Abstract
Objective. Early life factors have been associated with risk of developing autoimmune disease in adulthood. We investigated the association of preterm birth and being breastfed with the incidence of rheumatoid arthritis (RA) in 2 large prospective cohorts.
Methods. We studied participants from the Nurses’ Health Study (NHS) and the Nurses’ Health Study II (NHSII) who provided information on perinatal factors. The NHS (n = 121,701) and NHSII (n = 116,608) are large prospective cohorts of women followed since 1976 and 1989, respectively. Incident RA was confirmed using the American College of Rheumatology criteria and a medical record review. Cox models were used to estimate the hazard ratio of RA associated with being born preterm and being breastfed and its duration, adjusting for potential confounders. Random effects metaanalytic methods were used to compute combined estimates from the 2 cohorts.
Results. We found no statistically significant association between preterm birth and incident RA [relative risk (RR) = 1.1, 95% CI 0.8, 1.5]. Being breastfed was not associated with increased incidence of RA (RR = 1.0, 95% CI 0.7, 1.4), regardless of the duration of breastfeeding.
Conclusion. In these cohorts of women, neither being preterm birth nor being breastfed was associated with the onset of RA.
Footnotes
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J.F. Simard is supported by the Arthritis Foundation Doctoral Dissertation Award. Dr. Karlson is supported by National Institutes of Health (NIH) grants R01 AR49880, K24 AR0524-01. Dr. Costenbader is the recipient of NIH K12 HD051959 and an Arthritis Foundation/American College of Rheumatology Arthritis Investigator Award. Prof. Liang is supported by grants from Rheuminations, NIH Multipurpose Arthritis Center Grant, and the Arthritis Foundation.
- Accepted for publication July 2, 2009.
