Table 5.
Preworking, postworking and absolute change from preworking to postworking of lung function parameters in three occupational groups*
| Occupational groups | Preworking | Postworking | P values† | Mean (SD) of changes | β (95% CI)‡ | P values‡ |
| Mean (SD) | Mean (SD) | |||||
| Parameters | FVC (% predicted) | ΔFVC (% predicted) | ||||
| Conventional asphalt workers | 96.0 (11.8) | 95.7 (11.3) | 0.45 | −0.3 (4.5) | 0.6 (−0.7 to 1.9) | 0.38 |
| CRM asphalt workers | 98.2 (9.8) | 96.4 (9.9) | 0.06 | −1.2 (4.4) | −0.4 (−2.2 to 1.3) | 0.64 |
| Controls | 92.9 (11.1) | 92.0 (11.6) | 0.08 | −0.9 (4.9) | Ref | Ref |
| Parameters | FEV1 (% predicted) | ΔFEV1 (% predicted) | ||||
| Conventional asphalt workers | 99.9 (13.3) | 99.1 (12.5) | 0.16 | −0.7 (5.5) | 0.6 (−0.9 to 2.0) | 0.43 |
| CRM asphalt workers | 100.7 (12.8) | 99.1 (11.8) | 0.05 | −1.6 (5.4) | −0.6 (−2.6 to 1.3) | 0.51 |
| Controls | 97.6 (12.1) | 96.2 (12.3) | 0.008 | −1.3 (4.7) | Ref | Ref |
*Absolute change of FVC (% predicted) and FEV1 (% predicted) from preworking on Monday morning to postworking on Thursday afternoon; for example, ΔFVC (% predicted)=FVC (% predicted) (Thursday afternoon) − FVC (% predicted) (Monday morning). There were no missing data on lung function parameters.
†P values were derived from paired t-test.
‡β and p values were derived from general linear regression with smoking history, cigarette pack-year, allergy and pre-exposure FVC (% predicted) (or FEV1 (% predicted)) as adjustments.
CRM, crumb rubber modified; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; ref, reference.