In a major study, researchers have found that delirium -- a state of acute confusion associated with a higher risk of serious illness and death -- is a key symptom of COVID-19 in frail, older people.

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The findings, published in the journal Age and Ageing, highlight that doctors and carers should be aware of delirium as a possible early warning sign of COVID-19 in the elderly, even in the absence of more typical symptoms such as cough or fever. "Older, frailer people are at greater risk from COVID-19 than those who are fitter, and our results show that delirium is a key symptom in this group," said study author Rose Penfold from King's College London in the UK. For the study, the researchers analysed data from two groups of older people aged 65 or over from March through May.

The first group included 322 patients admitted to hospital with COVID-19 who had tested positive for COVID-19, while the second comprised 535 users of the COVID Symptom Study app who reported having had a positive test result. They found that older adults admitted to hospital who were classified as frail according to a standard scale were more likely to have had delirium as one of their symptoms than people of the same age who were not classed as frail. Delirium, along with tiredness and breathlessness, were also more common in frailer users of the app with COVID-19, compared with fitter people of the same age.

A third of app users experiencing delirium did not report suffering the 'classic' COVID-19 symptoms of cough and fever, while delirium was the only symptom for around one in five (18.9 percent) of hospitalised patients. This is the first study showing that delirium is a likely symptom of COVID-19 in frail older adults, although the precise biological connection between the two conditions still needs to be understood. The findings also highlight the need for systematic assessment of frailty for older people, along with awareness and screening for delirium for this vulnerable population in hospitals, care homes and the community. "Doctors and carers should watch out for any changes in mental state in elderly people, such as confusion or strange behaviour, and be alert to the fact that this could be an early sign of coronavirus infection," Penfold added.