Associations between exposure to phthalates and rheumatoid arthritis risk among adults in NHANES, 2007–2016

The etiology of rheumatoid arthritis (RA) is multifactorial, encompassing genetics and environment. Despite the widespread use of phthalates as chemical additives, their potential impact on RA has received limited investigation. This study aimed to evaluate the potential associations between exposure to phthalates and rheumatoid arthritis risk among adults. Participants ≥20 years were analyzed from the National Health and Nutrition Examination Survey (NHANES) 2007–2016. Multivariable logistic regression was used to examine the association between exposure to phthalates and RA in two models. Additionally, subgroup analyses stratified by gender and age were also performed. The nonlinear relationship between RA and phthalates was characterized by smooth curve fittings and generalized additive models. Ultimately, 9322 participants (RA: 601, without RA: 8632) were analyzed. The prevalence of RA increased with higher quantiles of MECPP (Q4, OR: 1.43, 95% CI: 1.07–1.91), MBP (Q2, OR: 1.30, 95% CI: 1.01–1.67), MEHHP (Q3, OR: 1.39, 95% CI: 1.07–1.81; Q4, OR: 1.35, 95% CI: 1.02–1.87) and MEOP (Q2, OR:1.35, 95% CI: 1.03–1.76) compared to the lowest quartile. A nonlinear relationship positive association was also observed between MECPP (P for non-linearity = 0.0074)) and MEHHP (P for non-linearity = 0.0046)) levels and RA. Subgroup analysis showed the association between phthalate levels and RA was mainly present in males or participants aged more than 60 years. Our results demonstrated that exposure to phthalates is associated with an increased prevalence of RA among adults. Notably, such associations appear to be more pronounced in males and older people.