RESEARCH - National cohort study of reproductive risk factors for RA in Denmark

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Ann Rheum Dis. 2009 Mar 15.

National cohort study of reproductive risk factors for rheumatoid

arthritis in Denmark - a role for hyperemesis, gestational

hypertension, and pre-eclampsia?

Jørgensen KT, Pedersen BV, sen S, Biggar RJ, Frisch M.

Statens Serum Institut, Denmark.

OBJECTIVES: While reproductive factors might plausibly be involved in

the etiology of rheumatoid ar-thritis (RA), the female predominance

remains unexplained. We aimed to address the possible impact of

livebirths, pregnancy losses, and pregnancy complications on

subsequent risk of RA in a nationwide cohort study.

METHODS: National register data were used to link reproductive

histories and later RA hospitalizations in a cohort of 4.4 million

Danes. As our measure of relative risk associated with different

reproductive histories we used ratios of first inpatient RA

hospitalization rates (RRs) with 95% confidence intervals (CIs)

obtained in Poisson regression analysis.

RESULTS: Overall, 7,017 women and 3,041 men were hospitalized with RA

during 1977-2004 (88.8 mil-lion person-years). RA risk was inversely

associated with age at birth of first child in both women and men

(P-trend <0.001). Overall, nulliparity and histories of pregnancy loss

were not associated with RA risk but, compared with one-child mothers,

women with two (RR=0.84; 95% CI: 0.78-0.90) or three (RR=0.83;

0.77-0.91) children were at reduced risk. RA risk was elevated among

women with a history of hyperemesis (RR=1.70; 1.06-2.54), gestational

hypertension (RR=1.49; 1.06-2.02), or pre-eclampsia (RR=1.42;

1.08-1.84).

CONCLUSIONS: One-child mothers and young parents were at increased

risk of RA later in life, possibly due to socioeconomic factors. The

novel finding of significantly elevated RA risk in women whose

pregnancies were complicated by hyperemesis, gestational hypertension,

or pre-eclampsia might reflect reduced immune adaptability to

pregnancy in RA disposed women or a role of fetal microchimerism in

the etiology of RA.

PMID: 19289384

http://www.ncbi.nlm.nih.gov/pubmed/19289384

Not an MD