We read with great interest the article of Dr. Blomster H and colleagues entitled: “Endothelial function is well preserved in obese patients with mild obstructive sleep apnea” [1]. In the manuscript, the authors clearly show that mild obstructive sleep apnea (OSA) does not correlate with endothelial dysfunction, measured by brachial artery flow-mediated dilatation (FMD), assuming that in mild OSA, endothelial function is still preserved. The data are very interesting, although the authors did not analyze the time of onset of symptoms, as well as the time from the diagnosis in their patients population.

In two recent studies [2, 3], endothelial peripheral dysfunction in OSA patients has been significantly found in mild OSA and in minimally symptomatic OSA. The endothelial dysfunction was also significantly decreased by CPAP treatment. Indeed, in our study [2], we demonstrated that moderate or severe OSA patients show an evident brachial endothelial dysfunction, measured by flow-mediated dilation (FMD) method. The most important finding was the considerable reversibility of FMD results for endothelial dysfunction, in the group of patients treated with CPAP therapy, for at least 3 months.

Taken these results together, we warmly emphasize that endothelial function is not always preserved in obese patients with mild obstructive sleep apnea. Its dysfunction might depend on the length of disease or might be increased by the coexistence of other important comorbidities.