‘Shelter-at-home’ restrictions did not change 90-day mortality for unplanned acute and emergency hospital contacts in Denmark: A nationwide observational case-cohort study

To determine the 90-day all-cause mortality risk of unplanned acute and emergency hospital contacts compared to the general population before and after the introduction of the shelter-at-home restrictions introduced during the COVID-19 pandemic in Denmark.

The study was a stratified population-based, case–cohort study performed on all Danish citizens with any unplanned hospital contacts. Cases were collected from March 1 to September 31 in 2019 and 2020, and 1,057,007 cases from a period without restrictions and 1,066,666 cases with restrictions. The primary outcome was 90-day all-cause mortality. Demographic and administrative data were extracted from the Danish National Patient Registry and Civil Registration System and cross-linked for individual citizens. The hazard ratio (HR) for cases was estimated for multiple age groups and adjusted for sex.

The overall 90-day all-cause mortality risk related to an unplanned hospital contact was HR 9.3 (95% CI 9.1 to 9.4). No significant differences were detected in any age group between periods. Women in the age-group of 55–59 without restrictions had the highest HR [24.30 (95% CI 20.50 to 29.01)], as well in the age-group of 50–54 with restrictions with HR 23.30 (95% CI 18.53 to 29.48). Men in the age-group 50–54 in both periods had the highest HR [17.20 (95% CI 14.46 to 20.52)], and with restrictions HR 17.60 (95% CI 14.68 to 21.22).

The COVID-19 pandemic, ensuing national safety measures, and changes in healthcare utilization did not affect the risk of 90-day mortality for unplanned hospital contacts compared to the general population.