Association between urinary DINCH concentration and rheumatoid arthritis: A cross-sectional study

The etiology of rheumatoid arthritis (RA) includes environmental factors, and although DINCH (cyclohexane-1,2-diisononyl ester) is considered less toxic than phthalates as a plasticizer, it has been associated with adverse clinical outcomes while its effect on RA remains unknown; this study therefore aimed to evaluate in adults the association between DINCH exposure and RA risk using data from the National Health and Nutrition Examination Survey (NHANES) 2013-2018, applying multivariate logistic regression, trend tests, mediation and subgroup analyses with sensitivity analyses for missing data, and found that among 4263 participants with complete data and 5189 with partial covariate missing data the prevalence of RA was higher in those with urinary DINCH concentrations > 1.0 ng/ml than in those with ≤ 1.0 ng/ml (OR = 1.44, 95 % CI = 1.02-2.03, P = 0.037; trend test P = 0.033), that DINCH may influence RA indirectly via vitamin D (mediation effect 4.7 %), and that this association was more evident in participants with low serum total vitamin D levels (OR 1.79, 95 % CI 1.09-2.94), suggesting that increased urinary DINCH concentration is associated with a higher prevalence of RA, particularly in individuals with low vitamin D.