All-cause mortality among Danish nursing home residents before and during the COVID-19 pandemic: a nationwide cohort study

A substantial part of mortality during the COVID-19-pandemic occurred among nursing home residents which caused alarm in many countries. We investigate nursing home mortality in relation to the expected mortality prior to the pandemic. This nationwide register-based study included all 135,501 Danish nursing home residents between 2015 until October 6, 2021. All-cause mortality rates were calculated using a standardization method on sex and age distribution of 2020. Survival probability and lifetime lost for 180 days was calculated using Kaplan Meier estimates. Of 3,587 COVID-19 related deaths, 1137 (32%) occurred among nursing home residents. The yearly all-cause mortality rates per 100,000 person-years in 2015, 2016, and 2017 were 35,301 (95% CI: 34,671–35,943), 34,801 (95% CI: 34,180–35,432), and 35,708 (95% CI: 35,085–36,343), respectively. Slightly elevated mortality rates per 100,000 person-years were seen in 2018, 2019, 2020, and 2021 of 38,268 (95% CI: 37,620–38,929), 36,956 (95% CI: 36,323–37,600), 37,475 (95% CI: 36,838–38,122), and 38,536 (95% CI: 37,798–39,287), respectively. For SARS-CoV-2-infected nursing home residents, lifetime lost difference was 42 days (95% CI: 38–46) in 2020 versus non-infected in 2018. Among vaccinated in 2021, lifetime lost difference was 25 days (95% CI: 18–32) for SARS-CoV-2-infected versus non-infected. Even though a high proportion of COVID-19 fatalities took place in nursing homes and SARS-CoV-2-infection increased the risk of individual death, the annual mortality was only slightly elevated. For future epidemics or pandemics reporting numbers of fatal cases in relation to expected mortality is critical. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10654-023-00994-6.