Table 4.
Estimated net effects of PCB exposure on risk of breast cancer before 50 years of age
| Level of adjustment | Quartile of PCB scorea | Odds ratio (95 % CI) |
|---|---|---|
| Unadjusted | Q1 | 1.00 |
| Q2 | 1.26 (0.53, 3.00) | |
| Q3 | 1.52 (0.64, 3.62) | |
| Q4 | 3.01 (1.34, 6.78) | |
| Cholesterol and triglycerides | Q1 | 1.00 |
| Q2 | 1.23 (0.53, 3.07) | |
| Q3 | 1.53 (0.64, 3.68) | |
| Q4 | 3.09 (1.34, 7.16) | |
| Cholesterol, triglycerides, race, parity, lactation, body mass index, and year of blood sampling | Q1 | 1.00 |
| Q2 | 1.36 (0.53, 3.52) | |
| Q3 | 1.78 (0.70, 4.55) | |
| Q4 | 2.81 (1.11, 7.09) |
CI confidence interval
aA post-hoc PCB score was defined to describe the net effect of PCB exposure in this study sample (described in text). PCB 203 was associated with increased risk, while PCBs 167 and 187 were associated with decreased risk (see final model, Table 2). Therefore, the PCB score was defined as the proportion of PCB 203 relative to the sum of PCBs 167 and 187: PCB 203/(PCB 167 + PCB 187). N = 112 age-matched case–control pairs for all models shown