Medical and economic evidence suggests that the desynchronization between the biological and the social clocks, i.e., chronodisruption or social jet-lag, is associated with considerable impairments on sleep, health and several life domains. Yet, the intertwine between chronotype, shift work, and health conditions is a complex phenomenon that still requires further research.
The aim of this PhD project is twofold: (1) to investigate whether chronotype influences the choice of work shift and occupation, assessing individuals’ level of awareness and/or prioritisation of own biological needs and (2) to estimate the impact of the chronodisruption on workers’ health overall, exploring a set of physical and mental health diseases generally associated with shift work.
In principle, innate circadian timing preferences could induce individuals to self-select into daily or night working shifts. Otherwise, individuals may be unaware of or don’t prioritise their biological needs and health when choosing job conditions, thus incurring the risk of developing several diseases, which could be mitigated with better-informed choices.
Answering matters for both contributing to the open health equity debate on whether night employment is an individual choice or not, and addressing potential selection bias to estimate unbiased causal effects, more useful to advise public-health policies.
Results will then inform a second part of the project, aiming at assessing the impact of the chronodisruption on physical and mental health.
In particular, longitudinal employment history data will allow assessing: (i) possible transitions towards job conditions more aligned with chronotype, revealing processes of understanding/prioritisation of individual biological (timing) needs and health, (ii) the effect of prolonged exposure to the chronodisruption and (iii) long-term effects on physical and mental health.
In the analyses, chronotype will be measured with polygenic scores, capturing the genetic predisposition component of chronotype. This allows addressing reverse adaptation of sleep-wake habits to work-schedules and providing causal estimates of the chronodisruption on health.
Considering the open discussion on night-work and health, as well as the impossibility to remove night-shifts, results could have important implications for occupational and public health.
By establishing causal relations, rather than associations, they will be more useful to help individuals and employers make health-promoting decisions and policies, aware of the risks related with the misalignment between work and biological clock. For example considering circadian-work shift alignment when choosing a job and allowing flexibility, respectively.
Moreover, (ii) and (iii) in particular will fill high-priority gaps where important evidence is mostly needed.