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 score z-score cognitive test calculated domain
cts_wli z_WLI word list episodic memory (cogn_ep)
cts_wlii z_WLII word list recall episodic memory (cogn_ep)
cts_wliii z_WLIII word list recognition episodic memory (cogn_ep)
cts_ebmt z_EBMT East Boston immediate recall episodic memory (cogn_ep)
cts_ebdr z_EBDR East Boston delayed recall episodic memory (cogn_ep)
cts_story z_Story Logical memory I (immediate) episodic memory (cogn_ep)
cts_delay z_Delay Logical memory II (delayed) episodic memory (cogn_ep)
cts_bname z_BName Boston naming (15 items) semantic memory (cogn_se)
cts_catflu z_CatFlu category fluency semantic memory (cogn_se)
cts_read_nart z_read_nart reading test - (10 items) semantic memory (cogn_se)
cts_df z_DF digits forward working memory (cogn_wo)
cts_db z_DB digits backward working memory (cogn_wo)
cts_doperf z_DOperf digit ordering working memory (cogn_wo)
cts_lopair z_LOpair line orientation perceptual orientation (cogn_po)
cts_pmat z_PMat progressive matrices (16 items) perceptual orientation (cogn_po)
cts_sdmt z_SDMT symbol digits modality-oral perceptual speed (cogn_ps)
cts_nccrtd z_NCcrtd number comparison perceptual speed (cogn_ps)
cts_stroop_cname z_cname stroop color naming perceptual speed (cogn_ps)
cts_stroop_wread z_wread stroop word reading perceptual 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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