Occupational asbestos exposure, smoking, genotype and IPF; interaction terms and stratified analysis (genotyped participants only, n=902)
| Exposure* | Adjusted OR† (95% CI; p value) |
| Interaction model (asbestos*smoking) | |
| Ever asbestos exposed | 0.6 (0.4 to 1.1; 0.08) |
| Ever smoked | 0.9 (0.6 to 1.5; 0.68) |
| Ever asbestos exposed and ever smoked interaction | 2.2 (1.2 to 4; 0.01) |
| Interaction model (asbestos*genotype) | |
| Ever asbestos exposed | 1.0 (0.7 to 1.5; 0.84) |
| Genotype | 3.7 (2.4 to 5.8; 0.001) |
| Ever asbestos exposed and genotype | 1.3 (0.8 to 2.3; 0.3) |
| Interaction model (smoking*genotype) | |
| Ever smoked | 1.29 (0.86 to 1.92; 0.22) |
| Genotype | 3.95 (2.33 to 6.69; 0.001) |
| Ever smoked and genotype | 1.15 (0.62 to 2.13; 0.65) |
| Stratified interaction model (asbestos*smoking) | |
| GT or TT | |
| Ever asbestos exposed | 0.4 (0.2 to 1; 0.06) |
| Ever smoked | 0.6 (0.3 to 1.3; 0.2) |
| Ever asbestos exposed and ever smoked interaction | 5.4 (1.8 to 15.6; 0.002) |
*Ever asbestos exposed was defined as ever having had a high or medium asbestos exposure risk job, defined on the basis of occupational proportional mortality ratios for mesothelioma.16 Genotype of MUC5B rs35705950, T is the minor allele.
†Adjusted for age±smoking, smoking was not adjusted for when it was considered as an exposure. Centre was not adjusted for in this analysis because numbers were too small for one centre. Analysis limited to the 20 centres which did have sufficient numbers showed that adjusting for centre did not significantly change our results.
IPF, idiopathic pulmonary fibrosis.