US pilots and flight attendants had higher odds of dying from cancers potentially related to radiation exposure than workers in other occupations, according to a large analysis of US death certificate data.

The researchers said their findings are consistent with prior epidemiologic studies linking aircrew work to higher cancer incidence, with the current study building on that research by examining cancer mortality among aircrew and about 500 other occupations.

The research, however, does not establish a causal link between cosmic radiation exposure and the higher cancer mortality observed among aircrew.

While the study, published in JAMA Internal Medicine, provides “compelling evidence that aircrew face a higher risk of dying from cancer than the two comparison groups studied,” it “cannot separate the effects of the different occupational exposures aircrew may experience,” said Chaya Moskowitz, PhD, attending biostatistician at Memorial Sloan Kettering Cancer Center in New York City, who wasn’t involved in the study.

Specifically, the findings cannot establish whether cosmic radiation is the primary factor driving this increased risk or whether “other occupational or lifestyle factors could also contribute to the observed differences,” Moskowitz said.

Aircrew members receive the highest average annual effective dose of ionizing radiation of any occupational group in the US. Prior studies have linked aircrew work to increased cancer incidence, but whether occupational radiation exposure contributes to increased cancer mortality remains less clear.

Vishal Patel, MD, MPH, and colleagues from Harvard Medical School in Boston, analyzed US death-certificate data from 2020-2024 linked to people’s main occupation. The analysis included 12.7 million deaths across 503 occupations, including 14,190 pilots and 7170 flight attendants.

The researchers classified a range of cancers as potentially radiation-related, including breast, central nervous system, multiple myeloma, leukemia (except chronic lymphocytic leukemia), lymphoma, thyroid, prostate cancer, melanoma, and nonmelanoma skin cancers. Lung cancer was excluded because of possible confounding from smoking.

The team used aircraft mechanics and assemblers as negative control cases because they work around aircraft but are not routinely exposed to cosmic radiation during flight. Nuclear technologists served as positive controls because of their known occupational radiation exposure.

After adjusting for age at death, sex, race, ethnicity, education, and marital status, potentially radiation-related cancers accounted for 6.9% of deaths among flight attendants and 6.7% among pilots — the highest and second-highest proportions, respectively, among the 503 occupations studied. Both groups ranked near the middle for deaths from cancers not classified as radiation-related.

Compared with workers in other occupations, the risk-adjusted odds of death from cancers considered potentially radiation-related were 50% higher among flight attendants and 36% higher among pilots. The odds of death from breast, central nervous system, prostate, and melanoma were significantly higher for both pilots and flight attendants. There was no significant association, however, for multiple myeloma, lymphoma, or nonmelanoma skin cancer, and only pilots had significantly higher odds of leukemia mortality.

Aircraft mechanics and assemblers did not show elevated cancer mortality from cancers classified as potentially radiation-related, whereas nuclear technologists ranked 12th.

What’s notable, Moskowitz said, is that the increased odds of cancer mortality among pilots and flight attendants were less pronounced for cancers that are less likely to be associated with cosmic radiation. “This finding raises important questions about whether occupational radiation exposure may play a role,” she told Medscape Medical News.

In an invited commentary, Catherine M. Olsen, PhD, of the University of Queensland, Brisbane, Australia, and Ken Karipidis, PhD, of the Australian Radiation Protection and Nuclear Safety Agency, wrote that the findings, especially the lack of excess mortality from non-radiation-related cancers, support “the hypothesis that occupational radiation exposure” underlies the excess mortality.

Still, the experts cautioned that disentangling the effects of cosmic radiation and other factors, such as UV-A exposure and circadian disruption, remains a central challenge. The study did not measure the degree of radiation exposure or look at the potential influence of unmeasured confounding factors. Additionally, death certificates are not a perfect measure of cause of death and occupation may have been misclassified on death certificates.

Olsen and Karipidis noted some “immediate practical relevance” for clinicians, including routinely asking patients about aircrew work, counseling pilots about occupational UV-A exposure and the importance of sun protection during flights, and potentially recommending annual skin examinations for aircrew.

On a policy level, Olsen and Karipidis recommended calling for “occupational radiation protections proportionate to aircrew exposure levels.”

The study had no specific funding. Disclosures for the authors are available with the original study publication. Moskowitz had no relevant disclosures.