Periodic leg movements in sleep before and after continuous positive airway pressure treatment in patients with obstructive sleep apnea

Abstract

Introduction Periodic leg movements in sleep (PLMS) are commonly reported to coexist together with obstructive sleep apnea syndrome (OSAS). Although PLMS usually disappear following continuous positive airway pressure (CPAP) treatment, an increasing number of patients have now introduced to have treatment-emergent PLMS. The underlying etiopathogenesis of temporal relationship between PLMS and CPAP treatment waits to be explored. Materials and methods Here we evaluated clinical and polysomnographic (PSG) data in four groups of OSAS patients: 10 patients with PLMS at first night and also at CPAP treatment night (present- present, PP group), 10 patients with PLMS at first night but not at CPAP treatment night (present-absent, PA group), 10 patients without PLMS at first night or at CPAP treatment night (absent-absent, AA group), and 10 patients without PLMS at first night but at CPAP treatment night (absent- present, AP group). Results Gender, age and presence of restless legs syndrome were similar between groups. Among PSG parameters, only the percentage of N3 sleep was significantly longer in patients without PLMS at first night (AA and AP group, p = 0.004).The comparison of variables between two nights in each group revealed that, other than significantly decreased RDI in every group, PLMS index was also significantly decreased in PA group (p = 0.005) and increased in AP group (p = 0.041).Decrease in PLMS index was positively correlated with decrease in RDI in PA group (p = 0.053), and increase in PLMS index positively correlated with increase in percentage of N3 sleep stage in AP group (p = 0.038). We performed cyclic alternating pattern (CAP) analysis. At first night analysis, time, rate, cycle and index of CAP were lowest in AA group, and highest in PA group (p 0.05). There was no significant difference in CAP parameters in different sleep stages as N1, N2 and N3. In PP group, CAP time of A1 subtype in N2 sleep stage; and CAP time, CAP cycle and CAP index of A2 subtype in N2 sleep stage were observed to persist without any decrease at second CPAP night. In AP group, CAP time, CAP rate, CAP cycle and CAP index of A1 and A2 subtypes were observed to persist, or even increase, in N1 and N2 sleep stages at CPAP night; while total CAP time of A3 subtype was decreased. In PA group, as well as in AA group, CAP parameters decreased prominently at CPAP night in compared to first night. Conclusion Different mechanisms are probably responsible from vanishing, non- vanishing or newly-emerging PLMS in OSAS patients following CPAP treatment. Macrostructural elements of sleep do not seem to explain them all. Microstructural CAP analysis of the sleep showed different patterns of cortical-subcortical activation in different stages of sleep. Activation of different sites within the same arousal system, triggered by internal (such as rebound NREM sleep) or external (CPAP) stimuli, may explain these differences.