Poor sleep is a major public health problem with implications for a wide range of critical health outcomes. Insomnia and sleep apnoea are the two most common causes of poor sleep. Recent studies showed that these disorders frequently co-occur. Comorbid insomnia and sleep apnoea can substantially impair the quality of life and increase the risk of overall mortality. However, the causal and physiological links between sleep apnoea and insomnia are unclear. It is also unknown whether having a higher risk for one condition can increase the risk of developing the other.
Here, we investigated links between sleep apnoea and insomnia in a British population by combining self-reported questionnaires and causal inference. We found that 54.3% of the cohort had moderate insomnia, 9.4% had moderate sleep apnoea and 6.2% scored high for both conditions. Importantly, having a higher risk of sleep apnoea was associated with a higher insomnia burden and vice versa. The analysis for this section is here.
To determine the causal directionality between sleep apnoea and insomnia, we used Mendelian randomisation and found evidence that sleep apnoea could cause insomnia, but not the reverse. The analysis for this section is here.
To elucidate how both sleep apnoea and insomnia were linked to each other, we looked at behavioural markers of poor sleep. We found that feeling fatigued after sleeping and having noticeable sleep problems were linked to a higher burden of both sleep apnoea and insomnia. The analysis for this section is here.
In conclusion, our results show that sleep apnoea increases the risk of developing insomnia, and both conditions can result in fatigue. We highlight the importance of considering and treating symptoms from both conditions. Additionally, our work showed that using digital methods to collect information on health information lead to similar results as studies using classical physical questionnaires.
We are currently applying for ethical approval to conduct a larger scale study on public health, using digital collection methods.