Why female night shift workers have increased risk of common cancers

Night shift work was associated with women having an increased risk of breast, skin, and gastrointestinal cancer, according to a meta-analysis.

Ma explained that because breast cancer is the most diagnosed cancer among women worldwide, most previous meta-analyses have focused on understanding the association between female night shift workers and breast cancer risk, but the conclusions have been inconsistent.

To build upon previous studies, Ma and colleagues analyzed whether long-term night shift work in women was associated with risk for nearly a dozen types of cancer.

The study was published in the journal Cancer Epidemiology Biomarkers & Prevention.

Ma and colleagues performed a meta-analysis using data from 61 articles comprising 114,628 cancer cases and 3,909,152 participants from North America, Europe, Australia, and Asia. The articles consisted of 26 cohort studies, 24 case-control studies, and 11 nested case-control studies.

These studies were analyzed for an association between long-term night shift work and risk of 11 types of cancer. A further analysis was conducted, which looked specifically at long-term night shift work and risk of six types of cancer among female nurses.

Overall, long-term night shift work among women increased the risk of cancer by 19 percent. When analyzing specific cancers, the researchers found that this population had an increased risk of skin (41 percent), breast (32 percent), and gastrointestinal cancer (18 percent) compared with women who did not perform long-term night shift work.

After stratifying the participants by location, Ma found that an increased risk of breast cancer was only found among female night shift workers in North America and Europe.