Patient Characteristics at Baseline, According to Criteria Used to Define Airflow Limitation
| Characteristic | Total (N = 4,882) | No Airflow Limitationa (n = 4,038) | Airflow Limitation | ||||
|---|---|---|---|---|---|---|---|
| FR+/LLN− (n = 297) | FR−/LLN+ (n = 15) | FR+/LLN+ (n = 532) | FR+ and Low FEV1b,c (n = 363) | LLN+ and Low FEV1b (n = 304) | |||
| Age, mean (SD), y | 57 (11) | 56 (11) | 68 (10) | 45 (3) | 62 (12) | 64 (11) | 63 (11) |
| Sex (male), No. (%) | 2,093 (43) | 1,668 (41) | 186 (63) | 1 (7) | 238 (45) | 177 (49) | 138 (45) |
| Postbronchodilator FEV1, mean (SD), % predicted | 95 (17) | 98 (15) | 92 (16) | 77 (18) | 77 (18) | 65 (12) | 64 (12) |
| Postbronchodilator FVC, mean (SD), % predicted | 97 (15) | 96 (15) | 101 (17) | 99 (12) | 98 (19) | 85 (14) | 86 (14) |
| Body mass index, kg/m2 | 28 (6) | 28 (6) | 27 (5) | 28 (5) | 28 (5) | 28 (6) | 28 (6) |
| Tobacco smoking status, No. (%)d | |||||||
| Never smoker | 2,091 (43) | 1,852 (46) | 95 (32) | 8 (53) | 136 (26) | 73 (20) | 100 (33) |
| Former smoker | 2,058 (42) | 1,657 (41) | 158 (53) | 1 (7) | 242 (46) | 178 (49) | 142 (47) |
| Current smoker | 729 (15) | 527 (13) | 43 (15) | 6 (40) | 153 (29) | 111 (31) | 61 (20) |
| Education ≤12 years, No. (%) | 493 (10) | 366 (9) | 43 (15) | 0 (0) | 83 (16) | 65 (18) | 55 (18) |
| Race (white), No. (%) | 4,464 (91) | 3,663 (91) | 277 (93) | 14 (93) | 510 (96) | 343 (94) | 290 (95) |
| Conditions, No. (%) | |||||||
| Chronic cough | 619 (13) | 432 (11) | 45 (15) | 6 (40) | 136 (26) | 113 (31) | 102 (34) |
| Chronic phlegm | 467 (10) | 312 (8) | 35 (12) | 1 (7) | 119 (22) | 96 (26) | 85 (28) |
| Chronic bronchitise | 213 (4) | 136 (3) | 17 (6) | 1 (7) | 59 (11) | 51 (14) | 65 (21) |
| Wheeze | 1,273 (29) | 939 (25) | 78 (31) | 8 (53) | 248 (52) | 192 (60) | 166 (61) |
| MRC dyspnea scalef | 1.4 (0.8) | 1.3 (0.7) | 1.4 (0.8) | 1.7 (1.2) | 1.8 (1.1) | 2 (1) | 2.03 (1.2) |
| SF-12 scores, mean (SD)g | |||||||
| Physical scale | 50 (9) | 51 (9) | 50 (9) | 46 (14) | 47 (11) | 45 (11) | 44 (12) |
| Mental scale | 52 (9) | 52 (9) | 54 (8) | 49 (11) | 52 (9) | 53 (9) | 52 (10) |
| Exacerbation, No. (%) | 996 (20) | 779 (19) | 58 (20) | 4 (27) | 155 (29) | 119 (33) | 100 (33) |
| Cardiovascular disease, No. (%) | 605 (12) | 436 (11) | 76 (26) | 1 (7) | 92 (17) | 81 (22) | 66 (22) |
FEV1 = forced expiratory volume in 1 second; FR = fixed ratio; FVC = forced vital capacity; LLN = lower limit of normal; MRC = Medical Research Council; SF-12 = Short Form 12-item health survey.
Notes: Continuous data are presented as mean (SD), dichotomous values as number (%). P value: univariate analysis of variance (ANOVA) or Kruskal-Wallis test for continuous variables and χ2 test for dichotomous variables.
↵a FR−/LLN−.
↵b FEV1 <80% of predicted.
↵c Collectively, these 2 criteria constitute Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 2 or higher disease.
↵d Tobacco smoking status includes both cigarette and pipe smoking.
↵e Chronic cough and chronic phlegm for more than 2 years.
↵f MRC dyspnea scale scores range from 0 to 5; higher scores indicate worse health/dyspnea.
↵g SF-12 Physical and Mental scale scores range from 0 to 100; higher scores indicate better health.