Do night shifts increase breast cancer risk in women?

"In modern society, about 10% to 20% of women work night shifts, so night shifts may be the biggest occupational problem related to cancer." Researchers found that women who work more than two night shifts a week may have an increased risk of breast cancer, and the risk is even higher if they work night shifts and like to get up early.

Night shifts and early mornings are more harmful

The research team collected data from more than 18,500 women who served in the Danish army between 1964 and 1999, found 200 breast cancer patients and 899 non-breast cancer patients of similar age, and asked them about their work patterns, lifestyle habits and other situations, including how they used contraceptives and hormone replacement therapy, sunbathing habits, etc. The researchers also asked the women to rate whether they were "early risers" or "night owls."

Results: 141 breast cancer patients and 551 non-breast cancer patients answered the questionnaire.

Researchers found that people who work night shifts have a 40% increased risk of breast cancer; if they work at least three night shifts a week for at least six years, the risk of breast cancer doubles; people who work night shifts and like to get up early have the highest risk of breast cancer, nearly four times higher than those who do not work night shifts; women who call themselves "night owls" also have double the risk of breast cancer.

Men should not take it lightly either

"In modern society, about 10% to 20% of women work night shifts, so night shifts may be the biggest occupational problem associated with cancer."

Experts say that since night shifts are unavoidable, their duration should be limited, with less than three night shifts a week, and people who like to get up early should especially reduce night shifts.

Although the researchers found an association between night shift work and breast cancer, they did not prove cause and effect. This is not the first time such a connection has been revealed. The International Agency for Research on Cancer, an agency under the World Health Organization, said in 2007 that night work is "probably carcinogenic."

Night shifts not only affect women's health, but three previous small studies have shown that night shifts may also increase the risk of prostate cancer in men.

Something to do with night lights?

The researchers did not understand why night shift work was associated with cancer risk.

Experts analyzed that this may be related to exposure to light, which reduces the production of melatonin, a hormone that may help prevent certain cancers.

In addition, night lights may disrupt the body's biological clock and affect the breasts. This repeated asynchrony may lead to loopholes in cell growth cycle management and uncontrolled cell growth.

Experts say that people who work night shifts often lack sleep, which causes the immune system to not function fully and may help cancer cells grow. Working night shifts disrupts the body's biological clock and increases stress, which affects overall health and increases the risk of breast cancer.