Mortality in Obstructive Sleep Apnea: Association with Impaired Wakefulness

Sleep fragmentation from obstructive sleep apnea (OSA) is correlated with a shortened sleep latency on the Maintenance of Wakefulness Test (MWT) and the Multiple Sleep Latency Test. Whether impairment of wakefulness is associated with increased mortality in OSA patients is unknown. We evaluated survival over an average timespan of 7.5 years from the date of diagnosis in a consecutive series of 322 OSA patients who had undergone nocturnal polysomnograpy and the MWT. Evaluable survival data were obtained in 142 patients. Twenty two had died. Deaths were predominantly due to cardiovascular disease. A comparison of the demographic and sleep study data between the alive and dead groups was significant for differences in MWT sleep latency and in age at time of diagnosis. The MWT mean sleep latency, when adjusted for age, was significantly shortened in the dead patients (28 +/- 11 min vs. 21 +/- 10 min, p < 0.005). Also, there was a significant decrease in survival in the patients whose MWT mean sleep latency was less than 20 min. These findings demonstrate an association between impairment of wakefulness and long-term mortality in OSA patients. This association was not evident for the other measures used to assess OSA severity.