The Cogstate is a battery of computerized cognitive tests used in Lifelines to broadly assess cognitive functioning of participants (section: mental health). The test battery was performed in ~68,000 able participants aged 13 years and older during 2A Visit 1, and is used again in the ongoing assessment 3A.
The Cogstate is used in conjunction with other cognition tests in Lifelines, i.e. the RFFT and the MMSE. Raw data of the Cogstate was used to calculate the Cogstate Speed Composite (CSC).

Lifelines uses the brief battery of Cogstate tests. Measuring different cognitive function domains which were completed in the following order:

1. Detection task (psychomotor function / speed of processing) (2 min)
2. Identification task (visual attention/vigilance) (2 min)
3. One back (working memory) (2 min)
4. One Card Learning task (visual learning & memory) (5 min)

NB: The Groton Maze Learning Task, which is part of the full Cogstate battery, was not used in Lifelines.

All subtests are based on playing card formats, with little reliance on assessment of verbal abilities. The Brief Battery can be administered un-supervised.
Written instructions are presented on the screen. Responses are made on a computer keyboard represented on the screen, with responses by using the “k” key for yes and “d” key for no. Outcome measures are:

1. number of errors/correct responses
2. reaction time

The participant should be able to use a computer keyboard or mouse with one hand and should be able to see the computer screen (i.e. normal vision observation). If participants use reading glasses, they are recommended to use them during this task.

cogstate_sop_in_dutch.pdf

Content validity: Content validity of the Cogstate can be considered good because it includes a broad range of cognitive functioning domains. The Cogstate testing method has been validated in international peer-reviewed journals. It targets a wide range of cognitive domains, including simple reaction time, attention, executive function and social-emotional cognition. The tests are designed to maximize the signal and minimize the noise from cognitive recordings taken in research trials. They have a proven ability to detect both improvement and decline in cognition.

Criterion/construct validity: No gold standard is currently available to measure cognitive functioning. However, The MMSE is a widely used screening instrument for cognitive function and measures global cognitive functioning ¹⁾. Based on a case control study including 21 subjects with mild cognitive impairment and 98 healthy controls (age > 60 year), the Cogstate had a sensitivity of 78% and specificity of 90%. This was much higher compared to the Mini Mental State examination (MMSE) (sensitivity: 44%, specificity: 69%). The study also investigated the sensitivity and specificity of the Hopkins Verbal Learning Test (HVLT) and this test had a slightly better sensitivity (79%) and specificity (95%) compared to the Cogstate ²⁾. However, the HVLT is based on a paper-and-pencil test, which needs to be conducted under guidance of an assistant which may influence sensitivity and specificity. In this case-control study, participants performing the Cogstate were supervised by one of three psychologists through a practice session on the Cogstate (to maximize good performance), followed by the test battery with minimal supervision/assistance.

The test-retest reliability of different Cogstate subtests has been described in various studies ^{3) 4) 5)}.

Responsiveness of the instrument has been assessed by measuring decline in cognitive performance of patients with mild Alzheimer’s Disease on the International Shopping List Test (ISLT); a subtest of the Cogstate⁶⁾. Results show that compared to controls, patients with Alzheimer’s Disease show deterioration in verbal memory over a period of one year. We would expect similar results on all other subtests of the CogState suggesting that the Cogstate is sensitive to changes in cognitive functioning in persons with Alzheimer’s disease. A longer period of follow-up would be needed to be able to say something about responsiveness among the general population (i.e. persons without cognitive impairments).

Cogstate in Lifelines: correlations between the Cogstate and RFFT scores are described in a paper by Kuiper et al. ⁷⁾

The Cogstate brief battery was measured during 2A Visit 1 and 3A Visit 1. During the third assessment (3A) the test was redesigned by the Cogstate research group. The test and protocol stayed the same for the participants, however more variables were measured during the test.
In 2A Visit 1 around 92.000 participants had valid Cogstate results. In 3A Visit 1 around 15.000 participants had valid results on the original brief battery and 24.000 on the redesigned version. At this moment assessment 3A is still going on, meaning the redesigned version number will increase overtime.

• To reflect the difference between the Cogstate variables and the redesigned Cogstate variables, please pay attention to how the variables are written in the column named 'Code' in the variable table.
• Most variables listed in the below table are test specific. For this reason a '_XX' will be added to the variable name in data releases. Due to a database variable continuity the '_XX' suffixes per test are different from the order in which the tasks were performed. The suffixes are as followed:

the Cogstate variables are, just as all other data, presented 'as-is'. Meaning that all available data will be present. The Cogstate research group has a completion criteria for all participants. This criteria determines when according to their standards the test was valid. If a participant scored to low on one of the following variables the results of the test is considered invalid.

ⁱ Only calculated on test _02 (Identification task)
ⁱⁱ Primary outcome is reaction time (Detection/Identification task) or accuracy (One Back/One Card Learning task)
ⁱⁱⁱ Only calculated on test _04 (One Back task)
^iv Calculated on tests _01,_02 and _04 (Detection, One back and One Card Learning task)