Clinical Edge

Summaries of Must-Read Clinical Literature, Guidelines, and FDA Actions

No Protective Effect Found in Fish Intake in RA

BMC Musculoskelet Disord; 2019 Jan 5; Sparks, et al

There was no clear protective effect of fish or marine omega-3 fatty acid intake on rheumatoid arthritis (RA) risk, overall or by serologic status, according to a recent study. Researchers studied fish intake and RA risk among 166,013 women in 2 prospective cohorts, the Nurses’ Health Study (NHS, 1984–2014) and NHSII (1991–2015). Fish intake was assessed using food frequency questionnaires at baseline and every 4 years. Incident RA during follow-up and serologic status were determined by medical record review. They found:

  • During 3,863,909 person-years of follow-up, 1,080 incident RA cases were identified.
  • Increasing fish intake was not associated with all RA (≥4 servings/week: multivariable HR 0.93 vs < 1 serving/month), seropositive RA, or seronegative RA, but had increased risk for RA diagnosed in persons aged >55 years.
  • Among women aged ≤55 years, frequent fish intake (vs infrequent) had HRs of: 0.73 for all RA, 0.85 for seropositive RA, and 0.55 for seronegative RA.

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. doi:10.1186/s12891-018-2381-3.


In this study, fish intake was recorded with food frequency questionnaires every 4 years in about 166,000 healthy nurses, and correlated with subsequent development of clinical RA. Only 1,080 of these nurses developed RA during at least 20 years of follow up. Overall, there was no relationship between the number of servings of fish eaten per week and the development of RA. Sub-group analysis by seropositivity, race, alcohol intake, and obesity were also not significant. In the sub-group of women, aged <55 years and ever smokers, infrequent fish intake was associated with a highly elevated risk for RA onset, but frequent fish intake substantially decreased that risk. It is not clear whether this apparent interaction of smoking, fish intake, and age is real or simply a chance occurrence because of the large number of sub-groups analyzed.—Harold E. Paulus, M.D.; Emeritus Professor; University of California, Los Angeles; Division of Rheumatology.