Table 1. Host Characteristics Stratified by Cumulative Number of Indoor Tanning Sessions, Norwegian Women and Cancer Study, 1991-2015a.
| Characteristic | Indoor Tanning (n = 138 474) | |||
|---|---|---|---|---|
| Never Use | Lowest Use | Medium Use | Highest Use | |
| Participants, No. (%) | 42 922 (31.0) | 63 979 (46.2) | 15 666 (11.3) | 15 907 (11.5) |
| Person-years of follow-up | ||||
| Total | 694 707 | 1 036 626 | 285 634 | 262 108 |
| Mean | 16.2 | 16.2 | 18.2 | 16.5 |
| Mean (SD) age, y | ||||
| At inclusion | 51.3 (8.7) | 49.1 (7.8) | 47.8 (7.9) | 49.0 (7.6) |
| At diagnosis | 68.6 (9.7) | 64.0 (8.6) | 63.3 (7.1) | 64.9 (8.1) |
| Incident SCC cases | 152 (30.8) | 207 (42.0) | 65 (13.2) | 69 (14.0) |
| Birth cohort | ||||
| 1927-1944 | 43.7 | 36.3 | 10.6 | 9.4 |
| 1945-1952 | 29.7 | 46.5 | 11.8 | 12.0 |
| 1953-1963 | 25.0 | 51.9 | 11.1 | 12.0 |
| Residential ambient UVR exposure | ||||
| Low (northern Norway) | 25.8 | 47.6 | 13.4 | 13.1 |
| Medium-low (central Norway) | 25.5 | 49.5 | 13.2 | 11.8 |
| Medium (southwestern Norway) | 36.2 | 47.0 | 8.5 | 8.3 |
| Highest (southeastern Norway) | 32.5 | 44.5 | 11.0 | 11.9 |
| Educational level, y (n = 131 909) | ||||
| ≤10 | 33.7 | 41.8 | 11.2 | 13.2 |
| 11-13 | 26.1 | 48.7 | 12.3 | 12.8 |
| ≥14 | 31.9 | 48.5 | 10.7 | 8.9 |
| Smoking status at baseline (n = 138 093) | ||||
| Never | 39.6 | 42.5 | 9.5 | 8.4 |
| Former | 27.2 | 48.8 | 12.0 | 12.0 |
| Current | 25.4 | 47.4 | 12.6 | 14.5 |
| Hair color (n = 137 521) | ||||
| Black or dark brown | 35.2 | 44.8 | 9.7 | 10.2 |
| Brown | 29.5 | 47.3 | 11.6 | 11.6 |
| Blond or yellow, red | 30.4 | 45.9 | 11.7 | 12.0 |
| Freckling when sunbathing (n = 121 018)b | ||||
| No | 30.5 | 46.3 | 11.4 | 11.7 |
| Yes | 27.2 | 48.0 | 12.5 | 12.2 |
| Untanned skin color (n = 118 311)b | ||||
| Light | 31.8 | 46.2 | 10.6 | 11.4 |
| Medium | 28.1 | 47.7 | 12.2 | 11.9 |
| Dark | 26.7 | 47.7 | 12.8 | 12.7 |
| Skin reaction to acute sun exposure (n = 74 874)b | ||||
| Brown | 27.9 | 42.1 | 15.4 | 14.6 |
| Red | 31.0 | 43.3 | 14.7 | 11.0 |
| Red with pain | 35.7 | 43.7 | 12.5 | 8.2 |
| Red with pain and blisters | 37.5 | 41.3 | 12.0 | 9.1 |
| Skin reaction to chronic sun exposure (n = 74 930)b | ||||
| Deep brown | 25.4 | 45.2 | 15.4 | 13.9 |
| Brown | 29.4 | 43.5 | 15.0 | 12.1 |
| Light brown | 36.6 | 41.3 | 13.0 | 9.1 |
| Never brown | 60.9 | 28.8 | 6.3 | 4.1 |
| Cumulative No. of sunburns (n = 118 642) | ||||
| None | 39.6 | 41.1 | 9.2 | 10.1 |
| Lowest tertile | 28.6 | 48.5 | 10.9 | 12.0 |
| Middle tertile | 28.1 | 48.5 | 12.2 | 11.2 |
| Highest tertile | 29.6 | 45.9 | 11.9 | 12.6 |
| Cumulative No. of weeks on sunbathing vacations (n = 129 810) | ||||
| None | 67.1 | 24.9 | 4.4 | 3.6 |
| Lowest tertile | 32.2 | 46.5 | 12.2 | 9.1 |
| Middle tertile | 25.3 | 50.4 | 11.8 | 12.6 |
| Highest tertile | 24.8 | 48.5 | 11.6 | 15.2 |
Abbreviations: SCC, squamous cell carcinoma; UVR, UV radiation.
a
Data are presented as row percentages or participants unless otherwise indicated. Because of rounding, percentages may not sum to 100%.
b
Recorded for a subsample of the cohort.