Markers, determinants, and outcomes of circadian disruption: An observational study of endogenous circadian rhythms, light exposure, and sleep regularity

A twenty-four hour timing system, known as the ‘circadian’ system, regulates and coordinates processes in the human body. The circadian system is synchronized by twenty-four hour rhythms in the environment and our behaviour. Disruption of the circadian system accompanies poor health. This thesis examines the relationships of light exposure and sleep with circadian disruption and risk of premature mortality. Exposure to light at night, and irregular sleep patterns, predicted higher risk of premature mortality across 85,000 research participants. This higher mortality risk may be due to disrupted communication within the human circadian system, leading to poor health.