Table 1.
Age and age adjusted characteristics of study population in the Nurses’ Health Study (n=117 200, 1976) across self-reported status of personal use of permanent hair dye. Data are percentages (numbers) unless indicated otherwise
| Characteristic | Status of personal permanent hair dye use | |
|---|---|---|
| Non-user | Ever user | |
| No of participants (%) | 79 430 (67.77) | 37 770 (32.23) |
| Age (mean (SD)) | 42.65 (7.22) | 43.23 (7.19) |
| Race | ||
| White | 96.27 (76 464) | 97.81 (36 941) |
| Black | 2.55 (2027) | 1.54 (581) |
| Other | 1.18 (939) | 0.66 (248) |
| Natural hair color | ||
| Black | 3.62 (2878) | 2.56 (968) |
| Dark brown | 34.32 (27 259) | 29.56 (11 166) |
| Red | 3.65 (2899) | 2.24 (846) |
| Light brown | 27.62 (21 942) | 32.45 (12 256) |
| Blond | 8.02 (6366) | 10.41 (3930) |
| Body mass index (mean (SD))* | 23.83 (4.22) | 23.62 (3.98) |
| Body mass index at age 18 (mean (SD))* | 21.37 (3.03) | 21.29 (2.96) |
| Smoking status | ||
| Never smoked | 47.33 (37 595) | 36.37 (13 737) |
| Past smoker | 21.85 (17 357) | 25.99 (9816) |
| Current smoker (<25 cigarettes/day) | 22.54 (17 906) | 26.83 (10 132) |
| Current smoker (≥25 cigarettes/day) | 8.27 (6572) | 10.81 (4085) |
| Pack years of smoking | ||
| 0 | 48.42 (38 458) | 37.61 (14 204) |
| >0 to 5 | 11.30 (8974) | 12.74 (4811) |
| >5 to 15 | 14.84 (11 786) | 17.50 (6610) |
| >15 | 25.45 (20 211) | 32.15 (12 145) |
| Alcohol intake (g/day; mean (SD)) | 5.89 (10.17) | 7.35 (11.24) |
Participants with a previous diagnosis of any cancer before or at baseline, or participants who reported no information on personal use of permanent hair dyes were excluded. Denominators for percentage calculations are of non-missing values. Percentages may not sum to 100% after rounding.
*
Calculated as weight in kilograms divided by height in meters squared.