Determinants of Cognitive Function in Individuals with Type 2 Diabetes Mellitus: A Meta-Analysis

Abstract

Background

Type 2 diabetes mellitus (T2DM) is associated with deficits across multiple cognitive domains; however, the determinants of cognitive impairment in T2DM are not well characterized. We aimed to evaluate body mass index (BMI), glycemic control, and T2DM duration as moderators of cognitive dysfunction in T2DM.

Methods

We conducted a meta-analytic review of the literature reporting data on BMI, hemoglobin A_lc(HbA_lc), T2DM duration, and validated measures of processing speed (ie, Digit Symbol Substitution Test, Trail Making Test [TMT]-A), verbal learning and memory (ie, Rey Auditory Verbal Learning Test), and working memory/executive function (ie, TMT-B) among individuals with vs without T2DM.

Results

Individuals with T2DM demonstrated deficits across multiple cognitive domains (/c = 40; n = 4,252 T2DM; n = 22,322 non-T2DM; effect sizes 0.21 to 0.35). Illness duration and BMI did not significantly moderate measures of cognition; however, higher HbA_lc levels were significantly associated with deficits in measures of processing speed (R ² values 0.41 to 0.73, P < .01) and working memory/executive function (R ² = 0.62, P <.001).

Conclusions

Adults with T2DM exhibited significant deficits across multiple domains of cognitive function. Additionally, we identified an association between poorer glycemic control and cognitive dysfunction. A clinical translation of our findings relates to the reduction in morbidity by improving glycemie control.