Table 1.
Characteristics of study participants by season (n = 555).
| Characteristics | Spring (n = 171) |
Summer (n = 178) |
Autumn (n = 99) |
Winter (n = 107) |
p |
|---|---|---|---|---|---|
| Mean age | 60.6 (8.9) | 62.6 (8.3) | 60.6 (9.0) | 59.9 (9.4) | 0.05 |
| Age categories | 0.04 | ||||
| <65 | 118 (69.0) | 104 (58.4) | 66 (66.7) | 79 (73.8) | |
| ≥65 | 53 (31.0) | 74 (41.6) | 33 (33.3) | 28 (26.2) | |
| Sex, male | 97 (56.7) | 101 (56.7) | 57 (57.6) | 57 (53.3) | 0.92 |
| Body mass index, kg/m2 | 24.1 (2.9) | 24.3 (2.7) | 24.1 (2.7) | 24.5 (3.2) | 0.67 |
| Smoking status | 0.32 | ||||
| Never-smoker | 78 (45.6) | 89 (50.0) | 48 (48.5) | 57 (53.3) | |
| Ex-smoker | 59 (34.5) | 34 (19.1) | 27 (27.3) | 16 (15.0) | |
| Current smoker | 34 (19.9) | 55 (30.9) | 24 (24.2) | 34 (31.8) | |
| Marital status | 0.64 | ||||
| Married | 151 (88.3) | 159 (89.3) | 91 (91.9) | 91 (85.1) | |
| Single/divorced/widowed | 19 (11.1) | 19 (10.7) | 7 (7.1) | 15 (14.0) | |
| Unknown | 1 (0.6) | 0 | 1 (1.0) | 1 (0.9) | |
| Employment status | 0.46 | ||||
| Current work | 98 (57.3) | 81 (45.5) | 49 (49.5) | 58 (54.2) | |
| No work | 72 (42.1) | 96 (53.9) | 49 (49.5) | 48 (44.9) | |
| Unknown | 1 (0.6) | 1 (0.6) | 1 (1.0) | 1 (0.9) | |
| Monthly family income | 0.19 | ||||
| <$3.000 | 54 (31.6) | 51 (28.7) | 23 (23.2) | 31 (29.0) | |
| ≥$3.000 | 87 (50.9) | 93 (52.3) | 54 (54.6) | 66 (61.7) | |
| Unknown | 30 (17.5) | 34 (19.1) | 22 (22.2) | 10 (9.4) | |
| Comorbidities | |||||
| Pulmonary comorbidities | |||||
| COPD | 40 (23.4) | 43 (24.2) | 26 (26.3) | 19 (17.8) | 0.49 |
| Asthma | 3 (1.8) | 8 (4.5) | 1 (1.0) | 3 (2.8) | 0.34 |
| ILD | 1 (0.6) | 2 (1.1) | 1 (1.0) | 2 (1.9) | 0.86 |
| Extra-pulmonary comorbidities | |||||
| Hypertension | 52 (30.4) | 72 (40.5) | 28 (28.3) | 35 (32.7) | 0.12 |
| Diabetes mellitus | 22 (12.9) | 27 (15.2) | 11 (11.1) | 7 (6.5) | 0.18 |
| Cardiovascular disease | 12 (7.0) | 20 (11.2) | 9 (9.1) | 9 (8.4) | 0.58 |
| Pathologic stage | 0.81 | ||||
| I | 128 (74.9) | 130 (73.0) | 75 (75.8) | 75 (70.1) | |
| II | 25 (14.6) | 31 (17.4) | 13 (13.1) | 16 (15.0) | |
| III | 18 (10.5) | 17 (9.6) | 11 (11.1) | 16 (15.0) | |
| Pulmonary function test | |||||
| FVC, L | 3.6 (0.9) | 3.4 (0.8) | 3.7 (0.9) | 3.7 (0.8) | 0.02 |
| FVC, % predicted | 93.4 (11.5) | 89.8 (12.9) | 94.3 (12.7) | 96.4 (12.1) | < 0.01 |
| FEV1, L | 2.7 (0.7) | 2.5 (0.6) | 2.7 (0.6) | 2.8 (0.6) | < 0.01 |
| FEV1, % predicted | 90.0 (13.2) | 87.5 (15.5) | 90.2 (14.9) | 95.0 (13.5) | < 0.01 |
| FEV1/FVC | 73.8 (8.2) | 73.6 (8.6) | 72.6 (8.6) | 75.1 (8.3) | 0.21 |
| DLco, % | 91.6 (16.0) | 89.2 (17.3) | 89.7 (15.2) | 91.3 (13.7) | 0.47 |
| Cardiorespiratory fitness | |||||
| 6 min walk distance (m) | 520.1(85.7) | 506.9(89.1) | 515.0(66.8) | 508.1(80.7) | 0.46 |
| 6 min walk distance | 0.69 | ||||
| Short distance (<500 m) | 68 (39.9) | 77 (43.3) | 37 (37.4) | 49 (45.8) | |
| Long distance (≥500 m) | 102 (59.7) | 97 (54.5) | 60 (60.1) | 56 (52.3) | |
| Unknown | 1 (0.6) | 4 (2.3) | 2 (2.1) | 2 (1.9) |
Values are presented as either n (%) or mean (SD). COPD, chronic obstructive pulmonary disease; ILD, interstitial lung disease; FVC, forced vital capacity; FEV1, forced expiratory volume in 1 s; DLco, diffusing capacity of carbon monoxide.