Risk of developing RA among workers exposed to organic dust in different number of censuses compared with never exposed workers (n=1 41 917)
| All RA cases | Seropositive RA | Seronegative RA | ||||
| Cases/controls | Mean average intensity (mg/m3) | Median years since last occupation classified as exposed | OR (95% CI)* | OR (95% CI)* | OR (95% CI)* | |
| Wood dust | ||||||
| Unexposed | 11976/123 510 | 1.0 | 1.0 | 1.0 | ||
| 1–2 censuses | 304/2875 | 0.84 | 23 | 0.9 (0.8 to 1.0) | 0.9 (0.8 to 1.0) | 1.0 (0.8 to 1.2) |
| 3–4 censuses | 137/949 | 0.73 | 16 | 1.1 (0.9 to 1.4) | 1.1 (0.9 to 1.4) | 1.3 (1.0 to 1.8) |
| 5–7 censuses | 33/281 | 0.76 | 8 | 0.9 (0.7 to 1.4) | 1.0 (0.7 to 1.5) | 0.8 (0.4 to 1.6) |
| P value for trend | 0.966 | 0.747 | 0.555 | |||
| Animal dust | ||||||
| Unexposed | 12057/124 786 | 1.0 | 1.0 | 1.0 | ||
| 1–2 censuses | 247/2054 | 0.04 | 23 | 1.2 (1.1 to 1.4) | 1.2 (1.0 to 1.4) | 1.3 (1.0 to 1.6) |
| 3–4 censuses | 112/911 | 0.03 | 18 | 1.2 (1.0 to 1.5) | 1.2 (0.9 to 1.5) | 1.4 (1.0 to 1.9) |
| 5–7 censuses | 57/405 | 0.03 | 12 | 1.5 (1.1 to 1.9) | 1.6 (1.1 to 2.2) | 1.3 (0.8 to 2.0) |
| P value for trend | 0.000 | 0.003 | 0.016 | |||
| Paper dust | ||||||
| Unexposed | 11664/120 452 | 1.0 | 1.0 | 1.0 | ||
| 1–2 censuses | 502/4929 | 0.10 | 21 | 1.0 (0.9 to 1.1) | 1.0 (0.9 to 1.1) | 1.0 (0.8 to 1.2) |
| 3–4 censuses | 96/893 | 0.12 | 15 | 1.1 (0.9 to 1.3) | 1.1 (0.9 to 1.5) | 0.9 (0.6 to 1.4) |
| 5–7 censuses | 20/222 | 0.09 | 8 | 0.9 (0.6 to 1.5) | 1.0 (0.6 to 1.7) | 0.8 (0.4 to 1.8) |
| P value for trend | 0.760 | 0.411 | 0.501 | |||
| Textile dust | ||||||
| Unexposed | 12086/124 486 | 1.0 | 1.0 | 1.0 | ||
| 1–2 censuses | 314/2740 | 0.14 | 32 | 1.1 (1.0 to 1.3) | 1.1 (1.0 to 1.3) | 1.1 (0.9 to 1.3) |
| 3–4 censuses | 55/428 | 0.13 | 21 | 1.2 (0.9 to 1.6) | 1.2 (0.9 to 1.7) | 1.2 (0.7 to 2.0) |
| 5–7 censuses | 8/66 | 0.13 | 15 | 1.2 (0.6 to 2.5) | 1.3 (0.6 to 3.1) | – |
| P value for trend | 0.021 | 0.014 | 0.564 | |||
| Flour dust | ||||||
| Unexposed | 12504/128 602 | 1.0 | 1.0 | 1.0 | ||
| 1–2 censuses | 62/617 | 1.13 | 26 | 1.0 (0.8 to 1.3) | 0.9 (0.7 to 1.3) | 1.1 (0.7 to 1.7) |
| 3–4 censuses | 12/81 | 1.21 | 18 | 1.4 (0.8 to 2.7) | 1.6 (0.8 to 3.2) | – |
| 5–7 censuses | 4/35 | 1.21 | 14 | – | – | – |
| P value for trend | 0.256 | 0.637 | 0.186 | |||
*Adjusted for county, age, sex, index year, education and silica dust.
RA, rheumatoid arthritis.