The Daily Observer London Desk: Reporter- John Furner
A new study has added fuel to concerns that America could face a surge in dementias in coming years and decades due to COVID.
The research found that nearly two-thirds of people over 65 who were hospitalized with the virus went on to suffer cognitive decline, which can be a precursor for dementia, weeks and months after the infection cleared.
Independent experts told Media.com this is a trend they’re watching closely, since if there is a link, it could affect the millions of older adults who were infected with the virus.
CDC data shows that over-65s accounted for nearly half of hospitalizations in the first two years of the pandemic, or roughly 1.7m people. The new study stops short of concluding that COVID and dementia are definitively linked, but experts described the evidence as ‘compelling’.
The study looked at people over 65 who were hospitalized with COVID-19 in 2020. This means their study population was very sick, and its difficult to say how people with less severe illness might be affected
Data from the CDC’s COVID-Net lab showed the cumulative amount of COVID hospitalizations from 2021 to 2022. Studies have estimated that roughly 1,701,300 people over 65 were hospitalized in this year
The researchers from the University of New South Wales reviewed 18 older studies as part of their paper.
It is available as a pre-print in the journal Ageing Research Reviews, which means that is has yet to be reviewed by other scientists.
The review looked at about 412,900 participants hospitalized with COVID-19 and 411,900 healthy participants – both groups only involved people over age 65. They included data from Europe, North America and Asia.
Most of the studies included in the review looked at trends from 2020 and 2021, before vaccinations were made widely available. The studies didn’t report vaccination status, what strain of COVID the patients had or whether or not they used personal protective equipment.
They were tested for their brain health by taking cognitive assessments which measures an individual’s memory, attention span, language skills, spatial orientation and visual skills, in both written and verbal formats.
Roughly 65 percent of over-65s in the study who were hospitalized with the virus had some degree of mild cognitive impairment, a brain-fog like condition which can sometimes be a precursor to dementia.
Some of the studies reported that this was evidence of new onset dementia, but Dr Vin Gupta, a pulmonologist and public health physician not involved in the research, told Media.com that it’s difficult to know if that’s accurate since they didn’t have information about the patients before they had COVID.
Researchers aren’t sure why COVID could be causing these changes in the brain, but theorize it could have to do with inflammation or changes in blood flow, Dr Gupta said.
Dr Gupta and other independent experts have also raised concerns about the study, however. The study failed to rule out other factors that add to dementia risk, like high blood pressure, heart disease and obesity.
‘This is another study that is directional and adds some incremental insights as to what might be happening with COVID and its impacts on human organ function, but I think it’s far from definitive,’ he said.
Dr Eve Elizabeth Pennie, general practitioner and medical contributor for Drugwatch who was not involved with the research, told Media.com that she found similar weaknesses in the study.
However, it is adding more evidence to a trend that public health experts have been watching.
‘Given the growing evidence from similar studies, the findings are compelling and somewhat expected,’ Dr Pennie said.
No prior studies have concluded that COVID-19 causes dementia, but multiple previous studies have shown that there may be a link between the two, Dr Gupta said.
Many diseases come with secondary side effects – like the link between chicken pox and shingles.
Therefore, it’s reasonable to suspect that this virus might have some downstream affects, experts say.
In previous outbreaks of similar viruses like SARS in 2003 and MERS in 2012, researchers noted cognitive impairment was a side effect.
COVID-19 causes a host of changes across the body – including an increase in inflammation and changes to blood pressure and clotting, both of which may cause changes in the brain, the study authors wrote.
In addition, in rare cases, COVID-19 can also cause more severe neurological conditions like encephalitis, a swelling of brain tissue which kills or harms swaths of neurons.
It’s less clear how COVID-19 would be directly linked to dementia. The study authors suggest that the virus may increase the amount of beta-amyloid, a protein that builds up in the brain of Alzheimer’s patients, in the body.
Dementia has been linked to COVID by a number of studies. But finding a link is not the same thing as proving a cause, Dr Gupta cautioned
Otherwise, the changes in blood flow could cause frequent, small injuries to the brain tissue, depriving it of oxygen often enough to cause long term effects that might lead to dementia. Researchers aren’t sure yet which theory may explain this link, Dr Gupta said.
Dr Pennie noted that though these findings are in line with current trends, they come with some big caveats.
First, the paper didn’t control for pre-existing conditions like high blood pressure, diabetes and heart disease, all factors common in people over 65 that make one more likely to develop dementia.
Second, most of the studies included didn’t have data from before their patients got COVID-19.
This means that their cognitive impairment could’ve been there before they were infected with the virus, and it’s difficult to know what COVID actually caused in them.
Also, most of the data was collected in 2020, before widespread vaccination, and all of the patients included had a very severe case of the disease, since they were hospitalized for it.
This makes it impossible to apply what we learned here to the general population today, who are more likely to be vaccinated and have a less serious case of COVID-19 Dr Gupta said.
Taken together, though it points to some trends, Dr Gupta said ‘it’s a very weak study from a design standpoint.’
