Deeply confused and distressed,they would,often shouting and screaming.
“You’re having these horrible nightmare-like hallucinations,that people are going to kill you. Or that you’re already dead,” says Associate Professor Peter Lange,director of geriatrics at Werribee Mercy Hospital,and an expert in delirium.
“It’s really a nightmarish state ... It just goes on for days and days.”
Associate Professor Michael Woodward,medical adviser for Dementia Australia.Jason South
Two years later,delirium is now well established as a of COVID-19. But could this state of acute confusion be the canary in the coalmine for deeper damage being done to the brain by the virus?
Scientists are now debating whether COVID-19 increases a person’s risk of dementia.
“It’s absolutely true,” says Associate Professor Michael Woodward,Dementia Australia’s medical adviser and spokesman. “There are about five different big studies that have shown an increased risk.
Residents of St Basil’s aged care home are evacuated to hospitals in July 2020 after a cluster of COVID-19 cases at the home.Justin McManus
“I would expect we would see more cases of dementia and Alzheimer’s as a result of people developing COVID — and not just long COVID either.”
If that is true,it has big implications both for individuals and for society at large. There are – and that number is projected to swell to about 850,000 by 2058.
Even a small increase in dementia risk could mean tens of thousands more Australians living with the disease — terrible for them and their families,and overwhelming for the country’s health system. “These are massive numbers,” says Woodward.
But other experts say the data is being misread. “I’m very sceptical of these findings,” says Associate Professor Stephen Macfarlane,head of clinical services at the Dementia Centre.
The data
In August,medical journal theLancetthe results of a two-year study of 1.4 million people. Measured two years after contracting COVID-19,4.5 per cent of people over 65 had been diagnosed with dementia — compared to 3.3 per cent in the control group of people who had other respiratory infections.
A second paper,,revealed in regions linked to decision-making and memory in people who had contracted COVID.
“It would be reasonable to suspect that contributes to reduced cognitive function they observe in these patients,” says Professor Bryce Vissel,head of the Centre for Neuroscience and Regenerative Medicine at St Vincent’s Hospital.
A third line of evidence comes from COVID’s link with known risk factors for dementia.
A slowdown and fuzziness in thinking over many years often predates a dementia diagnosis. tracking 1438 older COVID-19 survivors found they scored lower on a cognitive telephone test six and 12 months after diagnosis.
Professor Bryce Vissel.Nick Moir
“We don’t yet know if it’s going to increase the rates of dementia. But we do know it’s having long-term effects on subpopulations on memory function,and we do know it’s increasing the rate of dementia in the elderly after they have had a COVID infection,” says Vissel.
And we know falling into a state of delirium is a for later being diagnosed with dementia.
But that raises other scientists’ scepticism. Is it possible COVID-19 is causing delirium in those already vulnerable — andthereforemaking doctors more alert to signs of dementia?
“Any infection can unmask dementia in a cognitively vulnerable older person,” says the Dementia Centre’s Macfarlane.
And patients with undiagnosed dementia may be less likely to take actions to prevent themselves catching the virus. They are more likely to catch the virus,more likely to be seen by a doctor,and therefore more likely to be diagnosed with dementia.
Possible mechanisms
Why would an infection of the airways cause dementia? Possibly because the brain is vulnerable to the very symptoms it causes – inflammation and oxygen deprivation.
Inflammation is the body’s natural response to infection. It should go away after the virus is beaten — but in some people it hangs around for far too long. COVID-19 is also known to infect the nerves of the nose,which run directly into the brain — and there is in brain regions that connect to these nerves.
“It’s very clear inflammation is bad for your brain. Low levels of oxygen are bad for the brain. That’s undisputable,” says the Mercy Hospital’s Lange.
But there are mysteries here too. Changes in the brain leading to common forms of dementia typically occur decades before symptoms become apparent. For COVID to cause dementia within a year “seems biologically implausible”,says Macfarlane.
Those long years before dementia presents itself also hinder our ability to truly know what COVID is doing to the brain. “COVID is too new,” says Professor Lezanne Ooi,head of the neurodevelopment and neurodegeneration lab at the University of Wollongong. “I don’t think we can really address that at this point in time.”
It remains a mystery – to be confronted by our future selves.
Liam Mannix’s Examine newsletter explains and analyses science with a rigorous focus on the evidence..