A coronavirus infection can be incredibly concerning in high-risk groups, particularly the elderly, as its effects can be deadly, as the world has seen over the last couple of years. However, new research now suggests that an infection could result in highly problematic health conditions even if the patient survives, as a study from Denmark found that the likelihood of an Alzheimer's diagnosis is significantly higher in the 12 months after a COVID-19 infection.
Compared to non-infected people, infected people were 3.5 times more likely to be diagnosed with Alzheimer's disease by a doctor, Pardis Zarifkar and her team wrote in the Frontiers in Neurology journal.
However, two peers have questioned whether the coronavirus infection itself caused Alzheimer's in the research cases, and suggest that it may have simply triggered the symptoms of an already existing disease.
The team of researchers from the University Hospital of Copenhagen analyzed Danish health data and compared how often certain neurodegenerative diseases occurred in the period of one year in people with and without COVID-19 infections.
They found a similar correlation to Alzheimer's disease, for example, with Parkinson's disease and cerebral infarction.
The researchers emphasize, however, that for most of the diseases studied – including Alzheimer's – the effect was no greater than after influenza or bacterial pneumonia.
It has long been known that such respiratory diseases lead to inflammatory reactions that can increase a damaging effect on nerve cells in the brain, as Anja Schneider, research group leader at the German Center for Neurodegenerative Diseases (DZNE) told Deutsche Presse-Agentur (dpa).
The increased risk of diagnosis shown in the study could possibly be due to the fact that a coronavirus-induced inflammatory reaction accelerates the damage to nerve cells and symptoms become visible more quickly.
Peter Berlit, secretary general of the German Society for Neurology (DGN), told dpa that one cannot deduce from the study that a person has an increased risk of developing Alzheimer's at a later stage after a coronavirus infection.
It has only been shown that symptoms are diagnosed more frequently after an infection.
He points out that external factors – for example, losing one's familiar surroundings because one has to go to a clinic – can also cause an already existing Alzheimer's disease to become symptomatic.