To assess the association between dietary factors and risk of rheumatoid arthritis (RA) in a large prospective cohort.
Information about dietary intake was obtained from a detailed self-administered food frequency questionnaire completed by 57,053 individuals who participated in a prospective cohort. Linking the cohort to the Danish National Patient Registry we identified patients who developed RA. A rheumatologist scrutinized original medical records for these individuals in order to confirm the diagnosis of RA. Cox proportional hazards regression analyses were performed for dietary and lifestyle factors.
The average time of followup in the cohort was 5.3 years (range < 1 mo to 7.7 yrs). Sixty-nine individuals were identified with confirmed incident RA. In multivariate models each increase in intake of 30 g fat fish (> or = 8 g fat/100 g fish) per day was associated with 49% reduction in the risk of RA (p = 0.06), whereas medium fat fish (3-7 g fat/100 g fish) was associated with significantly increased risk of RA. Intake of fruit and coffee was not associated with risk of RA. Furthermore, no associations were found between risk of RA and intake of a range of other dietary factors including long chain fatty acids, olive oil, vitamins A, E, C, D, zinc, selenium, iron, and meat.
The limited number of patients who developed RA during followup of our large cohort prevented us from concluding that dietary factors are unimportant as risk factors for RA. It appears, however, that if dietary factors are important modifiers of RA risk, they must play a role more than a few years before clinical diagnosis.