The association of duration of type 2 diabetes with cognitive performance is modulated by long-term glycemic control

Objectives It is unclear why duration of type 2 diabetes (T2D) is associated with increased cognitive compromise. High hemoglobin A1c (HbA1c) has also been associated with dementia, and is the primary contributor to T2D complications. Here we investigated whether the association of duration of T2D with cognitive functioning is modulated by HbA1C levels. Methods This study examined nondemented community-dwelling T2D elderly (N = 897) participating in the Israel Diabetes and Cognitive Decline study, who were assessed with a broad neuropsychological battery. Subjects were all from the Maccabi Healthcare Services, which has a Diabetes Registry with complete HbA1c measurements since 1998. Partial correlations were performed to examine the modulating effect of HbA1c on the relationship of duration of T2D with five cognitive measures, controlling for sociodemographic and cardiovascular risk factors. Results An interaction of duration of T2D with HbA1c was associated with executive functioning (p = 0.006), semantic categorization (p = 0.019), attention/working memory (p = 0.011), and overall cognition (p = 0.006), such that the associations between duration of T2D and cognitive impairment increased as HbA1c levels increased-but not for episodic memory (p = 0.984). Conclusions Because duration of T2D was associated with cognition in higher HbA1c levels and overall no associations were found in lower HbA1c levels, our results suggest that individuals with T2D may limit their risk of future cognitive decline by maintaining long-term good glycemic control.