Background  National register-based studies on the influence of dementia on COVID-19 infection and outcomes are scarce. This study aims to evaluate the risk of COVID-19 infection, hospitalization, and mortality among older persons with and without dementia.

Methods  This population-based observational study utilized real-world data based on the combination of various national registries in Sweden. Outcomes included COVID-19 infection, hospitalization, and mortality between 01 March 2020 (index date) and 31 August 2020, which was usually considered as the first wave of COVID-19 in Sweden. We used flexible parametric survival regression to estimate the hazard ratios (HRs) between people with and without dementia at different time points after the index date.

Results  We compared people with and without dementia, who were living in community dwellings (40,818 versus 1,984,503 persons) or nursing homes (31,826 versus 87,398 persons). In community dwellings, the HRs of COVID-19 infection increased from 2.08 in one month to 2.46 in two months, then decreased to 0.70 in six months after the index date. In nursing homes, the HRs declined throughout the follow-up period (from 1.89 in one month to 0.91 in six months). In community dwellings, the HRs of COVID-19 hospitalization increased from 1.40 in one month to 1.64 in six months after the index date. In nursing homes, the HRs was less than 1 in one month, and higher than 1 from four months after the index date, however, not statistically significantly. The HRs for COVID-19 mortality rose from 1.96 in one month to 2.39 in two months and dropped to 1.65 in six months in community dwellings; and declined from 2.27 in one month to 1.69 in six months in nursing homes.

Conclusions  In the first wave of COVID-19 in Sweden, higher risks of COVID-19 infection, hospitalization and mortality were observed in older persons with dementia compared to those without dementia, except for the risk of COVID-19 hospitalization in nursing homes. Further studies on the quality of care for persons with dementia are essential to prepare for future pandemics.