Breastfeeding and risk of rheumatoid arthritis

Abstract

University of Washington Abstract Breastfeeding and risk of rheumatoid arthritis Bonny Chau Chair of the Supervisory Committee Daniel A. Enquobahrie Departments of Epidemiology and Health Services We analyzed data previously collected as part of the Oral Contraceptives Rheumatoid Arthritis (OCRA) study to investigate whether breastfeeding among women is associated with risk of new onset RA. This is a population-based case-control study with 231 cases and 1,093 controls. We used odds ratios (OR) and corresponding 95% confidence intervals (CI) from logistic regression models to assess associations of history of breastfeeding and duration of breastfeeding with new onset of RA. We fitted three models: unadjusted model, partially adjusted model (adjusted for age, race, oral contraceptive use, parity, and length of time between RA onset or reference date and last pregnancy), and a fully adjusted model (adjusted for variables included in the partially adjusted model as well as education, income, and smoking). Among cases, 68% had a history of breastfeeding while among controls, 72% had a history of breastfeeding. Women with a history of breastfeeding had similar risk of new onset RA, compared with women who had no history of breastfeeding in all models: unadjusted (OR: 0.82, 95%CI: 0.60-1.11), partially adjusted (OR: 0.84, 95%CI: 0.61-1.16), and fully adjusted (OR: 0.89, 95%CI: 0.64-1.23). Duration of breastfeeding was inversely associated with new onset RA in the unadjusted model (p-value for trend = 0.031), although the association was attenuated in the partially adjusted (p-value for trend = 0.053) and fully adjusted (p-value for trend = 0.150) models. In this study population, we found suggestive evidence that duration of breastfeeding, but not history (yes/no) of breastfeeding, may be inversely associated with new onset of RA. Future larger studies in diverse populations are needed to better examine the relationship between breastfeeding and RA. Findings can contribute to better understanding of risk factors of RA and identifying populations who are at higher risk.