Derived Arterial Stiffness is Increased in Patients with Obstructive Sleep Apnea and Periodic Limb Movements during Sleep

Study Objectives: Both periodic limb movements during sleep (PLMS) and obstructive sleep apnea (OSA) have been associated with increased risk of cardiovascular disease (CVD). OSA has also been linked to increased large arterial stiffness, which is considered an independent risk factor for CVD. We utilized a previously validated index of large artery stiffness (SIDVP) derived from the digital volume pulse (DVP) to seek comparison in patients with PLMS and OSA. Methods: Forty-nine adult male subjects, without known comorbidities that could affect arterial stiffness or on vasoactive medication, were retrospectively identified and categorized into controls (n = 8), PLMS (n = 13), OSA (n = 17), and OSA/PLMS (n = 11). The cutoff for PLMS was a periodic limb movement index (PLMI) > 15 events/h, and for OSA an apnea-hypopnea index (AHI) > 10 events/h. SIDVP was derived from the raw data of photoplethysmography of the nocturnal polysomnography, averaged for 2 min prior to sleep study initiation (baseline), after completion in the morning, and every half hour after sleep onset. Results: The groups were age/body mass index-matched. Controls showed lower baseline, morning, and overall SIDVP compared to the other groups (p < 0.01). Patients with PLMS (PLMI: 50.69 +/- 9.7 events/h) and the OSA group (AHI: 29.7 +/- 2 events/h) demonstrated similar overall SIDVP (6.78 +/- 0.08 versus 6.94 +/- 0.04, respectively, p = 0.5), whereas the OSA/PLMS (AHI: 29.35 +/- 8, PLMI: 50.63 +/- 7.2) group demonstrated the highest (7.40 +/- 0.06, p < 0.001). Conclusions: Based on an easily reproducible and applicable marker of large arterial stiffness, patients with significant PLMS had higher SIDVP when compared to controls and comparable to those with moderate/severe OSA. The OSA/PLMS group had the highest SIDVP, implying a possible additive effect of OSA and PLMS on arterial stiffness.