Working Long Hours Unlikely To Influence Cancer Risk Interview with:
Katriina Heikkila, PhD
Lecturer, London School of Hygiene and Tropical Medicine
Honorary Researcher, the Finnish Institute of Occupational Health What is the background for this study?

Dr. Heikkila:  Governments across the world have set regulations on working time, many recommending a maximum of 48- or 55-hour working week but many men and women today regularly work longer than recommended maximum hours. Working exceedingly hours is associated with many adverse health outcomes, such as an increased risk of cardiovascular disease, but the relationship of excess working hours with incident cancer has so far been unclear. To address this gap in the knowledge, we investigated the association between weekly working hours and incident cancer using individual-level data from over 116 000 initially cancer-free men and women from 12 research studies from Finland, Denmark, Sweden, Germany, the Netherlands and the UK.  What are the main findings?

Dr. Heikkila: During an average follow-up of nearly 11 years, over 4 000 participants developed cancer. We found no association between weekly working hours and incident colorectal, lung or prostate cancers. Working >55 hours per week was associated with slight increase in female breast cancer risk, but we suspect this observation may be due to residual confounding from parity. This means that the number of children the women had, which can impact on both their cancer risk and the hours they work, may have impacted on this finding. The relationship between working hours, breast cancer and parity would warrant further research.  What should patients and clinicians take away from this report?

Dr. Heikkila: Our findings can reassure patients that working long hours is unlikely to influence the risk of developing cancer. However, currently available evidence suggests that working longer than recommended hours can have other adverse effects on health, and clinicians and patients need work together to manage these.


Br J Cancer. 2016 Mar 29;114(7):813-818. doi: 10.1038/bjc.2016.9. Epub 2016 Feb 18.

Long working hours and cancer risk: a multi-cohort study.

Heikkila K1,2, Nyberg ST2, Madsen IE3, de Vroome E4, Alfredsson L5,6, Bjorner JJ3, Borritz M7, Burr H8, Erbel R9, Ferrie JE10,11, Fransson EI6,12,13, Geuskens GA4, Hooftman WE4, Houtman IL4, Jöckel KH14, Knutsson A15, Koskenvuo M16, Lunau T17, Nielsen ML18, Nordin M13,19, Oksanen T2, Pejtersen JH20, Pentti J2, Shipley MJ10, Steptoe A10, Suominen SB21,22,23, Theorell T13, Vahtera J2,21,24, Westerholm PJ25, Westerlund H13, Dragano N17, Rugulies R3,26, Kawachi I27, Batty GD10,28, Singh-Manoux A10,29, Virtanen M2, Kivimäki M2,10,3

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Katriina Heikkila (2016). Working Long Hours Unlikely To Influence Cancer Risk