Table 1.
The characteristics of the study subjects
| Characteristics | Normal lung function, n=1,280 | Mild AL, n=48 | Moderate-to-severe AL, n=50 | P-value |
|---|---|---|---|---|
| Sex | ||||
| Male, n (%) | 836 (65.3) | 38 (79.2) | 47 (94.0) | <0.001 |
| Female, n (%) | 444 (34.7) | 10 (20.8) | 3 (6.0) | |
| Age, years | 49.3 (8.8) | 53.0 (9.5)* | 55.9 (9.7)** | <0.001 |
| Height, cm | 165.7 (8.2) | 168.0 (8.4) | 167.9 (7.7) | 0.027 |
| Weight, kg | 64.1 (11.3) | 64.4 (11.1) | 68.2 (12.4)* | 0.112 |
| BMI, kg/m2 | 23.3 (3.2) | 22.7 (3.0) | 24.1 (3.2) | 0.048 |
| Smoking status | ||||
| Never, n (%) | 657 (51.3) | 16 (33.3) | 12 (24.0) | |
| Former, n (%) | 363 (28.4) | 12 (25.0) | 20 (40.0) | |
| Current, n (%) | 260 (20.3) | 20 (41.7) | 18 (36.0) | <0.001 |
| Pack-years | 10.0 (15.3) | 18.0 (24.0)* | 22.2 (26.6)** | <0.001 |
| Lung function | ||||
| FEV1, mL | 3,081.3 (631.1) | 2,885.0 (596.6) | 2,281.4 (517.0)**,## | <0.001 |
| FVC, mL | 3,861.1 (799.2) | 4,368.5 (896.8)** | 3,715.8 (829.5)## | <0.001 |
| FEV1/FVC, % | 80.1 (5.3) | 66.1 (2.4)** | 61.8 (6.9)**,## | <0.001 |
| FEV1%, predicted, % | 98.6 (11.1) | 89.1 (7.4)** | 69.4 (9.7)**,## | <0.001 |
| Clinical information | ||||
| Hypertension, n (%) | 410 (32.0) | 14 (29.2) | 23 (46.0) | 0.104 |
| Dyslipidemia, n (%) | 566 (44.2) | 21 (43.8) | 30 (60.0) | 0.088 |
| Hyperglycemia, n (%) | 167 (13.0) | 8 (16.7) | 12 (24.0) | 0.070 |
| Sleep duration | ||||
| 6–8 h, n (%) | 1,088 (85.0) | 39 (81.2) | 42 (84.0) | |
| <6 h, n (%) | 182 (14.2) | 8 (16.7) | 5 (10.0) | |
| >8 h, n (%) | 10 (0.8) | 1 (2.1) | 3 (6.0) | 0.006 |
| Work hours per day | ||||
| ≤8 h, n (%) | 674 (52.6) | 23 (47.9) | 26 (52.0) | |
| >8≤10 h, n (%) | 440 (34.4) | 16 (33.3) | 19 (38.0) | |
| >10 h, n (%) | 166 (13.0) | 9 (18.8) | 5 (10.0) | 0.743 |
| Smoking environment at workplace, n=1,307a | n=1,216a | n=43a | n=48a | |
| Smoke-free, n (%) | 403 (33.2)a | 10 (23.3)a | 13 (27.1)a | |
| Restrictive, n (%) | 707 (58.1)a | 28 (65.1)a | 23 (47.9)a | |
| Nonrestrictive, n (%) | 106 (8.7)a | 5 (11.6)a | 12 (25.0)a | 0.010 |
| Productivity loss at workb | ||||
| Quality, n (%) | 518 (40.5) | 22 (45.8) | 26 (52.0) | 0.211 |
| Quantity, n (%) | 515 (40.2) | 20 (41.7) | 27 (54.0) | 0.150 |
| Sick leave, n=1,111c | n=1,038c | n=36c | n=37c | |
| Sick leave, n (%) | 410 (39.5)c | 15 (41.7)c | 20 (54.1)c | 0.203 |
Notes: Total number of study subjects =1,378. Data presented are mean (standard deviation) unless otherwise stated.
P<0.05,
P<0.001 compared with normal lung function;
P<0.001 compared with mild airflow limitation. Airflow limitation was defined as FEV1/FVC <0.7. Pack-years: (number of cigarettes smoked per day × number of years smoked)/20.
Smoking environment at workplace was only recorded for 1,307 of the 1,378 total subjects, 1,216 of the 1,280 normal lung function, 43 of the 48 mild AL, and 48 of the 50 moderate-to-severe.
Total number of study subjects for productivity loss at work was 1,378.
Sick leave was only recorded for 1,111 of 1,378 total subjects, 1,038 of the 1,280 normal lung function, 36 of the 48 mild AL, and 37 of the 50 moderate-to-severe.
Abbreviations: AL, airflow limitation; BMI, body mass index; FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity; FEV1/FVC, forced expiratory volume in 1 second to forced vital capacity; FEV1% predicted, forced expiratory volume in 1 second as percentage of predicted; h, hours.