Table 4:
Exposure assessment to polycyclic aromatic hydrocarbons and breast cancer risk stratified by (first degree) family history of breast cancer‡
| No Family History | (First degree) Family History | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Exposure Assessment | Cases (%) | Controls (%) | OR | 95% CI | Cases (%) | Controls (%) | OR | 95% CI | p-interaction | ||
| Ever-Never: Any level | |||||||||||
| Never | 280 (32.0) | 381 (39.0) | ----- | 62 (28.6) | 73 (44.8) | ----- | |||||
| Ever | 594 (68.0) | 597 (61.0) | 1.23 | 1.01 | 1.51 | 155 (71.4) | 90 (55.2) | 1.84 | 1.16 | 2.92 | |
| p = 0.08 | |||||||||||
| Ever-Never: At maximum level† | |||||||||||
| Never | 280 (32.0) | 381 (39.0) | ----- | 62 (28.6) | 73 (44.8) | ----- | |||||
| Maximum level at low* | 76 (08.7) | 92 (09.4) | 1.04 | 0.73 | 1.48 | 14 (06.4) | 15 (09.2) | 0.95 | 0.40 | 2.24 | |
| Maximum level at medium¶ | 131 (15.0) | 150 (15.3) | 1.16 | 0.87 | 1.56 | 44 (20.3) | 28 (17.2) | 1.68 | 0.90 | 3.13 | |
| Maximum level at high◆ | 387 (44.3) | 355 (36.3) | 1.31 | 1.04 | 1.64 | 97 (44.7) | 47 (28.8) | 2.27 | 1.34 | 3.86 | |
| ptrend = 0.02 | ptrend < 0.01 | pint-trend = 0.03 | |||||||||
| Duration (years) of exposure at any level | |||||||||||
| None (0) | 280 (32.0) | 381 (39.0) | ----- | 62 (28.6) | 73 (44.8) | ----- | |||||
| Short (0.1–4.2) | 178 (20.4) | 194 (19.8) | 1.31 | 1.01 | 1.71 | 57 (26.2) | 35 (21.5) | 1.95 | 1.09 | 3.48 | |
| Moderate (4.3–13.0) | 202 (23.1) | 202 (20.7) | 1.22 | 0.94 | 1.59 | 54 (24.9) | 28 (17.2) | 2.16 | 1.17 | 3.97 | |
| Long (13.1–82.2) | 214 (24.5) | 201 (20.5) | 1.15 | 0.88 | 1.50 | 44 (20.3) | 27 (16.5) | 1.38 | 0.72 | 2.65 | |
| ptrend > 0.2 | ptrend > 0.1 | pint-trend > 0.2 | |||||||||
| Duration (years) of exposure at medium¶ or high◆ levels | |||||||||||
| None (0) | 280 (32.0) | 381 (39.0) | ----- | 62 (28.6) | 73 (44.8) | ----- | |||||
| Ever: Maximum at low levelΔ | 76 (08.7) | 92 (09.4) | 1.04 | 0.73 | 1.47 | 14 (06.4) | 15 (09.2) | 0.97 | 0.41 | 2.28 | |
| Short (0.1–2.7) | 159 (18.2) | 163 (16.6) | 1.36 | 1.03 | 1.80 | 44 (20.3) | 31 (19.0) | 1.64 | 0.90 | 3.00 | |
| Moderate (2.8–9.0) | 152 (17.4) | 169 (17.3) | 1.14 | 0.86 | 1.51 | 51 (23.5) | 27 (16.6) | 2.24 | 1.20 | 4.18 | |
| Long (9.1–80.8) | 207 (23.7) | 173 (17.7) | 1.29 | 0.98 | 1.70 | 46 (21.2) | 17 (10.4) | 2.53 | 1.24 | 5.16 | |
| ptrend = 0.09 | ptrend < 0.01 | pint-trend = 0.01 | |||||||||
| Duration (years) of exposure at the high level◆ | |||||||||||
| None (0) | 280 (32.0) | 381 (39.0) | ----- | 62 (28.6) | 73 (44.8) | ----- | |||||
| Ever: Maximum at low* or medium¶ levels◊ | 207 (23.7) | 242 (24.7) | 1.11 | 0.86 | 1.43 | 58 (26.7) | 43 (26.4) | 1.43 | 0.82 | 2.49 | |
