Meta-analysis of Incidence of Brain Cancer Among Aircrew

Introduction: Previous studies on Brain and other Nervous System Cancers (BNSC) and aircrew have shown inconsistent results, possibly due to their relatively small sample sizes; therefore, the current study aimed to increase the precision of risk estimates. Methods: Systematic searches of PubMed and Embase for pertinent studies up to August 2016 were performed and supplemented by manual reviews of bibliographies. The pooled standard incidence ratio (SIR) and corresponding 95% CIs were estimated with random effects models. Results: Among the 903 studies retrieved, 7 studies (5 cohort studies and 2 pooled analyses) were included in the current meta-analysis. The pooled SIR (95% CI) of BNSC incidence in aircrew was 1.01 (0.77, 1.31) with no significant heterogeneity (I2 = 36.1%, P = .199). The null association persisted when the analysis was stratified by geographic area (Europe or America), publication year (before or after 2001), air population (pilots or cabin crew), cancer site (brain, nervous system, or brain/nervous system), and gender (male or female). Conclusion: The current evidence is not sufficient to support a significant positive association between aircrew employment and BNSC risk. However, the interpretation and extrapolation of this meta-analysis are restricted by the possible impact exerted by health worker effect and potential clinical heterogeneity. More studies based on other populations, including Asian aircrews, are warranted.