Long working hours and cancer risk: a multi-cohort study
: Katriina Heikkila, Solja T Nyberg, Ida EH Madsen, Ernest de Vroome, Lars Alfredsson, Jacob J Bjorner, Marianne Borritz, Hermann Burr, Raimund Erbel, Jane E Ferrie, Eleonor I Fransson, Goedele A Geuskens, Wendela E Hooftman, Irene L Houtman, Karl-Heinz Jöckel, Anders Knutsson, Markku Koskenvuo, Thorsten Lunau, Martin L Nielsen, Maria Nordin, Tuula Oksanen, Jan H Pejtersen, Jaana Pentti, Martin J Shipley, Andrew Steptoe, Sakari B Suominen, Töres Theorell, Jussi Vahtera, Peter JM Westerholm, Hugo Westerlund, Nico Dragano, Reiner Rugulies, Ichiro Kawachi, G David Batty, Archana Singh-Manoux, Marianna Virtanen, Mika Kivimaäki
Publisher: Nature Publishing Group
: 2016
: British Journal of Cancer
: 114
: 7
: 813
: 818
: 6
: 0007-0920
: 1532-1827
DOI: https://doi.org/10.1038/bjc.2016.9
Background: Working longer than the maximum recommended hours is associated with an increased risk of cardiovascular
disease, but the relationship of excess working hours with incident cancer is unclear.
Methods: This multi-cohort study examined the association between working hours and cancer risk in 116 462 men and women
who were free of cancer at baseline. Incident cancers were ascertained from national cancer, hospitalisation and death registers;
weekly working hours were self-reported.
Results: During median follow-up of 10.8 years, 4371 participants developed cancer (n colorectal cancer: 393; n lung cancer: 247;
n breast cancer: 833; and n prostate cancer: 534). We found no clear evidence for an association between working hours and the
overall cancer risk. Working hours were also unrelated the risk of incident colorectal, lung or prostate cancers. Working X55 h per
week was associated with 1.60-fold (95% confidence interval 1.12–2.29) increase in female breast cancer risk independently of age,
socioeconomic position, shift- and night-time work and lifestyle factors, but this observation may have been influenced by residual
confounding from parity.
Conclusions: Our findings suggest that working long hours is unrelated to the overall cancer risk or the risk of lung, colorectal or
prostate cancers. The observed association with breast cancer would warrant further research
