The impact of occupational nonhypoxic hypobaria on cerebral function and integrity

Repetitive nonhypoxic hypobaria is nearly omnipresent in the aerospace environment and has been shown to be associated with subcortical white matter hyperintensities (WMH) on brain magnetic resonance imaging (MRI). This raises the question of whether such exposures may be detrimental to brain structure and function. A single-center observational study was conducted comparing individuals with repetitive nonhypoxic hypobaric exposure, specifically 19 altitude chamber personnel (ACP) from 4 European countries, with 28 healthy controls. MRIs were evaluated for WMH occurrence, volume and distribution, as well as white matter parcellation, cortical volume, and thickness. Additionally, Diffusion Weighted Imaging (DWI) acquisitions were analyzed. Furthermore, neurophysiological (VEP, AEP, OCT) and psychometric tests (Vienna test system, WinSCAT) were performed. Both groups exhibited WMH, although to a lesser extent than reported in the general population. The number and volume of WMH increased with age and were influenced by cumulative chamber exposure time to ACP. Noticeable were circumscribed significant reductions in lateral orbitofrontal cortical volume and thickness as well as decreases in the volume of the pars opercularis of both hemispheres in the study group. Neurophysiological and neuropsychological findings were not different. There are no hints that occupational nonhypoxic hypobaric exposure in ACP, as currently used in the participating NATO Air Forces, can cause brain damage.