When does the first nap in an MSLT typically commence after the overnight PSG concludes?

The first nap in a Multiple Sleep Latency Test (MSLT) typically begins 1.5 to 3 hours after the overnight polysomnography (PSG) concludes. This timing is crucial because the MSLT is designed to measure how quickly a person falls asleep in a quiet environment during the day, thereby assessing their level of daytime sleepiness.

Starting the MSLT within this 1.5 to 3-hour window allows the effects of the previous night's sleep to diminish, offering a clearer picture of the patient's daytime sleep propensity. If the first nap were to occur too soon, the individual might not yet be experiencing normal levels of daytime sleepiness due to residual sleepiness from the overnight study. Conversely, waiting too long might introduce factors such as increased alertness or fatigue from extended wakefulness that could skew the results of the test.

This strategic timing ensures that the results are more reliable in evaluating conditions such as narcolepsy, idiopathic hypersomnia, or other disorders affecting sleep-wake regulation.