Table II.
Sleep characteristics and breast cancer risk by ER tumor subtype, NIEHS Sister Study.
| Overall | ER+ invasive | ER− invasive | ||||||
|---|---|---|---|---|---|---|---|---|
| Sleep Measures – Baseline Survey | Person-years N=375,925 | All breast cancer N=2,736 | Age-adjusted HR (95% CI) | Adjusted HRa (95% CI)1 | ER+ N=1,574 | Adjusted HRa (95% CI)1 | ER− N=281 | Adjusted HRa (95% CI)1 |
| Bedtime consistency | ||||||||
| Consistent bedtime | 318,467 | 2,325 | 1 (referent) | 1 (referent) | 1,341 | 1 (referent) | 238 | 1 (referent) |
| Inconsistent (night) | 51,535 | 367 | 0.94 (0.84, 1.05) | 0.92 (0.82, 1.03) | 206 | 0.92 (0.79, 1.08) | 39 | 0.91 (0.63, 1.31) |
| Inconsistent and irregular (night and day) | 4,434 | 39 | 1.20 (0.87, 1.64) | 1.25 (0.90, 1.74) | 25 | 1.43 (0.93, 2.18) | 2 | NE |
| Usual sleep duration | ||||||||
| <6 hours | 87,472 | 626 | 0.94 (0.85, 1.04) | 0.96 (0.86, 1.06) | 321 | 0.87 (0.76, 1.00) | 80 | 1.26 (0.92, 1.73) |
| 7 hours | 133,141 | 1,008 | 1 (referent) | 1 (referent) | 593 | 1 (referent) | 92 | 1 (referent) |
| 8 hours | 129,057 | 895 | 0.9 (0.82, 0.98) | 0.90 (0.82, 0.99) | 534 | 0.90 (0.79, 1.01) | 90 | 1.05 (0.78, 1.42) |
| 9+ hours | 25,729 | 201 | 1.00 (0.86, 1.17) | 1.03 (0.88, 1.20) | 121 | 1.06 (0.87, 1.29) | 18 | 0.94 (0.54, 1.64) |
| Time it takes to fall asleep | ||||||||
| < 15 min | 167,636 | 1,249 | 1.07 (0.98, 1.16) | 1.05 (0.97, 1.15) | 730 | 1.06 (0.95, 1.19) | 123 | 1.02 (0.78, 1.34) |
| 15 – 30 min | 141,602 | 992 | 1 (referent) | 1 (referent) | 574 | 1 (referent) | 99 | 1 (referent) |
| 30 min–1 hour | 44,605 | 339 | 1.09 (0.96, 1.23) | 1.10 (0.97, 1.25) | 193 | 1.09 (0.92, 1.30) | 41 | 1.24 (0.84, 1.81) |
| 1 hour + | 21,471 | 152 | 0.99 (0.84, 1.18) | 0.98 (0.81, 1.17) | 73 | 0.85 (0.65, 1.10) | 18 | 1.02 (0.59, 1.77) |
| Sleep medication use in prior six weeks | ||||||||
| None | 285,228 | 2,091 | 1 (referent) | 1 (referent) | 1,190 | 1 (referent) | 219 | 1 (referent) |
| Yes | 90,591 | 644 | 0.95 (0.87, 1.04) | 0.97 (0.88, 1.06) | 383 | 0.99 (0.88, 1.12) | 62 | 0.9 (0.67, 1.21) |
| Frequency of waking up at night | ||||||||
| Most or every night | 234,799 | 1,809 | 1.09 (0.92, 1.29) | 1.05 (0.88, 1.24) | 1,050 | 1.07 (0.85, 1.35) | 191 | 1.18 (0.68, 2.04) |
| ≥ once a week | 93,708 | 612 | 0.97 (0.81, 1.16) | 0.92 (0.76, 1.10) | 347 | 0.94 (0.73, 1.20) | 62 | 1.00 (0.56, 1.79) |
| 1–3 days a month | 24,736 | 163 | 1.02 (0.81, 1.27) | 0.98 (0.78, 1.23) | 95 | 0.99 (0.73, 1.34) | 11 | 0.72 (0.33, 1.59) |
| < 1 a month | 22,396 | 151 | 1 (referent) | 1 (referent) | 81 | 1 (referent) | 17 | 1 (referent) |
| Times wake up per night | ||||||||
| Never | 8,359 | 50 | 1 (referent) | 1 (referent) | 30 | 1 (referent) | 7 | 1 (referent) |
| 1 | 216,804 | 1,538 | 1.17 (0.88, 1.56) | 1.08 (0.81, 1.44) | 896 | 0.97 (0.67, 1.40) | 149 | 1.06 (0.43, 2.59) |
| 2 | 97,253 | 743 | 1.23 (0.92, 1.65) | 1.14 (0.85, 1.53) | 425 | 1.00 (0.69, 1.45) | 85 | 1.32 (0.53, 3.26) |
| 3+ | 52,965 | 400 | 1.21 (0.90, 1.63) | 1.13 (0.83, 1.53) | 221 | 0.95 (0.64, 1.39) | 39 | 1.06 (0.41, 2.72) |
a
Adjusted for race, education, income, marital status, postmenopausal hormone use, use or oral contraceptives, alcohol consumption, age at menarche, parity, age at first birth, age at menopause, pack years of smoking, physical activity.