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How can I customize the sleep scoring algorithm in the Sleep Scoring tool in ActiLife?
How can I customize the sleep scoring algorithm in the Sleep Scoring tool in ActiLife?
Last Updated: Feb 08, 2012
Views: 148
Many customers have requested the ability to create their own custom sleep algorithm based on the two popular validated algorithms provided in ActiLife (Sadeh and Cole-Kripke). These two algorithms use a sliding-window approach to scoring epoch-by-epoch data as either sleep or wake. One limitation of these validated algorithms is that only the vertical acceleration axis is utilized when making the sleep/wake determination. Users have requested the ability to use any axis of their choice or all three axes in a vector magnitude configuration (sqrt[ (Axis 1)^2 + (Axis 2)^2 + (Axis 3)^2 ]). ActiLife version 5.10.0 and above provides this additional capability. (Note: this feature is only available for ActiSleep and ActiSleep+ devices) Validated tri-axial sleep algorithms will be added into the ActiLife tool as they become available. As of the time of this writing, no such algorithms have been validated against Polysomnography
To use the tool, navigate to the "Sleep Scoring" tab. A drop-down box is available that allows users to select the appropriate algorithm.
Select "Create New..." to load the custom sleep scoring algorithm building tool.
This tool can be used to create a custom sleep algorithm. Here's a summary of how the different options work.
Epoch Window
The sleep scoring tool basically iterates over all of the epochs in a file and determines if a particular epoch should be scored as a "sleep" or a "wake" epoch. The algorithm uses the value of the current epoch as well as the values of the surrounding epochs to make that determination. The Epoch Window option allows you to set your own desired weighting (or scaling) for those surrounding epochs. This functionality works similar to the Sadeh and Cole-Kripke algorithms. epoch-2, for instance, refers to the epoch that occurred 2 epochs before the current (epoch-0). A scaling of 0.05 (as shown in the example) means that a 5% weight is applied to this epoch in making the sleep/wake determination.
Use the boxes up top (Epochs to use before current and Epochs to use after current) to increase the number of epochs surrounding the current epoch that are included in the wake/sleep determination. As settings change, so too will the "Sleep/Wake Formula" at the bottom of of the dialogue. This formula gives the formula for determining whether epoch-0 (the current epoch) is scored as sleep or wake. In the example shown, the current epoch will be scored as "wake" if the formula results in a value greater than or equal to 10; otherwise, it will be scored as "sleep".
Count Parameters
Wake Threshold - This is the value that the epoch scaling formula is compared against. If the formula results in a value greater than or equal to the number entered here, the epoch-0 (current epoch) is scored as "wake". Otherwise, it is scored as "sleep".
Data to Use - This dropdown selects which actual data is used when calculating the sleep/wake formula. Choosing "All (VM)" means that the values used in the formula will take into account the Vector Magnitude of all three axes (sqrt[ (Axis 1)^2 + (Axis 2)^2 +(Axis 3)^2]. Otherwise, only the selected axis will be used when calculating the sleep/wake information.
Set Maximum Value of Count - Use this option to limit the maximum value of each epoch used in the calculation. For instance, if epoch+1 is 2000, setting this value to 300 will essentially cap (or replace) that value with 300, thus reducing the weight of an individual outlier.
Epoch Length Required (future feature) - In the future, this option will allow users to use other epoch length files (other than 60 seconds). Right now, files must be 60 second epoch files.
Sleep/Wake Formula
This section shows the formula used to determine whether the current epoch (epoch-0) is to be scored as "wake" or "sleep".
This FAQ Applies To:
ActiSleep+ Device
ActiLife Software
ActiLife6 Software
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