Though Covid was originally thought to be a respiratory virus, it’s become increasingly clear that the virus can have serious consequences on brain health.
Many people have experienced neurological symptoms – like loss of taste and smell, headache and memory and attention issues – while infected, and most people who develop long Covid experience brain fog and cognitive problems like reduced concentration.
Now, new research suggests that Covid may increase our risk of developing brain disorders like Alzheimer’s disease, too. The study, which was published this month in the Journal of Alzheimer’s Disease, found that older adults who were infected with Covid had a 50 to 80% higher chance of developing Alzheimer’s compared to people who’d never had Covid.
Doctors don’t think that Covid directly causes Alzheimer’s as much as it unmasks underlying illness or speeds up disease that’s already simmering. Scientists are still learning about the ways in which Covid can impact our ability to learn, remember, focus and perceive, but research suggests that infections, in general, can have a serious impact on our cognitive function, not only in the short term but in the long term as well.
“These findings are not surprising to me since there is increasing understanding that medical stressors, from surgery to urinary tract infections, can lead to abrupt declines in cognitive abilities called ‘delirium’ or ‘encephalopathy,’ which is increasingly recognised as a risk factor for subsequent dementia diagnosis,” Dr Joshua Cahan, an assistant professor of neurology at Northwestern University Feinberg School of Medicine, tells HuffPost.
People who get Covid have a greater risk of cognitive impairment
The researchers evaluated the health records of 6.2 million adults age 65 and older who had received medical treatment between February 2020 and May 2020. At the start of the study, no one had previously been diagnosed with Alzheimer’s disease.
The individuals were split into two groups: people who had Covid (over 400,000) and people who had not (about 5.8 million). The research team found that that the risk of getting Alzheimer’s doubled, from 0.35% to 0.68%, among those who had Covid. The risk was greatest in women who were 85 and older.
According to the researchers, it’s unclear if Covid directly contributes to the development of Alzheimer’s disease or if it speeds up degenerative changes in the brain that are already in progress.
“This study shows the patients with dementia may be detected earlier due to Covid but does not suggest that the infection itself causes dementia,” says Dr Santosh Kesari, a neurologist at Providence Saint John’s Health Center in Santa Monica, California and the regional medical director for the Research Clinical Institute of Providence Southern California.
The researchers hope that future studies are able to uncover the specific pathways in which Covid impacts brain function so that more targeted treatments and prevention methods can be developed. Historically, it’s been difficult for scientists to develop treatments targeting cognition, according to Cahan.
While researchers are looking into various medications – like antivirals, stimulants and corticosteroids – the research is still in the early stages and it’s unclear how well these approaches help enhance cognition. “We have not firmly established the mechanisms of long Covid or Alzheimer’s so our approach to treatment is limited,” Cahan says.
How illnesses like Covid lead to cognitive decline
This isn’t the first study to find that infectious diseases are associated with cognitive decline. Past research shows that pneumonia, urinary tract infections, herpes virus infections, osteomyelitis and cellulitis have all been linked to a higher risk of dementia. According to Cahan, we also know that Covid can lead to major issues with attention and processing speed in certain patients.
Some experts believe that cognitive decline is caused by the widespread inflammation that certain infections, including Covid, trigger throughout the body. Higher levels of inflammation often go hand-in-hand with cognitive problems. According to Kesari, all that systemic inflammation caused by Covid can lead to brain inflammation — and research shows that brain inflammation is at the root of Alzheimer’s disease.
There’s also a possibility that there may be a buildup of the proteins related to Alzheimer’s disease in patients who are severely ill or hospitalised, according to some research.
“More long-term follow-up is needed to see if these proteins persist and progress, as would be expected in Alzheimer’s disease,” Cahan says. It’s unknown what, exactly, causes Alzheimer’s disease, which is one of the major reasons why it’s so hard for scientists to figure out how Covid may lead to the disease, Cahan adds.
Ultimately, while it’s clear that Covid and brain health are connected in some way, it’ll take more research – and time – to get a clearer understanding of how different diseases and infections impact brain health. “We are currently in the phase where information is accumulating that Covid-19 leads to cognitive impairment, but the mechanisms are unclear,” Cahan says.
How to mitigate cognitive decline after Covid
Cahan says when he sees patients seriously struggling with cognitive decline after recovering from Covid, he often refers them to occupational and speech therapy to help strengthen the parts of their brain that were weakened by the infection. Cognitive therapy, which is currently being investigated as a treatment for post Covid cognitive impairment, can also help people develop new strategies to improve their cognition.
Cahan also generally recommends that people gradually build their cognitive endurance after Covid, rather than going from zero to 100 right after recovering. A healthy diet, physical activity, social connections and stress management are crucial aspects of maintaining cognitive function as well, Kesari says.
If the cognitive problems persist, it’s worth checking in with a doctor to see if there’s anything else going on.
“All patients should undergo a thorough workup to look for other potential contributors like sleep disturbance, psychological distress, metabolic disorders, vitamin deficiencies all of which have specific treatments,” Cahan says.
Experts are still learning about Covid-19. The information in this story is what was known or available at the time of publication, but guidance could change as scientists discover more about the virus. To keep up to date with health advice and cases in your area, visit gov.uk/coronavirus and nhs.uk.