Airways Obstruction From Asbestos Exposure: Categories
Each posteroanterior radiograph was scored for profusion category on the expanded ILO scale from 0/0 to 3/3. One experienced reader read all radiographs for consistency of interpretation. Periodically during the study, at intervals of 500 chest films, blinded sets of 100 chest films were reread for intrareader variation. Variation was confined to ILO profusion categories of 0/1, 1/0, and 1/1, was randomly above or below original readings, and never exceeded and testing their significance and the proportion of the variance each explained.
All pulmonary function values were adjusted for height and age of workers and expressed as means percent predicted. Because 81 percent of these men had smoked cigarettes for 1 year or longer, for current and ex-smokers, FEVi, flows, and TLC were adjusted for duration of smoking. These regression equations gave equivalent values to those of Morris et al in nonsmokers.
For current and ex-smokers, a coefficient for duration of smoking in years2 was included as follows: FEVi=0.566 Ht cm—0.0233 age—0.0094 duration of smoking—4.908. Log FEF25-75=0.0081 Ht cm—0.0096 age—0.0052 duration of smoking+0.3005. Log FEF75-85=0.0120 Ht cm—0.0222 age—0.0112 duration of smoking-1.0752 read natural asthma treatment. TLC=0.0971+0.0156 Ht cm—0.0017 Wt kg+0.0014 duration of smoking. The data on asbestos-exposed men and those with asbestosis were compared with those of 370 unexposed men, including 119 never smokers, 166 current smokers, and 85 ex-smokers (Table 1). This population was normally distributed for age and smaller than the matched asbestos exposed and asbestosis groups. Age distributions were skewed in the asbestos groups by 15 years, which was the latency or study entry interval. Since age matching of the non-asbestos-exposed group to the other groups was impossible, we relied on the linearity with age of the regression equations for volumes (FVC and TLC) and flows (FEVi, FEF25-75, and FEF75-85). Use of age, height, and duration of smoking adjusted regression equations (percent predicted) should not bias the comparisons. To check this procedure appropriateness, we calculated residuals by subtracting each man’s measured values for pulmonary function from his predicted values and t tested the mean differences for the paired groups (Tables 2 through 5).
Table 1—Comparison in Men by Smoking Groups for Demography and Airway Disease Expressed as Means and SDs Associated With Pulmonary Asbestosis (ILO Category Profusion of Opacities 1/0 or Greater) Compared With Age-Matched Asbestos-Exposed Men and to Men Without Exposure
ANo Exposure | ВAsbestos Exposure | СAsbestosis | |||||||
Mean | SD | Mean | SD | Mean | SD | ||||
Never smoked | |||||||||
No. | 119 | 119 | 119 | ||||||
Age, yr | 41.6 | 18.4 | 61.8 | 11.2 | 61.8 | 11.3 | |||
Height, cm | 176.3 | 7.1 | 173.7 | 7.6 | 174.6 | 6.8 | |||
Weight, kg | 97.8 | 7.4 | 85.6 | 13.9 | 88.0 | 14.7 | |||
Duration of asbestos exposure | 0 | 28.4 | 11.4 | 30.6 | 10.2 | ||||
Chronic bronchitis | 5.2 | 18.5 | 22.7 | ||||||
Asthma criteria, % | 6.5 | 7.6 | 15.1 | ||||||
Current smokers | |||||||||
No. | 166 | 722 | 722 | ||||||
Age, yr | 38.9 | 12.4 | 58.0 | 9.3 | 58.0 | 9.4 | |||
Height, cm | 175.2 | 6.6 | 174.2 | 6.6 | 174.8 | 9.4 | |||
Weight, kg | 97.3 | 6.9 | 82.8 | 32.7 | 86.6 | 15.7 | |||
