Table 4.
Hazard ratios (HR) of bladder cancer and 95% confidence interval (95% CI) according to exposure to crude oil, mineral oil, and diesel exhaust in the Norwegian Offshore Petroleum Workers cohort followed 1999–2017.
| Complete-case analysea | Multiple imputation analysea | |||||
|---|---|---|---|---|---|---|
| (n = 2156) | (n = 2254) | |||||
| Exposure variables | Cases | Non-cases | HR (95% CI)b | HR (95% CI)b | ||
| Crude oil skin exposure | ||||||
| Duration in years, n (%)c | ||||||
| 0 | 43 | 472 | 1.00 | (reference) | 1.00 | (reference) |
| >0–<6.7 | 47 | 508 | 1.02 | (0.65–1.59) | 0.98 | (0.63–1.51) |
| 6.7–<14.9 | 45 | 501 | 0.95 | (0.61–1.48) | 0.89 | (0.58–1.38) |
| 14.9–33.5 | 42 | 498 | 0.87 | (0.53–1.40) | 0.97 | (0.61–1.53) |
| p-trendd | 0.488 | 0.781 | ||||
| Continuous | 177 | 1979 | 1.00 | (0.97–1.01) | 1.00 | (0.98–1.02) |
| Cumulative exposure, n (%)c,e | ||||||
| 0 | 43 | 472 | 1.00 | (reference) | 1.00 | (reference) |
| >0–<7.5 | 41 | 511 | 0.86 | (0.54–1.37) | 0.83 | (0.53–1.30) |
| 7.5–<18.0 | 45 | 500 | 0.95 | (0.61–1.47) | 0.93 | (0.61–1.43) |
| 18.0–70.5 | 48 | 496 | 1.02 | (0.64–1,62) | 1.07 | (0.69–1,67) |
| p-trendd | 0.709 | 0.813 | ||||
| Continuous | 177 | 1979 | 1.01 | (0.99–1.02) | 1.01 | (0.99–1.02) |
| Mineral oil skin exposure | ||||||
| Duration in years, n (%)c | ||||||
| 0 | 72 | 774 | 1.00 | (reference) | 1.00 | (reference) |
| >0–<6.0 | 36 | 404 | 0.99 | (0.64–1.53) | 1.02 | (0.67–1.54) |
| 6.0–<13.5 | 31 | 404 | 0.83 | (0.54–1.30) | 0.80 | (0.51–1.23) |
| 13.5–30.7 | 38 | 397 | 1.07 | (0.69–1.66) | 1.16 | (0.77–1.77) |
| p-trendd | 0.978 | 0.745 | ||||
| Continuous | 177 | 1979 | 1.00 | (0.98–1.02) | 1.01 | (0.99–1.03) |
| Cumulative exposure, n (%)c,e | ||||||
| 0 | 72 | 774 | 1.00 | (reference) | 1.00 | (reference) |
| >0–<6.7 | 32 | 403 | 0.90 | (0.57–1.41) | 0.91 | (0.59–1.41) |
| 6.7–<19.6 | 38 | 397 | 1.06 | (0.70–1.62) | 1.04 | (0.69–1.57) |
| 19.6–60.0 | 35 | 405 | 0.92 | (0.60–1.42) | 1.00 | (0.66–1.51) |
| p-trendd | 0.838 | 0.887 | ||||
| Continuous | 177 | 1979 | 1.00 | (0.99–1.01) | 1.00 | (0.99–1.02) |
| Mineral oil inhalation exposure | ||||||
| Duration in years, n (%)c | ||||||
| 0 | 53 | 561 | 1.00 | (reference) | 1.00 | (reference) |
| >0–<6.1 | 45 | 469 | 1.03 | (0.67–1.56) | 1.04 | (0.69–1.57) |
| 6.1–<14.0 | 37 | 478 | 0.80 | (0.52–1.24) | 0.78 | (0.50–1.19) |
| 14.0–32.0 | 42 | 471 | 0.99 | (0.63–1.57) | 1.09 | (0.70–1.68) |
| p-trendd | 0.718 | 0.976 | ||||
| Continuous | 177 | 1979 | 1.00 | (0.97–1.02) | 1.00 | (0.98–1.02) |
| Cumulative exposure, n (%)c,e | ||||||
| 0 | 53 | 561 | 1.00 | (reference) | 1.00 | (reference) |
| >0–<6.8 | 42 | 469 | 0.97 | (0.63–1.49) | 0.96 | (0.63–1.46) |
| 6.8–<18.1 | 39 | 477 | 0.88 | (0.57–1.37) | 0.90 | (0.59–1.37) |
| 18.1–60.0 | 43 | 472 | 0.96 | (0.62–1.48) | 1.03 | (0.68–1.56) |
| p-trendd | 0.842 | 0.874 | ||||
| Continuous | 177 | 1979 | 1.00 | (0.99–1.01) | 1.00 | (0.99–1.02) |
| Diesel exhaust exposure | ||||||
| Duration in years, n (%)c | ||||||
| 0 | 99 | 1049 | 1.00 | (reference) | 1.00 | (reference) |
| >0–<4.0 | 28 | 309 | 0.97 | (0.62–1.52) | 0.98 | (0.63–1.51) |
| 4.0–<11.0 | 26 | 305 | 0.89 | (0.56–1.41) | 0.88 | (0.57–1.38) |
| 11.0–30.7 | 24 | 316 | 0.81 | (0.50–1.29) | 0.91 | (0.59–1.42) |
| p-trendd | 0.343 | 0.623 | ||||
| Continuous | 177 | 1979 | 0.99 | (0.97–1.02) | 1.00 | (0.98–1.03) |
| Cumulative exposure, n (%)c,e | ||||||
| 0 | 99 | 1049 | 1.00 | (reference) | 1.00 | (reference) |
| >0–<2.4 | 28 | 308 | 1.01 | (0.64–1.58) | 1.02 | (0.66–1.58) |
| 2.4–<7.5 | 24 | 311 | 0.82 | (0.51–1.31) | 0.80 | (0.50–1.26) |
| 7.5–61.2 | 26 | 311 | 0.84 | (0.53–1.33) | 0.97 | (0.63–1.47) |
| p-trendd | 0.404 | 0.787 | ||||
| Continuous | 177 | 1979 | 1.01 | (0.97–1.04) | 1.01 | (0.98–1.04) |
aAdjusted for age as timescale, year of first employment, tobacco smoking and education (Model 1).
bCox regression adapted to a case-cohort design. Missing: tobacco smoking (n = 79), education (n = 21). Missing values were imputet in the multiple imputation analysis.
cCategorised into unexposed (0) and tertiles among exposed.
dModelled by using the median of each category to test for linear trend.
eThe cumulative exposure metric, for crudoil, mineral oil and diesel exhaust, was based on an exposure rating derived from a likelihood-based JEM.