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Where can I find documentation for the Sadeh and Cole Kripke algorithms?

Last Updated: Mar 21, 2017 08:53AM CDT

There are two built-in algorithms available in the Sleep Scoring tool to users.  Both algorithms score individual epochs as either sleep or non-sleep. Based on the results of the algorithm, ActiLife is able to discern Sleep Onset, Latency, Total Sleep Time (TST), Wake after Sleep Onset (WASO), Number of Awakenings, and Efficiency (these variables are calculated through the Tudor-Locke auto detect method). 

Sadeh Sleep Scoring Algorithm

The Sadeh algorithm was derived from fundamental research performed by Avi Sadeh, Katherine Sharkey, and Mary Carskadon entitled Activity Based Sleep-Wake Identification: An Empirical Test of Methodological Issues.  This paper is available on ActiGraph's research database here.  This algorithm is primarily used for younger adolescents as most of the research was performed on children and young adults.

ActiGraph's Implementation of the Sadeh Algorithm

The Sadeh algorithm uses an 11-minute window that includes the five previous and five future epochs.

Note: any missing epochs are considered ZERO. This happens if the current epoch is at the beginning or end of a dataset.

The Sadeh algorithm uses the y-axis epoch data. If any of the epoch counts are over 300, it reduces them to 300.

The algorithm requires the following information about the window that you're looking at:

  •  Arithmetic mean (average) of the activity counts for the window (AVG)
  • Number of epochs that have counts >= 50 and < 100 (NATS)
  • Standard deviation for the first 6 epochs of the window (SD)
  • Natural (base e) logarithm of a current epoch. Note: If the epoch count is 0, we make this value 0 to avoid infinity problems (LG)

Those calculations are put through the following algorithm:

(7.601 - (0.065 * AVG) - (1.08 * NATS) - (0.056 * SD) - (0.703 * LG)) 

If the result of that algorithm is GREATER than -4, then current epoch is considered asleep.

Cole-Kripke Sleep Scoring Algorithm

The Cole Kripke algorithm was derived from research performed by Roger Cole, and Daniel Kripke in the technical note Automatic Sleep/Wake Identification from Wrist Actigraphy.  This paper is also available on ActiGraph's research database here.  This algorithm is primarly used to score adult populations.

ActiGraph's Implemenation of the Cole-Kripke Algorithm

First, we adjust the epoch data to help reduce the variation of the counts from the paper compared to our devices:

  1. Using the y-axis epoch data, scale the count values by 100.
  2. If any of those scaled values are over 300, set them to 300.

Once the counts have been adjusted, we determine if each epoch is sleep or awake based on a seven-minute window. It includes the four previous epochs and two epochs after the current.

Note: any missing epochs are considered ZERO. This happens if the current epoch is at the beginning or end of a dataset.

The window of data is put through the following algorithm:

.001 * (106 * Epochx-4 + 54 *Epochx-3 + 58 * Epochx-2 + 76 * Epochx-1 + 230 * Epochx+ 74 * Epochx+1+ 67 * Epochx+2); 

If the result of that algorithm is LESS than 1, then the current epoch is considered asleep.

Custom Sleep Scoring Algorithms

Users wishing to create their own sleep algorithm based on the techniques used in the Sadeh and Cole-Kripke may create their own algorithm using the Custom Sleep Score Algorithm Builder.
 

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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