Canadian scientists in the study found that the risk of breast cancer increases twice those of women, who for 30 years or more work at night. His scientific research assistants conducted among 1134 women suffering from breast cancer, and in 1179 healthy women. All the interviewees were of the same age and lived in two canadian cities - Vancouver and Kingston.
The scientists asked the participants the question, did they ever work in shifts. Every third representative of both groups had experience of working in the night shift. After analyses, the researchers found no risk of breast cancer in women who worked night shifts for 14-and 15-29 years, and for females who worked 30 or more years, the probability of occurrence of breast cancer was increased in 2 times.
According to the study authors, the night is very important for women, because it was at this time produces the hormone melatonin. Violation of its synthesis leads to an increase in the production of another hormone, estrogen, high levels of which can lead to the development of cancer. In addition, among the possible causes of this phenomenon scientists call vitamin D deficiency and impaired biorhythms.