FOR IMMEDIATE RELEASE
August 4, 2009
Contact: Donna Krupa
Office: (301) 634-7253
commoff@the-aps.org
Holding Breath for Several Minutes Elevates
Marker for Brain Damage
Study Adds to Questions about Whether Free-Diving Is Safe
 BETHESDA,
Md. (August 4, 2009) — Divers who held their breath for several minutes
had elevated levels of a protein that can signal brain damage, according to
a new study from the Journal of Applied Physiology. However, the
appearance of the protein, S100B, was transient and leaves open the question
of whether lengthy apnea (breath-holding) can damage the brain over the long
term.
“The results indicate that prolonged, voluntary apnea
affects the integrity of the central nervous system, and may have cumulative
effects,” the Swedish researchers said. The release of S100B into the blood
suggests that holding one’s breath for a long time disrupts the blood-brain
barrier, they said.
The concern is that repetitive exposures to severe
hypoxia (lowered oxygen supply), such as that experienced by individuals
training and competing in static apnea diving events, could cause
neurological damage over time. The researchers recommended further research
on free divers that would begin early in their careers and follow them for
years to monitor their neurological function.
The study is “Increased serum levels of the brain
damage marker S100B after apnea in trained breath-hold divers: a study
including respiratory and cardiovascular observations.” The researchers are
Johan P.A. Andersson, Mats H. Linér and Henrik Jönsson, of Lund University
in Sweden. The American Physiological Society published the study.
Free diving is a tradition
There is a tradition of breath-hold diving in Japan and
some other parts of the world that goes back hundreds of years, although the
occupation has been dying out. These divers harvest seaweed, shellfish and
other growth from the sea bottom, diving dozens of times per day. Some
divers routinely dive to depths of 90 feet on a single breath while others
dive in the 15-30 foot range.
More recently, breath-hold diving has become a
competitive sport. Competitive events include how long divers can remain
underwater, how far they can swim underwater and how deep they can dive.
Participants must undergo intense training to increase their lung capacity
while learning crucial safety measures.
Breath-hold diving often leads to hypoxia, elevated
blood pressure, slowed heartbeat and other physiological changes. However,
whether the sport causes any long-term damage to the brain has remained a
point of contention. Studies have produced conflicting results.
The authors of this study see cause for concern, noting
that in six international competitions between 1998 and 2004, 10% of the
contestants in the static apnea events were disqualified after they lost
either motor control or consciousness. In this event, participants float
face down on the water for as long as possible without coming up for air.
The world record for the event is 11 minutes 35 seconds. Divers at
international competitions routinely hold their breath 4-7 minutes.
“Whether such hypoxic episodes are associated with a
risk for brain damage in these athletes remains to be established,” the
researchers said. “Studying the changes in established biochemical markers
of brain damage after such performances offers the possibility to address
this question.”
Breath hold experiment
Nine competitive breath-hold divers (eight men and one
woman) took part in this study, along with six individuals who had limited
experience with breath-hold diving. The nine competitive divers formed the
experimental group, while the non-divers acted as the controls
The researchers told the participants to lie on their
backs on a cot and hold their breath for as long as possible. The conditions
were dry, but mimicked a static apnea dive in which the divers float face
down holding their breath. The divers used whatever preparatory techniques
they customarily use in competition, such as hyperventilating, insufflation
(filling the lungs with as much air as possible) and breath-holding
warm-ups.
The researchers took arterial blood samples from a
catheter inserted into the artery that runs through the wrist. They took
samples before the breath hold, at the end of the breath hold and at fixed
intervals for the two hours following the end of the breath hold. The
researchers also measured arterial blood gases. They did the same
measurements on the individuals in the control group, but the controls
rested on their backs for the entire experiment, without performing the
breath hold or the warm-ups.
Among the findings of this experiment:
-
The average breath-hold time was 5 minutes 35 seconds. The
longest was 6 minutes 43 seconds and the shortest was 4 minutes 41
seconds.
-
The marker for brain damage, S100B, rose in seven of the
nine divers.
-
The controls showed no change in S100B
-
On average, S100B rose 37% within 10 minutes after the
apnea ended.
-
S100B levels returned to normal within two hours for all
the participants.
-
The divers showed signs of asphyxia, that is, blood oxygen
levels fell, while carbon dioxide levels rose.
The S100B levels, while elevated, were well below
levels associated with brain injury. In brain-injured patients, the presence
of S100B in the blood can increase by several hundred percent.
In addition, the elevation of S100B was more transient
in the divers, compared to people who suffered brain injury. The divers had
a quick return to normal, while S100B levels peak in 24 hours in
brain-injured patients.
The transient nature of the increase in S100B among the
divers probably indicates the blood-brain barrier has been compromised,
allowing the protein to escape from the fluid in the brain into the
circulation. The blood-brain barrier controls what passes between the brain
and the circulation. S100B would normally remain in the brain.
Other sports have also been associated with a similar
transient increase in S100B, the researchers noted, including boxing,
headings in soccer, running and long-distance swimming. One study also
reported that individuals suffering sleep apnea had elevated levels of S100B
in the morning, although another study indicated there had been no change in
S100B overnight.
Editor’s Notes: To arrange an interview with Dr.
Andersson, please contact Donna Krupa (301) 634-7253 or at
commoff@the-aps.org.
The link to the study is at:
http://jap.physiology.org/cgi/search?sortspec=relevance&author1=Andersson&fulltext=divers&pubdate_year=2009&volume=&firstpage=
Physiology
is the study of how molecules, cells, tissues and organs function to create
health or disease. The American Physiological Society (APS) has been an
integral part of this scientific discovery process since it was established
in 1887.
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