Cognitive decline is common after COVID-19 infection, in new findings that provide much-needed information on the long-term dynamic trajectory of cognitive changes after COVID-19.

“We found that COVID-19, especially severe COVID-19, was associated with an increased risk of post-infection cognitive impairment and a faster speed of longitudinal cognitive decline,” Yan-Jiang Wang, MD, PhD, professor and director, Department of Neurology and Center for Clinical Neuroscience, Daping Hospital, Chongqing, China told Medscape Medical News.

What’s “most concerning,” said Wang, is that COVID-19 would “significantly increase the worldwide dementia burden in the post-COVID-19 era.”

The study was published online March 8 in JAMA Neurology.

Cognitive Consequences

The findings are based on 1438 COVID-19 survivors (48% male; median age, 69 years), including 260 with severe illness and 1178 with nonsevere illness, discharged from three COVID-designated hospitals in Wuhan, as well as 438 uninfected controls (51% male; median age, 67 years).

Before they were infected with COVID-19, none of the study participants had cognitive impairment; a concomitant neurological disorder or a family history of dementia; or severe cardiac, hepatic, or kidney disease or malignancy.

At 12 months postdischarge, 12.5% of COVID-19 survivors had developed cognitive impairment, defined by a Telephone Interview of Cognitive Status-40 score (TICS-40) of 20 or lower.

At 6 months, 10% of those with severe COVID-19 had dementia and at 12 months 15% had dementia. At 6 and 12 months, about 26% of patients who survived severe COVID-19 had mild cognitive impairment (MCI). 

The incidence of dementia and MCI was significantly higher in these severe COVID cases than in the nonsevere cases and controls.

In adjusted analysis, severe COVID-19 was associated with a higher risk of early-onset cognitive decline (odds ratio [OR], 4.87; 95% CI, 3.30 – 7.20), late-onset cognitive decline (OR, 7.58; 95% CI, 3.58 – 16.03), and progressive cognitive decline (OR, 19.00; 95% CI, 9.14 – 39.51), and nonsevere COVID-19 was associated with a higher risk of early-onset cognitive decline (OR, 1.71; 95% CI, 1.30 – 2.27).

Cognitive complications are common in the acute phase of COVID-19. However, the long-term consequences of COVID-19 on cognition remain unclear. This study adds novel information about the dynamic change in the cognition of COVID-19 survivors, Wang told Medscape Medical News.

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

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

“As survivors of severe COVID-19 are at high risk in developing long-term cognitive impairment, measures should be taken to protect the brain at acute stage of infection and to prevent the cognitive decline after hospital discharge,” Wang told Medscape Medical News.

This study is supported by the National Natural Science Foundation of China. The authors have disclosed no relevant financial relationships.

JAMA Neurology. Published online March 8, 2022. Full text

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