Neuroimmunoendocrine Pathology and Cognitive Function in Type 2 Diabetes

Cognitive impairment among older adults with type 2 diabetes may worsen health outcomes via negative impact on compliance with medical self-care recommendations. Results of several previous studies indicate that cognitive deficits are present in older European American adults with type 2 diabetes under some conditions, particularly related to glucose dysregulation (as evidenced by high glycated hemoglobin, i.e., HbA1c). Despite the fact African Americans are disproportionately affected by diabetes and suffer significantly greater numbers of complications and more severe complications relative to European Americans, no published studies have examined cognitive functioning among older African American adults with type 2 diabetes. Further, markers of systemic inflammation have been associated with cognitive impairment in several conditions, but this relationship has not been examined in older adults with type 2 diabetes. The purpose of the present study was to determine whether: 1) cognitive deficits are present in older African American adults with type 2 diabetes, and whether the deficits are related to 2) glucose dysregulation and 3) systemic inflammation. Several cognitive domains, including verbal memory and executive functions, were assessed in 71 African Americans with type 2 diabetes who ranged from 60 to 80 years of age. Exclusionary criteria included dementia, depression, neurological disease, or brain injury. Also measured were HbA1c and two markers of systemic inflammation: C-reactive protein (CRP) and interleukin-6 (IL-6). Results showed that higher HbA1c was significantly associated with poorer performance on several measures of executive function and verbal memory measures that tap executive function. Higher IL-6 was significantly associated with slower motor function and higher semantic fluency. Higher CRP was significantly associated with improved performance on measures of phonemic fluency, psychomotor speed and mental flexibility/working memory, and fine motor dexterity, but only for those with extremely high levels of CRP; when those participants were removed from the analyses, CRP was inversely related to cognitive performance