| Short (0.1–2.3) | 121 (13.8) | 114 (11.6) | 1.50 | 1.10 | 2.05 | 35 (16.1) | 20 (12.3) | 1.94 | 0.98 | 3.82 | |
| Moderate (2.4–7.4) | 109 (12.5) | 118 (12.1) | 1.15 | 0.83 | 1.58 | 27 (12.5) | 16 (09.8) | 2.31 | 1.07 | 5.01 | |
| Long (7.5–74.1) | 157 (18.0) | 123 (12.6) | 1.29 | 0.95 | 1.75 | 35 (16.1) | 11 (06.7) | 2.79 | 1.25 | 6.24 | |
| ptrend > 0.1 | ptrend < 0.01 | pint-trend = 0.03 | |||||||||
| Weighted Duration (Years) – Equation (1) | |||||||||||
| None (0) | 280 (32.0) | 381 (39.0) | ----- | 62 (28.6) | 73 (44.8) | ----- | |||||
| Short (0.1–0.4) | 181 (20.7) | 193 (19.7) | 1.25 | 0.96 | 1.63 | 53 (24.4) | 36 (22.1) | 1.66 | 0.94 | 2.94 | |
| Moderate (0.5–1.7) | 287 (21.4) | 201 (20.5) | 1.18 | 0.90 | 1.53 | 46 (21.2) | 28 (17.2) | 1.75 | 0.95 | 3.25 | |
| Long (1.8–55.1) | 226 (25.9) | 203 (20.8) | 1.25 | 0.97 | 1.63 | 56 (25.8) | 26 (15.9) | 2.26 | 1.19 | 4.28 | |
| ptrend > 0.1 | ptrend < 0.01 | pint-trend = 0.06 | |||||||||
| Average Probability – Equation (2) | |||||||||||
| None (0) | 280 (32.0) | 381 (39.0) | ----- | 62 (28.6) | 73 (44.8) | ----- | |||||
| Low (0.01–0.02) | 165 (18.9) | 191 (19.5) | 1.18 | 0.90 | 1.55 | 53 (24.4) | 38 (23.3) | 1.57 | 0.89 | 2.76 | |
| Medium (0.03–0.07) | 212 (24.3) | 202 (20.6) | 1.36 | 1.05 | 1.76 | 43 (19.8) | 27 (16.6) | 1.71 | 0.91 | 3.20 | |
| High (0.08–0.88) | 217 (24.8) | 204 (20.9) | 1.14 | 0.87 | 1.49 | 59 (27.2) | 25 (15.3) | 2.55 | 1.34 | 4.84 | |
| ptrend > 0.1 | ptrend < 0.01 | pint-trend = 0.03 | |||||||||
Adjusted for age, centre, education, ethnicity, smoking (pack-years). All ptrend values are calculated by treating ordinal categories as continuous values
Maximum level classification, regardless of duration, is the maximum exposure level to which the participant was exposed across all occupations.
Analysis for exposure at low level (estimated probability of exposure above 0.2 mg/m3 of coal tar pitch volatiles) is θ = (0.1 – 2.9%) in at least one job
Analysis for exposure at medium level (estimated probability of exposure above 0.2 mg/m3 of coal tar pitch volatiles) is θ = (3.0 – 8.9%) in at least one job
Analysis for exposure at high level (estimated probability of exposure above 0.2 mg/m3 of coal tar pitch volatiles) is θ ≥ 9% in at least one job
To ensure referent group are truly unexposed, a nuisance variable was created for the low-exposed group where value = 1, if highest duration at low level exposure, else 0
To ensure referent group are truly unexposed, a nuisance variable was created for the low/medium-exposed group where value = 1, if highest duration at low or medium level exposure, else 0