Table 2.
Cox proportional hazard ratios (95% confidence intervals) for overall and specific cancer incidence and cancer related deaths among women in the Nurses’ Health Study according to personal use of permanent hair dyes and natural hair color
| Type of cancer | Any hair color | Dark hair color | Light hair color | P value for interaction | |||||
|---|---|---|---|---|---|---|---|---|---|
| No of events | Hazard ratio (95% CI) | No of events | Hazard ratio (95% CI) | No of events | Hazard ratio (95% CI) | ||||
| All cancers* | 22 612 | 0.98 (0.96 to 1.01) | 8389 | 1.00 (0.96 to 1.05) | 9417 | 0.98 (0.94 to 1.02) | 0.42 | ||
| All solid cancers* | 20 805 | 0.98 (0.96 to 1.01) | 7648 | 0.99 (0.95 to 1.04) | 8708 | 0.98 (0.94 to 1.02) | 0.69 | ||
| Basal cell carcinoma† | 22 560 | 1.05 (1.02 to 1.08) | 7737 | 1.01 (0.96 to 1.06) | 11 334 | 1.06 (1.02 to 1.11) | 0.21 | ||
| Cutaneous squamous cell carcinoma† | 2792 | 1.00 (0.93 to 1.09) | 959 | 1.02 (0.89 to 1.16) | 1375 | 0.95 (0.85 to 1.06) | 0.36 | ||
| Melanoma† | 1198 | 1.01 (0.89 to 1.14) | 386 | 0.93 (0.75 to 1.16) | 580 | 1.00 (0.84 to 1.19) | 0.62 | ||
| Breast cancer‡ | 9252 | 1.02 (0.98 to 1.07) | 3565 | 1.06 (0.99 to 1.13) | 3902 | 1.02 (0.96 to 1.09) | 0.38 | ||
| Breast cancer (ER+)ठ| 5905 | 1.00 (0.95 to 1.05) | 2388 | 1.01 (0.93 to 1.10) | 2595 | 1.01 (0.93 to 1.09) | 0.61 | ||
| Breast cancer (ER−)‡§ | 1521 | 1.02 (0.92 to 1.14) | 610 | 1.16 (0.98 to 1.37) | 649 | 1.00 (0.85 to 1.17) | 0.12 | ||
| Breast cancer (PR+)ठ| 4826 | 0.97 (0.92 to 1.03) | 1933 | 0.99 (0.90 to 1.08) | 2148 | 0.96 (0.88 to 1.05) | 0.48 | ||
| Breast cancer (PR−)‡§ | 2379 | 1.05 (0.97 to 1.15) | 977 | 1.13 (0.99 to 1.29) | 1003 | 1.09 (0.96 to 1.24) | 0.48 | ||
| Breast cancer (ER+/PR+)ठ| 4634 | 0.97 (0.91 to 1.03) | 1848 | 0.98 (0.89 to 1.07) | 2079 | 0.96 (0.88 to 1.06) | 0.58 | ||
| Breast cancer (ER+/PR−)‡§ | 1086 | 1.09 (0.97 to 1.24) | 459 | 1.11 (0.92 to 1.35) | 441 | 1.20 (0.99 to 1.45) | 0.67 | ||
| Breast cancer (ER−/PR−)‡§ | 1287 | 1.03 (0.92 to 1.15) | 517 | 1.15 (0.96 to 1.38) | 561 | 1.02 (0.86 to 1.21) | 0.19 | ||
| Ovarian cancer¶ | 1215 | 1.09 (0.97 to 1.22) | 449 | 1.21 (1.00 to 1.47) | 509 | 1.06 (0.89 to 1.27) | 0.54 | ||
| Colorectal cancer** | 2394 | 1.05 (0.97 to 1.14) | 858 | 1.07 (0.93 to 1.23) | 991 | 1.03 (0.91 to 1.18) | 0.97 | ||
| Bladder cancer†† | 596 | 1.05 (0.90 to 1.24) | 227 | 1.06 (0.81 to 1.38) | 260 | 1.09 (0.85 to 1.39) | 0.81 | ||
| Kidney cancer | 477 | 1.03 (0.85 to 1.23) | 184 | 0.99 (0.73 to 1.34) | 190 | 1.13 (0.84 to 1.51) | 0.42 | ||
| Lung cancer | 2623 | 0.94 (0.87 to 1.01) | 908 | 0.81 (0.70 to 0.93) | 1017 | 0.97 (0.85 to 1.10) | 0.06 | ||
| Brain cancer | 277 | 0.72 (0.56 to 0.93) | 100 | 0.91 (0.60 to 1.37) | 100 | 0.53 (0.35 to 0.82) | 0.08 | ||
| All hematopoietic cancers | 1807 | 1.00 (0.91 to 1.10) | 741 | 1.08 (0.93 to 1.26) | 709 | 0.94 (0.81 to 1.10) | 0.14 | ||
| All non-Hodgkin lymphomas | 1277 | 0.94 (0.84 to 1.05) | 529 | 0.99 (0.83 to 1.18) | 510 | 0.92 (0.77 to 1.09) | 0.52 | ||
| T cell lymphoma | 51 | 1.24 (0.71 to 2.17) | 25 | 0.88 (0.38 to 2.04) | 15 | 1.64 (0.56 to 4.75) | 0.26 | ||
| Diffuse large B cell lymphoma | 190 | 1.06 (0.79 to 1.42) | 76 | 1.16 (0.72 to 1.84) | 79 | 0.87 (0.55 to 1.37) | 0.45 | ||
| Follicular lymphoma | 204 | 1.20 (0.91 to 1.59) | 83 | 1.45 (0.93 to 2.25) | 87 | 1.12 (0.73 to 1.72) | 0.33 | ||
| Chronic lymphocytic leukemia or small lymphocytic lymphoma | 272 | 0.69 (0.53 to 0.89) | 122 | 0.78 (0.54 to 1.14) | 111 | 0.62 (0.41 to 0.92) | 0.35 | ||
| Hodgkin lymphoma‡‡ | 70 | 1.32 (0.82 to 2.13) | 24 | 3.89 (1.61 to 9.40) | 31 | 0.70 (0.33 to 1.49) | 0.004 | ||
| Multiple myeloma‡‡ | 274 | 1.10 (0.86 to 1.40) | 113 | 1.07 (0.73 to 1.56) | 108 | 1.13 (0.77 to 1.67) | 0.85 | ||
| Myeloid leukemias | 170 | 0.99 (0.72 to 1.34) | 59 | 1.17 (0.69 to 1.97) | 64 | 0.90 (0.55 to 1.50) | 0.46 | ||
| Cancer related death§§ | 4860 | 0.96 (0.91 to 1.02) | 1661 | 1.01 (0.91 to 1.11) | 1801 | 0.94 (0.85 to 1.03) | 0.32 | ||
ER=estrogen receptor; MET=metabolic equivalent of task; PR=progesterone receptor.
