Sleep session definition

[PVoice]

I am helping with a clinical study using Fitbits to measure activity and sleep and the biostatistician will be analyizing all the patient data being presented in a csv file. He needs to know what defines a sleep session to help with the data analysis. For example, if someone is asleep for 3 hours and gets up for 5 minutes, walks around and then goes back to sleep, will that end the sleep session? In other words, can you provide information on the amount of time out of bed that will cause the sleep session to end? 

[AndrewFitbit]

@PVoice Going off your example, that would be a 3 hour sleep log since the tracker would detect the user being awake, then the second sleep session would be logged separately. It won't combine the two. You can read more about sleep on our help site, specifically the section "HOW DOES MY TRACKER AUTOMATICALLY DETECT SLEEP?" might be useful to you.

[PVoice]

My question is not about combining two separate sleep sessions, is what defines a break in a sleep session. If someone gets up for 1 minute and then goes back to bed, will that cause the sleep session to end? In other words, what is the amount of time out of bed that will cause the sleep session to end? 1 minute, 2 minutes, etc.

[AndrewFitbit]

@PVoice Right, that's why I linked the help article:

"Autodetection is based on your movement. When you haven’t moved in over an hour, algorithms assume that sleep has begun, which is confirmed by the length of time your movements are indicative of sleep behavior only (rolling over, etc). Morning movement tells your tracker that you’re awake."

There's no set amount of time it takes so I can't really answer that, it's mostly based on the amount of movement detected (and what the person is doing). There's also manual sleep sessions, and the session start/stop time would depend on the user.

[PVoice]

Thank you, Andrew, for the information. Does this mean that Fitbit doesn't provide the details on what specifically determines a sleep session has ended, that the information is proprietary? 

[AndrewFitbit]

@PVoice I think my previous post (and the help article) might be as specific as it gets. Time is certainly a factor along with movement, but I don't have specifics on how much it takes.