Table 1 Characteristics of cases and controls
Cases (n = 136)Controls (n = 544)
Age at RA diagnosis*63.3 (8.25)NA
RF positive68.4% (91/133 tested)NA
ANA positive30.5% (25/82 tested)NA
Anti-CCP positive66.7% (16/24 tested)NA
Age at screening*57.9 (7.33)58.0 (7.32)
Ever used OCs†63 (48.5%)254 (49.4%)
Never used OCs67 (51.2%)259 (51.2%)
Used OCs 1–5 years18 (14.0%)110 (21.7%)
Used OCs >5 years44 (34.1%)137 (27.1%)
Given birth to ⩾1 child106 (77.9%)445 (81.8%)
Breast fed for 0 months43 (31.6%)137 (25.2%)
Breast fed for 1–12 months74 (54.4%)297 (54.6%)
Breast fed for >13 months19 (14.0%)110 (20.2%)
  • *Values are mean (SD).

  • †Data on OC use were available for 130 cases and 514 controls.

  • ANA, anti-nuclear antibodies; CCP, cyclic citrullinated peptides; NA, not applicable; OC, oral contraceptive; RA, rheumatid arthritis; RF, rheumatoid factor.