CARWatch – An Open-Source Framework for Improving Cortisol Awakening Response Sampling

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Start date: 1. September 2019
End date:


Many studies investigating the cortisol awakening response (CAR) suffer from a lack of precise and objective methods for assessing the awakening and saliva sampling times. Failure to correctly report times or to adhere to the study protocol, which is common in unsupervised real-world studies, can lead to a measurement bias on CAR quantification and can even contribute to erroneous findings in psychoneuroendocrinological (PNE) research.

To address this gap in available methodology, we developed CARWatchCARWatch is an open-source framework to support objective and low-cost assessment of cortisol samples in unsupervised, real-world environments. It consists of an Android application that schedules sampling times and tracks them by scanning a barcode on the respective sampling tube as well as a Python package that provides tools to configure studies, prepare the study materials, and process the log data recorded by the app.

The CARWatch workflow is illustrated here:

Click here to get to the CARWatch Website!


Code and Datasets

All code used within CARWatch is available under an open-source license on GitHub:

  • carwatch-web: A website that helps to configure studies, prepare study materials, and process the log data recorded by the app.
  • carwatch: A Python package that provides tools to configure studies, prepare study materials, and process the log data recorded by the app. It is available on GitHub.
  • carwatch-analysis: All analysis code that was used to create the results used in our publications. It is available on GitHub.

Additionally, all collected data are also available:

  • CARWatch Dataset: This dataset contains cortisol awakening response (CAR) data, objective saliva sampling time logging from the CARWatch smartphone application, and IMU-based movement during the night. It was used as proof-of-concept validation of the CARWatch application for objective sampling time assessment and to assess the influence of the inner clock on the CAR and pre-awakening movement. It is available on OSF.