Covid-19 patients with neurological symptoms such as brain fog or loss of smell and taste may also have markers of Alzheimer’s disease, early research suggests.

Scientists have found increased levels of Alzheimer’s disease markers in blood of people who have been infected with coronavirus and presented with neurological complications.

The findings, which are yet to be published, were presented at the 2021 Alzheimer’s Association International Conference (AAIC) in Colorado.

Thomas Wisniewski, a professor of neurology, pathology and psychiatry at New York University Grossman School of Medicine, who led the research, said: “These findings suggest that patients who had Covid-19 may have an acceleration of Alzheimer’s-related symptoms and pathology.

More longitudinal research is needed to study how these biomarkers impact cognition in individuals who had Covid-19 in the long term

“However, more longitudinal research is needed to study how these biomarkers impact cognition in individuals who had Covid-19 in the long term.”

As part of the research, scientists in the US took blood from 310 people from Manhattan, Brooklyn and Long Island admitted to hospital with Covid-19.

They looked at the levels of markers in the blood associated with Alzheimer’s, such as neurofilament light chain (Nfl) and defective tau protein.

Nfl is a component of the brain’s nerve cells which can leak into the spinal fluid when nerve cells become damaged.

Normal tau proteins are found in nerve cells and perform vital functions for the brain, but defective ones can slow down a person’s ability to think and remember.

The researchers found Nfl and defective tau protein were strongly associated with the presence of neurological symptoms during Covid-19 infection.

Meanwhile, another piece of research, also presented at the AAIC, found a link between Covid-19 and long-term memory and thinking problems.

Researchers at the University of Texas looked at more than 200 adults from Argentina with Covid-19 and compared them against 64 healthy individuals.

These new findings underline that not only is Covid-19 a serious illness, but that we need to monitor potential long-term effects

They found that memory problems were associated with the loss of smell but not severity of Covid-19 infection.

Another study from Greece, presented at the AAIC, found that recovered Covid-19 patients who experience decline in memory were more likely to have poor physical health.

Cognitive problems were found to be associated with poor physical health and low oxygen saturation.

Commenting on the research, Dr Susan Kohlhaas, director of research at Alzheimer’s Research UK, said: “Relatively little is known about the long-term effects of Covid-19, including subsequent risk of memory and thinking problems, or the long-term risk of diseases like Alzheimer’s.”

She added: “These new findings underline that not only is Covid-19 a serious illness, but that we need to monitor potential long-term effects.

“The evidence for persistent problems with memory and thinking after a Covid-19 infection isn’t yet clear and like all findings presented at conferences, we must wait to see them published in full and scrutinised by other experts to draw firmer conclusions.

“These results make it clear that more long-term follow-up and studies of people experiencing Covid-19 are required.

“These studies are predominantly from hospitalised patients, and we need to see a broader focus to encompass the widespread impact of Covid-19.”