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Sleep apnea, left untreated for even a few days, can
increase blood sugar and fat levels, stress hormones
and blood pressure, according to a new study of
sleeping subjects.
A report of the study’s findings, published in the
August issue of The Journal of Clinical
Endocrinology & Metabolism, adds further support for
the consistent use of continuous positive airway
pressure (CPAP), a machine that increases air
pressure in the throat to keep the airway open
during sleep.
Obstructive sleep apnea (OSA) affects 20 – 30
percent of adults, according to studies published in
the American Journal of Epidemiology and Lancet
Respiratory Medicine.
It occurs when the upper airway closes off during
sleep, temporarily interrupting breathing.
While it is known that OSA is associated with risks
for diabetes and heart disease, there has been no
consensus on whether OSA is a cause of these
disorders or just a marker of obesity, which
predisposes one to diabetes and heart disease.
Previous metabolic studies in patients with OSA, the
Johns Hopkins researchers say, usually collected
data while participants were awake, thus obtaining
only a snapshot of OSA’s aftermath, not the actual
sleep period when OSA occurs.
To better understand how OSA affects metabolism,
researchers measured free fatty acids in the blood,
glucose, insulin and cortisol (a stress hormone)
while participants slept in a sleep laboratory at
the Johns Hopkins Bayview Medical Center.
Participants’ brain waves, blood oxygen levels,
heart rates and breathing, along with eye and leg
movements, were also recorded each night of the
study.
In total, Jun and colleagues drew blood samples from
31 patients with moderate to severe OSA and a
history of regular CPAP use for two nights.
The researchers drew samples every 20 minutes
starting at 9 p.m. and until 6:40 a.m. Every
participant spent one night at the lab with CPAP or
after CPAP had been stopped for two nights, in
random order, separated by one to four weeks.
The average age of all participants was 50.8 years
old and the average body mass index indicated
obesity, a common characteristic of those with sleep
apnea.
Two-thirds of the study group was male and a quarter
had a history of non-insulin dependent diabetes.
Some 22.6 percent of participants were African
American, 9.7 percent Asian, 64.5 percent Caucasian
and 3.2 percent Hispanic.
Jun and colleagues found that CPAP withdrawal caused
recurrence of OSA associated with sleep disruption,
elevated heart rate and reduced blood oxygen.
CPAP withdrawal also increased levels of free fatty
acids, glucose, cortisol and blood pressure during
sleep.
The more severe the OSA, the more these parameters
increased.
In addition, glucose increased the most in patients
with diabetes.
Increases in fatty acids, glucose and cortisol have
all been linked to diabetes.
The Johns Hopkins team also found that blood
pressure increased and the arteries showed signs of
stiffness in the morning without CPAP.
Over time, increased blood pressure and vascular
stiffness can contribute to cardiovascular disease.
Jun emphasized that the study was limited by
studying people with severe OSA and obesity, thus
limiting the ability to apply the findings to all
OSA patients.
The researchers also did not compare CPAP use to a
sham CPAP control group to exclude a potential
placebo effect.
But Jun says that the study provides further
evidence that sleep apnea isn’t just a manifestation
of obesity, diabetes and cardiovascular disease — it
can directly aggravate these conditions.
They are continuing to recruit patients in order to
answer more questions about which patients are most
vulnerable to the impacts of OSA.
This study emphasizes the importance of CPAP therapy
for OSA to prevent its metabolic and cardiovascular
consequences. Sometimes, patients with OSA have a
hard time tolerating CPAP. It is important that
these patients contact a sleep specialist who can
assist them with CPAP use, or who can recommend
alternative therapies.
Other authors on this paper include Swati Chopra,
Aman Rathore, Haris Younas, Luu V. Pham, Aleksandra
Beselman, Il-Young Kim, Robert R. Wolfe and Vsevolod
Y. Polotsky of The Johns Hopkins University;
Chenjuan Gu of the Shanghai Jiao Tong University
School of Medicine; and Jamie Perin of the
University of Arkansas for Medical Sciences.
For more information
Obstructive Sleep Apnea Dynamically Increases
Nocturnal Plasma Free Fatty Acids, Glucose, and
Cortisol During Sleep
JCEM - The Journal of Clinical Endocrinology &
Metabolism
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The Johns Hopkins Medicine
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