Variable Details

Available Studies

ROS, MAP, MARS, Clinical Core, LATC

Scaled? 

Scaled

Variable Type 

Longitudinal

Variable Name 

cogn_global

Categories

Cognition

Global cognitive function
Global cognitive function - Average of 19 tests

Cogn_global is the main variable for overall (i.e. global) cognitive function. This variable replaces GLOBCOG.

Raw scores from a battery of cognitive tests were converted to z-scores and averaged to yield a global cognitive function summary. Mean and standard deviation at baseline were used to compute the z-scores. Z-score has mean 0 and standard deviation of 1. Each z-score corresponds to a point in a normal distribution. Z-score describes how much a point deviates from a mean or specific point. A negative z-score simply means that someone has an overall score that is lower than the average of the entire cohort at baseline.

The following 19 tests are used to compute the global cognitive function score

Test scoreZ-scoreCognitive test nameComposite cognitive domain
cts_wliz_WLIWord listEpisodic memory (cogn_ep)
cts_wliiz_WLIIWord list recallEpisodic memory (cogn_ep)
cts_wliiiz_WLIIIWord list recognitionEpisodic memory (cogn_ep)
cts_ebmtz_EBMTEast Boston immediate recallEpisodic memory (cogn_ep)
cts_ebdrz_EBDREast Boston delayed recallEpisodic memory (cogn_ep)
cts_storyz_StoryLogical memory I (immediate)Episodic memory (cogn_ep)
cts_delayz_DelayLogical memory II (delayed)Episodic memory (cogn_ep)
cts_bnamez_BNameBoston naming (15 items)Semantic memory (cogn_se)
cts_catfluz_CatFluCategory fluencySemantic memory (cogn_se)
cts_read_nartz_read_nartReading test - (10 items)Semantic memory (cogn_se)
cts_dfz_DFDigits forwardWorking memory (cogn_wo)
cts_dbz_DBDigits backwardWorking memory (cogn_wo)
cts_doperfz_DOperfDigit orderingWorking memory (cogn_wo)
cts_lopairz_LOpairLine orientationVisuospatial ability/perceptual orientation (cogn_po)
cts_pmatz_PMatProgressive matrices (16 items)Visuospatial ability/perceptual orientation (cogn_po)
cts_sdmtz_SDMTSymbol digits modality-oralPerceptual speed (cogn_ps)
cts_nccrtdz_NCcrtdNumber comparisonPerceptual speed (cogn_ps)
cts_stroop_cnamez_cnameStroop color namingPerceptual speed (cogn_ps)
cts_stroop_wreadz_wreadStroop word readingPerceptual speed (cogn_ps)

Item level variables are available upon request.

Note: This variable is calculated if more than half of the z-scores are non-missing. Since the variable is calculated based on the number of valid test scores independent of the domain score calculations, participants may have a valid global score but be missing one or more domain scores.

The number of tests used to compute the global cognitive function score may vary based on the combination of studies used in analysis.


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