Introduction: Poor sleep is associated with an increased risk of infections and all-cause mortality and acute sleep loss and disruption have been linked with inflammation and poorer immune control. Previous studies, however, have been unable to evidence causality between the chronic effects of poor sleep and respiratory infection risk. In light of the ongoing COVID-19 pandemic and future disease outbreaks, understanding the risk factors for these infections is of great importance.
Aim: Our goal was to understand if chronic poor sleep could be identified as a causal risk factor for respiratory infections including influenza, upper respiratory infections and COVID-19.
Methods: We used population cohorts from the UK Biobank (N=230,000), and FinnGen (327,000) with ICD10-based electronic health record and questionnaire based information on self-reported short sleep and insomnia, diagnosis of insomnia and diagnosis of respiratory infections at primary care and hospitals. We computed logistic regression to assess association between poor sleep and infections, disease free survival hazard ratios, and used data from genetic studies of insomnia, COVID-19 and infections in Mendelian randomization analyses to assess the causal direction of association.
Results: Utilizing 20 years of registry data and follow-up, we saw that Insomnia diagnosis associated with increased risk for infections in FinnGen and in UK Biobank (FinnGen influenza HR = 5.32 [4.09, 6.92], P = 1.02e-35, UK Biobank influenza HR = 1.67 [1.52, 1.84], P = 3.12e-27). Mendelian randomization suggested that insomnia predisposed to influenza (OR = 1.59, P = 6.23e-4), upper respiratory infections (OR = 1.71, P = 7.60e-13), COVID-19 infection (OR = 1.08, P = 0.037), and severity of respiratory infection measured as COVID-19 hospitalization (OR = 1.47, P = 4.96e-5) and death from COVID-19 (OR = 1.64, P = 1.02e-3).
Conclusions: Our findings indicate that chronic poor sleep is a causal risk factor for contracting respiratory infections, and in addition contributes to the severity of respiratory infections. These findings highlight the role of sleep in maintaining sufficient immune response against pathogens as suggested by earlier work. As the current COVID-19 pandemic has increased the number of people suffering from poor sleep, safe interventions such as sleep management and treating individuals with insomnia could be promoted to reduce infections and save lives.
Acknowledgements: We acknowledge the participants of the FinnGen and the UK Biobank studies for making this research possible. We also acknowledge the work of the international COVID-19 Human Genetics Initiative for making their genetic association results publicly available.