Association Between Menopausal Factors and the Risk of Seronegative and Seropositive Rheumatoid Arthritis: Results From the Nurses' Health Studies

ObjectiveTo investigate whether menopausal factors are associated with the development of serologic rheumatoid arthritis (RA) phenotypes. MethodsData were analyzed from the Nurses' Health Studies (NHS; 1976-2010 and NHSII 1989-2011). A total of 120,700 female nurses ages 30-55 years in the NHS, and a total of 116,430 female nurses ages 25-42 years in the NHSII, were followed via biennial questionnaires on lifestyle and disease outcomes. In total, 1,096 incident RA cases were confirmed by questionnaire and chart review. Seropositive RA was defined as rheumatoid factor positive (RF) or antibodies to citrullinated protein antigen (ACPA) positive, and seronegative RA was defined as RF negative and ACPA negative. We used Cox proportional hazards models to obtain multivariable-adjusted hazard ratios (HRs) with 95% confidence intervals (95% CIs) of seropositive/seronegative RA associated with menopausal status, age at menopause, type of menopause, ovulatory years, and postmenopausal hormone therapy (PMH) use. ResultsPostmenopausal women had a 2-fold increased risk of seronegative RA, compared with premenopausal women (NHS: HR 1.8 [95% CI 1.1-3.0], NHSII: HR 2.4 [95% CI 1.4-3.9], and pooled HR 2.1 [95% CI 1.4-3.0]). Natural menopause at early age (44 years) was associated with an increased risk of seronegative RA (pooled HR 2.4 [95% CI 1.5-4.0]). None of the menopausal factors was significantly associated with seropositive RA. We observed no association between PMH use and the risk of seronegative or seropositive RA, except that PMH use of 8 years was associated with increased risk of seropositive RA (pooled HR 1.4 [95% CI 1.1-1.9]). ConclusionPostmenopause and natural menopause at an early age were strongly associated with seronegative RA, but only marginally with seropositive RA, suggesting potential differences in the etiology of RA subtypes.