The Causal Association between Alcohol, Smoking, Coffee Consumption, and the Risk of Arthritis: A Meta-Analysis of Mendelian Randomization Studies

Wang J, Zhang B, Peng L, Wang J, Xu K, Xu P · Nutrients

Pools the genetic evidence for three habits at once. Alcohol: no causal association with arthritis (OR 1.02, 95% CI 0.94-1.11). Smoking: positive (OR 1.44, 1.27-1.64), holding for both OA (1.44, 1.22-1.71) and rheumatoid arthritis (1.37, 1.26-1.50). Coffee: positive but very small for OA (OR 1.02, 1.00-1.03), larger for RA (1.56, 1.19-2.05).

Population

84 Mendelian randomization studies assessed, 11 pooled, plus the authors' own MR analyses across four lifestyle exposures and five arthritis outcomes

Intervention

Genetically predicted alcohol intake, smoking, and coffee consumption

Comparator

Lower genetically predicted exposure

Limitations

Pooling Mendelian randomization studies pools their shared weaknesses: overlapping GWAS samples, instruments for self-reported consumption behaviours, and near-total European ancestry. A coffee odds ratio of 1.02 with a lower bound of 1.00 is statistically positive and biologically negligible.