Hi Mike and Stephanie,
Thank you very much for double-checking and a great resource. That helps a lot!
I have a somewhat general question regarding the wakefulness stage during sleep. I'm currently looking at the hypnogram data in the XML files from both the nsrr and profusion annotations. It looks one can have many episodes of wakefulness during sleep (figure below shows about 25 episodes and many subjects have hypnograms like this). Since wakefulness is a conscious state (i.e. one knows that he's awake and can perceive the environment), I wonder if one can have that many brief episodes of wakefulness at night even considering the aging population from the MESA study. Are there any artifacts in the hypnogram data? Does any filter need to be applied? I'm asking as a non-expert in sleep analysis.