Risk of skin cancer by rotating night shift work and sleep duration 2001–2011 among women in Nurses' Health Study II
| Skin cancer | Person-years | Number of case participants | Age-adjusted HR (95% CI)* | Multivariable Model HR (95% CI)† |
|---|---|---|---|---|
| Melanoma | ||||
| Years on rotating night shift | ||||
| Never | 195 698 | 67 | 1.00 (referent) | 1.00 (referent) |
| <2 | 185 319 | 54 | 0.86 (0.60 to 1.23) | 0.85 (0.59 to 1.22) |
| 2–5.9 | 164 389 | 45 | 0.83 (0.57 to 1.21) | 0.84 (0.57 to 1.23) |
| 6–9.9 | 76 144 | 28 | 1.11 (0.71 to 1.73) | 1.13 (0.72 to 1.77) |
| ≥10 | 64 556 | 18 | 0.86 (0.51 to 1.45) | 0.95 (0.55 to 1.61) |
| Per 5 years | 0.99 (0.84 to 1.17) | 1.02 (0.86 to 1.21) | ||
| Hours per night of sleep | ||||
| ≤ 6 | 196 562 | 44 | 0.64 (0.45 to 0.92) | 0.68 (0.46 to 0.98) |
| 7 | 292 182 | 100 | 1.00 (referent) | 1.00 (referent) |
| 8 | 160 869 | 60 | 1.09 (0.79 to 1.51) | 1.12 (0.80 to 1.56) |
| ≥9 | 36 394 | 8 | 0.64 (0.31 to 1.31) | 0.64 (0.31 to 1.34) |
| Per 1 hour | 1.14 (1.00 to 1.30) | 1.12 (0.96 to 1.30) | ||
| Basal cell carcinoma | ||||
| Years on rotating night shift | ||||
| Never | 180 825 | 1333 | 1.00 (referent) | 1.00 (referent) |
| <2 | 171 484 | 1179 | 0.94 (0.87 to 1.02) | 0.93 (0.86 to 1.01) |
| 2–5.9 | 152 152 | 1032 | 0.95 (0.88 to 1.03) | 0.96 (0.88 to 1.04) |
| 6–9.9 | 70 873 | 416 | 0.82 (0.73 to 0.92) | 0.83 (0.75 to 0.93) |
| ≥10 | 59 310 | 348 | 0.79 (0.70 to 0.89) | 0.83 (0.74 to 0.94) |
| Per 5 years | 0.92 (0.88 to 0.95) | 0.93 (0.90 to 0.97) | ||
| Hours per night of sleep | ||||
| ≤6 | 182 096 | 1117 | 0.89 (0.82 to 0.96) | 0.93 (0.86 to 1.00) |
| 7 | 270 200 | 1904 | 1.00 (referent) | 1.00 (referent) |
| 8 | 148 947 | 1075 | 1.03 (0.95 to 1.11) | 1.03 (0.95 to 1.11) |
| ≥9 | 33 401 | 212 | 0.92 (0.80 to 1.06) | 0.95 (0.82 to 1.09) |
| Per 1 hour | 1.04 (1.01 to 1.07) | 1.03 (0.99 to 1.06) | ||
| Squamous cell carcinoma | ||||
| Years on rotating night shift | ||||
| Never | 181 704 | 106 | 1.00 (referent) | 1.00 (referent) |
| <2 | 172 281 | 93 | 0.95 (0.72 to 1.26) | 0.94 (0.71 to 1.24) |
| 2–5.9 | 152 832 | 74 | 0.89 (0.66 to 1.20) | 0.86 (0.63 to 1.16) |
| 6–9.9 | 71 151 | 34 | 0.86 (0.58 to 1.26) | 0.85 (0.57 to 1.26) |
| ≥10 | 59 512 | 27 | 0.77 (0.50 to 1.17) | 0.81 (0.53 to 1.25) |
| Per 5 years | 0.91 (0.79 to 1.04) | 0.92 (0.80 to 1.06) | ||
| Hours per night of sleep | ||||
| ≤6 | 182 851 | 97 | 1.00 (0.77 to 1.29) | 1.07 (0.82 to 1.41) |
| 7 | 271 436 | 145 | 1.00 (referent) | 1.00 (referent) |
| 8 | 149 642 | 79 | 1.01 (0.77 to 1.33) | 0.97 (0.73 to 1.28) |
| ≥9 | 33 552 | 13 | 0.73 (0.41 to 1.28) | 0.73 (0.41 to 1.31) |
| Per 1 hour | 0.97 (0.88 to 1.08) | 0.94 (0.83 to 1.06) | ||
*Age-adjusted models include shiftwork and hours of sleep duration.
†Covariates included in the multivariable model: years of shift work (≤2, 2–5.9, 6–9.9, ≥10), hours of sleep per night (≤6, 7, 8, ≥9), sleep adequacy (yes/no), sleepy days per week (none, 1–3, 4–6, 7), snoring (never, occasionally, few, most, every night per week), restless legs syndrome (yes/no), family history of melanoma (yes/no), hours spent in sun per week ages 25–35 (<1, 2–4, ≥5), number of severe sunburns from ages 15 to 20 (none, 1, 2, 3–4, 5–9, ≥10), sunburn severity after ≥2 hours in the sun during childhood (no reaction, some redness, burn, painful burn/blisters), artificial tanning frequency per year ages 25–35 (never, 1–2, 3–5, 6–11, ≥12 per year), annual UV at residence (<104, 104–112, 113–119, 120–144, ≥145 R-B units), moles on lower legs (1–2, 3–4, 5–9, 10–14, 15–20, ≥21), natural hair colour in adolescence (red, blonde, light brown, dark brown, black), marital status (single, married, divorced/separated/widow), financial status on 10-rung ladder (top rungs 9–10, rungs 7–8, rungs 5–6, bottom rungs 1–4), body mass index, kg/m2 (BMI; <22, 22–24.9, 25–28.9, ≥29), physical activity (metabolic equivalents from recreational and leisure-time activities (MET) hours/week: <3, 3–8.9, 9–17.9, 18–26.9, 27–41.9, ≥42), smoking status (never, past, current), menopausal status (premenopausal, postmenopausal, dubious menopause), postmenopausal hormones (no use, past use, current use), oral contraceptive use (never,<4 years, 4 to<8 years, ≥8 years), g/day alcohol intake (none, > 0 to<5; 5 to<10, ≥10); Alternate Healthy Eating Index (0–29, 30–39, 40–49, 50–59, 60–100).