Table 2 Characteristics at the time of blood draw according to pre-RA ACPA results for RA cases and their matched controls in the Nurses’ Health Studies (n = 1133)
|  | Pre-RA ACPA+ casesb (n = 96) | Matched controls (n = 286) | p value | Pre-RA ACPA− cases (n = 188) | Matched controls (n = 563) | p value |
|---|---|---|---|---|---|---|
Mean age, years (SD)a | 51.3 (7.3) | 50.8 (7.7) | 0.67 | 51.6 (8.2) | 51.9 (8.0) | 0.65 |
Mean time to RA diagnosis or matched index date for controls, years (SD)a | 8.1 (5.8) | 8.1 (5.8) | 0.96 | 10.5 (5.6) | 10.5 (5.6) | 0.99 |
CCP+ at diagnosis by medical record review, % | 58.3 | N/A | – | 9.4 | N/A | – |
RF+ at diagnosis by medical record review, % | 70.8 | N/A | – | 52.7 | N/A | – |
CCP+ or RF+ at diagnosis by medical record review, % | 79.2 | N/A | – | 53.7 | N/A | – |
White, % | 96.9 | 96.5 | 0.86 | 92.6 | 96.8 | 0.01 |
Mean body mass index, kg/m2 (SD) | 26.1 (5.2) | 24.9 (4.2) | 0.05 | 25.6 (4.6) | 25.0 (4.7) | 0.08 |
Mean pack-years (SD) | 13.3 (17.6) | 11.1 (17.2) | 0.18 | 11.1 (14.7) | 8.6 (14.8) | 0.02 |
Mean pack-years among smokers (SD) | 22.4 (17.9) | 21.0 (18.8) | 0.45 | 21.4 (14.1) | 19.0 (17.0) | 0.02 |
Smoking pack-year category, % | ||||||
 Never | 40.6 | 47.2 | 0.24 | 47.9 | 54.7 | 0.005 |
 >0 to 10 | 17.7 | 20.6 | 13.8 | 19.2 | ||
 >10 | 41.7 | 32.2 | 38.3 | 26.1 | ||
Parent(s) smoked at home during childhood, % | 68.8 | 66.1 | 0.63 | 62.8 | 63.4 | 0.87 |
Ever lived with a smoker, % | 64.6 | 53.9 | 0.07 | 58.0 | 57.9 | 0.99 |
Asthma, % | 17.7 | 6.3 | 0.0008 | 8.0 | 8.5 | 0.81 |