Table 1.
Baseline characteristics of study participants stratified by exposure level in 2011.
| Characteristic | Silk nonsmoker | Cotton nonsmoker | Silk smoker | Cotton smoker |
|---|---|---|---|---|
| Observations, n | 158 | 164 | 62 | 80 |
| Age, years | 63.5 ± 8.8 | 63.8 ± 8.7 | 65.8 ± 9.9 | 63.8 ± 9.3 |
| Male | 17 (10.8%) | 19 (11.6%) | 60 (96.8%) | 72 (90.0%) |
| Current smoker | 0 (0%) | 0 (0%) | 43 (69.4%) | 58 (72.5%) |
| Pack-years | 0 | 0 | 28.4 ± 20.5 | 27.5 ± 18.6 |
| Height, cm | 157.9 ± 6 | 159.2 ± 6.5 | 167.2 ± 6.1 | 168.2 ± 7.2 |
| Body mass index, cm/kg2 | 23.8 ± 3.0 | 24.9 ± 3.6 | 24.0 ± 3.2 | 24.6 ± 3.2 |
| Follow-up time, years | 29.4 ± 0.1 | 29.6 ± 0.1 | 29.3 ± 0.0 | 29.6 ± 0.0 |
| Work duration, years | 25.4 ± 8.2 | 24.5 ± 7.3 | 28.5 ± 9.7 | 26.6 ± 7.9 |
| Retirement duration, years | 18.4 ± 4.1 | 17.4 ± 5.1 | 17.4 ± 4.3 | 16.9 ± 4.7 |
| Cumulative endotoxin exposure, EU/m3-yearsa | 0 | 38233.8 ± 31962.6 | 0 | 61123.6 ± 54849.7 |
| FEV1, mL | 2159.8 ± 440.4 | 2193.0 ± 491.5 | 2683.3 ± 678.0 | 2540.3 ± 811.7 |
| FEV1, % predicted | 112.0 ± 16.8 | 111.4 ± 14.7 | 110.4 ± 21.3 | 100.4 ± 20.5 |
| FEV1/FVC | 0.8 ± 0.1 | 0.8 ± 0.1 | 0.7 ± 0.1 | 0.7 ± 0.1 |
| FEV1/FVC < 0.7 | 15 (9.5%) | 14 (8.5%) | 19 (30.6%) | 19 (23.8%) |
| FEV1/FVC < LLN | 4 (2.5%) | 3 (1.8%) | 9 (14.5%) | 7 (8.8%) |
| Annual FEV1 decline, mL/yrb | –15.1 ± 10.4 | –18.3 ± 9.4 | –28.4 ± 11.8 | –31.9 ± 13.6 |
| FEV1 change since 1981, mLc | –442.0 ± 304.2 | –542.3 ± 179.5 | –832.8 ± 347.3 | –941.9 ± 401.2 |
| Any respiratory symptoms | 38 (24.1%) | 38 (23.2%) | 22 (35.5%) | 29 (36.2%) |
| Chronic bronchitis | 6 (3.8%) | 8 (4.9%) | 9 (14.5%) | 14 (17.5%) |
| Chronic cough | 4 (2.5%) | 3 (1.8%) | 3 (4.8%) | 3 (3.8%) |
| Dyspnea | 35 (22.2%) | 36 (22.0%) | 14 (22.6%) | 21 (26.2%) |
| Abbreviations: EU, endotoxin units; FEV1, forced expiratory volume in 1 sec; FVC, forced vital capacity; LLN, lower limit of normal. aA limited number of full-shift samples obtained in silk mills had endotoxin levels below the lower limit of normal (0.001 EU/m3) by the Limulus amoebocyte lysate assay; thus, silk workers were considered to be exposed to negligible amounts of endotoxin at work. bCalculated by taking the difference in FEV1 between 2011 and 1981 divided by elapsed time. Significant differences in annual FEV1 decline noted between exposure groups; p = 0.008 for linear trend. cSignificant differences in FEV1 between 1981 and 2011; p < 0.001 for linear trend. | ||||