Night Shifts Could Increase Breast Cancer Risk, Study Says

lt;pgt;A new study on lab mice suggests that shift work and irregular sleeping patterns could increase the risk of developing breast cancer.lt;/pgt; lt;pgt;Researchers found that, when exposed to alternating periods of light and dark — designed to mimic the experience of night shift work — cancerous tumours developed in female mice on average eight weeks earlier than in mice who maintained normal sleeping patterns. The study also found that mice exposed to irregular sleeping patterns became 20 percent heavier than those with regular sleeping patterns, despite eating the same amount of food.lt;/pgt; lt;pgt;quot;To our knowledge, this is the first study that unequivocally shows a link between chronic light-dark inversions and breast cancer development,quot; write the authors of lt;a href=quot;http://www.cell.com/current-biology/pdf/S0960-9822(15)00677-6.pdfquot; rel=quot;nofollowquot;gt;the studylt;/agt;, lt;a href=quot;http://www.cell.com/current-biology/pdf/S0960-9822(15)00677-6.pdfquot; rel=quot;nofollowquot;gt;published in the journal lt;emgt;Current Biologylt;/emgt;.lt;/agt;lt;/pgt; lt;pgt;Both groups of mice used in the study had a genetic mutation equivalent to mutations in the human lt;emgt;BRCAlt;/emgt; gene; those mice not exposed to the alternating light/dark periods developed mutations, on average, after 50 weeks. lt;emgt;BRCAlt;/emgt; mutations affect the production of tumour-suppressing proteins, and the mutations account for about lt;a href=quot;http://www.cancer.gov/about-cancer/causes-prevention/genetics/brca-fact-sheet#r1quot; rel=quot;nofollowquot;gt;5-10 percent of all breast cancerslt;/agt;, according to the U.S. National Cancer Institute.lt;/pgt; lt;pgt;Gijsbertus van der Horst, a professor in the genetics department at Erasmus Medical Centre in the Netherlands, and one of the study#039;s co-authors, says the research could have implications for women with a familial history of breast cancer. quot;If you have a woman with a familial form of breast cancer... I think it#039;s not very wise to start working as a flight attendant, but maybe also [they should] refrain from shift work,quot; says van der Horst.lt;/pgt; lt;pgt;The study did not identify the precise causes for the higher risk of breast cancer, though the researchers speculated that the timing at which food is eaten and the body#039;s circadian rhythm being out of sync with the sleep-wake cycle could be contributing factors. Circadian rhythm refers to the body#039;s natural clock of physiological and mental changes, which follows a 24-hour cycle.lt;/pgt; lt;pgt;Van der Horst says that further research is also needed to pinpoint how long people have to be undertaking shift work before the cancer risk becomes significant. He hopes the results of this study will prompt government funding to undertake further research using mice to model risk factors in other types of cancer, such as prostate and colon cancer. quot;I think the impact on society is pretty large,quot; he says. Breast cancer is the most deadly type of cancer in women worldwide. Globally, around 522,000 people died from the disease in 2012, according to lt;a href=quot;http://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/breast-cancer/mortality#heading-Threequot; rel=quot;nofollowquot;gt;Cancer Research UKlt;/agt;. Colon (bowel) cancer claimed 694,000 lives in the same year, while prostate cancer is the third most common cancer in European men.lt;/pgt; lt;pgt;The health risks of night shifts and disruption of the body#039;s circadian rhythm have been reported before. A lack of sleep or irregular sleeping patterns have previously been linked to an lt;a href=quot;http://stm.sciencemag.org/content/4/129/129ra43quot; rel=quot;nofollowquot;gt;increased risk of type-2 diabetes and obesitylt;/agt;, as well as a lt;a href=quot;http://www.bmj.com/content/345/bmj.e4800quot; rel=quot;nofollowquot;gt;higher occurrence of heart attackslt;/agt;.lt;/pgt;