Shift work, light at night and risk of breast cancer

The rates of shift work outside of daylight hours have increased in recent years, and nighttime shift work is now considered a potential carcinogenic occupational exposure. Light at night exposure, lower melatonin production, and the production of stress-related mediators disrupt normal sleep–wake cycles. Women who work lower-wage jobs and part-time workers whose shifts are determined entirely by their supervisors (rotating shifts) may be subject to stress related to efforts to align childcare and other needs with the unpredictable nature of rotating shift work. The causal link between breast cancer and the sleep cycle or circadian disruption are yet to be established; however, disruption of the circadian cycles by light at night exposure or chronic exposure to stress-related mediators have all been linked to the increased risk of breast cancer. We review the existing literature on shift work and breast cancer, identify knowledge gaps, and suggest future directions for research.

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The influence of shift work and light at night exposure on melatonin levels and breast cancer risk

Occupational and Environmental Medicine ◽

10.1136/oemed-2011-100382.287 ◽

2011 ◽

Vol 68 (Suppl_1) ◽

pp. A87-A88

Author(s):

A. Grundy ◽

J. Tranmer ◽

H. Richardson ◽

C. Bajdik ◽

C. Graham ◽

...

Keyword(s):

Breast Cancer ◽

Breast Cancer Risk ◽

Cancer Risk ◽

Shift Work ◽

Light At Night

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CLOCK GENES VS. BREAST CANCER

Problems in oncology ◽

10.37469/0507-3758-2019-65-1-43-55 ◽

2019 ◽

Vol 65 (1) ◽

pp. 43-55

Author(s):

Aleksey Golubev ◽

Andrey Panchenko ◽

Yekaterina Gubareva ◽

Galina Kireeva ◽

Viktor Anisimov

Keyword(s):

Breast Cancer ◽

Shift Work ◽

Clock Genes ◽

Significant Risk ◽

Significant Risk Factor ◽

Diurnal Changes ◽

Light At Night ◽

Experimental Findings ◽

Meta Analyses ◽

Risk Of Cancer

Clock genes (CG) are responsible for adapting body to diurnal changes in environmental conditions (circadian cycles, CC). Discordances caused by changes in both environmental СС (shift work, excess light at night, or jet lag) and bodily CC, in particular due to changes in CG expression, increase the risk of cancer, the breast being the most vulnerable site. The present discussion is based on the reviews of relevant epidemiological and experimental findings, including meta-analyses, mainly published within the last five years. The conclusions related to translational medicine are, with regard to prevention, that shift work is a significant risk factor of breast cancer and, with regard to treatment, that melatonin properties make it feasible to develop regimens of its administration able to synchronize tumor and body CC so that cancer becomes most sensitive to treatment when body is least vulnerable to its side effects.

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