Clinicians should keep in mind that delirium is an early warning sign of COVID-19 in frail, elderly adults — even when cough, fever and other typical signs are absent, say physician researchers from King’s College London.

Investigators analyzed health data from 800 older hospitalized adults and users of the COVID Symptom Study app. Hospitalized participants classified as frail were more likely to have had delirium as a presenting symptom of COVID-19 than same-age peers who were not frail. Likewise, delirium was more common in frail, older adult app users (along with tiredness and breathlessness) than in less-frail users of the same age, reported Rose Penfold, M.D.

A third of app users who experienced delirium did not report having cough and fever symptoms. Similarly, delirium was the only symptom for around one in five (19%) of hospitalized patients.

“The past six months have shown us that COVID-19 can spread catastrophically through [nursing homes],” said Claire Steves, M.D. “Knowing that delirium is a symptom in frail, elderly people will help families and carers spot the signs earlier of COVID-19 … to protect this highly vulnerable group.”

The COVID Symptom Study app was upgraded in April to allow users to log health reports for friends and family who aren’t able to access the app. This significantly increased the number of older people in the study, providing deeper insight into their COVID-19 experiences, the researchers said.