OR of RA together with 95% CI for male workers classified as exposed to asbestos or silica exposure compared with workers classified as never exposed, by number of occupations* exposed (n=40 887)
| All RA cases | Seropositive RA | Seronegative RA | |||||||
| Cases/controls | Median intensity for asbestos (fibre/cm3) and silica (mg/m3) | Median years since last occupation classified as exposed | Crude OR (95 % CI) * | Adjusted OR (95 % CI) † | Crude OR (95 % CI) * | Adjusted OR (95 % CI) † | Crude OR (95 % CI) * | Adjusted OR (95 % CI) † | |
| Asbestos | |||||||||
| Unexposed workers | 2151/24 033 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | ||
| One occupation | 96/892 | 0.11 | 37 | 1.2 (1.0 to 1.5) | 1.0 (0.8 to 1.3) | 1.3 (1.0 to 1.7) | 1.0 (0.8 to 1.4) | 1.1 (0.8 to 1.6) | 1.1 (0.7 to 1.5) |
| Two occupations | 102/889 | 0.09 | 35 | 1.3 (1.1 to 1.6) | 1.0 (0.8 to 1.3) | 1.2 (1.0 to 1.6) | 0.9 (0.6 to 1.2) | 1.4 (1.0 to 2.0) | 1.3 (0.9 to 1.9) |
| Three occupations | 162/1142 | 0.09 | 34 | 1.6 (1.4 to 1.9) | 1.3 (1.0 to 1.5) | 1.8 (1.5 to 2.2) | 1.3 (1.0 to 1.6) | 1.3 (1.0 to .8) | 1.2 (0.8 to 1.6) |
| Four occupations | 169/1234 | 0.08 | 33 | 1.6 (1.3 to 1.9) | 1.2 (1.0 to 1.5) | 1.7 (1.4 to 2.1) | 1.3 (1.0 to 1.6) | 1.3 (1.0 to 1.8) | 1.1 (0.8 to 1.6) |
| Five occupations | 74/467 | 0.09 | 33 | 1.8 (1.4 to 2.3) | 1.4 (1.0 to 1.8) | 1.8 (1.3 to 2.5) | 1.4 (0.9 to 2.0) | 1.8 (1.2 to 2.6) | 1.5 (1.0 to 2.2) |
| Test for trend (p value) | <0.0001 | 0.0016 | <0.0001 | 0.0075 | 0.0001 | 0.0596 | |||
| Silica | |||||||||
| Unexposed workers | 2956/32 361 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | ||
| One occupation | 298/2355 | 0.10 | 31 | 1.4 (1.2 to 1.6) | 1.2 (1.0 to 1.4) | 1.5 (1.3 to 1.7) | 1.2 (1.0 to 1.5) | 1.2 (1.0 to 1.5) | 1.1 (0.9 to 1.4) |
| Two occupations | 117/865 | 0.07 | 25 | 1.5 (1.2 to 1.8) | 1.3 (1.1 to 1.6) | 1.5 (1.2 to 1.9) | 1.3 (1.0 to 1.7) | 1.4 (1.0 to 2.0) | 1.3 (0.9 to 1.9) |
| Three occupations | 108/668 | 0.07 | 20 | 1.8 (1.5 to 2.2) | 1.5 (1.2 to 1.9) | 1.8 (1.4 to 2.3) | 1.5 (1.1 to 2.0) | 1.7 (1.2 to 2.4) | 1.5 (1.1 to 2.2) |
| Four occupations | 116/641 | 0.06 | 18 | 2.0 (1.6 to 2.4) | 1.8 (1.4 to 2.3) | 2.3 (1.8 to 2.9) | 2.1 (1.5 to 2.8) | 1.4 (1.0 to 2.1) | 1.3 (0.9 to 1.9) |
| Five occupations | 39/174 | 0.08 | 17 | 2.5 (1.7 to 3.5) | 2.1 (1.4 to 3.1) | 2.8 (1.8 to 4.2) | 2.3 (1.4 to 3.8) | 2.1 (1.2 to 3.7) | 1.7 (0.9 to 3.1) |
| Test for trend (p value) | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | 0.0046 | |||
*Adjusted for county, age and index year.
†Adjusted for county, age, index year, pack-years of smoking and alcohol consumption. Asbestos and silica were adjusted for each other.
‡One occupation corresponds to information on occupational title in one census. Censuses were carried out in 1960, 1970, 1975, 1980 and 1990.
RA, rheumatoid arthritis.