Obstructive sleep apnea (OSA) has been shown to be an important risk factor for metabolic syndrome and cardiovascular disease. Endothelial dysfunction plays a pivotal role in the pathophysiology of these diseases. However, little is known about the relationship between sleep apnea and microvascular endothelial dysfunction, as assessed by digital reactive hyperemia.

The study population consisted of 80 patients (mean age, 48 ± 12 years-old; 65 men; 59 hypertensive). We measured apnea-hypopnea index (AHI) and mild OSA was defined as 5 < AHI <15 and moderate to severe OSA as AHI ≥ 15. Reactive hyperemia index (RHI) derived from peripheral arterial tonometry (PAT) as measurement of endothelium-mediated vasodilatation.

There were 61 OSA patients in the study population (AHI, 21.5 ± 16.7 vs. 2.7 ± 1.6 in non-OSA; p < 0.001). There were no significant difference in RHI and peripheral augmentation index (pAIx) between OSA and non-OSA group (RHI, 2.04 ± 0.48 vs. 2.06 ± 0.42; p = 0.894; pAIx, 21.7% ± 24.0% vs. 21.7% ± 30.0%; p = 1.000, respectively). Also, there was no significant difference in RHI and pAIx between mild (n = 31) and moderate to severe (n = 30) OSA group (RHI, 2.10 ± 0.47 vs. 1.98 ± 0.49; p = 0.333; pAIx, 24.2% ± 20.7% vs. 19.0% ± 27.2%; p = 0.407, respectively), either. Overall, no significant correlation between AHI and RHI was observed (r = -0.023, p = 0.837). The other OSA severity indices such as oxygen desaturation index, mean and minimum oxygen saturation were not correlated with RHI or pAIx. In the subgroup analysis for the OSA group, we could not find any significant relationships between AHI and PAT parameters, either.

OSA was not observed to be associated with reactive hyperemia measured by PAT.