Sleep disturbances in long-term immigrants with chronic mountain sickness: a comparison with healthy immigrants at high altitude.

The aim of this study was to examine sleep disturbances in patients with chronic mountain sickness (CMS). The sleep of 14 patients with CMS and 11 healthy controls with or without sleep disorders (control N: without sleep disorders; control D: with sleep disorders) was studied by polysomnography. Hypopnea was the sleep disorder most commonly suffered by CMS patients and control D subjects. No major differences were observed in sleep structure between CMS and control groups, with the exception of shorter rapid eye movement latency in controls and increased deep non-rapid eye movement in the control N group. Periodic breathing was observed in only two study participants, one each in the CMS and control D groups. The level of saturated oxygen was significantly lower in the CMS group during sleep than the control groups (P<0.05). CMS scores were positively correlated with the apnea-hypopnea index, and negatively correlated with saturated oxygen levels. These results demonstrate that sleep disorders and nocturnal hypoxia are important in the development of CMS.