Response to Letter by Drager and Lorenzi-Filho
The authors make a note highlighting the importance of the biological plausibility as a condition to establish the causative relationship between a risk factor and a disease. In their study,1 they have found that the severity of sleep apnea (expressed as AHI) was directly correlated with the presence of early markers of atherosclerosis in middle-aged patients, as are arterial stiffness and intima-media thickness. However, another marker, carotid diameter, correlated better with oxygen desaturation.
In line with this study, we have found that AHI is the only significant variable that correlates with risk of incident stroke, and not oxygen desaturation (T90). In our opinion, those different findings are not in contradiction because, as we know, pathophysiological mechanisms leading to stroke are different and interrelated. Assuming this point, we agree with Drager and colleagues in that better knowledge of sleep apnea and other emergent stroke risk factors brings us a great opportunity to make progress in prevention and treatment of multiple mechanisms of cerebrovascular diseases.2