Women working night shifts have 30 percent higher risk of developing breast cancer

Female night shift workers should be given more rest periods to stave off the risk of breast cancer.
Photo credit: PA Photos

By Lorna Hutchinson

Lorna Hutchinson is Deputy Editor of The Parliament Magazine

15 Oct 2018

Working night shifts gives women a significantly higher risk of developing breast cancer due to reduced melatonin secretion, it has been revealed.

Initial findings highlighted in the 2010 French ‘CECILE’* study confirmed that the risk of breast cancer is elevated by 30 percent in women working full nights (from 11pm until 5am).

Sylvie Pioli, President of Cyclosein, a French association which raises awareness on the link between breast cancer and night working, said she was diagnosed with breast cancer in January 2015 after working nightshifts for more than 30 years as a nurse.


“I had no idea there was a link between working at night and breast cancer,” Pioli said, adding, “as a woman, you only have to work night shift for four years to increase your risk.”

Pioli explained that working night shifts disturbs the circadian rhythm - the body’s natural sleep-wake cycle - and in turn disrupts melatonin secretions. The production and release of melatonin in the brain is connected to the time of day, increasing when it is dark and decreasing in daytime.

However, exposure to artificial light – which is the case for night shift workers - supresses the secretion of melatonin and its anticarcinogenic effects. It can also elevate women’s oestrogen levels, which is a breast cancer risk factor.

“At night time we make melatonin. There is a peak of melatonin between 2am and 5am, which is really when night workers should be allowed to lie down and have a twenty-minute nap,” she said.

“I had no idea there was a link between working at night and breast cancer” Sylvie Pioli, President of Cyclosein

Pioli added that female night workers’ risk of breast cancer rises in line with the length of night work and the frequency of nights worked per week.

Greens/EFA group MEP Michèle Rivasi said that this crucial information was not disseminated widely enough to the public, or even to doctors.

“We need to increase rest periods for women working nightshifts. We also need more awareness on sleep hygiene,” Rivasi said.

Sleep hygiene for those working nightshifts involves reducing stimulants such as tea, coffee and alcohol; avoiding eating between 2am and 4am; eating balanced meals; taking regular physical exercise; taking a cool shower in the morning to refresh the body and favour sleep and sleeping in a dark room without noise disturbance.

On rest days, night shift workers should rebalance their sleep-wake cycle to recover a normal sleep rhythm.

According to figures from 2012, breast cancer was the leading cause of cancer-related death in women, with a mortality rate of 15.7 per 100,000.

*Entitled ‘Breast Cancer , An epidemiological study on the environment in Côte-d'Or and Ille-et-Vilaine

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