Causality between coffee intake and bone health: A Mendelian randomization study

Observational studies have reported associations between coffee intake and osteoarthritis (OA), rheumatoid arthritis (RA), and osteoporosis (OP). However, it remains unknown whether these relationships are causal. In this study, we applied a 2-sample bidirectional Mendelian randomization (MR) analysis to comprehensively evaluate the causal association between coffee intake and OA, RA, and OP. Genetic data for OA (40,425 controls and 10,083 cases), RA (22,350 controls and 74,823 cases), OP (476,847 controls and 7751 cases), and coffee intake (263,464 Europeans) were obtained from the UK Biobank. The causal relationship between coffee intake and OA-, RA-, and OP-related traits was investigated using 2-sample MR analysis with a pooled dataset from genome-wide association studies. Inverse variance weighting (IVW) was used as the main outcome, whereas MR-Egger and weighted median were used to supplement the IVW estimates. Heterogeneity was assessed using Cochran Q statistic. Confounding-related single-nucleotide polymorphisms and single-nucleotide polymorphisms with P < .05 in MR-PRESSO analysis were excluded. There was no evidence of a causal relationship between coffee intake and the risk of RA (odds ratio [OR]: 0.84; 95% confidence interval [CI]: 0.24-2.93) using the IVW with random effect. Genetic predisposition to coffee intake was not associated with OA (OR: 1.21; 95% CI: 1.01-1.45) and OP (OR: 1; 95% CI: 0.99-1.0) using the main IVW method. Reverse MR analysis did not reveal evidence of a significant causal effect of OA, RA, and OP on coffee intake. Our findings do not support a causal relationship between coffee intake and the risk of OA, RA, and OP.