Table 1

Relative risk of ACPA-positive and ACPA-negative RA according to parity, in different age-groups, EIRA, Sweden, 1996–2009.

18–44 years45–70 years
ACPA statusParousCases/controlsOR*95% CICases/controlsOR*95% CI
Yes136/5462.1 (1.4 to 3.2)458/17660.9 (0.7 to 1.3)
Yes237/5460.9 (0.7 to 1.2)797/17661.0 (0.8 to 1.2)
RA overallNo230/3601.0177/2381.0
Yes373/5461.1 (0.9 to 1.5)1255/17661.0 (0.8 to 1.2)
  • *Adjusted by matching variables (age and residential area). Adjustments for smoking (pack-years), body mass index (BMI <25/≥25), use of oral contraceptives (ever/never), breast feeding (<24/≥24 months in total), age of menarche (≤11, 12, 13 and ≥14 years) and formal education (compulsory, vocational/theoretical upper secondary school, university degree, other education) did not substantially change the ORs and were therefore not retained in the final analyses.

  • ACPA,  antibodies to citrullinated peptide antigens; EIRA, Epidemiological Investigation of Rheumatoid Arthritis; RA, rheumatoid arthritis.