Patients hospitalised with COVID-19 pneumonia have a higher risk of developing dementia than those with other types of pneumonia, according to a study.

Researchers at the University of Missouri (MU) in the US pulled electronic medical records of 1.4 billion encounters prior to July 31, 2021, in Cerner Real-World Data. They selected patients hospitalised with pneumonia for more than 24 hours.

Among 10,403 patients with COVID-19 pneumonia, 312 (3 per cent) developed new-onset dementia after recovering, compared to 263 (2.5 per cent) of the 10,403 patients with other types of pneumonia diagnosed with dementia.

The risk of new-onset dementia was more common in COVID-19 pneumonia patients over the age of 70 in our study, said lead researcher Adnan I. Qureshi, a professor of clinical neurology at the MU School of Medicine.

The type of dementia seen in survivors of COVID-19 infection mainly affects memory, ability to perform everyday tasks and self-regulation. Language and awareness of time and location remained relatively preserved, Qureshi said in a statement.

The median time interval between infection and dementia diagnosis was 182 days for COVID-19 patients, according to the researchers. The study, published in the journal Open Forum Infectious Diseases, only included new-onset dementia associated with hospital admission during a short follow-up period.

"Approximately 3 per cent of patients with pneumonia associated with SARS-CoV-2 infection developed new-onset dementia, which was significantly higher than the rate seen with other pneumonia," the authors of the study noted.

Qureshi said further study over longer periods of time would provide a more complete picture and may help to determine the underlying reasons why COVID-19 pneumonia might increase dementia risk.

The findings suggest a role for screening for cognitive deficits among COVID-19 survivors. If there is evidence of impairment during screening and if the patient continues to report cognitive symptoms, a referral for comprehensive assessment may be necessary, Qureshi added.