Duration of asbestos exposure | 0 | 30.5 | 10.8 | 30.6 | 10.9 | ||||
Duration smoke | 22.3 | 13.7 | 32.7 | 13.4 | 34.3 | 12.8 | |||
Cigarettes/day | 23.0 | 15.0 | 29.1 | 14.7 | 29.4 | 13.5 | |||
Chronic bronchitis | 16.2 | 30.5 | 38.8 | ||||||
Asthma criteria, % | 13.9 | 13.3 | 20.8 | ||||||
Ex-smokers | |||||||||
No. | 85 | 305 | 305 | ||||||
Age, yr | 51.1 | 14.6 | 63.2 | 9.8 | 63.2 | 9.9 | |||
Height, cm | 174.4 | 6.6 | 174.1 | 5.8 | 175.0 | 6.3 | |||
Weight, kg | 95.9 | 6.9 | 85.8 | 14.0 | 88.4 | 14.8 | |||
Duration of asbestos exposure | 0 | 31.1 | 11.4 | 32.2 | 11.1 | ||||
Duration smoke | 30.2 | 15.2 | 25.8 | 13.6 | 30.0 | 14.0 | |||
Cigarettes/day | 28.8 | 15.4 | 28.7 | 17.7 | 28.8 | 16.3 | |||
Chronic bronchitis | 16.5 | 20.0 | 32.8 | ||||||
Asthma criteria, % | 8.2 | 14.1 | 20.0 |
Table 2—Pulmonary Function Measurements as (Percent Predicted) Means for Men With Asbestos Exposure (B) and With Asbestosis (C) Compared With Unexposed (A) by Smoking Groups (Significant p Values Are Underlined)
Percentage of Predicted Mean | p Values for Comparisons | |||||
AUnexposed | ВAsbestosExposed | СAsbestosis | В to A Asbestos Exposed to Unexposed | С to A Asbestosis to Unexposed | С to В Asbestosis to Asbestos Exposed | |
Never smoked | ||||||
FVC | 99.7 | 97.9 | 94.3 | 0.772 | 0.004 | 0.065 |
FEVi | 97.3 | 93.3 | 89.3 | 0.082 | 0.0002 | 0.086 |
FEF25-75 | 97.6 | 89.1 | 82.9 | 0.089 | 0.0004 | 0.222 |
FEF75-85 | 99.0 | 80.6 | 72.8 | 0.0001 | 0.0001 | 0.204 |
TLC | 99.6 | 106.5 | 106.2 | 0.0001 | 0.0001 | 0.868 |
RV/TLC | 30.3 | 42.5 | 44.8 | 0.0001 | 0.0001 | 0.19 |
FEVi/FVC | 80.0 | 75.6 | 75.2 | 0.0001 | 0.0001 | 0.709 |
Current smokers | ||||||
FVC | 95.7 | 93.9 | 90.3 | 0.139 | 0.0003 | 0.0001 |
FEVi | 95.1 | 87.7 | 85.0 | 0.0001 | 0.0001 | 0.016 |
FEF25-75 | 94.8 | 71.8 | 70.0 | 0.0001 | 0.0001 | 0.378 |
FEF75-85 | 106.5 | 76.3 | 71.4 | 0.0001 | 0.0001 | 0.049 |
TLC | 102.3 | 115.1 | 112.3 | 0,0001 | 0.0001 | 0.0001 |
RV/TLC | 34.1 | 47.9 | 48.4 | 0.0001 | 0.0001 | 0.434 |
FEVi/FVC | 77.3 | 67.8 | 68.2 | 0.0001 | 0.0001 | 0.519 |
Ex-smokers | ||||||
FVC | 97.3 | 95.2 | 89.5 | 0.2807 | 0.0002 | 0.0001 |
FEVi | 98.4 | 91.2 | 84.8 | 0.003 | 0.0001 | 0.0004 |
FEF25-75 | 97.9 | 78.2 | 71.0 | 0.0001 | 0.0001 | 0.026 |
FEF75-85 | 118.4 | 78.5 | 76.1 | 0.0001 | 0.0001 | 0.545 |
TLC | 100.0 | 111.9 | 111.4 | 0.0001 | 0.0001 | 0.68 |
RV/TLC | 35.9 | 47.1 | 49.4 | 0.0001 | 0.0001 | 0.085 |
FEVi/FVC | 77.2 | 70.2 | 68.3 | 0.0001 | 0.0001 | 0.05 |
Table 3—Comparison of Differences From Predicted and Statistical Significance by t Test for Pulmonary Function Measurements of Asbestos-Exposed Men and Unexposed Men by Smoking Categories
Range of Differences | MeanDifference | t | p Value | ||
Mean | SD | ||||
Never smoked | |||||
FVC | 0.114 | 0.692 | |||
0.017 | 0.642 | 0.098 | 1.13 | 0.2606 | |
FEVi | 0.246 | 0.614 | |||
0.105 | 0.542 | 0.141 | 1.87 | 0.0626 | |
FEF25-75 | 0.297 | 1.294 | |||
-0.079 | 0.998 | 0.376 | 2.50 | 0.0131 | |
FEF75-85 | 0.142 | 0.379 | |||
-0.025 | 0.443 | 0.167 | 3.12 | 0.0020 | |
TLC | -0.403 | 0.997 | |||
0.031 | 0.882 | -0.494 | -4.04 | 0.0001 | |
Current smokers | |||||
FVC | 0.282 | 0.706 | |||
0.205 | 0.710 | 0.076 | 1.25 | 0.2120 | |
FEVi | 0.408 | 0.713 | |||
0.187 | 0.617 | 0.221 | 4.03 | 0.0001 | |
FEF25-75 | 0.719 | 1.065 | |||
