The aim of the present study was to examine the associations between circulating carotenoids and future risk of rheumatoid arthritis (RA).
We conducted a nested case-control study consisting of 227 incident RA cases and 671 matched controls with prospectively measured plasma carotenoids (α-carotene, β-carotene, β-cryptoxanthin, lycopene and lutein/zeaxanthin) levels in the Nurses' Health Study (NHS) and Nurses' Health Study II (NHS II). Each incident RA case was matched with 3 healthy controls. Serologic phenotype of RA was determined by rheumatoid factor or anti-citrullinated peptide antibody (ACPA) obtained by chart review. Multivariable logistic regressions were used to estimate odds ratios (OR) and 95% confident intervals (95% CI) for RA risk associated with each circulating carotenoid after adjusting for matching factors and other covariates.
The median time from blood draw until RA diagnosis was 8.6 years. In the multivariable models, no significant associations were found between any plasma carotenoids and risk of RA. We further examined the associations for two subtypes of RA, and found associations of circulating α-carotene and β-carotene with reduced risk of seronegative RA. After correction for multiple comparisons using the Bonferroni method, the findings did not reach statistical significance.
Circulating carotenoids levels are not associated with reduced risk of RA. Further investigations using large prospective cohorts are needed to confirm our findings.