1. Do airline pilots and cabin crew have raised risks of melanoma and other skin cancers? Systematic review and meta-analysis
Kyoko Miura1*, Catherine M Olsen1*, Stephanie Rea1, Jeremy Marsden2, Adèle C Green1,3
1 Population Health Department, QIMR Berghofer Medical Research Institute, 300 Herston Road, Herston, Queensland, 4006 Australia
2 Queen Elizabeth Hospital, Birmingham B15 2GW, UK
3 CRUK Manchester Institute and Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
* KM and CMO contributed equally to this work
British Journal of Dermatology. DOI: /bjd.17586

2. This project was lead by Professor Adèle C Green

3. Introduction What’s already known?
Airline pilots are exposed to cosmic and ultraviolet (UV) radiation in their occupations and cabin crews are occupationally exposed to cosmic radiation
Airline pilots and cabin crews appear to be at significantly increased risk of developing melanoma
Pilots are at increased risk of dying from melanoma

4. Objective
To establish precise risks of melanoma and keratinocyte cancer (KC) for airline pilots and for cabin crew based on all studies published to date

5. Methods
Searched Medline, ISI science citation index, EMBASE, SCOPUS, and CINAHL to June 2018
Inclusion
prospective and retrospective cohort studies
any language
incidence of or mortality from melanoma or KC (i.e. BCC or SCC) in airline pilots or cabin crew compared with the general population
studies with histological confirmation of melanoma
for mortality, record linkage (ICD codes), death registries, death certificates, and physician records

6. Methods continued
Multiple reports from the same population or subpopulation
included the report with the longest follow-up or the most comprehensive data
Data extraction
Two reviewers independently abstracted data
study design, location, years of data collection, sources and definition of cohort, definition of exposure (e.g. flying hours, radiation dose), No. of cases, person-year of follow-up, age of the study population, variables used for statistical adjustment, point estimates (odds ratio, hazard ratio or standardized incidence or mortality ratio) and 95% CIs
Quality assessment – Newcastle-Ottawa Quality Assessment

7. Methods: Data synthesis & analysis
DerSimonian and Laird: a random-effects model
Pooled standardised incidence ratios (pSIR) and pooled standardised mortality ratios (pSMR) with 95% CI
Statistical heterogeneity among studies – Q-statistic inconsistencies were quantified using the I2 statistic.
Sensitivity analyses – excluding each study in turn to examine the effect on the pooled estimate.
Publication bias – visual inspection of funnel plots + Begg’s & Egger’s tests
STATA (version 15)

8. Results
Identified 5866 articles, assessed 44 full-text, 12 studies included in quantitative synthesis
Published between 1990–2017
3 studies were based in North America, 5 in Europe, 4 were multinational
retrospective cohort = 10 studies
retrospective & prospective cohort = 2 studies
Newcastle-Ottawa Quality Assessment Scale (ranges 0–9)
7 studies = scored 7
4 studies = scored 6
1 study = scored 5
higher score = better quality

9. Results: Melanoma Pilots Cabin crew incidence: 7 studies
pooled SIR (pSIR) 2.03 (95% CI 1.71–2.40)
no evidence of heterogeneity (I2=0.0%, p=0.84); no evidence of publication bias (Begg p=0.76; Egger p=0.66)
mortality: 3 studies
pSMR 1.99 (95% CI 1.17–3.40)
no evidence of heterogeneity (I2=41.6%, p=0.18); no evidence of publication bias (Begg p=0.60; Egger p=0.75)
Cabin crew
incidence: 2 studies reported
pSIR 2.12 (95% CI 1.71–2.62)
no evidence of heterogeneity (I2=0.0%, p=0.55)
mortality: 1 study
SMR 1.18 (95% CI 0.73–1.89)

10. Results: Keratinocyte cancer (KC)
Pilots
Incidence
BCC (1 study) SIR 2.46 (95% CI 1.88–3.16)
KC (4 studies) pSIR 1.86 (95% CI 1.54–2.25)
No evidence of heterogeneity (I2=1.4%, p=0.39); no evidence of publication bias (Begg p=0.73; Egger p=0.16)
Mortality
KC (1 study) SMR 0.93 (95% CI 0.15–3.04)
Cabin crew
BCC (1 study) SIR 2.33 (95% CI 1.77–3.01)
KC (1 study) SIR 1.97 (95% CI 1.25–2.96)
KC (1 study) SMR 8.01 (95% CI 2.98–17.33)
KC: Keratinocyte cancer

11. Discussion Airline pilots Compared with the general population:
risk of melanoma & keratinocyte skin cancers ≈ ↑ 2 x
risk of dying from melanoma ≈ ↑ 2 x, but not KC
Cabin crew
Risk of melanoma & keratinocyte skin cancers ≈ ↑ 2 x
Risk of dying from melanoma was similar to the general population

12. Discussion continued
UV-B from the sun – main environmental cause of melanoma & skin cancer
Occupational UV exposure
Cabins
Flight deck
UV-A levels in flight deck in the 20th century – unknown
almost all reviewed evidence is out-of-date (studied in the mid- to late 20th century)
→ limitations
Cosmic radiation
elevated in pilots and cabin crew but below hazardous level
→ unlikely the cause
UV-B radiation is not detectable or not increased above ground level values in modern airline cabins and flight decks

13. Discussion continued Circadian rhythm disruption – carcinogenic
melanoma + skin cancer from short-haul routes
→ unlikely the cause
Recreational UV-exposure among pilots & cabin crews
during recreational activities including during stopovers
absence of direct evidence but cannot be ruled out

14. Conclusions What does this study add?
Risk of melanoma and other skin cancer is approximately doubled in airline pilots and cabin crew compared with the population; occupational exposure to ultraviolet radiation is unlikely to explain the raised risk
Causal roles of occupational exposure to ionising radiation, and recreational exposure to ultraviolet radiation, are plausible but there is little supporting evidence
Almost all relevant evidence is out-of-date and is restricted to the Northern Hemisphere: research is needed that better reflects the occupational environment and recreational behaviour of current pilots and cabin crews

15. Research team
K. Miura
C. Olsen
S. Rea
J. Marsden
A. Green