The groups that performed best on cognition were those with stable and relatively low HbA1c levels over the course of the disease. Findings regarding the role of glycemic control in prevention of other T2D complications are heterogeneous, with results varying by study population, outcome and type of intervention. In the ACCORD study, higher levels of HbA1c at entry were associated with lower cognitive performance at,45 days afterwards. Interestingly, in the 40-months follow up phase of the ACCORD study, the intensive treatment arm was associated with greater total brain volume but not with DSST score, compared to standard treatment. The authors concluded that such results, combined with the increased mortality in the intensive care group and the non-significant effects on other ACCORD outcomes, do not support the use of intensive therapy to reduce the adverse effects of T2D on the brain. A departure from some disease-state homeostasis by enforcing too strict glycemic control was hypothesized to render some subjects to hypoglycemic episodes or other conditions with negative consequences on cognition. The present results suggest that stabilization of glycemic control over many years may be advantageous. Despite lower cognitive function in some domains, the subjects participating in the IDCD were all broadly within cognitive normal limits. Previous studies have demonstrated that people with normal, albeit lower range of cognitive function, are at higher risk of developing cognitive decline and dementia. The numerous HbA1c assessments available for the IDCD cohort, enabled detection of trajectories in glycemic control that are particularly deleterious, suggesting target T2D subjects who are at higher risk for lower cognitive function and for future incident dementia and thus candidates for evolving therapies to maintain or slow cognitive decline. The HbA1c trends were measured from several years before the cognitive assessment, and the cognitive outcomes were all within the normal range, suggesting that glycemic control affects cognition rather than an incipient dementing process affecting glycemic control. However, this study is observational and at this point only cross-sectional cognitive data is available. Thus causality should not be inferred; we cannot rule out the possibility that poor, albeit normal, cognitive performance is associated with poor self-care, leading to high HbA1c levels. When longitudinal cognitive follow-ups become available, evaluations of the relationships of patterns of glycemic control with cognitive decline, and incident MCI and dementia will elucidate the direction of the relationship between glycemic control and cognition. Examination of the association, within each trajectory group, of each trajectory component, to assess their unique contribution to cognition was not possible.