Women in Denmark who developed breast cancer after many years of working night shifts have received compensation despite only limited research supporting the link. The ruling could have implications for compensation claims elsewhere in the world.

Out of 78 cases notified to the national board of industrial injuries in Denmark, 38 have received compensation through their employers’ insurance schemes. All of the women had worked night shift patterns for at least 20 years and were otherwise at low risk, for example, they had low alcohol consumption and no family history of breast cancer.

The Danish decision was based on a ruling by the International Agency for Research on Cancer in December 2007 that “shiftwork that involves circadian disruption is probably carcinogenic to humans.” The agency, which is part of the World Health Organization, classed shift work as a group 2A cancer risk. Category 1 risks are known carcinogens, such …