Night shift work and breast cancer: a pooled analysis of population-based case–control studies with complete work history

Feb 22, 2018European journal of epidemiology

Night shift work and breast cancer risk: combined analysis of studies with full work history

AI simplified

Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

The odds ratio for breast cancer in women who ever worked at night for at least 3 hours between midnight and 5 a.m. is 1.12.

Among pre-menopausal women, the odds ratio increases to 1.26.
Higher risks are observed with night shifts lasting ≥ 10 hours (OR = 1.36) and for work ≥ 3 nights/week (OR = 1.80).
The combination of night work duration ≥ 10 years and exposure intensity ≥ 3 nights/week is associated with an odds ratio of 2.55.
Current or recent night workers show an increased breast cancer risk (OR = 1.41) compared to those who ceased night work over 2 years ago.
No association is found between night work and breast cancer in post-menopausal women.
Increased risk is limited to ER+ tumors, especially those that are both ER+ and HER2+.

AI simplified

Night shift work has been suspected to increase breast cancer risk but epidemiological studies have been inconsistent due to heterogeneous assessment of exposure to night work. To overcome this limitation, we pooled data of five population-based case-control studies from Australia, Canada, France, Germany, and Spain into a single harmonized dataset using a common definition of night work including 6093 breast cancer cases and 6933 population controls. The odds ratio for breast cancer in women who ever worked at night for at least 3 h between midnight and 5 a.m. as compared to never night workers was 1.12 (95% CI 1.00-1.25). Among pre-menopausal women, this odds ratio was 1.26 [1.06-1.51], increasing to 1.36 [1.07-1.74] for night shifts ≥ 10 h, 1.80 [1.20-2.71] for work ≥ 3 nights/week, and 2.55 [1.03-6.30] for both duration of night work ≥ 10 years and exposure intensity ≥ 3 nights/week. Breast cancer risk in pre-menopausal women was higher in current or recent night workers (OR = 1.41 [1.06-1.88]) than in those who had stopped night work more than 2 years ago. Breast cancer in post-menopausal women was not associated with night work whatever the exposure metric. The increase in risk was restricted to ER+ tumors, particularly those who were both ER+ and HER2+ . These results support the hypothesis that night shift work increases the risk of breast cancer in pre-menopausal women, particularly those with high intensity and long duration of exposure. Risk difference between pre- and post-menopausal women deserves further scrutiny.

Full Text

Full text is available at the source.

View full text (HTML) ↗View full text (PDF) ↗

Night shift work and breast cancer: a pooled analysis of population-based case–control studies with complete work history

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief

Abstract

Full Text

Related papers

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief