Soft water exposure increases the effect of genetic susceptibility on the risk of rheumatoid arthritis
Authors' conclusion
These results suggest that exposure to hard water may reduce the risk of RA, particularly in individuals with high genetic susceptibility.
Study context
- Population
- Rheumatoid arthritis (RA)-free individuals with complete data on water mineral levels, genetic profiles, lifestyle factors and physical measurements at baseline5,880 new RA cases
- Participants
- 434,958 individuals
- Exposure
- Higher vs lower calcium carbonate concentration in domestic water; Polygenic risk score (PRS) tertiles; combined PRS and water hardness categories
- Outcome
- Incident RA
Methodological detailsCox regression, stratified analyses, multiple sensitivity analyses
- Cox regression
- Stratified analyses
- Multiple sensitivity analyses
Main finding
As reported in the abstract
Incident RA by calcium carbonate concentration in domestic water · median follow-up 15 years
Higher calcium carbonate concentration in domestic water, HR (95% CI 0.90 to 0.95; p = 1.74 × 10-9), adjusted for multiple covariates
0.93
Observational data: associations, not effects.
Further findings
Incident RA by PRS: highest vs lowest tertile
- Increased risk of RA in highest vs lowest PRS tertile
- 53 % to 74 %
Incident RA: highest PRS with soft water vs lowest PRS with very hard water
- Increased risk of RA
- 92 % (95% CI 71 % to 115 %)
Original publication
Soft water exposure increases the effect of genetic susceptibility on the risk of rheumatoid arthritis. Semin Arthritis Rheum. Published 16 July 2025. doi:10.
Composed by AI from the published abstract and checked against it. How Briefs are made →