Time Zones & Cancer Risks

Could where we live in different time zones be associated with a slightly increased risk of developing cancers that have been linked to disruptions of the biological clock?  There is currently a new study that suggests this as true.

As we all know our biological clocks can become out of control, or as they call it, we can have circadian disruptions.  These disruptions, such as working in the night, have been linked to an increased cancer risk, according to Dr. Neil Caporaso, an epidemiologist at the National Cancer Institute and the lead author of this study.

The disruptions experienced for shift workers in their circadian rhythms are major.  They switch from working during the day to working at night. The team were curious if smaller and subtler disruptions to the biological clock could also have an effect on cancer risk on people.  

When we travel, most likely we all feel a social jet lag when crossing a time zone.  Moving just 5 degrees of longitude westward across a time zone is equal to a 20-minute delay in sunrise.  When it’s 8 a.m. in Boston the lights are out but those living in Ohio could be getting up in darkness. The sunlight in Boston tells a person’s biological clock it’s morning, but the people in Ohio don’t get that same cue.  There is a discord between the time on the clock and your biological clock.

Having jet lag has also been linked to other conditions that include obesity and diabetes.  The new study focuses on cancer. Data was reviewed on 4 million white adults having been diagnosed with cancer between the years 2000 and 2012.  They lived in more than 600 counties in 11 states within the U.S.

For every 5 degrees of longitude toward the west that they lived from the Eastern edge of the time zone, the risk of developing any type of cancer increased by 3% in men and 4% in women.  Specific cancers and the risks were also looked at. Men living in the western-most part of a time zone had 4% greater risk of prostate cancer and 13% greater risk of chronic lymphocytic leukemia, compared to those living in the eastern-most regions of the time zone.  Women in the western-most regions had 4% greater risk of breast cancer, 12% greater risk of chronic lymphocytic leukemia and a 10% greater chance of a type of uterine cancer, compared with those living in the eastern-most region of the time zone.

These are relatively small and more studies are required to establish if there may be a cause-and-effect relationship between cancer and disturbances to a person’s biological clock.  A relatively recent change in humans’ daily lives may have something to do with the mechanism that may link circadian rhythms and cancer.

The lower levels of melatonin could possible affect the immune system and raise a person’s risk of cancer, however, more research is needed.  Everyone could benefit from exposure to more natural light during the day and avoiding light at night. This article was originally published in Live Science.

Dr Fredda Branyon