Sleep onset: scoring criteria in patients with sleep apnea syndrome

It has been suggested that in patients with sleep apnea syndrome (SAS) modified scoring criteria may improve accuracy in the determination of sleep onset in the Multiple Sleep Latency Test (MSLT). Scoring in 30-sec epochs according to the standard criteria requires more than 50% of the epoch asleep to score sleep latency (SL). In patients with SAS, short apneas with arousals could prevent the accurate determination of SL. This study compared three time-duration epochs (5-sec, 10-sec, 30-sec) for scoring SL in patients with SAS. Sleep onset during a single sleep latency test, the morning subsequent to a nocturnal polysomnogram, was determined by the criterion of at least 50% of the epoch asleep. Neuropsychological evaluation was performed immediately after the single sleep latency test. There was no statistically significant difference in time to fall asleep as defined by 10-sec and 30-sec epochs, but SL defined by 5-sec epochs was significantly shorter than SL defined by 10-sec and 30-sec epochs. Wilkinson Addition Test correct score correlated better with SL as defined by 30-sec epochs. The results imply that the level of sleepiness measured by 30-sec epochs may be more useful to appreciate behavior and performance.