| Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory disease affecting the joints and can result in severe pain and disability. RA affects about 1% of adults aged 15 and older and is more common in women than men. With the exception of smoking, risk factors for RA are uncertain. The three studies described herein assessed case definitions of RA and investigated the role of selected dietary factors on the risk of developing RA in African-American women, a population in which RA has been little studied. All three studies used data from the Black Women's Health Study (BWHS), a follow-up study of African-American women established in 1995.The first study evaluated the predictive value of three case definitions of RA, each based on self-reported data on RA diagnosis and use of arthritis medications. Subjects included a sample who reported an incident RA diagnosis on the 1999 or 2001 follow-up survey categorized according to reported medications: disease-modifying anti-rheumatic drugs (DMARDs), non-steroidal anti-inflammatory drugs (NSAIDs), or no arthritis medications. The DMARDs group had the highest positive predictive value of confirmed RA.The second and third studies investigated the relation between diet and risk of RA. Dietary factors were obtained from a food frequency questionnaire included in the BWHS baseline and 2001 questionnaires. Incident RA cases included women who reported RA on the 1997-2005 follow-up surveys, reported taking DMARDs, and did not report other rheumatic conditions.The second study prospectively evaluated the associations of coffee and tea consumption with risk of RA. We found no association between caffeinated coffee consumption and incident RA. Relative to those who drank <1 cup per week, the incidence rate ratio of RA for women who drank &ge 2 cups per day was 1.7 (95%CI 0.9-3.2) for decaffeinated coffee and 0.6 (95% CI 0.3-1.2) for tea.The third study prospectively examined the associations of vitamins A, C and E with risk of RA. Risk of RA decreased with increasing dietary intake of vitamin A, pro-vitamin A carotenes, and 13-carotene. For the highest relative to the lowest quartile, the IRR was 0.5 (95% CI 0.3-0.9) for pro-vitamin A carotenes. |
