Table 2.
Effect of categorized density on breast cancer risk by centre, age-adjusted
| Population | Percent breast density (%) | Number (%) of cancers | Number (%) of noncancers | OR (95% CI) | Significance (trend) |
| All subjects | 0 to 10 | 18 (6) | 1022 (11) | 1.00 (-) | P < 0.001 |
| 11 to 25 | 76 (24) | 2997 (31) | 1.43 (0.85 to 2.42) | ||
| 26 to 50 | 117 (38) | 3519 (36) | 1.87 (1.13 to 3.11) | ||
| 51 to 75 | 82 (26) | 1875 (19) | 2.44 (1.45 to 4.10) | ||
| 76 to 100 | 18 (6) | 324 (3) | 3.07 (1.57 to 5.99) | ||
| Manchester | 0 to 10 | 2 (1) | 367 (7) | 1.00 (-) | P < 0.001 |
| 11 to 25 | 24 (18) | 1397 (28) | 3.14 (0.73 to 13.35) | ||
| 26 to 50 | 60 (44) | 2229 (44) | 4.89 (1.18 to 20.08) | ||
| 51 to 75 | 41 (30) | 951 (19) | 7.66 (1.83 to 31.93) | ||
| 76 to 100 | 8 (6) | 103 (2) | 13.53 (2.81 to 65.10) | ||
| Aberdeen | 0 to 10 | 16 (9) | 655 (14) | 1.00 (-) | P = 0.12 |
| 11 to 25 | 52 (30) | 1600 (34) | 1.33 (0.75 to 2.35) | ||
| 26 to 50 | 57 (32) | 1290 (28) | 1.80 (1.02 to 3.17) | ||
| 51 to 75 | 41 (23) | 924 (20) | 1.80 (0.99 to 3.25) | ||
| 76 to 100 | 10 (6) | 221 (5) | 1.82 (0.81 to 4.10) | ||
CI, confidence interval; OR, odds ratio.