Sleep Latency Test

The stages of sleep range from light to deep. Each stage has characteristics that can be measured. A sleep study is a number of tests done at the same time during sleep. The tests measure specific sleep characteristics and help to diagnose sleep disorders.

Sleep latency refers to the time it takes to fall asleep. The multiple sleep latency test (MSLT) is a "nap" study conducted on the day following your sleep study. The MSLT begins two hours after your normal rise time and is a series of four to five naps at two-hour intervals in between naps. Your sleep patterns will be monitored with most of the same recording equipment used during the sleep study.

Physicians trained in sleep medicine evaluate test results to treat sleep issues. This test provides an objective measure of the degree of your daytime sleepiness.

To obtain the most accurate sleep test results, keep a sleep diary of your sleeping patterns and habits for at least two weeks prior to your sleep test. Bring the diary with you to your scheduled appointment. Completion of this diary is not required to perform your sleep test, but it aids in the interpretation of your results.

In a sleep diary, you will track:

  • Date
  • Time you went to bed
  • Estimated hours of sleep you obtained
  • Time you got out of bed
  • Quality of sleep (1-5, 1=poor)
  • Number of times you woke up during the night and why
  • Activities or exercise within two hours of bedtime
  • Caffeine/alcohol/food two hours before bedtime

A sleep diary may be helpful for people with the following conditions:

  • Circadian rhythm disorders
  • Insomnia
  • Parasomnias
  • Other sleep disorder
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