Table 6.
Multivariable-adjusted associations of relaxer use and characteristics of use with breast tumor clinicopathologic features in the overall study sample of breast cancer casesa, N=2,998
| Regular relaxer useb | Duration of relaxer useb |
Early relaxer useb |
Typical relaxer applicationc |
Joint use of hair dye and relaxerd | ||||
|---|---|---|---|---|---|---|---|---|
| ≤10 Years | >10 Years | Did not use before age 12 | Used before age 12 | Home kit | Combination | |||
|
| ||||||||
| Tumor feature | OR (95% CI) | OR (95%CI) | OR (95%CI) | OR (95%CI) | OR (95%CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) |
|
| ||||||||
| Tumor grade | ||||||||
| Well differentiated | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| Moderately differentiated | 0.77 (0.51–1.17) | 0.77 (0.50–1.17) | 0.94 (0.42–2.23) | 0.79 (0.52–1.21) | 0.92 (0.43–1.99) | 0.84 (0.45–1.57) | 0.83 (0.48–1.44) | 0.70 (0.41–1.17) |
| Poorly differentiated | 0.76 (0.49–1.16) | 0.75 (0.49–1.15) | 0.98 (0.44–2.18) | 0.78 (0.51–1.21) | 0.90 (0.42–1.93) | 0.68 (0.36–1.27) | 0.95 (0.55–1.64) | 0.69 (0.41–1.18) |
| Ptrend = 0.037 | Ptrend = 0.050 | Ptrend = 0.20 | Ptrend = 0.051 | Ptrend = 0.16 | Ptrend = 0.97 | Ptrend = 0.82 | Ptrend = 0.38 | |
| Tumor size | ||||||||
| <1.0 cm | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| 1.0–2.0 cm | 1.11 (0.83–1.48) | 1.11 (0.83–1.48) | 1.72 (1.04–2.87) | 1.22 (0.91–1.64) | 1.65 (1.02–2.68) | 1.29 (0.85–1.97) | 1.34 (0.93–1.94) | 1.11 (0.78–1.59) |
| >2.0 cm | 0.88 (0.66–1.19) | 0.90 (0.67–1.22) | 1.03 (0.60–1.76) | 1.03 (0.76–1.39) | 1.03 (0.62–1.71) | 1.45 (0.92–2.29) | 1.82 (1.23–2.69)* | 0.67 (0.46–0.99) |
| Ptrend = 0.16 | Ptrend = 0.31 | Ptrend = 0.0086 | Ptrend = 0.021 | Ptrend = 0.015 | Ptrend = 0.24 | Ptrend = 0.13 | Ptrend = 0.17 | |
| ER status | ||||||||
| Negative | 1.18 (0.88–1.59) | 1.22 (0.91–1.65) | 0.80 (0.47–1.33) | 1.24 (0.92–1.67) | 0.83 (0.51–1.36) | 0.87 (0.58–1.30) | 0.80 (0.56–1.13) | 1.08 (0.75–1.58) |
| Positive | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| Ptrend < 0.001 | Ptrend = 0.099 | |||||||
| HER2 status | ||||||||
| Negative | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| Positive | 0.97 (0.70–1.36) | 0.98 (0.71–1.37) | 1.09 (0.61–1.93) | 1.00 (0.72–1.41) | 1.04 (0.60–1.78) | 0.93 (0.58–1.49) | 0.84 (0.56–1.26) | 1.11 (0.73–1.70) |
| Ptrend = 0.47 | Ptrend = 0.35 | |||||||
| Lymph node status | ||||||||
| Negative | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| Positive | 1.04 (0.77–1.40) | 1.06 (0.78–1.43) | 1.09 (0.66–1.81) | 1.05 (0.77–1.43) | 1.06 (0.65–1.71) | 0.95 (0.62–1.45) | 0.84 (0.58–1.21) | 0.87 (0.60–1.25) |
| Ptrend = 0.078 | Ptrend = 0.0075 | |||||||
| Tumor subtype | ||||||||
| Luminal A | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| HER2-positive | 1.00 (0.71–1.41) | 1.02 (0.72–1.45) | 0.87 (0.47–1.60) | 1.04 (0.73–1.49) | 0.82 (0.46–1.47) | 0.87 (0.52–1.45) | 0.80 (0.52–1.25) | 1.16 (0.75–1.80) |
| Triple-negative | 1.14 (0.79–1.64) | 1.18 (0.82–1.70) | 0.64 (0.34–1.20) | 1.20 (0.83–1.73) | 0.67 (0.37–1.23) | 0.76 (0.46–1.26) | 0.78 (0.50–1.19) | 1.10 (0.69–1.75) |
| Ptrend = 0.052 | Ptrend = 0.25 | |||||||
The multivariable-adjusted model included the following covariates: 1) family history of breast cancer, 2) oral contraceptive use, 3) education, 4) BMI, 5) age, 6) race, and 7) mode of detection.
Never-users of chemical relaxers/straighteners composed the referent group.
Those reporting salon application as the typical application of relaxers composed the referent group.
Those reporting no regular hair dye use and no regular relaxer use (i.e., never-users of both products) composed the referent group.
Significant after correction for multiple comparisons (Bonferroni correction, P <0.01).