The Utility of Brief Cognitive Tests for Patients With Type 2 Diabetes Mellitus: A Systematic Review.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is associated with an increased risk for mild cognitive impairment and dementia in both middle-aged and older individuals. Brief cognitive tests can potentially serve as a reliable and cost effective approach to detect for cognitive decrements in clinical practice.

OBJECTIVE: This systematic review examined the utility of brief cognitive tests in studies with patients with T2DM.

METHOD: This systematic review was conducted according to guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. "PubMed," "PsychINFO," "ScienceDirect," and "ProQuest" electronic databases were searched to identify articles published from January 1, 2005 to December 31, 2015.

RESULTS: The search yielded 22 studies, with only 8 using brief tests as a cognitive screening tool, whereas the majority using these tests as a measure of global cognitive functions. In regard to cognitive screening studies, most had failed to fulfil the standard reporting of diagnostic test accuracy criteria such as Standards for Reporting of Diagnostic Accuracy for dementia and cognitive impairment. Moreover, few studies reported discriminant indices such as sensitivity, specificity, and positive and negative predictive values of brief cognitive tests in detecting cognitive impairment in patients with T2DM. Among studies which used brief cognitive tests as a measure of global cognitive function, patients with diabetes tended to perform worse than patients without diabetes. Processing speed appeared to be particularly impaired among patients with diabetes, therefore, measures of processing speed such as the Digit Symbol Substitution Test may add value to brief cognitive tests such as the Montreal Cognitive Assessment.

CONCLUSIONS: The Montreal Cognitive Assessment supplemented by the Digit Symbol Substitution Test indicate initial promise in screening for cognitive impairment in T2DM.