How can time zones affect the risk of developing cancer?

Time zones in which people live can be associated with a slight increase in the risk of developing certain cancers, a new study suggests. This risk is related to the violation of your biological clock.

Disorders of circadian rhythm

A person's biological clock can get stuck if he works on a night shift, for example. Scientists call such disorders circadian. They were associated with an increased risk of developing cancer in shift workers, according to Dr. Neil Caporoso, an epidemiologist at the National Cancer Institute and lead author of the study.

However, changes in the circadian rhythms experienced by people working on a rotational basis are the main ones, as they move from work during the day to work at night. Caporoso and his team drew attention to smaller and more subtle abnormalities in the work of biological clocks, which can also affect the risk of developing cancer.

In fact, many people experience small disruptions in the circadian rhythm in the form of social reactive delay. It happens when you stick to sleep for a week, but break it during the weekend, when you do not need to get up early.

But social reactive delay can also occur because of the time zone, notes Caporoso.

At what time does the sun rise?

Depending on the time zone, the time for sunrise and sunset can vary: moving 5 degrees long in the west through the time zone leads to a 20-minute delay in sunrise, according to a study presented April 2 at the annual meeting of members of the American Cancer Research Association. These results have not yet been published in the peer-reviewed journal.

For example, if a person wakes up at 8 am in Boston, it may already be light outside. But if he lives in Ohio and wakes up at the same time, in the same time zone, it can still be dark outside the window. Sunlight "tells" the biological clock of a person in Boston that the morning has come, but for an Ohio resident this does not happen when he wakes up. This leads to a discord between the time on the clock and the biological clock.

Social reactive delay was associated with various conditions, including obesity and diabetes. In a new study, scientists drew attention to cancer.

Cancer and biological clock

The researchers analyzed the data of 4 million adults who were diagnosed with cancer between 2000 and 2012. People in the study lived in 11 states within the continental US.

The results showed that for every 5 degrees of longitude from east to west within one time zone, the risk of developing any type of cancer increased by 3 percent in men and by 4 in women.

Researchers also studied the risk of developing specific types of cancer. For example, people who lived in the westernmost region of the time zone had a 4 percent higher risk of developing prostate cancer and 13 percent had chronic lymphocytic leukemia (cancer that affects white blood cells) compared to those living in the easternmost Parts of time zone.

Women living in the western regions of the time zone had a 4% higher risk of developing breast cancer, 12% of chronic lymphocytic leukemia, and 10% of uterine cancer, compared to those living in the extreme eastern region of the same time zone , The researchers found.

All these increases in the risk of developing cancer are relatively small, and scientists say that more research is needed to establish whether there is a causal relationship between cancer and disturbances in a person's biological clock.

Causes

The mechanism that can bind circadian rhythms and cancer remains unknown. However, they may find a relatively recent change in people's daily lives.

Throughout life on earth, the daily routine of man corresponded to the movement of the sun. People were active during the day and rested at night. But suddenly everything changed. People stay indoors during the day and are exposed to bright light at night. This can lead to a decrease in the level of melatonin. It is possible that lower levels of melatonin can affect the immune system, as well as increase the risk of developing cancer in humans.

Although more research is needed, Caporaso says that, probably, each of us can benefit from natural light during the day and from reducing artificial lighting at night.