| | Author | Year | Data collection | Breast cancer ascertainment | Sleep duration (h/d) and risk (95% CI) | Adjusted variable | Quality assessment |
| | Xiao et al. [9] | 2016 | Questionnaire | State cancer registries; pathology reports;
medical records | <6: 1.09 (0.83–1.44)
6: 1.01 (0.78–1.30)
7: 1.19 (0.92–1.53)
8: reference
≥9: 1.07 (0.80–1.43) | Age, enrollment year, enrollment state, race, education, income, marital status, BMI, physical activity, overall sitting, smoking, pack-year, number of live birth, age at first birth, length of breastfeeding, age at menarche, menopause status, hormone therapy, multivitamin, aspirin, diabetes, family history of cancer, alcohol consumption, and dietary intakes of total fat, fiber, folate and total calories | 8 |
| | Hurley et al. [10] | 2015 | Questionnaire | California cancer registry | 3–6: 0.97 (0.91–1.04)
7–9: reference
≥10: 1.13 (0.86–1.50) | Race/ethnicity, alcohol consumption, menopausal status, hormone therapy use | 6 |
| | Wang et al. [11] | 2014 | Face-to-face interview | Medical records | ≤6: 1.62 (1.18–2.21)
6.1–8.9: reference
≥9: 1.58 (1.18–2.12) | Age, education, BMI, age at menarche, menopausal status, parity, physical activity, breastfeeding, family history of breast cancer, other sleep factors | 7 |
| | Vogtmann et al. [12] | 2013 | Interview | Pathology reports; medical records | ≤5: 0.89 (0.80–1.00)
6: 0.92 (0.85–0.98)
7: reference
8: 1.00 (0.93–1.07)
≥9: 1.05 (0.92–1.20) | Age, clinical trial arm assignment, number of live births, age at menarche, age at menopause, BMI, energy expenditure, education, income, race/ethnicity, marital status, age at first birth, use of hormone therapy, history of benign breast disease, family history of breast cancer, alcohol consumption, smoking status | 8 |
| | Wu et al. [13] | 2012 | In-person interview | National cancer registry | ≤6: reference
7: 1.00 (0.84–1.19)
8: 1.00 (0.84–1.21)
≥9: 0.89 (0.64–1.22) | Age, year, dialect group, education, parity, BMI, menopausal status | 8 |
| | Girschik et al. [14] | 2012 | Self-administered postal questionnaire | Western Australian cancer registry | <6: 1.04 (0.83–1.32)
6-7: 0.95 (0.79–1.14)
7-8: reference
>8: 1.05 (0.83–1.33) | Age, number of children, age at first birth, breastfeeding, menopausal status, use and duration of hormone therapy, alcohol consumption, comparative weight at the age of 30 years, melatonin, physical activity | 8 |
| | Kakizaki et al. [15] | 2008 | Questionnaire | Miyagi prefectural cancer registry | ≤6: 1.67 (1.002–2.78)
7: reference
8: 0.99 (0.59–1.65)
≥9: 0.29 (0.09–0.98) | Age, BMI, history of disease, family history of cancer, marital status, education, alcohol consumption, time spent walking, caloric intake, menopausal status, age at menarche, age at first delivery, number of deliveries, oral contraceptive drugs, hormone drug | 8 |
| | Pinheiro et al. [16] | 2006 | Mailed questionnaire | Blinded medical chart review | ≤5: 0.93 (0.79–1.09)
6: 0.98 (0.91–1.06)
7: reference
8: 1.05 (0.97–1.13)
≥9: 0.95 (0.82–1.11) | Age, BMI, height, history of benign breast disease, family history of breast cancer, parity and age at first birth, age at menarche, postmenopausal hormone use, physical activity, alcohol, caloric intake, smoking | 7 |
| | McElroy et al. [17] | 2005 | Telephone interviews | State cancer registries | <5: 0.94 (0.62–1.44)
5–5.9: 0.82 (0.65–1.05)
6–6.9: 0.89 (0.79–1.01)
7–7.9: reference
8–8.9: 1.01 (0.91–1.11)
≥9: 1.01 (0.84–1.23) | Age, state, parity, age at first full-term pregnancy, family history of breast cancer, alcohol consumption, BMI, menopause status, age at menopause, postmenopausal hormone use, marital status | 8 |
| | Verkasalo et al. [18] | 2005 | Questionnaires | Finnish cancer registries | ≤4: 0.88 (0.11–6.91)
5: 0.91 (0.36–2.32)
6: 0.74 (0.44–1.27)
7: 0.81 (0.60–1.10)
8: reference
9: 0.64 (0.40–1.02)
≥10: 0.65 (0.24–1.75) | Age, zygosity, social class, number of children, use of oral contraceptives, BMI, alcohol use, smoking, physical activity | 8 |
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