Investigating causal links between smoking behaviour and sleep using Mendelian randomisation (360G-Wellcome-207306_Z_17_Z)

Smoking is associated with sleep disturbance and difficulties. However, it is unknown whether this relationship is causal and if so, in which direction the association occurs. Inferring causality from observational data is difficult due to the problems of confounding and reverse causality. The aim of this project is to investigate causal relationships between smoking and sleep using a bidirectional Mendelian randomisation approach. This project will involve secondary data analysis of publicly available genomewide association study data. Genetic variants which associate with smoking behaviour (smoking initiation, smoking cessation and cigarettes smoked per day) will be used as proxies for smoking in analyses to investigate causal effects of smoking on sleep. Genetic variants which associate with sleep duration will be used as proxies for sleep in analyses to investigate causal effects of sleep on smoking behaviour. These analyses should be less affected by confounding than conventional observational analyses. Understanding the causal nature of the relationship between smoking and sleep is important for development of smoking cessation strategies as sleep may be a factor influencing relapse to smoking following a quit attempt.