Prevalence of sleep apnoea in patients over 40 years of age with spinal cord lesions

Twenty two patients over the age of 40 with stable spinal cord damage underwent overnight sleep studies to investigate the prevalence of sleep apnoea. Ten patients had some evidence of obstructive sleep apnoea (OSA). Hypoxic events were scored as number of dips of SaO2 more than 4% below the preceding 10 minute average (> 4% SaO2 dip rate). All the patients had more than five such dips per hour and six had clearly abnormal dip rates of more than 15 per hour. Two other patients had dip rates above 10 per hour without apnoeas but periods of central hypoventilation mainly during rapid eye movement (REM) sleep. OSA appears to be more common in older patients with spinal cord injury than in the general population. Possible relevant factors include patient selection, reduced ventilatory function secondary to spinal cord damage, sleep posture and medication.