Effect of Hypoxia on Periodic Limb Movement in Sleep Related Breathing Disorders

Introduction: The relationship between periodic limb movements during sleep (PLMS) and sleep related breathing disorder (SRBD) is not clear. Factors affecting the occurrence of PLMS in patients with SRBD, and a possible relation of PLMS and sleep related hypoxia in patients with obstructive sleep apnea syndrome and sleep related hypoventilation-hypoxemic syndromes was investigated. Methods: Patients with snoring and/or witnessed apnea were tested with polysomnography. Respiratory events and PLMS were scored. Serology and arterial blood lactate levels were measured. Results: 80 patients, 58 male and 22 female were included (Mean age: 49.1 years, SD: 9.0). 62 had SRBD and 18 had no SRBD, where 29 were in periodic limb movement index over and equal to 15 (PLMI >= 15) group and 51 were in the PLMI below 15 (PLMI<15) group. The rate of sleep-time spent below 90% oxygen saturation (T90%) and T80% were significantly higher in patients with PLMI >= 15 than patients with PLMI<15. PLMI<15 group spent longer time in NREM III than PLMI >= 15 group. Apnea hypopnea index, the rate of sleep-time spent below 90% oxygen saturation (T90%), T80%, T70%, ESS and sleep NREM I-II% were significantly higher in patients with PLMI >= 15 plus SRBD, than patients with PLMI >= 15 without SRBD. PLMI was not correlated with overnight lactate change. Conclusion: As the rate of sleep-time spent below 90% oxygen saturation is longer in patients with PLMI >= 15 than PLMI<15, hypoxemia may play role in the pathophysiology of PLMS. Further studies with nasal CPAP treatment would reveal more information about the etiopathogenesis of PLMS in SRBD.