Ischemic preconditioning as a possible explanation for the age decline relative mortality in sleep apnea.

Breathing disorders in sleep are prevalent phenomena profoundly affecting the cardiovascular system. Mortality studies of sleep apnea patients revealed maximum risk of dying in younger patients and a pronounced age-decline in relative mortality reaching non significant levels in patients older than 50 years. We hypothesize that the age decline mortality risk in sleep apnea can be explained by cardiovascular and cerebrovascular protection conferred by ischemic preconditioning resulting from the nocturnal cycles of hypoxia-reoxygenation. The association of ischemic preconditioning with increase levels of vascular endothelial growth factor, increased production of oxygen reactive species, heat shock proteins, adenosine, and TNF-alpha, all demonstrated in sleep apnea, provide preliminary support to our hypothesis.