To assess if occupational exposure to hypobaria may lead to accelerated aging of cerebral white matter.

Repeated human exposure to extreme hypobaria is associated with increased white matter hyperintensities (WMH) as observed on T2-weighted imaging and decline of axonal integrity measured by fractional anisotropy (FA).  The underlying pathophysiology is thought to be due to occlusion of small vessels and activation of innate immune response but has not been fully elucidated.  Increase in WMH volume and decline in FA values are also observed in normal WM aging. We hypothesize that occupational exposure to hypobaria leads to accelerated aging of cerebral white matter. We tested this by comparing aging trends in U-2 pilots and Air Force physiologists/chamber technicians to age-and-health matched controls.

The U-2 group accumulated subcortical WMH volume at a faster rate as a function of age compared to age-matched controls.  This group also showed an accelerated decline in whole-brain and regional FA values.  Accumulation of whole brain and subcortical WMH and reduction in FA values were also linearly associated with the degree/severity of hypobaric exposure.