Night shifts 'cause 500 breast cancer deaths a year' Specialists believe that disruption of the normal sleep-wake cycle affects production of melatonin, the so-called sleep hormone, that is thought to have anti-cancer qualities. Dr Lesley Rushton, an epidemiologist at Imperial College London, the lead author on the report, explained that the figures were based on the numbers of women estimated to have been in occupations involving night shift work for at least a decade. The report, published in the British Journal of Cancer, and funded by the Health and Safety Executive, estimated that around 8,000 cancer deaths - one in 20 - can be linked to occupations. About half are in construction workers, who are most likely to be exposed to asbestos and other carcinogens like silica and diesel fumes. Although asbestos has long been phased out, because related cancers take so long to develop the number is expected to continue to rise.