Covid-19 is associated with persistent cognitive deficits, including the acceleration of Alzheimer’s disease pathology and symptoms, according to researchers.

Experts from the US Alzheimer’s Association-led global SARS-CoV-2 consortium reported the findings at the Alzheimer’s Association International Conference (AAIC) 2021, held virtually and in Denver, Colorado.

They revealed that older adults frequently suffer persistent cognitive impairment, including persistent lack of smell, after recovery from SARS-CoV-2 infection.

Biological markers of brain injury, neuro-inflammation and Alzheimer’s correlate strongly with the presence of neurological symptoms in Covid-19 patients.

Individuals experiencing cognitive decline post-Covid-19 infection were also more likely to have low blood oxygen following brief physical exertion as well as poor overall physical condition, the findings showed.

“These new data point to disturbing trends showing Covid-19 infections leading to lasting cognitive impairment and even Alzheimer’s symptoms,” said Heather M. Snyder, Alzheimer’s Association vice president of medical and scientific relations.

“With more than 190 million cases and nearly 4 million deaths worldwide, Covid-19 has devastated the entire world. It is imperative that we continue to study what this virus is doing to our bodies and brains,” Snyder added.

Researchers at the University of Texas studied a cohort of nearly 300 older adults from Argentina who had Covid-19.

More than half showed persistent problems with forgetfulness, and roughly one in four had additional problems with cognition including language and executive dysfunction.

These difficulties were associated with persistent problems in smell function, but not with the severity of the original Covid-19 disease.

Further, New York University researchers found certain biological markers in blood, including total tau, neurofilament light, glial fibrillary acid protein, ubiquitin carboxyl-terminal hydrolase L1, and species of amyloid beta and phosphorylated tau, which are indicators of injury in the brain, neuroinflammation and Alzheimer’s disease.

For their study, the team took plasma samples from 310 patients with Covid-19. Of the patients, 158 were positive for SARS-CoV-2 with neurological symptoms and 152 were positive for SARS-CoV-2 without neurologic symptoms. The most common neurological symptom was confusion due to toxic-metabolic encephalopathy.

Another team from the University of Thessaly (UTH) examined 32 previously hospitalised mild to moderate Covid-19 patients two months after discharge from the hospital. Among them, 56.2 per cent presented with cognitive decline. Short-term memory impairments and multidomain impairment without short-term memory deficits were the predominant patterns of cognitive impairment.

Worse cognitive test scores correlated with higher age, waist circumference and waist-to-hip ratio. Worse memory and thinking scores were independently associated with lower levels of oxygen saturation.