MANY people who have had COVID-19 battle 'brain fog' in the weeks or months following.
But a new study sought to measure the illness' effect on people whose brain function had already begun deteriorating.
A group of researchers from universities in India and Spain monitored 14 people who'd had Covid, who also had pre-existing dementia diagnoses.
"Most cognitive post-COVID-19 studies have been performed on previously healthy individuals without any cognitive impairment prior to the COVID-19 infection," they wrote in the Journal of Alzheimer's Disease Reports.
They found their dementia had rapidly progressed a year after falling sick.
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Four participants had Alzheimer's, five had vascular dementia, three suffered from Parkinson’s disease dementia, and two from the behavioural variant of frontotemporal dementia.
Researchers assessed their cognitive functioning, using a few different tests that gave a picture of participants' attention and language capabilities, memory, fluency and perception of space.
They performed these roughly three months before the patients got Covid and roughly a year afterwards, to compare how the virus had affected their brain function.
Researchers also performed MRI brain scans on the dementia patients pre- and post-Covid.
The patients experienced increase in fatigue and depression in the year after catching the virus.
Depression is very common in people with dementia, according to the researchers, especially in Alzheimer’s disease and vascular dementia.
The participants' attention, memory, fluency, language and sense of space also worsened, and brain scans showed 'significant' brain deterioration in a way that is typical of dementia.
"Slowly progressive dementias like Alzheimer’s disease and vascular dementia, which usually have a fluctuating course, showed relatively unusual significant, relentless, and rapid progression in terms of deterioration [...] at one year post-COVID-19," the team observed.
"All 14 patients, one year after SARS-CoV-2 infection, had fatigue, depression, objective attention/concentration difficulties, executive dysfunctions, slowed information processing speed, and sub-cortical type memory impairments, irrespective of their previous cognitive status," they added.
Previous studies have revealed that the risk of developing Alzheimer’s disease almost doubles in older people for up to one-year after having Covid.
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The Sun has also reported that patients suffering with dementia are three times more likely to develop a severe case of coronavirus.
Studies show that one in 20 people who catch Covid may permanently lose their sense of smell or taste (anosmia).
But research has warned that losing sense of smell may be a signal for dementia.