A large study, that collected data for more than two years of the pandemic, has linked dementia with increased mortality risk in COVID-19 patients but the association was weaker than in previously published studies.

The main outcome of the study was the association of dementia diagnosis with an increased risk of death during the hospital stay.

"Dementia was associated with an increased mortality risk, but the association was weaker than that reported in the majority of previous publications," said Marc Axel Wollmer, director of the department of Geronto-psychiatry from the Asklepios Hospital Nord-Ochsenzoll in Hamburg, Germany.

This is one of the first studies, to be published in the Journal of Alzheimer's Disease, to have investigated the association between dementia and COVID-19 mortality using data collected for more than two years and applying two different statistical methods in parallel.

The association between dementia and death was studied using "multivariable logistic regression" adjusted for age, sex, cancer, diabetes mellitus, lipid metabolism disorder, obesity, heart failure, ischemic heart disease, cerebrovascular disease, cirrhosis of the liver, and probable COVID-19 variant.

The goal was to verify the association of dementia diagnosis with the risk of mortality as a result of COVID-19 among patients.

"It is possible that the effects of dementia on COVID-19 mortality may have changed over time, especially after vaccines became available and were broadly administered and as different variants of SARS-CoV-2 evolved," explained Karel Kostev, from the Department of Epidemiology at the healthcare organisation IQVIA.

Of the 28,311 patients diagnosed with COVID-19, 3,317 (11.3 per cent) had a dementia diagnosis.

Although SARS-CoV-2 has changed over time and vaccination has greatly improved the prognosis of individuals who contract COVID-19 in general, "further studies are needed to identify, prevent, and treat risk factors for mortality of this disease," said researchers.