Table 3. Distribution and HRsa with 95% CIs for breast cancer risk according to quintiles of cooking method, doneness level, and meat mutagens.
| Characteristic | Q1 | Q2 | Q3 | Q4 | Q5 | P trendb |
|---|---|---|---|---|---|---|
| Cooking method and doneness | ||||||
| Pan-fried meat | ||||||
| Cases/Person-years | 233/56 615 | 243/57 881 | 248/57 319 | 245/57 316 | 235/57 245 | |
| Median (range) (g per 1000 kcal) | 0.1 (⩽0.4) | 0.7 (>0.4–1.1) | 1.7 (>1.1–2.4) | 3.4 (>2.4–5.0) | 8.1 (>5.0–77.1) | |
| HR (95% CI) | 1.00 | 1.01 (0.84–1.21) | 1.05 (0.87–1.27) | 1.04 (0.85–1.27) | 1.03 (0.84–1.27) | 0.76 |
| Grilled meat | ||||||
| Cases/Person-years | 222/56 653 | 246/58 049 | 252/57 887 | 236/57 289 | 248/56 498 | |
| Median (range) (g per 1000 kcal) | 0.1 (⩽0.7) | 1.2 (>0.7–1.9) | 2.8 (>1.9–3.9) | 5.4 (>3.9–7.6) | 11.9 (>7.6–161.1) | |
| HR (95% CI) | 1.00 | 1.07 (0.89–1.29) | 1.09 (0.90–1.31) | 1.02 (0.84–1.24) | 1.10 (0.90–1.34) | 0.54 |
| Well/very well done meat | ||||||
| Cases/Person-years | 235/56 101 | 235/57 952 | 239/57 865 | 236/57 662 | 259/56 796 | |
| Median (range) (g per 1000 kcal) | 1.9 (⩽3.2) | 4.4 (>3.2–5.7) | 7.1 (>5.7–8.9) | 11.1 (>8.9–14.3) | 20.2 (>14.3–158.8) | |
| HR (95% CI) | 1.00 | 0.94 (0.78–1.13) | 0.96 (0.79–1.15) | 0.95 (0.78–1.15) | 1.09 (0.90–1.32) | 0.17 |
| Grilled/pan fried well/very well done meat | ||||||
| Cases/Person-years | 227/56 511 | 250/58 079 | 249/57 823 | 215/57 470 | 263/57 493 | |
| Median (range) (g per 1000 kcal) | 0.3 (⩽0.9) | 1.5 (>0.9–2.3) | 3.1 (>2.3–4.2) | 5.7 (>4.2–7.7) | 11.6 (>7.7–158.8) | |
| HR (95% CI) | 1.00 | 1.07 (0.89–1.29) | 1.07 (0.89–1.29) | 0.94 (0.77–1.14) | 1.20 (0.99–1.45) | 0.10 |
| Meat mutagens | ||||||
| DiMeIQx | ||||||
| Cases/Person-years | 236/58 051 | 236/57 899 | 227/57 868 | 245/57 303 | 261/57 127 | |
| Median (range) (ng per day) | 0.0 (⩽0.1) | 0.2 (>0.1–0.3) | 0.5 (>0.3–0.7) | 1.0 (>0.7–1.6) | 2.5 (>1.6–76.2) | |
| HR (95% CI) | 1.00 | 1.03 (0.86–1.24) | 0.99 (0.83–1.20) | 1.08 (0.90–1.30) | 1.18 (0.98–1.42) | 0.04 |
| MeIQx | ||||||
| Cases/Person-years | 220/58 585 | 255/58 100 | 245/57 333 | 241/57 223 | 244/57 007 | |
| Median (range) (ng per day) | 1.5 (⩽2.8) | 4.2 (>2.8–5.7) | 7.6 (>5.7–10.0) | 13.3 (>10.0–18.2) | 27.8 (>18.2–516.2) | |
| HR (95% CI) | 1.00 | 1.20 (1.00–1.43) | 1.18 (0.98–1.43) | 1.17 (0.97–1.42) | 1.26 (1.03–1.55) | 0.12 |
| PhIP | ||||||
| Cases/Person-years | 238/58 305 | 224/57 940 | 255/57 611 | 235/57 528 | 253/56 865 | |
| Median (range) (ng per day) | 3.7 (⩽7.6) | 12.5 (>7.6–18.7) | 25.9 (>18.7–36.8) | 51.0 (>36.8–75.2) | 121.1 (>75.2–3178.8) | |
| HR (95% CI) | 1.00 | 0.95 (0.79–1.15) | 1.09 (0.91–1.31) | 1.00 (0.83–1.21) | 1.11 (0.92–1.34) | 0.22 |
| B[a]P | ||||||
| Cases/Person-years | 234/58 269 | 257/58 144 | 244/57 638 | 244/57 278 | 226/56 918 | |
| Median (range) (ng per day) | 0.5 (⩽1.3) | 2.2 (>1.3–3.7) | 5.4 (>3.7–7.4) | 11.9 (>7.4–16.7) | 29.9 (>16.7–697.7) | |
| HR (95% CI) | 1.00 | 1.11 (0.93–1.33) | 1.08 (0.90–1.30) | 1.08 (0.90–1.30) | 1.01 (0.83–1.23) | 0.59 |
| Mutagenic activity | ||||||
| Cases/Person-years | 231/58 649 | 241/57 870 | 212/57 517 | 274/57 358 | 247/56 854 | |
| Median (range) (revertant colonies per day) | 235 (⩽448) | 672 (>448–925) | 1247 (>925–1640) | 2205 (>1640–3031) | 4691 (>3031–225039) | |
| HR (95% CI) | 1.00 | 1.08 (0.90–1.30) | 0.96 (0.80–1.17) | 1.26 (1.05–1.52) | 1.18 (0.97–1.44) | 0.05 |
Abbreviations: B[a]P=benzo[a]pyrene; CI=confidence interval; DiMeIQx=2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline; HR=hazard ratio; MeIQx=2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline; PhIP=2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine; Q=quintile.
Adjusted for age (continuous), race (non-Hispanic white, non-Hispanic black, Hispanic, Asian, other), education (⩽11 years, 12 years or high school graduate, post high school training, some college, college graduate or postgraduate education, missing), study centre, randomisation group, family history of breast cancer (yes, no, missing), age at menarche (<10, 10–11, 12–13, 14–15, ⩾16 years, missing), age at menopause (<40, 40–44, 45–49, 50–54, ⩾55 years, missing), age at first birth and number of live births (nulliparous; <20 years and 1, 2, or ⩾3 births; 20–29 years and 1, 2, or ⩾3 births; ⩾30 years and 1, 2, or ⩾3 births; missing), history of benign breast disease (yes, no, missing), number of mammograms during past 3 years (0, 1, >1, missing), menopausal hormone therapy use (never, ⩽1, 2–5, 6–9, ⩾10 years), body mass index (18.5–24.9, 25–29.9, ⩾30 kg m−2), alcohol intake (<5, 5–14.9, ⩾15 g per day), total fat intake (continuous, g per 1000 kcal), and total energy intake (continuous, kcal per day).
P trend calculated using the median of each quintile.