Association of Diet Quality With Risk of Incident Rheumatoid Arthritis in the Women's Health Initiative.

Background: Various foods and nutrients are linked with higher or lower risk of rheumatoid arthritis (RA), yet these associations are inconsistent across studies. Limited research has been done evaluating the association between diet quality and RA in a larger-scale prospective study on postmenopausal women.

Objective: The objective of this study was to evaluate the association between dietary quality and risk of incident RA in postmenopausal women.

Design: This was a prospective cohort study as part of the Women's Health Initiative (WHI), with an average follow-up time of 8.1 years. Baseline diet was measured using a food frequency questionnaire (FFQ). Diet quality was evaluated by the Healthy Eating Index (HEI)-2015 total score. In addition, intake of food groups and nutrients that align with HEI-2015 components was assessed.

Participants/setting: Postmenopausal women (N = 109 591) were included in this study, which was conducted at various clinical centers across the United States with recruitment from 1993 to 1998. Women's Health Initiative participants who were missing outcome data, had unreliable/missing FFQ data, or had RA at baseline were excluded.

Main Outcome Measures: The primary outcome measure was incident RA. Statistical analyses performed Multivariable Cox proportional regression analysis was performed evaluating the association of diet quality with self-reported physician-diagnosed RA after adjusting for age, race, ethnicity, education status, income, and body mass index (BMI).

Results: During 857 517 person-years of follow-up, 5823 incident RA cases were identified. After adjustment for multiple comparisons, compared with quartile 1, quartiles 2, 3, and 4 of the HEI-2015 total scores were associated with lower RA risks of 1%, 10%, and 19%, respectively (P-trend < .001). Greater consumption of total fruits (P-trend = .014), whole fruits (P-trend < .0002), total vegetables (P-trend = .008), greens and beans (P-trend < .0002), whole grains (P-trend = .008), and dairy (P-trend = .018) were significantly associated with lower rates of incident RA. Conversely, higher consumption of saturated fat (P-trend = .002) was significantly associated with higher rates of incident RA.

Conclusion: A higher-quality diet reflected by higher HEI-2015 total scores was inversely associated with incident RA in postmenopausal women.