Night shift work and risk of breast cancer in women

Jones, M.E. et al. | 2019|Night shift work and risk of breast cancer in women: the Generations Study cohort | British Journal of Cancer |

Scientists have examined risk of breast cancer in relation to timing of night shift work and receptor status, in a large UK cohort study- The Generations Study (GS)- of more than 113,700 females aged 16 or over from the United Kingdom. Breast and other cancers occurring in the cohort were identified from recruitment and follow-up questionnaires, and spontaneous reports to the study centre. Their detailed analysis found no evidence for an overall increase in risk of breast cancer for women who had been night shift workers within the last 10 years, or by hours worked per night, nights worked per week, average
hours worked per week, cumulative years of employment, cumulative hours, or time since cessation of such work. With the research found no significantly raised risks with type of night shift occupation (Source: Jones et al, 2019)


Background: It is plausible that night shift work could affect breast cancer risk, possibly by melatonin suppression or circadian clock disruption, but epidemiological evidence is inconclusive.
Methods: Using serial questionnaires from the Generations Study cohort, we estimated hazard ratios (HR) and 95% confidence intervals (95% CI) for breast cancer in relation to being a night shift worker within the last 10 years, adjusted for potential confounders.
Results: Among 102,869 women recruited in 2003–2014, median follow-up 9.5 years, 2059 developed invasive breast cancer. The HR in relation to night shift work was 1.00 (95%CI: 0.86–1.15). There was a significant trend with average hours of night work per week (P = 0.035), but no significantly raised risks for hours worked per night, nights worked per week, average hours worked per week, cumulative years of employment, cumulative hours, time since cessation, type of occupation, age starting night shift work, or age starting in relation to first pregnancy.
Conclusions: The lack of overall association, and no association with all but one measure of dose, duration, and intensity in our data, does not support an increased risk of breast cancer from night shift work in women.

The full article is available to read in full from British Journal of Cancer

In the news:

The Independent | May 2019 | Night shift work does not increase breast cancer risk, study suggests 

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