Causal relationship between years of education and the occurrence of rheumatoid arthritis

Objective To search out whether or not years of education is causally related to rheumatoid arthritis (RA). Method We conducted a two-sample Mendelian randomisation (MR) analysis employing inverse-variance weighted (IVW), weighted median and MR-Egger regression analysis. We chose statistic data of years of education from the UK Biobank genome-wide association studies (GWASs) (n=293 723) as the exposure and a meta-analysis of GWASs of RA with autoantibody (n=5539) and European controls (n=20 169) as the outcome. Results We selected a total of 49 single nucleotide polymorphisms as instrumental variables (IVs). The IVW method instructed an inverse causative relationship between years of education and RA (β=- 0.039, SE=0.283, p=0.008). MR-Egger regression test showed that directional pleiotropy seems not to bias the MR results (intercept=0.028; p=0.358). MR-Egger analysis demonstrated no causative relationship between RA and years of education (β=- 2.320, SE=1.709, p=0.181). However, the weighted median approach indicated a causative association between RA and years of education (β=-0.950, SE=0.355, p=0.008). Conclusions The MR analysis supported a potential inverse causative relationship between years of education and development of RA.