sleep are by now beyond dispute, emerging findings suggest that the timing (sleep on- and offset) and regularity (consistency in the timing of sleep from one day to the next) may be just as important for health as sleep duration. Using two recent metrics – 'Composite Phase Deviation’ (CPD) and 'Sleep Regularity Index’ (SRI) – the proposed research project aims to (i) quantify a dose-response relationship of exposure to mistimed and irregular sleep with health outcomes in a Hispanic US population; and (ii) identify influencing factors and potential interventions using a physiology- based mathematical model. The two metrics (CPD and SRI) have been developed independently by the applicant, Dr. Dorothee Fischer, and her mentors on this project, Drs. Andrew Phillips and Elizabeth Klerman (Brigham and Women’s Hospital/Harvard Medical School, Boston, USA). In Objective 1, the CPD and SRI metrics will be applied to actimetry data of 1,912 participants of the “Sueño Ancillary Study” (age 19-66 years, 36% male) and used to examine the dose-response relationship with several health outcomes (e.g., hypertension and diabetes) in the same dataset. The Sueño study is a prospective multi-center cohort study that started in 2010 as part of the parent “Hispanic Community Health Study/Study of Latinos” to define the impact of poor sleep on health in Hispanic populations living in the US. In Objective 2, an established physiology-based mathematical model of human sleep and circadian rhythms will be used to understand how an individual’s physiology (e.g., circadian period) and their social/work constraints (e.g., working times, self- selected light exposure) interact to generate mistimed and irregular sleep patterns, providing the basis for future intervention designs, such as schedules that are tailored to individuals to protect against mistimed and irregular sleep. Ultimately, the proposed project aims at identifying targets for interventions to minimize exposure to mistimed and irregular sleep, and thereby reduce associated long-term health risks.

• DFG Programme: Research Grants