Table 1.
Characteristic | Comparison n = 24,018 n (%) | All RA cases | Incident cases | ||
---|---|---|---|---|---|
Case n = 275 n (%) | OR (95% CI) | Case n = 132 n (%) | OR (95% CI) | ||
Age at enrollment | |||||
< 40 years old | 7,548 (31) | 35 (13) | 1.0 (referent) | 21 (16) | 1.0 (referent) |
40–49 years old | 7,178 (30) | 65 (24) | 2.0 (1.3, 2.9) | 37 (28) | 1.9 (1.1, 3.2) |
50–59 years old | 5,726 (24) | 107 (39) | 4.0 (2.7, 5.9) | 47 (36) | 2.8 (1.8, 4.9) |
≥ 60 years old | 3,566 (15) | 68 (25) | 4.1 (2.7, 6.2) | 27 (20) | 2.9 (1.5, 4.8) |
State | |||||
North Carolina | 6,929 (29) | 105 (38) | 1.0 (referent) | 46 (35) | 1.0 (referent) |
Iowa | 17,089 (71) | 170 (62) | 0.75 (0.58, 0.96) | 86 (65) | 0.83 (0.58, 1.2) |
Race | |||||
White | 23,089 (98) | 262 (97) | 1.0 (referent) | 128 (98) | 1.0 (referent) |
Nonwhite | 523 (2) | 9 (3) | 1.4 (0.71, 2.7) | 2 (2) | 0.67 (0.16, 2.7) |
Education | |||||
≤ High school | 9,155 (43) | 119 (49) | 1.0 (referent) | 50 (43) | 1.0 (referent) |
> High school | 11,921 (57) | 122 (51) | 1.0 (0.80, 1.3) | 67 (57) | 1.3 (0.87, 1.9) |
Smoking pack-years | |||||
None | 18,027 (75) | 200 (73) | 1.0 (referent) | 93 (70) | 1.0 (referent) |
< 5 pack-years | 2,639 (11) | 22 (8) | 0.85 (0.55, 1.3) | 14 (11) | 1.1 (0.64, 2.0) |
5–18 pack-years | 1,964 (8) | 24 (9) | 1.2 (0.77, 1.8) | 12 (9) | 1.3 (0.68, 2.3) |
> 18 pack-years | 1,388 (6) | 29 (11) | 1.5 (1.0, 2.2)* | 13 (10) | 1.5 (0.84, 2.7) |
Grew up on farm | |||||
No | 9,202 (39) | 94 (35) | 1.0 (referent) | 47 (37) | 1.0 (referent) |
Yes | 14,196 (61) | 172 (65) | 0.94 (0.73, 1.2) | 80 (63) | 0.93 (0.64, 1.3) |
Years on farm | |||||
< 11 years | 3,168 (14) | 15 (6) | 1.0 (referent) | 10 (8) | 1.0 (referent) |
11–20 years | 3,936 (17) | 36 (13) | 1.6 (0.88, 3.0) | 18 (14) | 1.3 (0.60, 2.9) |
21–30 years | 4,237 (18) | 53 (20) | 1.8 (0.99, 3.2) | 24 (19) | 1.3 (0.62, 2.9) |
≥ 31 years | 11,986 (51) | 163 (61) | 1.3 (0.75, 2.3) | 74 (59) | 1.1 (0.55, 2.3) |
Note: ORs and 95% CIs for all RA cases and incident cases were adjusted for age. *p < 0.05. |