Night Shift Work and Breast Cancer Incidence: Three Prospective Studies and Meta-analysis of Published Studies
Open accessAbstract
BACKGROUND: It has been proposed that night shift work could increase breast cancer incidence. A 2007 World Health Organization review concluded, mainly from animal evidence, that shift work involving circadian disruption is probably carcinogenic to humans. We therefore aimed to generate prospective epidemiological evidence on night shift work and breast cancer incidence. METHODS: Overall, 522 246 Million Women Study, 22 559 EPIC-Oxford, and 251 045 UK Biobank participants answered questions on shift work and were followed for incident cancer. Cox regression yielded multivariable-adjusted breast cancer incidence rate ratios (RRs) and 95% confidence intervals (CIs) for night shift work vs no night shift work, and likelihood ratio tests for interaction were used to assess heterogeneity. Our meta-analyses combined these and relative risks from the seven previously published prospective studies (1.4 million women in total), using inverse-variance weighted averages of the study-specific log RRs. RESULTS: In the Million Women Study, EPIC-Oxford, and UK Biobank, respectively, 673, 28, and 67 women who reported night shift work developed breast cancer, and the RRs for any vs no night shift work were 1.00 (95% CI = 0.92 to 1.08), 1.07 (95% CI = 0.71 to 1.62), and 0.78 (95% CI = 0.61 to 1.00). In the Million Women Study, the RR for 20 or more years of night shift work was 1.00 (95% CI = 0.81 to 1.23), with no statistically significant heterogeneity by sleep patterns or breast cancer risk factors. Our meta-analysis of all 10 prospective studies included 4660 breast cancers in women reporting night shift work; compared with other women, the combined relative risks were 0.99 (95% CI = 0.95 to 1.03) for any night shift work, 1.01 (95% CI = 0.93 to 1.10) for 20 or more years of night shift work, and 1.00 (95% CI = 0.87 to 1.14) for 30 or more years. CONCLUSIONS: The totality of the prospective evidence shows that night shift work, including long-term shift work, has little or no effect on breast cancer incidence.
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A number of studies found no association between cancer and shift work.
“However, a number of studies have found no association between cancer and shift work [64,65,66,67].”
From Shift Work: Disrupted Circadian Rhythms and Sleep—Implications for Health and Well-being (2017) · cites this paper as [67]
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References 26 · Cited by 192
- Authors
- Travis, R. C., Balkwill, A., Fensom, G. K., Appleby, P. N., Reeves, G. K., Wang, X.-S., Roddam, A. W., Gathani, T., Peto, R., Green, J., Key, T. J., & Beral, V.
- Affiliations
- GlaxoSmithKline (United Kingdom) (GB)
- Corresponding author
- Travis, Ruth C.
- ORCID
- Venue
- Journal of the National Cancer Institute
- Publisher
- Oxford University Press (OUP)
- Published
- 2016-10-06
- Volume
- 108
- Issue
- 12
- Pages
- djw169
- ISSN
- 0027-8874 (ISSN-L)
- 1460-2105
- PMC
- PMC5241898
- OpenAlex
- W2528723127
- Cited by
- 192
- References
- 26
- Citations by year
- 2026: 2 · 2025: 11 · 2024: 11 · 2023: 15 · 2022: 24 · 2021: 21 · 2020: 20 · 2019: 26 · 2018: 26 · 2017: 31 · 2016: 4 · 2014: 1
- FWCI
- 3.82
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- cc-by
- Locations
- JNCI Journal of the National Cancer Institute (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- HighWire Press Open Archive (submittedVersion)
- Funders
- Cancer Research UK (C570/ A16491, 16896, K02700X, MR/M012190/1, 16491, C8221/A19170, A16491, A19170)
- Health and Safety Executive
- Medical Research Council (M012190/1, C570/A16491, MR/M012190, MR/K02700X/1, C8221/A19170, MC_PC_12028, MR/M012190/1)
- Topics
- Social Sciences › Psychology › Experimental and Cognitive Psychology › Sleep and Work-Related Fatigue
- Life Sciences › Neuroscience › Endocrine and Autonomic Systems › Circadian rhythm and melatonin
- Health Sciences › Medicine › Oncology › Cancer Risks and Factors
- Keywords
- night shift work, breast cancer incidence, circadian rhythm disruption, shift work, cancer risk, sleep patterns, women's health
- MeSH terms
- Adolescent, Adult, Aged, Breast Neoplasms, Circadian Rhythm, Female, United Kingdom, Humans, Middle Aged, Personnel Staffing and Scheduling, Prospective Studies, Surveys and Questionnaires, Work Schedule Tolerance, Incidence, Young Adult
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