Morphological brain changes in high-altitude careers and spaceflights: a systematic review and meta-analysis

Occupational exposure to high-altitude environments, such as those experienced by pilots and astronauts, has been associated with unique challenges, including neurocognitive implications. White matter hyperintensities (WMH) detected through neuroimaging have emerged as potential markers of brain pathology in individuals with high-altitude careers. This meta-analysis aimed to explore the association between occupational high-altitude exposure and WMH burden.

A systematic literature search was conducted following PRISMA guidelines in databases such as PubMed, Scopus, Web of Science, and Cochrane. Studies reporting WMH in pilots were included without language or date restrictions. Data extraction and quality assessment were performed independently by two reviewers. Pooled analyses were conducted using R software, and the risk of bias was assessed using the Newcastle-Ottawa scale.

A total of 1,036 articles were screened, with five studies meeting the inclusion criteria. These studies included 441 individuals, comprising 264 pilots and 177 controls. Pilots exhibited a significantly higher mean number (MD: 3.57, 95% CI: 1.71 - 5.43, p-value = 0.0002) and volume (MD: 0.09, 95% CI: 0.04 - 0.14, p-value = 0.0001) of WMH compared to non-flying personnel. No heterogeneity was observed in the analyses.

Occupational exposure to high altitudes is associated with a higher prevalence and volume of WMH, highlighting the possible need for regular screening and monitoring of individuals in high-altitude careers to mitigate the risk of cerebral diseases, and their implications. This meta-analysis underscores the importance of addressing the neurocognitive consequences of high-altitude professions in aviation and space exploration industries.