Oct. 24, 2008 -- Sleep apnea -- even if it is so mild that people have no
daytime drowsiness -- may increase the risk of cardiovascular disease, a study
The study, published in the American Journal of Respiratory and Critical
Care Medicine, compared patients with mild sleep apnea to a comparison
group that didn't have sleep apnea. There were 64 participants with mild sleep
apnea and 15 participants without sleep apnea.
To compare the risk for heart
disease, researchers tested endothelial function, which is how well the
cells in the lining of the blood vessels work, and artery stiffness.
Endothelial dysfunction and arterial stiffness are involved in developing atherosclerosis, or hardening of the arteries. Moderate
to severe sleep apnea has already been linked to increased artery stiffness,
endothelial dysfunction, and high blood
Malcolm Kohler, MD, from the Oxford Centre for Respiratory Medicine in
England, and colleagues found that patients with mild sleep apnea had worse
endothelial function and greater arterial stiffness than the comparison group
without sleep apnea.
Researchers also tested blood
pressure, another way to gauge cardiovascular disease risk. The groups
tested similarly on blood pressure.
The researchers write that "although this was not associated with
significantly increased blood pressure, the findings of this study suggest that
patients with minimally symptomatic OSA [obstructive sleep apnea] are at increased
cardiovascular risk, as has been demonstrated in more severe disease."
"It was previously known that people with OSA (obstructive sleep apnea)
severe enough to affect their daytime alertness and manifest in other ways are
at increased risk of cardiovascular disease, but this finding suggests that
many more people -- some of whom may be completely unaware that they even have
OSA -- are at risk than previously thought," Kohler says in a news release.
In an accompanying editorial, Geraldo Lorenzi-Filho MD, PhD, points out that
just one in five patients with sleep apnea complains of drowsiness during the
day. "It is now recognized that OSA triggers a cascade of biological reactions,
including increased sympathetic activity, systemic inflammation, oxidative
stress, and metabolic alterations that are potentially harmful to the
cardiovascular system," he writes in the editorial.
Kohler and colleagues are now investigating the effects of continuous
positive airway pressure (CPAP) therapy on arterial stiffness and endothelial
function in patients with sleep apnea.