Inflammation and Alzheimer's disease
While inflammatory biomarkers showed evidence for causal associations with inflammatory diseases, evidence was weak that a common inflammatory biomarker affected both inflammatory disease and Alzheimer's disease.
What is the current knowledge on this topic?
Links between brain disorders and inflammation have been reported in scientific research. For example, the brains of dementia patients show a sustained brain innate immune response. On the other hand, higher levels of blood inflammatory biomarkers were observed in Alzheimer’s disease (AD) patients compared to healthy individuals. Observational studies and meta-analyses have reported a higher risk of dementia among patients with inflammatory diseases. However, whether chronic autoimmune inflammatory diseases causally affect the risk of AD remains controversial.
What is the research question(s) and aim(s) of this study?
We performed observational analyses for chronic autoimmune inflammatory diseases and the risk of AD using clinical data from the UK Clinical Practice Research Datalink (CPRD). We also used data from a total of more than 1,100,000 individuals from large-scale genome-wide association study (GWAS) datasets, and performed two-sample Mendelian randomisation (MR) to investigate the relationships between chronic autoimmune inflammatory diseases, circulating inflammatory biomarker levels, and risk of AD.
What did we find?
Our data suggest that the associations between inflammatory diseases and risk of AD are unlikely to be causal. In support, while inflammatory biomarkers showed evidence for causal associations with inflammatory diseases, evidence was weak that a common inflammatory biomarker affected both inflammatory disease and AD.
For more details, see Huang J, Su B, et al. Inflammatory Diseases, Inflammatory Biomarkers, and Alzheimer Disease: An Observational Analysis and Mendelian Randomization. Neurology. 2022.