Silent Strokes Linked to Sleep Apnea

TOKYO, March 15 -- Obstructive sleep apnea patients have a high rate of silent brain infarctions that can be seen by magnetic resonance imaging, according to researchers here.

They also have elevated levels of biochemical markers associated with cerebrovascular disease, found Kenji Minoguchi, M.D., Ph.D., of Showa University School of Medicine.

On the other hand, treatment with nasal continuous positive airway pressure (nCPAP) over three months reduced the level of disease markers and may lower the risk of disease, Dr. Minoguchi and colleagues said in the second March issue of the American Journal of Respiratory and Critical Care Medicine.

For reasons that could not be explained, the silent brain infarctions had no obvious clinical consequences.

The researchers enrolled 50 men with newly diagnosed obstructive sleep apnea and 15 obese men who had no sleep disorder to serve as controls. None had other co-morbidities.

The men were given a whole-brain MRI scan, with a silent brain infarction defined as a lesion at least 3 mm in diameter. The researchers also measured the levels of soluble CD40 ligand (sCD40L) and soluble P-selectin (sP-selectin), proteins regarded as precursors of atherosclerosis.

The study found that 16% of the men with sleep apnea had evidence of silent brain infarction, compared with 6.7% of the controls, a difference that was significant (P

He noted that "clinically identified stroke represents the tip of the iceberg in terms of cerebral vascular disease by at least an order of magnitude." While silent brain infarctions have no obvious clinical manifestations, he added, "it is hard to believe, however, that loss of brain tissue should go without consequences."

It may be that the brain has the ability to reorganize and adapt to loss of function after these events, Dr. Murray said, but sooner or later it will be unable to do so.

The findings of Dr. Minoguchi and colleagues therefore have clinical significance, he said, in that they point out the importance of preventing these lesions in the first place.

Also, he said, nCPAP appears from this study to be useful in lowering markers associated with cerebrovascular disease risk, and may also reduce the incidence of brain ischemia.

The authors pointed out several limitations of study. Thus "the current study reports findings from male subjects only, and potentially a different relationship between obstructive sleep apnea, C-reactive protein, sCD40L, sP-selectin, and the prevalence of silent brain infarctions may exist in female subjects," they wrote. "In addition, the study was conducted on a relatively small number of subjects,"