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Matera, Joana Leonie (2015): Chronobiology meets work life: chronotype-dependent nap behaviour and light exposure on work- and free days. Dissertation, LMU München: Faculty of Medicine



This thesis addresses two important features of circadian biology: sleep-wake behaviour and light patterns. Napping and light treatment are beneficial countermeasures against sleep deprivation and circadian disruption. Both are extremely high in shift workers, but also normal office workers suffer from a chronic sleep curtailment and circadian misalignment, especially on workdays. In order to provide recommendations, the first step is to analyse how daily life behaviour is like without any intervention. Though shift-working times are very restrictive, the impact of chronotype on napping behaviour in everyday work was explored. For the first time it was shown that not only sleep duration, also chronotype and even circadian disruption influenced shift workers’ nap behaviour. Furthermore, first hints were provided that main sleep duration influences nap length and that nap timing affects succeeding main sleep. In a second study, light profiles of normal office workers were continuously measured. This study attempted to close the lack in regard to light exposure of our everyday life. Light patterns were analysed separately for work- and free days. Additionally, different effects of light on the circadian system were considered, either compressing or expanding internal period length. Study findings can be explained with the hypothesis that clocks embedded themselves into the 24-hour light-dark cycle that they experienced light at the ‘right’ internal time of day, in order to entrain accurately to the external zeitgeber.