Characteristics of cases and controls at time of blood draw.
| RA Cases, n = 93 | Matched Controls, n = 279 | p | |
|---|---|---|---|
| Nurses’ Health Survey cases, n (%) | 81 (87) | 243 (87) | > 0.99* |
| Age at blood draw, yrs, mean ± SD | 54.6 ± 8.2 | 54.6 ± 8.1 | 0.96** |
| Age at RA diagnosis, yrs, mean ± SD | 60.2 ± 9.7 | NA | NA |
| Time to RA diagnosis, yrs, mean ± SD | 5.6 ± 3.6 | NA | NA |
| Anti-CCP level, continuous (U/ml), median (min–max) | 3 (0–>100) | 2 (0–4) | < 0.0001† |
| Smoking and pack-yrs | 0.47* | ||
| Never smoker, n (%) | 44 (48) | 124 (45) | |
| Ever-smoker, < 11 pack-yrs | 15 (16) | 62 (22) | |
| Ever-smoker, ≥ 11 pack-yrs | 33 (36) | 92 (33) | |
| Pack-yrs for ever-smokers, mean ± SD | 20.3 ± 14.7 | 22.3 ± 19.8 | 0.46** |
| Parity and breastfeeding | |||
| Nulliparous | 4 (4) | 25 (9) | |
| Parous/no breastfeeding | 30 (32) | 69 (25) | |
| Parous/≤ 1 yr | 46 (49) | 130 (47) | |
| Parous/> 1 yr | 13 (14) | 55 (20) | |
| Caucasian, n (%) | 92 (99) | 275 (99) | > 0.99†† |