High-flying pilots at increased risk of brain lesions

A new study suggests that pilots who fly at high altitudes may be at an increased risk for brain lesions.

For the study, published in Neurology, the medical journal of the American Academy of Neurology, 102 U-2 United States Air Force pilots and 91 non-pilots between the ages of 26 and 50 underwent MRI brain scans. The scans measured the amount of white matter hyperintensities, or tiny brain lesions associated with memory decline.

“Pilots who fly at altitudes above 18,000 feet are at risk for decompression sickness, a condition where gas or atmospheric pressure reaches lower levels than those within body tissues and forms bubbles,” said study author Stephen McGuire, MD, with the University of Texas in San Antonio, the US Air Force School of Aerospace Medicine and a fellow of the American Academy of Neurology. “The risk for decompression sickness among Air Force pilots has tripled from 2006, probably due to more frequent and longer periods of exposure for pilots. To date however, we have been unable to demonstrate any permanent clinical neurocognitive or memory decline.”

Symptoms affecting the brain that sometimes accompany decompression sickness include slowed thought processes, confusion, unresponsiveness and permanent memory loss.

The study found that pilots had nearly four times the volume and three times the number of brain lesions as non-pilots. The results were the same whether or not the pilots had a history of symptoms of decompression sickness.

The research also found that while the lesions in non-pilots were mainly found in the frontal white matter, as occurs in normal aging, lesions in the pilots were evenly distributed throughout the brain.

“These results may be valuable in assessing risk for occupations that include high-altitude mountain climbing, deep sea diving and high-altitude flying,” McGuire said.

The study was supported by the United States Air Force Surgeon General.

For more information: AAN.com/patients


  1. AF-doc says

    There are several problems with this research; they have NO causal linkage, NO proposed mechanism for pure altitude exposure to produce the lesions, and NO animal studies which were able to produce hyperintense white matter lesions (WML). If (and that is a BIG ‘if’) exposure to unpressurized flight causes these WMLs, then we should have seen huge numbers of veterans from WWII with them. As you might recall, WWII bombers (B-17s & B-24s) had service ceilings of ~30K’, WWII fighters (P-47s & P-51s) had ceilings over 40K’. All of those WWII aircraft flew long duration missions – frequently 6-8 hours. If the WMLs were caused by a pure “altitude effect”, shouldn’t we have seen thousands of these pilots and crew members exhibiting clinical symptoms? WE HAVEN’T. In fact, we don’t know if the observed WMLs were present before the altitude exposure, decompression sickness event, or even entry into the AF. We don’t know if the WMLs are part of a pre-existing disease process. We don’t know what other common exposures could cause the WMLs (e.g., disease, alcohol, drugs, chemicals, noise, blast injury, gamma radiation, etc.).

    BOTTOM LINE: Lets not go into a tizzy about an observation before we find out what is really CAUSING the problem.

    • Burr says

      Thanks AF-doc. That sounds like the quiet voice of reason backed up by solid scientific method. I completely agree that WWII should have produced lots of examples, but apparently did not.

      Aren’t WMLs also connected with Alzheimer’s patients? I had heard quite a while back that Alzheimer’s brains also contained elevated levels of aluminum. If that is true, could it be because we now use so much aluminum is packaging, cooking utensils, etc.? That struck me as a possible link, though it is purely a supposition.

  2. Mack says

    There it is!

    That’s why I’m so slow!

    The real consequence is, after the MRI bill, I can’t afford to buy food!

    I got lesions on my hunger pangs!

  3. Burr says

    Decompression sickness? That doesn’t make any sense. We fly pressurized aircraft whose cabins seldom if ever exceed 8000 feet. Certainly no grater risk than living in Denver. I think the fellows running this study are scamming the government coffers through the USAF Surgeon General’s office.

    I have known several old eagles who have developed brain tumors that some thought may have been caused by greater exposure to radiation due to extended periods of flight high in the atmosphere, but even that was never proven and was probably never really studied, as it was nothing close to an epidemic.

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