Since 2021, the Spanish Association of Cabin Crew (AETCP) collaborates with the Biobank of the National Center for Oncological Research (CNIO) donating blood and saliva, as well as providing urine, stool and nail samples collected at home in tubes for the Biobank to keep and manage their transfer to the international scientific community.
The objective? To investigate the influence of circadian rhythms on the immune system and its relationship with cancer. The biological samples from this group of workers allow us to study the effect on the body of being subjected to constant time difference or ‘jet lag’. The body has an internal clock to adapt to day and night conditions, so When there is a disruption of circadian rhythms that lasts for a long time, there could be an impact on health..
Specifically, the first request to access the samples came immediately from the CNIO itself, through its Cancer Immunity Group. Maria Casanova-Acebes y Dawn of John They are investigating whether constantly altering biorhythms increases the risk of cancer, taking into account metabolism as well. “Our immune system has a 24-hour cycle, with a resting phase and an active phase, in which there are more leukocytes – white blood cells – in the tissues,” explains De Juan. “We think that in people constantly subjected to jet lag or shift changes, this cycle becomes desynchronized, the number and functions of their leukocytes are no longer optimal,” he adds.
Check in humans
The International Agency for Research on Cancer (IARC) classifies work that disrupts circadian rhythms as “probably carcinogenic.” However, there is only “sufficient” experimental evidence in animals and “limited” evidence in humans.
And these hypotheses, already corroborated in animal models, are the ones that are going to be tested with the cohort of cabin crew. To do this, they have established three groups: crew members of long-haul flights –long distance–, short-haul flights –with less distance, but with more variable and shorter shifts–, and a control group with individuals who do not fly and lead a life with regular schedules and habits.
From left to right: Nuria Ajenjo (Biobank), Maria Casanova-Acebes and Alba de Juan (Cancer Immunity Group), Cecilia Sobrino and Sergio Fernandez (Biobank), Virginia Lopez del Alcazar (AETCP). Seated: Daniel Alba (Biobank), David J. Quesada (AETCP), Maria Jesus Artiga (Biobank). Credit: Laura M. Lombardia / CNIO.
“In March 2023 we started to collect samples from them every six months, “We will be monitoring them for four years to include variability due to seasonal changes,” says Casanova-Acebes. “We will be monitoring them for four years,” she explains. To detect changes, they will study the number of immune system cells in their blood “and whether these have a profile more favourable to inflammation,” adds De Juan.
The initial disruption of circadian rhythms is not only caused by the perception of natural light. There are other external stimuli that condition the body to behave in ‘day mode’ or ‘night mode’: heavy meals, artificial light, noise or interaction with screens can be an activation factor. It is known that when these external activation stimuli are not in tune with biorhythms, they can trigger inflammatory distortions. Thus, Casanova-Acebes seeks to “establish What changes in the immune system perpetuated over time will be responsible for inflammatory diseases, including cancer?“.
Occupational risk
According to Virginia Lopez del Alcazarhead of AETCP, it was necessary to “scientifically demonstrate that our health is affected by our profession.” “Only in this way could we ask for recognition of an occupational risk that is considered in other professions in the sector, such as pilots and aerial photographers,” he points out.
“Along with the samples, donors provide detailed information about their medical and family history, diet, exercise, tobacco use, and hours and type of flight, among other data,” he said. Maria Jesus Artigaacting director of the CNIO Biobank. “This information gives the sample extraordinary value for different types of research,” she adds.
The collection is longitudinal, since samples are collected from the same donors every year, which makes it a valuable tool for studying as well early markers of different diseasesas highlighted by the CNIO in a press release. In the Biobank, the donor’s identity is replaced by a code, thereby ensuring the confidentiality of data and samples.
