Dietary intake of fish or marine omega-3 fatty acids does not have a protective effect against rheumatoid arthritis (RA), according to results published in BMC Musculoskeletal Disorders. Furthermore, the results indicated that fish intake reduced the strong association between smoking and RA diagnosed in patients younger than 55 years, but this association requires further study.

The study included women from 2 cohorts: the Nurses’ Health Study and the Nurses’ Health Study II (n=166,013). The researchers assessed fish intake using food frequency questionnaires at baseline and every 4 years. They used medical record reviews to determine incident RA and serologic status. The researchers used pooled Cox regression models to estimated hazard ratios (HRs) for RA for fish intake frequency. Additionally, they tested for a smoking-fish interaction for RA risk.

After analyzing 3,863,909 person-years of follow-up, the researchers identified 1080 incident cases of RA.

Compared with <1 serving of fish a month, increased fish intake of ≥4 servings per week was not associated with all RA (multivariable HR 0.93; 95% CI, 0.67-1.28; P =.42), seropositive RA (P =.066), or seronegative RA (P =.45).

Among women ≤55 years, those who ate fish frequently had HRs of 0.73 for all RA, 0.85 for seropositive RA, and 0.55 for seronegative RA compared with those who had infrequent fish intake.

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Ever smokers age ≤55 years with infrequent fish intake had a highly increased risk for RA onset (HR 2.59; 95% CI, 1.65-4.06). Ever smokers with frequent fish intake also had an increased risk, but it was more modest (HR 1.29; 95% CI, 1.07-1.57).

“Our study does not provide evidence to recommend fish or omega-3 fatty acid intake to those at risk for RA,” the researchers wrote.

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Reference

Sparks JA, O’Reilly ÉJ, Barbhaiya M, et al. Association of fish intake and smoking with risk of rheumatoid arthritis and age of onset: a prospective cohort study. BMC Musculoskelet Disord. 2019;20(1):2.