Hospitalisation and Mortality Rates in Denmark During the COVID-19 Pandemic: A Nationwide Population-Based Cohort Study

Background: The Coronavirus disease 2019 (Covid-19) pandemic may confer collateral effects on incidence and prognosis of hospitalisations for non-Covid-19 medical conditions.  Methods: Using nationwide, population-based healthcare registries encompassing the entire Danish population, hospitalisation and mortality rates during the Covid-19 pandemic (March 11 through November 30, 2020) were compared with the pre-pandemic baseline (March 1, 2019 through March 10, 2020). All individuals were followed until migration, death, or end of follow-up, whichever came first. Hospitalisation rate ratios (RR) were computed using Poisson regression and were directly standardised using the Danish population on January 1, 2019 as reference. 30-day mortality rate ratios (MRRs) were examined by Cox regression adjusted for age and sex, and using Covid-19 diagnosis as competing risk.  Results: The study included 5,960,934 Danish residents during 530,420,002 weeks of observation. Following national lockdown, the overall hospitalisation RR was 0·72 (95% confidence interval [CI] 0·71-0·73) followed by a gradual return to baseline levels. This pattern was mirrored in all major diagnosis groups except for respiratory diseases (RR 0·58 [95% CI 0·57-0·60]), nervous system diseases (RR 0·90 [95% CI 0·86-0·95]), circulatory diseases (RR 0·95 [95% CI 0·92-0·97]) including heart failure (RR 0·79 [95% CI 0·73-0·86]), cancer (RR 0·87 [95% CI 0·84-0·90]), and non-Covid-19 infections, which remained lower at study conclusion. Mortality was higher across many major diagnosis groups during national lockdown including sepsis (MRR 1·41 [95% CI 1·23-1·62]) and urinary tract infections (MRR 1·45 [95% CI 1·24-1·71]), and remained higher for sepsis (MRR 1·31 [95% CI 1·12-1·53]) and respiratory diseases (MRR 1·19 [95% CI 1·07-1·32]) at end of follow-up.  Interpretation: Hospitalisations for major non-infectious disease groups declined during national lockdown and mortality was higher for patients hospitalised with non-Covid-19 medical conditions including respiratory diseases, sepsis, and urinary tract infections. Increased attention towards management of serious non-Covid-19 diseases may be warranted.  Funding: None. Declaration of Interests: All authors declare no conflicts of interests. Ethics Approval Statement: The study was approved by the legal representatives of North Denmark Region (2020-046). In Denmark, patient consent or approval from an Ethics Committee is not necessary for this type of study. The data were provided by the Danish Health Data Authority.