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How does Sedentary Analysis work?

Last Updated: Nov 28, 2016 02:36PM CST

Sedentary Analysis Description

The Sedentary Analysis feature identifies bouts of low activity in *.agd datasets.  Following Wear Time Validation, this feature will identify details about a subject's sedentary behavior (rather than identifying non-wear as sedentary time).  When enabled, this feature yields following outputs in the Data Scoring tool:

  • Summary Screen
    • Total Sedentary Bouts - the number of sedentary bouts detected in the entire dataset
    • Total Length of Sedentary Bouts - The total sedentary time detected in the entire dataset.  
    • Max Length of Sedentary Bouts - The length of the longest sedentary bout in the entire dataset
    • Min Length of Sedentary Bouts - The length of the shortest sedentary bout in the entire dataset
    • Daily Average of Sedentary Bouts - The Total Length of Sedentary Bouts divided by the total valid days in the dataset
    • Total Sedentary Breaks - The total number of breaks in sedentary activity for the entire dataset.
    • Total Length of Sedentary Breaks - The sum of all the times between sedentary bouts in the dataset.
    • Average Length of Sedentary Breaks - An average of all of the times between sedentary bouts (Total Length of Sedentary Breaks/Total Sedentary Breaks)
    • Max Length of Sedentary Breaks - The length of the longest sedentary break in the entire dataset
    • Minimum Length of Sedentary Breaks - The length of the shortest sedentary break in the entire dataset
    • Daily Average of Sedentary Breaks - The Total Length of Sedentary Breaks divided by total valid days in the dataset
An example Summary Screen is shown below.

 Sedentary_Analysis.png

  • Details View - After clicking "Details" button
    • Total Sedentary Bouts - the number of sedentary bouts detected in the specified day/hour
    • Total Length of Sedentary Bouts - The total sedentary time detected in the specified day/hour
    • Max Length of Sedentary Bouts - The length of the longest sedentary bout in the specified day/hour
    • Min Length of Sedentary Bouts - The length of the shortest sedentary bout in the specified day/hour
    • Daily Average of Sedentary Bouts - The Total Length of Sedentary Bouts divided by the total valid days in the specified day/hour
    • Total Sedentary Breaks - The total number of breaks in sedentary activity for the specified day/hour
    • Total Length of Sedentary Breaks - The sum of all the times between sedentary bouts in the specified day/hour
    • Average Length of Sedentary Breaks - An average of all of the times between sedentary bouts (Total Length of Sedentary Breaks/Total Sedentary Breaks) in the specified day.
    • Max Length of Sedentary Breaks - The length of the longest sedentary break in the specified day/hour
    • Minimum Length of Sedentary Breaks - The length of the shortest sedentary break in the specified day/hour

A sample "Details" view is shown below

Sedentary_Analysis_Details.png

 

Sedentary Analysis Setup

To setup and run a sedentary analysis, check the box beside the "Sedentary Analysis" option in Data Scoring and click "edit..." to define sedentary analysis parameters.  A sample window and a description of the parameters is given below.

Sedentary_Analysis_Options.png

  • Bout Name - Uneditable
  • Length
    • Minimum - The minimum allowable amount of consecutive time that can be considered a sedentary bout
    • Use Maximum - (optional) The maximum allowable amount of consecutive time above the minimum that can be considered a sedentary bout
    • Drop Time - The tolerance, or allowable amount of total time (not consecutive) that can break a sedentary bout.  
  • Count Levels
    • Minimum - The minimum count level to be considered a sedentary bout
    • Use Maximum - (optional) The maximum count level to be considered a sedentary bout
    • Use Vector Magnitude - This option uses the Vector Magnitude of all three axes when considering the count level values defined in the Minimum and Maximum.
    • Ignore First Sedentary Break of Each Day - If this option is checked it will not factor the time between the first sedentary bout of the day and the last one on the day before when calculating stats. So if you have a sedentary bout from 9:00pm to 9:30pm one night and then the next morning you have one from 9:30am to 10:00am, ActiLife does not assign the time from 9:30pm to 9:30am as a sedentary break.

Example: Consider a 60s epoch file.  If a 10 minute minimum is set, a drop time of 2 minutes is entered, and a maximum count level is 99, the following sequence would be considered a sedentary bout: 

  • 10:01am - 50 counts
  • 10:02am - 150 counts
  • 10:03am - 0 counts
  • 10:04am - 0 counts
  • 10:05am - 0 counts
  • 10:06am - 0 counts
  • 10:07am - 500 conts
  • 10:08am - 40 counts
  • 10:09am - 30 counts
  • 10:10am - 0 counts

 

Why Would The Total Time In Sedentary Breaks Be Larger Than The Total Wear Time?

The problem here is in how we calculate Sedentary Breaks. Essentially, we first qualify all sedentary bouts throughout the file (you can get a list of these by clicking "Details" in the Data Scoring tab after running the calculation). After that, we calculate the time in between those bouts. That time becomes the "Break" time. We do not take non-wear time into consideration during this process. There are a few reasons for that (e.g., just because someone removed the monitor doesn't condense the time in between their sedentary bouts).

For example, if you refer to the attached AGD file, the total time in the file is 24,323 minutes - only 4521 are wear minutes. However, ActiLife detected a sedentary bout starting on 11/1/2008 at 11:37pm and lasting until 11/1/2008 at 11:59pm. The user didn't wear the device for a while - then the next sedentary bout is found on 11/4/2008 at 8:59am. The calendar time in between those bouts is 3,441 minutes (much of which is non-wear). This is how your "Total length of sedentary breaks" time can be higher than the wear time. We do realize that this can cause confusion and we plan to address it soon.

One thing to note. There is an option in the Sedentary Analysis that says "Ignore first sedentary break of each day." That option basically tells ActiLife to use "0" for the "Time since last bout" for the first sedentary bout of each day and is useful for cases in which you don't want to consider your first activity of the day as a "break" from sedentary (sleep). In the case of this example, checking this option drops the subject's "Total length of sedentary breaks" down to 2685 minutes - considerably better than before.

 

How Can The Total Time of a Sedentary Bout Be Larger Than One hour in hourly view?

Sedentary breaks are marked on the hour they end on. For example, in the below image you see several hours with no sedentary bounts and then 1 bout with a total time of 304 minutes. The bout started at sometime in the 24rh row and ended on the 29th row.

actigraph_excel_screenshot.png

 

If you need any further assistance, please visit our support portal at https://help.theactigraph.com/home. From there, you can view many helpful FAQ's and Troubleshooting Articles; log in to check any existing Support Requests; or create a new Support Ticket if you are unable to find a solution. You can also email us at support@theactigraph.com or give us a call at (877) 497-6996, Monday through Friday, 8 am to 5 pm CST.

 

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