Study population characteristics
| Total | Male smokers | Male non-smokers | Female smokers | Female non-smokers | P values | |
| (n=21 148) | (n=7178) | (n=1.626) | (n=808) | (n=11 536) | ||
| Age* | 57.4 (10.9) | 57.8 (11.0) | 57.9 (11.3) | 57.4 (12.5) | 57.1 (10.8) | <0.001 |
| 40–49 | 6048 (28.6) | 1998 (27.8) | 464 (28.5) | 273 (33.8) | 3313 (28.7) | <0.001 |
| 50–59 | 6131 (29.0) | 1981 (27.6) | 431 (26.5) | 199 (24.6) | 3520 (30.5) | |
| 60–69 | 5387 (25.5) | 1913 (26.7) | 430 (26.4) | 158 (19.6) | 2866 (25.0) | |
| 70– | 3582 (16.9) | 1286 (17.9) | 301 (18.5) | 178 (22.0) | 1817 (15.8) | |
| BMI* | 24.2 (3.0) | 24.2 (2.8) | 24.3 (2.8) | 23.8 (3.6) | 24.2 (3.2) | 0.007 |
| Education | <0.001 | |||||
| Elementary | 7229 (34.2) | 1763 (24.6) | 321 (19.7) | 381 (47.2) | 4764 (41.3) | |
| Middle school | 3315 (15.7) | 1216 (16.9) | 267 (16.4) | 112 (13.9) | 1720 (14.9) | |
| High school | 6427 (30.4) | 2366 (33.0) | 458 (28.2) | 228 (28.2) | 3375 (29.3) | |
| More than college | 4169 (19.7) | 1831 (25.5) | 580 (35.7) | 87 (10.8) | 1671 (14.5) | |
| Household income | <0.001 | |||||
| First quartile | 4763 (22.5) | 1440 (20.1) | 289 (17.8) | 315 (39.0) | 2719 (23.6) | |
| Second quartile | 5427 (25.7) | 1874 (26.1) | 391 (24.1) | 223 (27.6) | 2939 (25.5) | |
| Third quartile | 5162 (24.4) | 1869 (26.1) | 414 (25.5) | 145 (17.9) | 2734 (23.7) | |
| Fourth quartile | 5780 (27.3) | 1988 (27.7) | 530 (32.6) | 125 (15.5) | 3137 (27.2) | |
| Comorbidity* | 0.9 (1.1) | 0.9 (1.0) | 0.8 (0.9) | 1.0 (1.2) | 1.0 (1.1) | <0.001 |
| Pack-years* | 4.7 (13.6) | 13.3 (20.3) | 0.2 (2.2) | 3.3 (11.9) | 0.0 (0.0) | <0.001 |
| Alcohol | 17 554 (83.0) | 6877 (95.8) | 1399 (86.0) | 714 (88.4) | 8564 (74.2) | <0.001 |
| Energy intake (kcal/day)* | 1901.5 (797.8) | 2266.5 (869.7) | 2212.6 (855.9) | 1538.2 (653.4) | 1656.0 (630.0) | <0.001 |
| Vitamin A (μg RE/day)* | 822.5 (1118.5) | 881.9 (1067.5) | 925.5 (1095.2) | 600.3 (644.2) | 786.6 (1173.9) | <0.001 |
| Carotene (μg/day)* | 4337.3 (6206.0) | 4596.2 (5557.8) | 4803.8 (5506.6) | 3143.5 (3682.6) | 4194.1 (6780.6) | <0.001 |
| Vitamin C (mg/day)* | 111.9 (107.6) | 111.8 (97.9) | 128.8 (107.1) | 84.8 (96.9) | 111.5 (113.5) | <0.001 |
| FEV1 (mL)* | 2.60 (0.67) | 3.02 (0.68) | 3.09 (0.66) | 2.23 (0.56) | 2.30 (0.46) | <0.001 |
| FVC (mL)* | 3.38 (0.84) | 4.07 (0.72) | 4.04 (0.73) | 2.88 (0.62) | 2.89 (0.51) | <0.001 |
| FEV1/FVC (%)* | 77.3 (7.9) | 73.9 (9.1) | 76.6 (7.9) | 77.2 (8.0) | 79.5 (6.1) | <0.001 |
| COPD | 3005 (14.2) | 1893 (26.4) | 256 (15.7) | 119 (14.7) | 737 (6.4) | <0.001 |
*Numbers represent mean percentages (SD).
BMI, body mass index; COPD, chronic obstructive pulmonary disease; FVC, forced vital capacity; FEV1, forced expiratory volume in 1 s; RE, retinol equivalent.