Picture: A train at night 
The lost hours of sleep at night
at least do not seem to
raise cancer risk; © Pixelio.de

Judith Schwartzbaum, study’s lead author and an associate professor of epidemiology at Ohio State University, and colleagues found no link between working the night shift and the risk of developing any kind of cancer. They came to this conclusion after analyzing nearly 20 years’ worth of data that compared people who reported jobs that required working during the day to people who said they had jobs that required night shift work.

The study included all Swedish citizens who worked at least 20 hours a week in 1970, and who were included in both the 1960 and 1970 population censuses – a total of about 3.2 million people. The researchers gathered job information from each census. They categorized the occupations according to the percentage of people who reported shift work: more than 70 percent, more than 40 percent, less than 30 percent, and no employees reporting shift work.

Schwartzbaum and her colleagues defined shift work as work that had a rotating schedule with three or more possible shifts per day, or where the schedule included working between 1 and 4 a.m., which the researchers defined as working at night. The final results showed no relationship between shift work and an increased risk of developing prostate, colon or breast cancers or nearly any other kind of cancer, regardless of how much the occupation depended upon shift work.

Schwartzbaum points out that the current results don’t agree with a number of recently published studies, two of which found an increased risk of prostate cancer among rotating shift workers, and another half-dozen studies that suggested an increase in breast cancer risk among female shift workers.

“Many of these studies included very specific worker populations,” she said. “For example, studies of female flight attendants have found an increased risk of breast cancer and also a higher-than-expected risk for developing malignant melanoma.

MEDICA.de; Source: Ohio State University