Researchers from University Rostock, Department of Sociology and Demography, developed the Cogstate Speed Composite (CSC) to reflect all possible Cogstate tasks of the Cogstate Brief Battery, from assessment 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 CSC 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 CSC 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 CSC 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 CSC 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 CSC value. For example, when you want to interpret them as differences to the global mean.
  
• 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 produce a lot of wrong answers. From our methodological understanding it is good to include this as a control variable. We included two different versions: 1) The number of total trials in the used tasks of the CSC (correct trials and error trials). 2) The number of error trials only. The first version has been used in the reference paper listed above.
• Age groups: The specific age groups were based on information from the Cogstate Research Group they refer to the following references:
  - 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.