March 9, 2022 -- Problems with mental skills like thinking, remembering, and learning are common after severe COVID-19 infection, according to new research.

These long-term effects of COVID-19 could "significantly increase the worldwide dementia burden,” says study leader Yan-Jiang Wang, MD, PhD, director of the Department of Neurology and Center for Clinical Neuroscience at Daping Hospital in Chongqing, China.

The study, which compared rates of dementia and its precursor, mild cognitive impairment, in people who recovered from COVID-19 to people who didn’t get infected, was published online March 8 in JAMA Neurology.

The researchers identified nearly 1500 people age 60 and older who’d been hospitalized for COVID-19 in Wuhan, China, 260 of whom had severe illness, and followed up with them 6 months and 1 year later to assess their cognitive function. The researchers also assessed the cognitive function of over 400 spouses of the hospitalized people who did not get COVID-19, as a comparison group.

Before they were infected with COVID-19, none of the study participants had cognitive problems, a neurological disorder or a family history of dementia, or severe heart, liver or kidney disease or cancer.

A year after leaving the hospital, 12.5% of the COVID-19 survivors had developed cognitive problems.

Dementia and mild cognitive impairment were significantly more common in people who’d had severe COVID-19 than in ones who’d had cases that weren’t severe or didn’t get the disease.

About 15% of the people with severe COVID-19 had dementia a year after leaving the hospital, and about 26% had mild cognitive impairment.

Fewer than 1% of the people hospitalized with cases of COVID-19 that weren’t severe and those who didn’t get the disease developed dementia, and about 5% of the people in each group developed mild cognitive impairment.

Cognitive issues are common when a person is sick with COVID-19. However, the long-term consequences of COVID-19 on mental abilities remain unclear. This study adds new information about changes in the cognition of COVID-19 survivors, Wang says.

Of note, say the researchers, is the fact that 21% of people with severe COVID-19 had progressive cognitive decline, suggesting that the disease may cause long-lasting damage to mental abilities.

"These findings imply that the pandemic may substantially contribute to the world dementia burden in the future," they add.