image via publications.nigms.nih.gov
The casualties of sleep apnea are many: high blood pressure, cardiovascular disease, stroke, diabetes, various psychological disorders... not to mention injuries from accidents due to lack of sleep. Now, researchers at the University of Bern in Switzerland have established a link between sleep apnea and liver disease.
Obstructive sleep apnea, which was only seriously studied as a disorder
since the late 1960's, is estimated to occur in nine percent of middle
aged women and 24 percent of middle aged men. It prevents oxygen from
entering the bloodstream during sleep due to the muscles of the tongue
and surrounding pharynx relaxing. In relaxing, they come together,
closing off the airway - in effect, stopping breathing. While it is
true that snoring is an indication of sleep apnea, not all persons who
snore are deprived of oxygen in the way described for sleep apnea
You may think that liver disease (steatohepatitis) is largely the result of drug or alcohol abuse, but 40 percent of the population with liver disease suffer from non-alcoholic liver disease, or NASH. Though NASH has few outward symptoms - thus, it is known as the "silent liver disease" - an ultrasound and liver biopsy would reveal fat and inflammation in the liver. This condition needs to be treated before the damage becomes irreversible (cirrhosis).
Stages of liver disease (from digestive.niddk.nih.gov)
The Link Between Sleep Apnea And Liver Disease
The Bern research involved studies of normal mice kept in a low oxygen
environment for seven days; the control group was kept in a normal
oxygen environment. After seven days, the mice in the low oxygen
atmosphere showed pronounced fat deposits and inflammation in the
livers. These effects were not observed in the normal oxygen group.
Also observed were the genes of the low oxygen
group. The genes responsible for fat synthesis were shown to be highly active, while
the genes responsible for fat breakdown showed reduced activity.
The third observation of the low oxygen group was that the mice were less
sensitive to insulin than the control group.
Dr Anne-Christine Piguet, head of the research team, concluded "Hypoxia (lack of oxygen)
may be the link leading to accumulation of fat in the liver and to the
progression of non-alcoholic steatohepatitis. Our findings show that it
is important both to screen obese patients for obstructive sleep apnoea [British spelling] to prevent it contributing to fatty liver disease and to treat those
patients who already have NASH for hypoxia which may be making their
In this experiment we see sleep apnea as causal to NASH and possibly to diabetes. In human patients, it has been observed that obesity
predisposes patients to fatty liver diseases and to obstructive sleep
apnea. It remains for the lose ends to be tied up, but it looks like
the team from Bern are onto something.
Sources: Medical News Today, NIDDK, Wikipedia