Researchers from University Rostock, Department of Sociology and Demography, developed the Cogstate Speed Sum to reflect all possible Cogstate tasks of the Cogstate Brief Battery, from assesment 2A, in one measurement. Please note, during the third assessment two versions of the Cogstate have been administered making it impossible to copy paste the current results (sections: Mental health (Cogstate) and secondary & linked variables).

The Cogstate Speed Sum can be requested in the Lifelines catalogue or by email (data@lifelines.nl). When this data has been used in your research, you will have to include a reference to the following paper:

• Aretz et al. (2021): Long-term exposure to fine particulate matter, lung function and cognitive performance: A prospective Dutch cohort study on the underlying routes. Environmental Research 201(5).

The researchers were in contact with the Cogstate Research Group, it was decided to calculate the Cogstate Speed Sum based on the Detection, Identification and One back task. As the Cogstate Research Group stated that speed (or reaction time) is not a primary outcome of the One Card Learning task. More information on the different tasks can be found on the Cogstate page.

The creation of the Cogstate Speed Sum consisted of three steps, listed below. Please note that calculations are performed for adults (18+) only.

1. Mean and standard devation were determined per age group (18-34, 35-49, 50-59, 60-69, 70-79, 80-89 and 90+).
2. The task specific variables were standardized with the extracted age-specific means and standard deviations.
3. Finally, the three standardized measurements were summed up to get the Cogstate Speed sum value for each participant.

The Rostock researchers listed the following points of attention:

• Additional z-standardizing: In some cases it could make sense to additionally z-standardize each of the three measures before you sum them up to one composite score.
  
• Corrected for accuracy of responses given: We think that it is important to control for accuracy because participants can be fast (= fast processing speed) but producing a lot of wrong answers. Other researchers might use the speed measure “uncontrolled”. From our methodological understanding it is good to include this as a control variable. We tried two different version: 1) The number of total trials in the used tasks of the Cogstate Speed Sum (correct trials + error trials). This is what we used in our final paper due to better model performance. 2) Only the number of error trials.

• Hammers, D. B., Jung, M., P., Pressler, S. J., Sullivan, B., Koelling, T., & Giordani, B. (2012). Clinical utility of auditory memory testing in a heart failure population. Journal of Cardiovascular Nursing, 28, 444-452.
  
• Yoshida, T., Suga, M., Arima, K., Muranaka, Y., Tanaka, T.,…Hashimoto, K. (2011). Criterion and Construct Validity of the CogState Schizophrenia Battery in Japanese Patients with Schizophrenia. PLos ONE, 6, 1-7.
  
• Cromer, J., Schembri, A., Harel, B., & Maruff, P. (2015). The nature and rate of cognitive maturation from late childhood to adulthood. Frontiers In Psychology, 6.