People, working flextime, have a heightened risk of prostate, breast and bowels cancer development

People, working flextime, have a heightened risk of prostate, breast and bowels cancer development. Japanese scientists came to such conclusion after they carried out a research with participation of 14000 people.
 
A 10 years research showed that people, who worked flextime, suffered from prostate cancer four times more often, than those, who worked only day and night shifts. Besides, while such working schedule a risk of development of breast and bowels cancer increased too.
 
Scientists didn’t determine a reason of such dependence, however, they suppose, that reduction of “sleep hormone” melatonin secretion, which has an anti-cancer qualities, underlies here. When melatonin secretion is lowered, production of sexual hormones increases, and they play an important role in development of prostate cancer.
 
Nevertheless, a number of British experts consider that results of the research cannot be called clear.
“The research didn’t show that sleep disorders by themselves are responsible for moderate increase of risk of cancer”, - they stated. - “It’s not an exception, that this risk is connected with something else, for example, with smoking or wrong nutrition”.
 
Prostate cancer is one of the most widespread oncological diseases. Every year about 543000 of new cases of  this cancer are diagnosed in the world.