The Cog-4 Subset of the National Institutes of Health Stroke Scale as a Measure of Cognition : Relationship with Baseline Factors and Functional Outcome after Stroke Using Data from the Virtual International Stroke Trials Archive

Abstract EN

Background.

Assessing poststroke cognitive impairment is complex.

A subscale of the NIHSS, the Cog-4, has been proposed as a quick test of “cognitive impairment.” but a study of its properties in a larger dataset is lacking.

Methods.

Data from 9,147 patients with acute stroke from the VISTA archive was used to generate Cog-4 scores.

The statistical properties of Cog-4, its relationship with baseline clinical characteristics, and other functional outcome measures at day 90 were assessed.

Results.

Mean age of patients was 69.2 years and 45.8%, were females.

Day-90 Cog-4 was highly positively skewed (skewness 0.926).

Patients with left hemispheric stroke had higher day-90 Cog-4 score (P<0.001).

Age, stroke severity, and previous stroke were significant predictors of Cog-4.

Cog-4 was significantly correlated with dependency (modified Rankin Scale, rs=0.512), and disability (Barthel Index, rs=−0.493).

Conclusions.

The Cog-4 scale at day 90 cannot be considered a useful test of cognition since it only superficially measures cognition.

It is heavily dependent on the side of stroke, is inevitably associated with functional outcome (being a subset of the NIHSS), and suffers from a profound “floor” effect.

Specific and validated measures are more appropriate for the assessment of poststroke cognition than Cog-4.