Dietary Long-Chain n-3 Fatty Acid Intake and Arthritis Risk in the Women's Health Initiative.

BACKGROUND: The prevalence of arthritis in the United States is substantial and on the rise. Long-chain n-3 polyunsaturated fatty acids, which have anti-inflammatory properties, have been shown to provide therapeutic benefit to arthritis patients; however, to date few have examined these associations with arthritis risk.

OBJECTIVE: The study objective was to examine the associations of long-chain n-3 polyunsaturated fatty acids intake with osteoarthritis (OA) and rheumatoid arthritis (RA) risk among postmenopausal women.

DESIGN: This was a prospective cohort study.

PARTICIPANTS: The sample for this analysis consisted of 80,551 postmenopausal women, aged 55 to 79 years and with no history of arthritis, recruited into the Women's Health Initiative Observational Study and Clinical Trials cohort between 1993 and 1998. Women completed a 120-item food frequency questionnaire at baseline.

MAIN OUTCOME MEASURES: After a median follow-up of 8 years, 22,306 incident OA and 3,348 RA cases were identified.

STATISTICAL ANALYSES PERFORMED: Adjusted Cox regression models were used to estimate hazard ratios and 95% CI for the associations between dietary LCn-3PUFA intake and OA and RA risk.

RESULTS: Individual and total long-chain n-3 polyunsaturated fatty acids (Quintile 5 vs Quintile 1: hazard ratio 1.04, 95% CI 0.99 to 1.09 for OA; hazard ratio 1.01, 95% CI 0.90 to 1.13 for RA) were not associated with OA and RA risk. Further, no associations were observed between n-6 polyunsaturated fatty acids intake and either arthritis outcome.

CONCLUSIONS: This study is the first to examine associations of long-chain n-3 polyunsaturated fatty acids intake with OA risk and the largest to examine associations with RA risk. Despite their therapeutic potential, the study provides no evidence of benefit of these nutrients in relation to arthritis risk.