The stewardess had a higher incidence of cancer and the doctor thought he knew why.

A new study finds that flight attendants are at increased risk of several cancers, radiation exposure (at high altitudes, the atmosphere's protection against cosmic radiation from space is weakened) and so-called circadian rhythm disorders (hello, red-eye shifts and persistent jet lag) are considered potential causes.

class= "article-image_ inner-caption"> Aircrew are exposed to more radiation than any other worker, but this may sound more than the actual situation. Even worse. (Image: @jtobiason via twenty20)

Cancer incidence and crew use data from the Harvard Stewardess Health Survey, which includes responses from more than 5,300 stewardesses. The latest study is published in the Journal of Environmental Health. They compared these findings with data from nearly 3,000 adults with similar socioeconomic backgrounds: people who participated in the National Health and Nutrition Examination Survey (nhanes).

The results showed that the prevalence of breast cancer in female flight attendants was 1.5 times higher than that in the general population, while the prevalence of melanoma was 2 times higher than that in the general population, and the prevalence of non-melanoma skin cancers (such as basal cell and squamous cell carcinomas) was 4 times higher than that in the general population. Flight attendants also have a higher risk of uterine, cervical, thyroid and gastrointestinal cancers.

In a report, Irina Mordukhovich, the author of the study and a researcher at Harvard T.H. Chan School of Public Health, said the finding was striking given the low obesity and smoking rates of stewardesses. Eight percent of stewardesses were current smokers and comp accounted for 16% of NHANES respondents.

The role of radiation So, what should be blamed for the cancer prevalence of flight attendants? Although the study did not find the cause (which is not its purpose), Mordukhovich and her colleagues offered some possible explanations, including the exposure of flight attendants to cosmic ionizing radiation (or radiation from outer space).

Although our atmosphere provides some protection, we are always exposed to a small amount of ionizing radiation. At high altitudes where the air is thin, more radiation passes through, and some researchers speculate that this may increase the risk of cancer.

The study authors point out that the annual ionizing radiation dose of crew members is the largest among all American workers. The radiation dose is measured in milliSievert (msv) per year. Previous studies have shown that the average dose for crew members is 3.07 msv, compared with 0.59 mSv for U.S. Department of Energy staff.

In order to help us correctly view these figures, Livestrong.com interviewed Dr. Timothy J. Jorgensen, director of the Graduate Program in Health Physics and Radiation Protection at Georgetown University.

He explained that in high altitudes like Denver, the natural background radiation dose (that is, the amount of radiation we receive on the solid ground here) ranges from about 3.0 millisieverts per year for New York City residents to 12.0 millisieverts per year.

&Jorgenson said: "So you can see that most of the crew's radiation doses are lower than those of Denver residents." & Since no one in Denver or other areas with higher background doses has ever been at a higher cancer risk because of exposure to radiation, I do not understand how radiation doses can be used to explain the alleged higher cancer risk of crew members. It's undeniably very small. & Experts estimate that exposure to 1 milliSievert increases your cancer risk by 0.005%, so if a flight attendant works for 30 years and is exposed to 90 millisieverts, her lifetime risk of potentially fatal cancer will increase by 0.45%.

Considering the small increase in risk, Jorgensen believes that another explanation for the high incidence of cancer by the study authors is more likely to be responsible than radiation.

In addition to radiation exposure, flight attendants are exposed to other potentially carcinogenic substances, such as aircraft fuel, insecticides and flame retardant chemicals used to kill insects on board. But perhaps the most supported explanation is the irregular schedule of flight attendants.

In fact, a recent meta-analysis of 61 studies shows that shift work and disruption of circadian rhythms are associated with an increased risk of breast, skin and gastrointestinal cancers in women.

Why? A 2017 study in the Journal of Occupational and Environmental Medicine showed that our bodies are more capable of repairing DNA damage when we sleep at night than when we sleep during the day. The authors found that low levels of melatonin in shift workers may be one of the reasons. Photosuppressive hormones, usually secreted at night.

Dr. Pavin Batty, an epidemiologist at Fred Hutchinson Cancer Research Center, explained in a report that "melatonin now seems to normally promote the repair of damage, which is supported by many animal and cellular evidences." & Therefore, in the case of low melatonin content, their maintenance machine can not work at the best level.

Batty and other researchers are investigating whether melatonin supplements can help combat the effects of night work. At the same time, the stewardesses are dealing with their own affairs. The stewardess association, the main trade union of workers'groups, calls on airlines and regulators to change working conditions to reduce risks. The organization also plans to educate its members about the potential risks of radiation exposure and disruption. Leep mode.

If nothing else, it will at least raise people's awareness and may contribute to early detection of cancer.

What do you think? Do you know the link between circadian rhythm disorders and cancer? Does the increased risk of cancer affect you personally (or anyone you know)? Do you think the results of this study will hinder people from pursuing flight-related careers? Please let us know in the comments below.