COVID‐19 and the risk of Alzheimer's disease, amyotrophic lateral sclerosis, and multiple sclerosis

BACKGROUND: The coronavirus disease 2019 (COVID‐19) pandemic has had an unprecedented impact on the healthcare system, economy, and society. Studies have reported that COVID‐19 may cause various neurologic symptoms, including cognitive impairment. We aimed to assess the causal effect of COVID‐19 on neurodegenerative diseases using two‐sample Mendelian randomization (MR) study. METHODS: Genetic variants were obtained from genome‐wide association studies (GWAS) summary‐level data and meta‐analyses. We used the inverse variance–weighted (IVW) method as the primary analysis to estimate causal effects. Sensitivity analyses were performed to make the conclusions more robust and reliable. RESULTS: We found that the COVID‐19 infection phenotype was associated with a higher risk of AD and inverse associated with the risk of ALS and MS. The hospitalized COVID‐19 phenotype was associated with the risk of AD and wasn't associated with ALS and MS. We also found that the severe COVID‐19 (main analysis) phenotype was associated with the AD outcome from UK biobank datasets but was not associated with other outcomes. The severe COVID‐19 infection phenotype, the severe COVID‐19 (subtype analysis) phenotype and the hospitalization risk of COVID‐19 were not associated with each outcome. CONCLUSION: This MR study suggests a potential association between genetically predicted COVID‐19 and a higher risk of AD and a reduced risk of ALS and MS. Further elucidations of this association and underlying mechanisms may inform public health messages to prevent COVID‐19 and AD.