However, experts said it was not clear whether Covid raised the risk of brain disorders or if people with early undiagnosed conditions were more likely to catch Covid or have symptoms spotted by doctors. Researchers analysed the health records of more than half of the Danish population, including 43,000 who caught Covid.
The jump in risk after Covid was roughly the same as seen for flu and pneumonia.
Dr Pardis Zarifkar, of Rigshospitalet, a specialist hospital in Copenhagen, said: “More than two years after the onset of the Covid-19 pandemic, the precise nature and evolution of the effects of Covid-19 on neurological disorders remained uncharacterised.”
“Reassuringly, apart for ischemic stroke, most neurological disorders do not appear to be more frequent after Covid-19 than after influenza or community-acquired bacterial pneumonia.”
“These findings will help to inform our understanding of the long-term effect of Covid-19 on the body and the role that infections play in neurodegenerative diseases and stroke.”
Dr Zarifkar said there was a theory that neuroinflammation could lead to accumulation of proteins that play a role in some brain disorders.
But patients who have had Covid may also have more contact with doctors, making it more likely that other symptoms are spotted, leading to a diagnosis.
Dr Sara Imarisio, head of research at Alzheimer’s Research UK, said diseases like Alzheimer’s take many years to develop and Covid has only been circulating in Europe for around two years.
She said: “It may be that people in the very early stages of Alzheimer’s are more susceptible to catching diseases like Covid-19.”
“While the announcement of these findings is potentially concerning, we will need to see results of this study in a peer-reviewed publication before we can draw any real conclusions from this research.”
“If anyone is worried about their memory and thinking, or long-term effects of Covid-19, they should consult with their doctor.”
The findings were presented at the European Academy of Neurology Congress.
Meanwhile, people are being urged to get up to date with Covid jabs as a new wave of infections looms.
Some 1.7 million people were estimated to have had the virus across the UK last week, up almost a quarter from the previous week.
Infections are now at levels last seen at the end of April, according to the Office for National Statistics.
The UK Health Security Agency said new Omicron subvariants called BA.4 and BA.5 were driving the increase and now account for more than half of cases.
BA.5 is spreading 35 percent faster than the previous BA.2 strain, and BA.4 19 percent faster.
Data shows 17.5 percent of over 75s have not had a vaccine in the past six months, putting them at higher risk of severe illness.
Professor Susan Hopkins, chief medical advisor at the UKHSA said: “It is clear that the increasing prevalence of Omicron BA.4 and BA.5 are significantly increasing the case numbers we have observed in recent weeks.”
“We have seen a rise in hospital admissions in line with community infections but vaccinations are continuing to keep ICU admissions and deaths at low levels.”
“As prevalence increases, it’s more important than ever that we all remain alert, take precautions, and ensure that we’re up to date with Covid-19 vaccinations, which remain our best form of defence against the virus.”
“It’s not too late to catch up if you’ve missed boosters, or even first doses so please take your recommended vaccines.”