Work­ing nights may in­crease a woman’s risk of breast can­cer

Al­though we are not fully cer­tain, we be­lieve that this risk could be re­lated to the hy­poth­e­sis that night work dis­rupts cir­ca­dian rhythm and in­hibits the se­cre­tion of mela­tonin, which may pro­tect against can­cer.

The Borneo Post - Nature and health - - Front Page - Anne Grundy, study co-au­thor

AC­CORD­ING to new in­ter­na­tional re­search, work­ing at night could in­crease a woman’s risk of breast can­cer, es­pe­cially in those who are pre-menopause. Car­ried out by Cana­dian, Aus­tralian, and Euro­pean re­searchers, the new study sur­veyed more than 13,000 women aged on av­er­age 55-59 from five dif­fer­ent coun­tries (Aus­tralia, Canada, France, Ger­many and Spain). The par­tic­i­pants in­cluded 6,093 women who had been di­ag­nosed with breast can­cer and 6,933 women with­out breast can­cer who acted as con­trols.

The find­ings, which were pub­lished in the Euro­pean Jour­nal of Epi­demi­ol­ogy, sug­gested that the risk of de­vel­op­ing breast can­cer in­creases with the num­ber of hours worked per night, as well as the num­ber of years spent on the night shift. Women who worked at least three hours be­tween midnight and 5 am ev­ery night had a 12 per cent greater risk of de­vel­op­ing breast can­cer than women who had never worked at night. Among pre-menopausal women, this risk in­creases to 26 per cent.

In ad­di­tion, the team also found that pre-menopausal women who work night shifts longer than 10 hours showed a 36 per cent in­creased risk of breast can­cer com­pared to those who have never worked nights, with the risk as high as 80 per cent among women who work night shifts longer than 10 hours for more than three nights per week. How­ever, the risk ap­peared to de­crease two years af­ter stop­ping night shift work, with women who were still work­ing nights at the time of the study show­ing a breast can­cer risk 26 per cent higher than those who had stopped work­ing at night at least two years pre­vi­ously.

Al­though the anal­y­sis of the five sur­veys did not specif­i­cally con­sider the type of night work, the Cana­dian sur­vey did com­pare women work­ing in health­care and other sec­tors. “The risk as­so­ci­ated with breast can­cer and night work var­ied lit­tle among re­spon­dents, re­gard­less of job type,” ex­plained study co-au­thor Anne Grundy, from the Univer­sité de Mon­tréal. “Al­though we are not fully cer­tain, we be­lieve that this risk could be re­lated to the hy­poth­e­sis that night work dis­rupts cir­ca­dian rhythm and in­hibits the se­cre­tion of mela­tonin, which may pro­tect against can­cer.” The re­searchers also added that fur­ther re­search should be car­ried out to in­ves­ti­gate the dif­fer­ence in risk be­tween pre- and post- menopausal women. – Re­laxnews

Reg­u­larly work­ing through the night could af­fect a woman’s risk of breast can­cer ac­cord­ing to new re­search. – iStock photo

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