Table 4.
Association between hair product use in the 12 months prior to enrollment and uterine cancer by subtypes
| Hair product usea | Ever |
Frequentb |
P trend e | ||
|---|---|---|---|---|---|
| Case | HR (95% CI)d | Case | HR (95% CI)d | ||
| No. (%)c | No. (%)c | ||||
| Permanent dyes | |||||
| Premenopausal casesf | 12 (50.0) | 0.66 (0.29 to 1.48) | 7 (29.2) | 0.82 (0.32 to 2.13) | .61 |
| Postmenopausal casesf | 173 (50.1) | 0.95 (0.76 to 1.18) | 114 (33.0) | 1.00 (0.79 to 1.28) | .96 |
| Medically confirmed casesg | |||||
| All uterine cancer | 123 (47.9) | 0.80 (0.63 to 1.03) | 86 (33.5) | 0.92 (0.70 to 1.21) | .44 |
| Endometrial cancerh | 119 (49.0) | 0.83 (0.64 to 1.06) | 83 (34.2) | 0.94 (0.71 to 1.24) | .56 |
| Type I endometrial canceri | 97 (49.7) | 0.83 (0.62 to 1.10) | 72 (36.9) | 1.01 (0.74 to 1.37) | .92 |
| Type II endometrial cancerj | 19 (48.7) | 0.90 (0.48 to 1.70) | 11 (28.2) | 0.80 (0.38 to 1.69) | .58 |
| Semipermanent dyes | |||||
| Premenopausal casesf | 5 (20.8) | 0.89 (0.33 to 2.41) | 1 (4.2) | —k | —k |
| Postmenopausal casesf | 59 (17.0) | 0.98 (0.73 to 1.31) | 28 (8.1) | 1.05 (0.71 to 1.55) | .97 |
| Medically confirmed casesg | |||||
| All uterine cancer | 44 (17.1) | 0.98 (0.70 to 1.36) | 20 (7.8) | 1.02 (0.65 to 1.62) | .98 |
| Endometrial cancerh | 39 (16.0) | 0.92 (0.65 to 1.30) | 17 (7.0) | 0.93 (0.56 to 1.52) | .67 |
| Type I endometrial canceri | 33 (16.8) | 0.98 (0.67 to 1.43) | 15 (7.7) | 1.05 (0.62 to 1.79) | .98 |
| Type II endometrial cancerj | 5 (12.8) | 0.73 (0.28 to 1.88) | 2 (5.1) | —k | —k |
| Straighteners, relaxers, or pressing products | |||||
| Premenopausal casesf | 5 (20.8) | 1.56 (0.26 to 9.29) | 5 (2.08) | 1.56 (0.26 to 9.29) | —l |
| Postmenopausal casesf | 33 (9.5) | 1.90 (1.16 to 3.13) | 21 (6.1) | 2.52 (1.39 to 4.55) | .003 |
| Medically confirmed casesg | |||||
| All uterine cancer | 21 (8.2) | 1.94 (1.10 to 3.42) | 14 (5.4) | 2.78 (1.39 to 5.55) | .005 |
| Endometrial cancerh | 17 (7.0) | 1.89 (1.04 to 3.43) | 11 (4.5) | 2.68 (1.30 to 5.53) | .005 |
| Type I endometrial canceri | 13 (6.7) | 1.89 (1.01 to 3.54) | 9 (4.6) | 2.94 (1.42 to 6.08) | .009 |
| Type II endometrial cancerj | 2 (5.1) | —k | 2 (5.1) | —k | —k |
| Hair permanents or body waves | |||||
| Premenopausal casesf | 4 (15.7) | —k | 3 (12.5) | —k | —k |
| Postmenopausal casesf | 49 (14.2) | 0.96 (0.69 to 1.32) | 27 (7.8) | 0.96 (0.63 to 1.46) | .80 |
| Medically confirmed casesg | |||||
| All uterine cancer | 33 (12.8) | 0.93 (0.64 to 1.36) | 19 (7.4) | 1.07 (0.66 to 1.74) | .95 |
| Endometrial cancerh | 31 (12.8) | 0.94 (0.64 to 1.39) | 19 (7.8) | 1.18 (0.72 to 1.92) | .87 |
| Type I endometrial canceri | 26 (13.3) | 1.04 (0.68 to 1.59) | 16 (8.2) | 1.36 (0.80 to 2.32) | .51 |
| Type II endometrial cancerj | 5 (12.8) | 0.82 (0.31 to 2.16) | 3 (7.7) | —k | —k |
Missing: permanent dyes (2 cases, 137 overall); semipermanent dyes (150 overall); straighteners, relaxers, or pressing products (1 case, 98 overall); hair permanents or body waves (2 cases, 93 overall). CI = confidence interval; HR = hazard ratio.
Definition of frequent use: >4 times in the past 12 months (permanent dyes; semipermanent dyes; straighteners, relaxers, or pressing products); >2 times in the past 12 months (hair permanents or body waves).
Participants with complete confounder information. Percentage of ever or frequent users among cases.
Compared with never users. Adjusted for race and ethnicity (African American and/or Black, Hispanic and/or Latina non-Black, non-Hispanic White, other), education (high school or less, some college, college and above), body mass index (restricted cubic spline, continuous, kg/m2), physical activity (metabolic equivalent [MET] hours per week, continuous), menopausal status at enrollment (premenopausal, postmenopausal), parity (0, 1, 2, ≥3), smoking (never, past, or current), alcohol (never or past, current <1 drink, current ≥1 drinks), oral contraceptive use duration (none, <2 years, 2 to <10 years, ≥10 years), hormone replacement therapy (none, estrogen alone, estrogen plus progestin but never estrogen alone), age at menarche (<13 years, ≥13 years old).
Assessed using Wald tests for continuous variables of hair product use frequency (never, infrequent, frequent use).
Person-time is stratified by menopausal status.
Confirmed diagnosis with medical records or death certificates from National Death Index (NDI).
International Classification of Disease (ICD)–10 code of C54.1 = malignant neoplasm of endometrium.
ICD-Oncology-3 histology codes: 8140, 8262, 8380, 8382, 8480, 8560, and 8570.
ICD-Oncology-3 histology codes: 8310, 8323, 8441, 8460, 8950, and 8980.
Data not presented as small number of cases (<5) within any stratum in the model.
Unable to assess Ptrend because all cases are frequent users.