A cohort study on the associations between age at natural menopause and rheumatoid arthritis in postmenopausal women from the Canadian Longitudinal Study on Aging.

Menopause represents a significant phase in a woman's life, marked by profound physiological changes. An early onset of menopause has been associated with a variety of negative outcomes. Estrogen has been shown to be protective of bone and joint health. Hormonal links to rheumatoid arthritis have been found; previous studies exploring age at natural menopause (ANM) and Rheumatoid arthritis have produced conflicting results. This study investigated the association between ANM and incidence of rheumatoid arthritis among postmenopausal Canadian women. The study included women between the ages of 45-85 years from the Canadian Longitudinal Study on Aging followed over a 10-year period. Analysis was restricted to naturally postmenopausal women that did not have rheumatoid arthritis prior to menopause. ANM was examined using the following categories ≤ 44 (reference), 45-49, and ≥50. Survival analysis was used to determine time to onset of rheumatoid arthritis. Unadjusted and adjusted multivariable Cox regression models were used to examine the relationship between ANM and incidence of rheumatoid arthritis. The adjusted multivariable Cox regression model showed significantly lower risk of rheumatoid arthritis in women with an older ANM of ≥50 years and who have been on hormone replacement therapy for ≥8 years with a hazard ratio of 0.2 (95 % CI: 0.1-0.7) compared to women with an ANM ≤ 44 who have never used hormone replacement therapy. Our findings suggest a potential beneficial effect of longer estrogen exposure on the risk of developing rheumatoid arthritis.