Table 3.
Associations between hair product use frequency, dye color or duration, and incident invasive ovarian cancer in the Sister Study
| Person-timea | Non-cases; n = 39 648 N (%)a | Ovarian cancer cases; n = 238 N (%)a | Adjusted hazard ratiob (95% CI) | |
|---|---|---|---|---|
| Permanent hair dye | ||||
| Frequency of use in 12 months prior to baseline | ||||
| Never | 181 362 | 17 551 (44) | 108 (46) | 1.00 |
| ≤4 times/year | 93 855 | 9242 (23) | 53 (22) | 1.06 (0.76, 1.48) |
| >4 times per year | 128 938 | 12 652 (32) | 7 (32) | 1.07 (0.79, 1.45) |
| p-for-trend | 0.64 | |||
| Color used in the 12 months prior to baseline | ||||
| Never | 181 362 | 17 551 (44) | 108 (46) | 1.00 |
| Light colorsc | 20 345 | 11 743 (54) | 68 (53) | 0.95 (0.71, 1.27) |
| Dark colorsc | 31 465 | 12 158 (56) | 72 (56) | 1.09 (0.82, 1.45) |
| Duration of use, lifetime | ||||
| Never | 145 914 | 14 099 (36) | 91 (39) | 1.00 |
| 0–<10 years | 129 513 | 12 624 (32) | 60 (26) | 0.80 (0.58, 1.12) |
| ≥10 years | 127 856 | 12 638 (32) | 84 (36) | 1.06 (0.78, 1.43) |
| p-for-trend | 0.75 | |||
| Semi-permanent hair dye | ||||
| Frequency of use in 12 months prior to baseline | ||||
| Never | 324 911 | 31 670 (80) | 185 (79) | 1.00 |
| ≤4 times/year | 47 188 | 4657 (12) | 26 (11) | 1.05 (0.69, 1.59) |
| >4 times per year | 31 779 | 3092 (8) | 24 (10) | 1.33 (0.87, 2.04) |
| p-for-trend | 0.23 | |||
| Color used in the 12 months prior to baseline | ||||
| Never | 324 911 | 31 670 (80) | 185 (79) | 1.00 |
| Light colorsc | 21 427 | 2838 (37) | 13 (26) | 0.72 (0.42, 1.23) |
| Dark colorsc | 29 393 | 5168 (67) | 35 (70) | 1.27 (0.88, 1.82) |
| Duration of use, lifetime | ||||
| Never | 283 620 | 27 696 (70) | 169 (73) | 1.00 |
| 0–<10 years | 89 434 | 8651 (22) | 53 (22) | 0.79 (0.56, 1.12) |
| ≥10 years | 30 197 | 3004 (8) | 76 (32) | 1.17 (0.76, 1.82) |
| p-for-trend | 0.90 | |||
| Straighteners/relaxers, frequency of use in 12 months prior to baseline | ||||
| Never | 369 104 | 35 717 (90) | 213 (90) | 1.00 |
| ≤4 times/year | 16 532 | 1780 (5) | 4 (2) | 0.50 (0.17, 1.44) |
| >4 times per year | 18 931 | 1990 (5) | 20 (8) | 2.19 (1.12, 4.27) |
| p-for-trend | 0.03 | |||
| Hair permanents/body waves, frequency of use in 12 months prior to baseline | ||||
| Never | 354 978 | 34 654 (88) | 200 (84) | 1.00 |
| ≤4 times/year | 44 864 | 4345 (11) | 32 (13) | 0.98 (0.67, 1.44) |
| >4 times per year | 4597 | 480 (1) | 6 (3) | 1.77 (0.75, 4.19) |
| p-for-trend | 0.53 |
aAmong participants with complete covariate information.
bHazard ratio is adjusted for race/ethnicity, education, BMI, age at menarche, menopausal status, parity, oral contraceptive use, hormone therapy use, hysterectomy status, tubal ligation status, smoking, and alcohol use.
cHair color is non-exclusive: participants could be both light and dark users. Percents of color users are calculated based on % of ever users who reported using that color, with some participants reporting using neither (126 non-case semi-permanent users; 3 case semi-permanent users; 201 non-case permanent users) and some missing data for color (37 non-case semi-permanent users; 68 non-case permanent users). In regression models we adjust for use of the opposing color.