The burden of COVID-19-related intensive care admissions in the Nordic countries, 2020–2023

BACKGROUND: The COVID-19 pandemic caused a significant burden on populations and intensive care units (ICU) globally. We assessed the population burden of admissions to the ICU with COVID-19 in the Nordic countries in 2020-2023 to inform pandemic planning. METHODS: We used data from national health registries and applied national case definitions to identify patients admitted to the ICU with and due to confirmed COVID-19. We calculated cumulative incidence per 100,000 inhabitants by country, and described the characteristics of the patients including age, sex, and disease severity. RESULTS: In 2020-2023, 21,587 patients were admitted to the ICU with COVID-19, of whom > 13,000 patients were admitted due to COVID-19. Sweden had the highest cumulative incidence of patients admitted due to COVID-19 (78.5 per 100,000, n = 8,179), and a peak incidence twice that of the other countries. The median age of ICU patients increased over time in all countries, and the majority (62-72%) of patients were men. The longest length of stay in 2020-2021 was recorded in Norway (median 14, lower - upper quartile 7.0-23.5 days), and it decreased to 2, 3 or 4 days in most countries in 2022-2023. Seventy-nine percent of patients received ventilatory support and 25% of patients died, with increasing in-ICU mortality in Norway and Sweden towards 2023. Differences in data sources and case definitions limited the comparability of data from the countries. CONCLUSIONS: The burden of ICU admissions with COVID-19 varied in the Nordic countries and was associated with non-modifiable factors like age and sex, and evolving ones including virus dynamics, and increasing population immunity. Even in the presence of vaccination programmes with documented effectiveness against severe disease, ICUs should be prepared to treat patient groups with suboptimal responses to vaccination. Continued collaboration between the Nordic countries, including the harmonisation of case definitions and protocols for future studies, will improve pandemic preparedness. CLINICAL TRIAL NUMBER: Not applicable.