Table 1 Demographics and risk factors by allergic symptoms in the PIFCOPD population (N = 10,142)
|  | ALL |  < 2 allergic symptoms |  ≥ 2 allergic symptoms | p-value |
|---|---|---|---|---|
N = 10,142 | N = 9721 | N = 421 | ||
Sex | Â | Â | Â | 0.797 |
 Female | 6386 (63) | 6118 (63) | 268 (64) |  |
 Male | 3756 (37) | 3603 (37) | 153 (36) |  |
Age, y | 59.27 (8.41) | 59.28 (8.42) | 59.03 (8.17) | 0.549 |
BMI group | Â | Â | Â | 0.684 |
 < 25 kg/m2 | 5938 (59) | 5691 (59) | 247 (59) |  |
 25–29.9 kg/m2 | 3548 (35) | 3405 (35) | 143 (34) |  |
 ≥ 30 kg/m2 | 656 (6.5) | 625 (6.4) | 31 (7.4) |  |
Education level |  |  |  |  < 0.001 |
 No schooling or primary school | 1824 (18) | 1795 (18) | 29 (6.9) |  |
 Middle school | 4555 (45) | 4409 (45) | 146 (35) |  |
 High school | 2387 (24) | 2236 (23) | 151 (36) |  |
 College or higher | 1376 (14) | 1281 (13) | 95 (23) |  |
 Passive smoking | 975 (9.6) | 901 (9.3) | 74 (18) |  < 0.001 |
Smoking type | Â | Â | Â | 0.003 |
 Never smoker | 8234 (81) | 7916 (81) | 318 (76) |  |
 Former or current smoker | 1908 (19) | 1805 (19) | 103 (24) |  |
Cumulative smoking exposure, pack-years | Â | Â | Â | 0.011 |
 0 | 8234 (81) | 7916 (81) | 318 (76) |  |
 1–19 | 706 (7.0) | 668 (6.9) | 38 (9.0) |  |
 ≥ 20 | 1202 (12) | 1137 (12) | 65 (15) |  |
Biomass exposure | 495 (4.9) | 466 (4.8) | 29 (6.9) | 0.063 |
Household cooking | 5896 (58) | 5599 (58) | 297 (71) |  < 0.001 |
Occupational exposure | 771 (7.6) | 699 (7.2) | 72 (17) |  < 0.001 |
Family history of asthma | 295 (2.9) | 256 (2.6) | 39 (9.3) |  < 0.001 |
Geographic region |  |  |  |  < 0.001 |
 North | 6627 (65) | 6283 (65) | 344 (82) |  |
 East | 1678 (17) | 1647 (17) | 31 (7.4) |  |
 Northeast | 768 (7.6) | 724 (7.4) | 44 (10) |  |
 Northwest | 1069 (11) | 1067 (11) | 2 (0.5) |  |
Seasona |  |  |  |  < 0.001 |
 Winter | 373 (3.7) | 369 (3.8) | 4 (1.0) |  |
 Spring | 1594 (16) | 1525 (16) | 69 (16) |  |
 Summer | 6325 (62) | 6095 (63) | 230 (55) |  |
 Autumn | 1850 (18) | 1732 (18) | 118 (28) |  |