People over 60 who survive COVID-19 have higher risks of dementia, mild cognitive impairment, and cognitive decline — particularly if they had severe COVID-19 — according to a study out this week in JAMA Neurology.
The study followed over 1,400 older COVID survivors in Wuhan, China, who were among some of the first people in the world to be hospitalized for COVID-19. The patients were discharged between February 10 and April 10, 2020, from three COVID-19 – designated hospitals in Wuhan. Researchers followed their neurological health for a full year afterwards.
Their experiences in that year do not bode well for the rest of the world. The study authors, led by neurologist Yan-Jiang Wang of the Third Military Medical University, found that long-term cognitive decline is common after an infection with the pandemic coronavirus, SARS-CoV-2. As such, health care systems around the world need to prepare for what could be a substantial increase in the number of people requiring dementia care.
For the study, researchers screened 3,233 COVID-19 survivors from the early days of the pandemic and 1,317 uninfected spouses who could potentially act as age- and demographics-matched controls. The researchers only included people in the study if they were over 60, had no preexisting cognitive impairment or any neurological condition linked to cognitive impairment, had no family history of dementia, and had no severe diseases, namely cancer or severe heart, liver, or kidney diseases.
In the end, the researchers found 1,438 COVID survivors and 438 uninfected controls who met the criteria and completed 12 months of follow-up. Of the survivors, 1,178 were categorized as having non-severe disease, and 260 had severe disease (defined as having at least one of the following: a respiratory rate higher than 30 breaths per minute, severe respiratory distress, or oxygen saturation less than 90 percent on room air). There were no significant differences between survivors and controls in age, sex distribution, education level, body mass index, or frequency of comorbidities, such as hypertension and diabetes.
In the follow-up period, researchers started by interviewing family informants on cognitive changes to get baseline data early in the study. They then assessed participants directly at six and 12 months using a preexisting telephone-based cognitive interview method, which is used to identify mild cognitive impairment (MCI) and dementia.
After the 12-month follow-ups, 12 percent of COVID survivors had cognitive impairment; specifically, 3 percent had dementia and 9 percent had MCI. Among just the survivors with severe disease, 15 percent had dementia at the end of the year and 26 percent had MCI. Among both the non-severe COVID survivors and the control group, the incidences of dementia and MCI were around 1 percent and 5 percent, respectively.
But apart from meeting clinical indications for dementia and MCI, the researchers also had a year’s worth of cognitive test results, which can reveal the cognitive trajectories of participants. The researchers broke these trajectories up into four categories: stable function, meaning stable scores in the first six months and second six months of follow-up; early-onset decline, meaning a decline in the first six months that was stable in the second; late-onset decline, meaning stable scores at first but declines in the last six months; and progressive decline, meaning declining scores throughout the year.
About 76 percent of people in the control group were categorized as having stable function in the study, while about 68 percent of non-severe COVID survivors and only 30 percent of severe COVID survivors had stable function. While non-severe COVID survivors fared well when looking at MCI and dementia rates, the trajectory analysis found they were at significantly higher risk than the control group of having early-onset cognitive decline. Risk modeling that adjusted for complicating demographic factors estimated that survivors of non-severe COVID were 71 percent more likely to have early-onset decline than uninfected controls.
Those who survived severe COVID, however, saw substantially increased risks in all three categories with declines. Compared with uninfected controls, survivors of severe COVID were nearly 5 times more likely to have early-onset decline, 7.5 times more likely to have late-onset decline, and 19 times more likely to have progressive decline.
As always, the authors acknowledge that the study has limitations. For one, in-person cognitive assessments may have offered more accurate results than the telephone-based assessments used. The researchers also would have liked to have cognitive assessments pre-dating COVID infections, as well as more people in their control group. They also note that the findings may not be generalizable because they screened out people with family histories of dementia. Thus, the study could underestimate risks in a general population that includes those with predispositions for dementia.
Still, the general conclusions of the study echo those from several others finding cognitive decline and higher risks of dementia following COVID-19. Overall, the authors conclude that their new findings “imply that the pandemic may substantially contribute to the world dementia burden in the future.”