Delirium may be one of the presenting symptoms of COVID-19, complicating diagnosis and care of elderly patients with dementia.

The autors aim to identify the prevalence and prognostic significance of delirium as the sole onset manifestation of COVID-19 in a retrospective single-centre study based on review of medical charts, conducted during the outbreak peak (March 27-April 18, 2020) in a Lombard dementia facility, including 59 elderly subjects with dementia and laboratory-confirmed COVID-19. Of the 59 residents, 57 (96⋅6%) tested positive (mean age: 82⋅8; women: 66⋅7%).

Comorbidities were present in all participants, with 18/57 (31⋅6%) having three or more concomitant diseases.

Delirium -Onset COVID-19 (DOC) was observed in 21/57 (36⋅8%) subjects who were chiefly older (mean age: 85⋅4 y/o) and with multiple comorbidities. Eleven/21 DOC patients (52⋅4%) had hypoactive delirium, while hyperactive delirium occurred in ten/21 (47⋅6%). Lymphopenia was present in almost all subjects (median: 1⋅3 × 10 9 /L).

Overall mortality rate was 24⋅6% (14/57) and dementia severity per se had no impact on short-term mortality due to COVID-19.

DOC was strongly associated with higher mortality ( p <0⋅001). Also, DOC and male gender were independently associated with increased risk of mortality (OR: 17⋅0, 95% CI: 2⋅8–102⋅7, p  = 0⋅002 and 13⋅6, 95% CI: 2⋅3–79⋅2, p  = 0⋅001 respectively).

Delirium occurrence in the elderly with dementia may represent a prodromal phase of COVID-19, and thus deserves special attention, especially in the presence of lymphopenia. Hypoxia and a severe inflammatory state may develop subsequently. DOC cases have higher short-term mortality rate.