Cancer Causes & Control

, Volume 21, Issue 12, pp 2281–2285 | Cite as

Light at night and breast cancer risk: results from a population-based case–control study in Connecticut, USA

  • Qian Li
  • Tongzhang ZhengEmail author
  • Theodore R. Holford
  • Peter Boyle
  • Yawei Zhang
  • Min Dai
Original paper



To investigate the potential association between domestic exposure to light at night (LAN) and the risk of human breast cancer.


A case–control study of female breast cancer was conducted in Connecticut. A total of 363 incident breast cancer cases and 356 age frequency-matched controls were interviewed using a standardized, structured questionnaire to obtain information on sleeping patterns and bedroom light environment. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by unconditional multivariate logistic regression.


A non-significantly increased risk of breast cancer was observed among postmenopausal women for those keeping lights on while sleeping (OR = 1.4, 95% CI 0.7, 2.7), those who reported mainly sleeping in the daytime (OR = 1.4, 95% CI 0.5, 4.3), and those not drawing the curtains/window shades while sleeping at night (OR = 1.2, 95% CI 0.8, 1.9).


The results from this study suggest a potential increased risk of breast cancer associated with domestic exposure to LAN. Further studies with larger sample size are needed to confirm the results.


Light at night Breast cancer Case–control study 



Preparation of the manuscript is partly supported by grants: 5D43TW008323 and 5D43TW007864. This study was supported by a grant CA-62986 from National Cancer Institute/National Institute of Environmental Health Science. We also appreciate the support of personnel at the hospitals of Connecticut. The following Connecticut hospitals have participated in the study: Yale-New Haven Hospital, Hospital of St. Raphael, Hartford Hospital, St. Francis Hospital and Medical Center, New Britain General Hospital, Middlesex Hospital, Mt. Sinai Hospital, Manchester Memorial Hospital, UCONN Health Center/John Dempsey Hospital, Windham Community Memorial Hospital, Day Kimball Hospital, Rockville General Hospital, and Johnson Memorial Hospital.


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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • Qian Li
    • 1
  • Tongzhang Zheng
    • 2
    Email author
  • Theodore R. Holford
    • 3
  • Peter Boyle
    • 4
  • Yawei Zhang
    • 2
  • Min Dai
    • 5
  1. 1.Department of Social Medicine, School of Public Health, Tongji Medical CollegeHuazhong University of Science and TechnologyWuhanChina
  2. 2.Division of Environmental Health SciencesYale School of Public HealthNew HavenUSA
  3. 3.Division of BiostatisticsYale School of Public HealthNew HavenUSA
  4. 4.International Prevention Research Institute (IPRI)LyonFrance
  5. 5.Cancer Institute and HospitalChinese Academy of Medical SciencesBeijingChina

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