0.163 | 1.174 | 0.882 | 8.87 | 0.0001 | |
FEF75-85 | 0.131 | 0.282 | |||
0.014 | 0.481 | 0.117 | 3.00 | 0.0030 | |
TLC | -1.072 | 0.953 | |||
-0.172 | 0.925 | -0.900 | -11.22 | 0.0001 | |
Ex-smokers | |||||
FVC | 0.221 | 0.666 | |||
0.117 | 0.748 | 0.104 | 1.16 | 0.2498 | |
FEVi | 0.286 | 0.662 | |||
0.062 | 0.615 | 0.224 | 2.91 | 0.0042 | |
FEF25-75 | 0.539 | 1.006 | |||
-0.055 | 1.078 | 0.594 | 4.56 | 0.0001 | |
FEF75-85 | 0.121 | 0.241 | |||
0.088 | 0.419 | 0.032 | 0.68 | 0.4977 | |
TLC | -0.841 | 0.927 | |||
-0.006 | 0.865 | -0.835 | -7.74 | 0.0001 |
Table 4—Comparison of Differences From Predicted and Statistical Significance by t Test for Pulmonary Function Measurements of Men With Asbestosis and Unexposed Men by Smoking Categories
Range of Differences | MeanDifference | t | p Value | ||
Mean | SD | ||||
Never smoked | |||||
FVC | 0.281 | 0.731 | |||
0.017 | 0.642 | 0.265 | 2.97 | 0.0033 | |
FEVi | 0.383 | 0.625 | |||
0.105 | 0.542 | 0.277 | 3.65 | 0.0003 | |
FEF25-75 | 0.491 | 1.092 | |||
0.079 | 0.998 | 0.570 | 4.21 | 0.0001 | |
FEF75-85 | 0.200 | 0.297 | |||
0.025 | 0.442 | 0.225 | 4.60 | 0.0001 | |
TLC | 0.446 | 0.919 | |||
0.031 | 0.882 | 0.478 | -4.09 | 0.0001 | |
Current smokers | |||||
FVC | 0.446 | 0.717 | |||
0.205 | 0.710 | 0.241 | 3.94 | 0.0001 | |
FEVi | 0.494 | 0.657 | |||
0.187 | 0.617 | 0.307 | 5.70 | 0.0001 | |
FEF25-75 | 0.770 | 1.021 | |||
-0.163 | 1.174 | 0.934 | 9.46 | 0.0001 | |
FEF75-85 | 0.158 | 0.253 | |||
0.014 | 0.481 | 0.144 | 3.73 | 0.0003 | |
TLC | -0.877 | 1.016 | |||
-0.172 | 0.925 | 0.705 | -8.68 | 0.0001 | |
Ex-smokers | |||||
FVC | 0.475 | 0.791 | |||
0.117 | 0.747 | 0.358 | 3.85 | 0.0002 | |
FEVi | 0.489 | 0.723 | |||
0.062 | 0.615 | 0.427 | 5.44 | 0.0001 | |
FEF25-75 | 0.703 | 1.054 | |||
0.055 | 1.078 | 0.757 | 5.76 | 0.0001 | |
FEF75-85 | 0.126 | 0.273 | |||
0.088 | 0.419 | .037 | 0.78 | 0.4381 | |
TLC | -0.813 | 1.104 | |||
-0.006 | 0.865 | -0.807 | -7.12 | 0.0001 |
Table 5—Comparison of Differences From Predicted and Statistical Significance by t Test for Pulmonary Function Measurements of Men With Asbestosis Compared to Age-Matched Asbestos-Exposed Men
Range of Differences | MeanDifference | t | p Value | ||
Mean | SD | ||||
Never smoked | |||||
FVC | 0.281 | 0.731 | |||
0.114 | 0.691 | 0.167 | 1.80 | 0.0726 | |
FEVi | 0.383 | 0.625 | |||
0.246 | 0.613 | 0.136 | 1.69 | 0.0916 | |
FEF25-75 | 0.491 | 1.092 | |||
0.297 | 1.294 | 0.195 | 1.25 | 0.2120 | |
FEF75-85 | 0.200 | 0.297 | |||
0.142 | 0.379 | 0.057 | 1.30 | 0.1947 | |
TLC | -0.446 | 0.919 | |||
0.463 | 0.997 | 0.017 | 0.13 | 0.8934 | |
Current smokers | |||||
FVC | 0.446 | 0.717 | |||
0.281 | 0.706 | 0.165 | 4.39 | 0.0001 | |
FEVi | 0.494 | 0.657 | |||
0.408 | 0.713 | 0.086 | 2.38 | 0.0175 | |
FEF25-75 | 0.770 | 1.021 | |||
0.719 | 1.065 | 0.516 | 0.94 | 0.3479 | |
FEF75-85 | 0.158 | 0.254 | |||
0.131 | 0.282 | 0.027 | 1.91 | 0.0562 | |
TLC | -1.877 | 0.016 | |||
-1.072 | 0.954 | 0.195 | 3.75 | 0.0002 | |
Ex smokers | |||||
FVC | 0.475 | 0.792 | |||
0.221 | 0.666 | 0.254 | 4.29 | 0.0001 | |
FEVi | 0.489 | 0.723 | |||
0.286 | 0.662 | 0.204 | 3.62 | 0.0003 | |
FEF25-75 | 0.703 | 1.054 | |||
0.539 | 1.006 | 0.163 | 1.95 | 0.0512 | |
FEF75-85 | 0.126 | 0.273 | |||
0.121 | 0.241 | 0.005 | 0.24 | 0.8080 | |
TLC | -0.813 | 1.104 | |||
0.841 | 0.927 | 0.028 | 0.34 | 0.7346 |