The Link Between Viral Infections and Neurodegenerative Disease
Post by Megan McCullough
The takeaway
In a broad study of biobank health data, 45 different kinds of viral exposures were linked to the development of neurodegenerative disease. This builds on previous research that has linked viral infections with neurodegeneration.
What's the science?
Recent studies have linked an increased risk of developing multiple sclerosis with prior infection of the Epstein-Barr virus. The results of these studies linking viral infection with neurodegenerative disease (NDD), combined with current concerns about the long-term impacts of COVID-19 on cognition, have increased attention and funding towards this area of research. Although previous research has suggested a link between virus infections and the development of a neurodegenerative disease later in life, there are limited longitudinal data on the relationship between the timing of a viral diagnosis and the risk of developing NDD. This week in Neuron, Webb and colleagues aimed to investigate potential associations between viral exposures and developing a common NDD using open-source biobank data.
How did they do it?
The authors utilized health data from over 400,000 individuals from FinnGenn, a Finnish biobank, and from the UK biobank. The FinnGen cohort was used as the discovery set and the UK biobank data was used as the replication set. The authors combed through this dataset searching for individuals who had a diagnosis of either Alzheimer’s disease, ALS, dementia, vascular dementia, Parkinson's disease, or multiple sclerosis. The authors then checked if these individuals ever had a viral infection that had caused them to be hospitalized. Once the associations between NDD and a viral infection had been recorded from this dataset, the authors then searched the UK biobank for the same parameters. An example of an association is an individual diagnosed with Alzheimer's who also was hospitalized for viral encephalitis.
What did they find?
The authors found 45 associations of viral exposures with the development of an NDD in the FinnGenn biobank, with 22 of those associations also being found in the UK biobank. All viruses were associated with an increased risk of developing an NDD, and none showed a protective effect against NDD. Influenza and pneumonia were associated with five of the six neurodegenerative diseases, suggesting the risk of NDD increased after a severe case of those common infections. When associations were checked at different time points (between <1 and 15 years), many associations remained significant for up to 15 years (meaning, risk of an NDD was elevated for up to 15 years post-virus exposure). In general, however, there was a tendency for associations to be highest at the <1 year mark.
What's the impact?
This study is the first systematic investigation of the association between viruses and multiple neurodegenerative disorders. This research provides further evidence of the link between a serious viral infection and developing neurological problems later in life. Since many of the viruses included in this study have vaccinations that are known to reduce hospitalization rates of those infected, vaccinations may lessen the risk of developing neurodegenerative diseases.