No significant associations were observed in meta-regression between the effect size and age (t = 0.10, p = 0.92), sex distribution (t = − 0.64, p = 0.54), publication year (t = − 1.54, p = 0.14), number of participants (t = 0.33, p = 0.75), CRP (t = 1.06, p = 0.31), ESR (t = 1.70, p = 0.12), RA duration (t = 0.83, p = 0.43), or use of DMARDs (t = − 0.54, p = 0.60) and glucocorticoids (t = − 0.87, p = 0.41). The gene discussed is ESR1; the disease is rheumatoid arthritis.