Background/Purpose

Female sex and older age are known risk factors for rheumatoid arthritis (RA). The disease is however heterogeneous, and a common division occurs between the presence/absence of autoantibodies to citrullinated peptide antigens (ACPA) where ACPA-positive disease generally has a worse outcome. In a recent study we reported that parous women of reproductive age (18 to 44 years at diagnosis) had an increased risk of ACPA-negative, but not of ACPA-positive RA, and that this association was stronger closer to partum[1]. There are diverging results regarding the effect of parity on the severity of RA.

Our purpose was to explore if parity has impact on disease severity of RA, stratified into different phenotypes.

Methods

We studied female RA cases aged 18-70, who participated in the Epidemiological Investigation of Rheumatoid arthritis, EIRA, a population-based case-control study from the middle and southern parts of Sweden. All patients included fulfilled the American Collage of Rheumatology (ACR) 1987 criteria for RA and were diagnosed by a rheumatologist, and included within 1 year of diagnosis. Information on disease severity (Health Assessment Questionnaire, HAQ and disease activity score 28, DAS28) was gathered from the Swedish Rheumatology Register, SRQ at inclusion, 3, 6, 12 and 24 months after diagnosis. Mixed models for repeated measurements over time were used to take account of the variation at different time point at individual level and to compare mean DAS28 and HAQ-scores over time. ANCOVA analysis was used to compare mean differences of clinical outcome measures at all time points

Results

A total of 1237 female cases, with complete information, were included in the study with a mean age of 51 at inclusion.  In all, 82% had ever given birth to a child before diagnosis and 65 % were ACPA-positive. Mixed models analysis showed associations between parity and ACPA negative but not ACPA positive disease. Parous women, aged 18-44, who would develop ACPA negative disease, had on average 1.17 higher DAS 28 (p< 0.001) and 0.43 higher HAQ  (p< 0.001) compared to nulliparous women during the follow up time, adjusted for age. These findings remained after individually adjustment for smoking, living area and level of education. There was an opposite trend among parous ACPA negative women (aged 45 to 70), were parous women had 0.26 lower DAS 28 (p=0.14) and 0.06 lower HAQ (p=0.46). ANCOVA analysis for different time points noted an association between higher DAS 28 and HAQ levels and parity in the ACPA negative reproductive age group at all time points, except at baseline. In ACPA negative older age group we observed a milder disease in parous women, although only significant at baseline.

Conclusion

Parity influenced ACPA negative disease, where parous women who developed RA during their fertile years had on average higher DAS 28 and HAQ compared to nulliparous women. Parity was not a predictor of severity in ACPA positive disease.

References

1. Orellana C, Wedren S, Kallberg H, et al. Parity and the risk of developing rheumatoid arthritis: results from the Swedish Epidemiological Investigation of Rheumatoid Arthritis study. Annals of the Rheumatic Diseases2013.

 

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/parity-and-severity-of-acpa-positivenegative-rheumatoid-arthritis-results-from-the-swedish-eira-study/