Table 5.
Multivariate Analysis of Association Between 8-Hour Time-Weighted Average Endotoxin and Spirometry
| 8-Hour TWA Endotoxina (EU/m3) | FEV1 | P Value | pp FEV1 | P Value | FEV1/FVC | P Value |
|---|---|---|---|---|---|---|
| All (N = 404) | ||||||
| Survey year 2011 | ||||||
| ≤ 50 | ||||||
| 50-1,500 | 17.546 | .759 | 0.090 | .972 | –0.003 | .717 |
| 1,500-2,300 | –121.286 | .091 | –7.022 | .027 | 0.008 | .484 |
| 2,300-3,900 | –9.607 | .892 | –0.553 | .859 | –0.012 | .314 |
| > 3,900 | –135.806 | .071 | –6.717 | .043 | –0.014 | .274 |
| Survey year 2016 | ||||||
| ≤ 50 | ||||||
| 50-1,500 | –54.546 | .341 | –2.386 | .345 | –0.009 | .364 |
| 1,500-2,300 | –164.020 | .023 | –8.570 | .007 | –0.003 | .774 |
| 2,300-3,900 | –50.986 | .472 | –1.253 | .688 | –0.008 | .495 |
| > 3,900 | –155.622 | .041 | –6.634 | .048 | 0.003 | .788 |
| Difference | ||||||
| ≤ 50 | ||||||
| 50-1,500 | –72.093 | .013 | –2.477 | .065 | –0.005 | .455 |
| 1,500-2,300 | –42.734 | .245 | –1.549 | .361 | –0.012 | .181 |
| 2,300-3,900 | –41.379 | .248 | –0.700 | .671 | 0.004 | .656 |
| > 3,900 | –19.816 | .598 | 0.083 | .962 | 0.017 | .058 |
| Cotton workers (n = 178) | ||||||
| Survey year 2011 | ||||||
| ≤ 50 | ||||||
| 50-1,500 | –17.182 | .901 | –0.922 | .871 | –0.006 | .786 |
| 1,500-2,300 | –148.325 | .303 | –7.517 | .208 | 0.006 | .778 |
| 2,300-3,900 | –51.750 | .728 | –1.928 | .754 | –0.015 | .508 |
| > 3,900 | –161.792 | .290 | –7.134 | .260 | –0.018 | .429 |
| Survey year 2016 | ||||||
| ≤ 50 | ||||||
| 50-1,500 | –71.708 | .603 | –3.451 | .546 | –0.028 | .185 |
| 1,500-2,300 | –175.111 | .225 | –9.170 | .126 | –0.023 | .308 |
| 2,300-3,900 | –76.496 | .608 | –2.747 | .657 | –0.028 | .213 |
| > 3,900 | –166.739 | .280 | –7.070 | .268 | –0.018 | .439 |
| Difference | ||||||
| ≤ 50 | ||||||
| 50-1,500 | –54.526 | .408 | –2.529 | .394 | –0.022 | .150 |
| 1,500-2,300 | –26.786 | .701 | –1.653 | .598 | –0.029 | .070 |
| 2,300-3,900 | –24.745 | .720 | –0.819 | .792 | –0.013 | .407 |
| > 3,900 | –4.947 | .944 | 0.063 | .984 | <0.001 | .990 |
Coefficients and P values from the linear mixed model with a random intercept are reported. P < .05 was considered significantly different from zero. Spirometry was the outcome, and 8-h TWA endotoxin was the exposure variable in the model. The linear mixed models were adjusted for age, sex, height, smoking intensity, survey year, and the interaction between 8-h TWA endotoxin and survey year (8-h TWA endotoxin × survey year). E/I MLA = expiratory-to-inspiratory ratio of mean lung attenuation; Exp−856 = percentage of voxels with attenuation less than -856 HU on expiratory CT scans; HU = Hounsfield unit; pp FEV1 = percent predicted FEV1; Residual–856 = residuals from the linear regression of Exp−856 on the percentage of voxels with attenuation less than –950 HU; RVC−856 to −950 = relative volume change in voxels with attenuation between –856 HU and –950 HU; TWA = time-weighted average.
50 EU/m3 represents the reference level. 1,500 EU/m3 is the 40th percentile, 2,300 EU/m3 is the 60th percentile, and 3,900 EU/m3 is the 80th percentile. There are 237 textile workers exposed to ≤ 50 EU/m3 endotoxin, 61 workers exposed to 50 to 1,500 EU/m3 endotoxin, 35 workers exposed to 1,500 to 2,300 EU/m3 endotoxin, 37 workers exposed to 2,300 to 3,900 EU/m3 endotoxin, and 34 workers exposed to more than 3,900 EU/m3.