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Int J Cancer. 2017 Dec 1;141(11):2204-2214. doi: 10.1002/ijc.30920. Epub 2017 Aug 22.

Sleep characteristics, light at night and breast cancer risk in a prospective cohort.

Author information

1
Epidemiology Branch, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC.
2
Biostatistics Branch, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC.
3
Social & Scientific Systems, Durham, NC.
4
Division of Cancer Epidemiology and Genetics, Metabolic Epidemiology Branch, National Cancer Institute, NIH, Bethesda, MD.
5
Department of Epidemiology, University of North Carolina, Chapel Hill, NC.

Abstract

Increasing numbers of women in the US are getting too little sleep. Inadequate sleep has been associated with impaired metabolic function and endocrine disruption. Sister Study cohort participants (n = 50,884), completed baseline and follow-up questionnaires on sleep patterns. Incident breast cancers estrogen receptor (ER) status of the tumor were ascertained from questionnaires and medical records. Cox regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs). Analyses of sleep characteristics reported at the first follow-up interview included only participants who were breast cancer-free at time of follow-up interview. Over ∼7 years of follow-up, 2,736 breast cancer cases (invasive and ductal carcinoma in situ) were diagnosed. There was little evidence that usual sleep duration or other sleep characteristics were associated with breast cancer. However, relative to those with no difficulty sleeping, women who reported having difficulty sleeping ≥ 4 nights a week were at an increased risk of overall (HR = 1.32, 95% CI: 1.09-1.61) and postmenopausal breast cancer (HR = 1.51, 95% CI 1.24-1.85). Risk of ER+ invasive cancer was elevated for women who reported having a light or television on in the room while sleeping (HR = 1.20, 95% CI: 0.97-1.47) or who typically got less sleep than they needed to feel their best (HR = 1.21, 95% CI: 0.98-1.50). In our study, most sleep characteristics, including sleep duration, were not associated with an increased risk although higher risk was observed for some markers of inadequate or poor quality sleep.

PMID:
28791684
PMCID:
PMC5633507
DOI:
10.1002/ijc.30920
[Indexed for MEDLINE]
Free PMC Article

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