Cognitive impairment in nondiabetic middle-aged and older adults is associated with insulin resistance.

To determine whether the cognitive impairments observed in adults with type 2 diabetes mellitus (T2DM) exist in preclinical disease, we compared 38 adult participants with evidence of insulin resistance (IR) to 54 age-, gender-, and education-matched control participants on a battery of neuropsychological tests. We found that participants with IR had performance reductions in declarative memory and executive functioning. When we examined IR simultaneously with other biomedical indicators with which it co-occurs, only IR itself was associated with declarative memory, and hemoglobin A1c (HbA1c) was associated with executive functioning and working memory. We conclude that individuals with insulin resistance already demonstrate similar reductions in cognitive performance as those described in T2DM.

C-reactive protein is linked to lower cognitive performance in overweight and obese women.

Our objective was to ascertain the nature of the associations between C-reactive protein (CRP) and cognition, and to examine how they are affected by gender and obesity. We evaluated 62 females and 63 males between 42 and 82 years of age. There were 20 lean females with a body mass index (BMI) of <25 kg/m2 and 42 overweight or obese females, with BMIs > or =25 kg/m2. There were 14 lean males and 49 with BMIs >/=25 kg/m2. CRP was associated with lower scores on cognitive tests of frontal lobe function among females and these associations were driven by the overweight/obese female group. In these data no associations between CRP and cognition were found among males. Obesity-associated inflammation is much more prominent in females and it appears to be associated with cognitive dysfunction, particularly of frontal lobe tasks.

Hippocampal damage and memory impairments as possible early brain complications of type 2 diabetes.

AIMS/HYPOTHESIS: There is evidence that type 2 diabetes mellitus is associated with cognitive impairment. Most studies investigating this association have evaluated elderly individuals, after many years of diabetes, who generally have poor glycaemic control and significant vascular disease. The aim of the current study was to investigate the early cognitive consequences and associated brain correlates of type 2 diabetes. MATERIALS AND METHODS: With regard to cognition and brain measures, we compared 23 age-, sex- and education-matched control subjects with 23 mostly middle-aged individuals with relatively well-controlled diabetes of less than 10 years from the time of diagnosis. RESULTS: We found deficits in hippocampal-based memory performance and preservation of other cognitive domains. Relative to control subjects, individuals with diabetes had reductions in brain volumes that were restricted to the hippocampus. There was an inverse relationship between glycaemic control and hippocampal volume; in multivariate regression analysis, HbA(1c) was the only significant predictor of hippocampal volume, accounting for 33% of the observed variance. Other variables commonly associated with type 2 diabetes, such as elevated BMI, hypertension or dyslipidaemia, did not independently contribute to the variance in hippocampal volume. CONCLUSIONS/INTERPRETATION: These results suggest that the medial temporal lobe may be the first brain site affected by type 2 diabetes and that individuals in poorer metabolic control may be affected to a greater extent.