Association of Type 2 Diabetes Mellitus with Cognitive Function in Adults: A Prospective Cohort Study

Background: The cognitive role of untreated type 2 diabetes mellitus (T2DM) has been less well substantiated. Objective: We sought to explore the prospective association of T2DM and untreated T2DM with cognitive function among middle-aged and older Chinese adults. Methods: Data of 7,230 participants without baseline brain damage/mental retardation, or memory-related diseases in China Health and Retirement Longitudinal Study (CHARLS) from 2011-2012 to 2015, were analyzed. Fasting plasma glucose and self-reported information on T2DM diagnosis and treatment were assessed. Participants were categorized into normoglycemia, impaired fasting glucose (IFG), and T2DM (including untreated and treated T2DM) groups. Episodic memory and executive function were assessed by modified Telephone Interview for Cognitive Status every two years. We used generalized estimating equation model to examine the association of baseline T2DM status with cognitive function in succeeding years. Results: Compared to those with normoglycemia, T2DM was associated with worse overall cognitive function after controlling for demographic variables, lifestyles, follow-up time, major clinical factors, and baseline cognitive function, although the associations were statistically non-significant (beta = -0.19, 95% CI: -0.39, 0.00). However, a significant association was mainly observed for those with untreated T2DM (beta = -0.26, 95% CI: -0.47, -0.04), especially in the domain of executive function (beta = -0.19, 95% CI: -0.35, -0.03). In general, IFG and treated T2DM individuals had similar levels of cognitive function with normoglycemia participants. Conclusion: Our findings supported a detrimental role of untreated T2DM on cognitive function among middle-aged and older adults. Screening and early treatment for T2DM are warranted for maintaining better cognitive function in later life.