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Ann Rheum Dis doi:10.1136/annrheumdis-2014-205459
  • Clinical and epidemiological research
  • Extended report

Being overweight or obese and risk of developing rheumatoid arthritis among women: a prospective cohort study

  1. Elizabeth W Karlson1
  1. 1Division of Rheumatology, Immunology & Allergy, Brigham & Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
  2. 2Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA
  1. Correspondence to Dr Bing Lu, Division of Rheumatology, Immunology & Allergy, Brigham & Women's Hospital and Harvard Medical School, 75 Francis Street PBB-B3, Boston, MA 02115, USA; blu1{at}partners.org
  • Received 22 February 2014
  • Revised 12 June 2014
  • Accepted 11 July 2014
  • Published Online First 23 July 2014

Abstract

Objectives To examine the relationship between being overweight or obese and developing rheumatoid arthritis (RA) in two large prospective cohorts, the Nurses’ Health Study (NHS) and Nurses’ Health Study II (NHSII).

Methods We followed 109 896 women enrolled in NHS and 108 727 in NHSII who provided lifestyle, environmental exposure and anthropometric information through biennial questionnaires. We assessed the association between time-varying and cumulative Body Mass Index (BMI) in WHO categories of normal, overweight and obese (18.5–<25, 25.0–<30, ≥30.0 kg/m2) and incident RA meeting the 1987 American College of Rheumatology (ACR) criteria. We estimated HRs for overall RA and serologic subtypes with Cox regression models adjusted for potential confounders. We repeated analyses restricted to RA diagnosed at age 55 years or younger.

Results During 2 765 195 person-years of follow-up (1976–2008) in NHS and 1 934 518 person-years (1989–2009) in NHSII, we validated 1181 incident cases of RA (826 in NHS, 355 in NHSII). There was a trend toward increased risk of all RA among overweight and obese women (HR (95% CI) 1.37 (0.95 to 1.98) and 1.37 (0.91, 2.09), p for trend=0.068). Among RA cases diagnosed at age 55 years or younger, this association appeared stronger (HR 1.45 (1.03 to 2.03) for overweight and 1.65 (1.34 to 2.05) for obese women (p trend <0.001)). Ten cumulative years of being obese, conferred a 37% increased risk of RA at younger ages (HR 1.37 (1.11 to 1.69)).

Conclusions Risks of seropositive and seronegative RA were elevated among overweight and obese women, particularly among women diagnosed with RA at earlier ages.

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