All models were adjusted for age (continuous, months), follow-up cycle (each two year interval), race (white, black, other), natural hair color (dark brown, light brown, black, blond, red, missing), cumulative average body mass index (<20.0, 20.0-24.9, 25.0-29.9, ≥30.0), body mass index at age 18 (<20.0, 20.0-24.9, 25.0-29.9, ≥30.0), smoking status (non-smoker, past smoker, current smoker <25 cigarettes/day, current smoker ≥25 cigarettes/day), pack years of smoking (0, >0 to 5, >5 to 15, >15), and alcohol intake (0, 0.1-4.9, 5-14.9, ≥15 g/day). In analyses stratified by natural hair color, models were not further adjusted for natural hair color. Any hair color included participants whose natural hair color was black, dark brown, red, blond, or light brown, or who had missing information on natural hair color. Dark natural hair color included participants with black and dark brown hair; light natural hair color covered participants with red, blond, and light brown hair. Participants were excluded from stratified analyses if they had missing information on natural hair color. Number of events among women with dark hair color and light hair color does not add up to total number of events in any hair color because of inclusion of women with missing hair color information in the any hair color group.
Not including basal cell carcinoma and cutaneous squamous cell carcinoma.
Models were additionally adjusted for childhood reaction to sun (practically none, some redness, burn, or painful burn/blisters), lifetime blistering sunburns (never, 1-2, 3-5, and ≥6 times), number of moles on arms (0, 1-2, 3-5, and ≥6), and cumulative ultraviolet flux since baseline (×10−4 Robertson-Berger units: an estimate of amount of ultraviolet radiation reaching Earth’s surface of residence within one year, fifths).
Models were additionally adjusted for menopausal status (premenopausal, postmenopausal), postmenopausal hormone use (no use, past use, current use), oral contraceptive use (no use, ever use), adolescent body size (average of diagram scores at ages 10 and 20 years; 1.0, 1.5-2.0, 2.5-3.0, 3.5-4.0, and ≥4.5), age at menarche (<12, 12-13, and ≥14 years), age at first birth (<25, 25-29, and ≥30 years), parity (nulliparous, parous), breastfeeding (ever, never), first degree family history of breast cancer (yes, no), history of benign breast disease (yes, no), and current mammography use (yes, no).
Hormone receptor status was not available for all breast cancers.
Models were additionally adjusted for menopausal status (premenopausal, postmenopausal), postmenopausal hormone use (no use, past use, current use), age at menarche (<12, 12-13, and ≥14 years), oral contraceptive use (no use, ever use), and parity (nulliparous, parous).
Models were additionally adjusted for physical activity (MET hours/week, fifths), menopausal status (premenopausal, postmenopausal), postmenopausal hormone use (no use, past use, current use), family history of colorectal cancer (yes, no), history of diabetes mellitus (yes, no), screening colonoscopy or sigmoidoscopy in the previous two years (yes, no), regular use of aspirin (yes, no), regular use of non-aspirin non-steroidal anti-inflammatory drugs (yes, no), multivitamin use (yes, no), total calorie intake (kcal/day, fifths), red or processed meat intake (servings/day, fifths), and intake of fiber, folate, calcium, and vitamin D (fifths).
Models were additionally adjusted for total fluid intake (mL/day, quarters).
Models were additionally adjusted for regular use of aspirin (yes, no).
Models were additionally adjusted for physical activity (MET hours/week, fifths), menopausal status (premenopausal, postmenopausal), postmenopausal hormone use (no use, past use, current use), parity (nulliparous, parous), regular use of aspirin (yes, no), regular use of non-aspirin non-steroidal anti-inflammatory drugs (yes, no), multivitamin use (yes, no), total calories intake (kcal/day, fifths), history of hypertension (yes, no), history of hypercholesterolemia (yes, no), and history of diabetes mellitus (yes, no).