Diabetes and cognitive systems in older black and white persons

Microinfarct pathology, dementia, and cognitive systems

BACKGROUND AND PURPOSE

Little is known about the role of microinfarcts in dementia and cognition. We examined microinfarcts and dementia, global cognition, and 5 cognitive systems in community-dwelling older persons.

METHODS

Four hundred twenty-five subjects enrolled in the Religious Orders Study underwent annual clinical evaluations, including 19 neuropsychological tests and assessment for dementia, and brain autopsy (39% men; mean age at death, 87; Mini-Mental State Examination score, 21). Neuropathologic examination documented the presence, number, and location of chronic microinfarcts on 6-μm hematoxylin-eosin-stained sections from cortical and subcortical regions. Multiple regression analyses adjusted for age at death, sex, education, macroscopic infarcts, Alzheimer disease pathology, and Lewy bodies.

RESULTS

Microinfarcts were present in 129 of 425 (30%) persons (54 cortical, 80 subcortical, 49 multiple); 58 of 129 (45%) of persons with microinfarcts did not exhibit macroscopic infarcts. Persons with microinfarcts had increased odds of dementia (OR, 1.77; 95% CI, 1.07-2.92), especially those persons with multiple cortical microinfarcts. Microinfarcts were also associated with lower average global cognition (estimate, -0.287; SE, 0.113; P=0.012), particularly for persons with multiple cortical microinfarcts. Microinfarcts were specifically associated with lower episodic memory (estimate, -0.279; SE, 0.138; P=0.044), semantic memory (estimate, -0.391; SE, 0.130; P=0.003), and perceptual speed (estimate, -0.400; SE, 0.117; P<0.001). In addition, single, multiple, and cortical microinfarcts were associated with worse semantic memory and perceptual speed (all P<0.028). Neither macroscopic infarcts nor AD pathology modified these associations (all P>0.154).

CONCLUSIONS

Microinfarcts are common, and persons with multiple cortical microinfarcts have higher odds of dementia. Microinfarcts are also associated with lower cognition, specifically perceptual speed and semantic and episodic memory.

Elevated cerebral glutamate and myo-inositol levels in cognitively normal middle-aged adults with metabolic syndrome

Metabolic syndrome (MetS) is a cluster of risk factors associated with significant cardiovascular morbidity and mortality and diminished cognitive function. Given that the cerebral mechanisms mediating the relationship between peripheral metabolic dysfunction and cognitive impairment are unknown, we set out to examine the relationship between diagnosis of metabolic syndrome and cerebral metabolism. Thirteen participants with MetS (aged 48 ± 6 years) and 25 healthy adults (aged 51 ± 6 years) underwent neuropsychological assessment, health screen and proton magnetic resonance spectroscopy ((1)H MRS) examining N-acetyl-aspartate (NAA), myo-inositol (mI), creatine (Cr), choline (Cho), and glutamate (Glu) concentrations in occipitoparietal grey matter. Cerebral metabolite ratios (NAA/Cr, Cho/Cr, mI/Cr, and Glu/Cr) of participants with MetS, defined by the International Diabetes Federation criteria, were compared with controls matched for age, education, cognition, and emotional function. There were no significant differences in global cognitive function, memory, language, and psychomotor performance between the groups. Diagnosis of MetS was associated with significantly higher mI/Cr (F(1,36) = 5.02, p = 0.031) and Glu/Cr ratio (F(1,36) = 4.81, p = 0.035). Even in cognitively normal adults, MetS is related to cerebral metabolic disturbances, a possible indication of early brain vulnerability. Longitudinal studies that begin in mid-life can help validate the use of (1)H MRS markers as indicators of long-term cognitive outcomes.

Cerebral amyloid angiopathy pathology and cognitive domains in older persons

OBJECTIVE

To examine the relation of cerebral amyloid angiopathy (CAA) to cognitive domains in older community-dwelling persons with and without dementia.

METHODS

Subjects were 404 persons in the Religious Orders Study, a cohort study of aging, who underwent annual clinical evaluations, including 19 neuropsychological tests from which 5 cognitive domain and global summary scores were derived, and brain autopsy at time-of-death (mean age-at-death 86). Using amyloid-β immunostaining, CAA severity was graded in 5 regions (midfrontal, inferior temporal, angular, calcarine, and hippocampal cortices), as 0 = none, 1 = mild, 2 = moderate, 3 = severe, and 4 = very severe. Because severity was related across regions (all r(s) > 0.63), and almost all persons had some CAA, we averaged regional CAA scores and created class variable predictors for no-to-minimal (<0.5), mild-to-moderate (0.5-2.5) and moderate-to-very severe CAA (>2.5).

RESULTS

CAA was very common (84.9%; 94 had no-to-minimal, 233 mild-to-moderate, and 76 moderate-to-very severe disease) and was related to AD pathology (r(s) = 0.68). In linear regression analyses controlling for age, sex, education, AD pathology, infarcts, and Lewy bodies, moderate-to-very severe CAA was associated with lower perceptual speed (p = 0.012) and episodic memory (p = 0.047), but not semantic memory, working memory, visuospatial skills, or a composite of all cognitive measures. No associations of mild-to-moderate CAA with cognition were found. Dementia did not modify these findings.

INTERPRETATION

CAA pathology is very common in older community-dwelling persons and is associated with AD pathology. Moderate-to-very severe CAA, but not mild-to-moderate CAA, is associated with lower performance in specific cognitive domains, most notably perceptual speed, separately from the effect of AD pathology.

Insulin resistance, diabetes and cognitive function: consequences for preventative strategies

Cognitive decline and dementia both place a heavy burden on patients and their relatives, and any means of preventing such age-related changes are worthy of consideration. Those who have the metabolic syndrome with or without diabetes suffer more often from dysexecutive problems and slower psychomotor speed than do other patients. In epidemiological studies, diabetes has appeared to be a risk factor for all types of dementia, including vascular dementia, although the role of the metabolic syndrome in the risk of Alzheimer's disease is still a matter of debate. The possible mechanisms of cognitive alterations are multiple, and may differ according to age group and duration of diabetes or the metabolic syndrome. Drug interventional trials addressing the prevention of cognitive decline through action on the metabolic syndrome are disappointing-albeit scarce at this time. Lifestyle interventions in middle-aged or younger-elderly subjects should also be implemented in the general population.

Self-reported experiences of everyday discrimination are associated with elevated C-reactive protein levels in older African-American adults

Self-reported experiences of "everyday" discrimination have been linked to indices of cardiovascular disease and overall mortality and findings have been particularly pronounced for African-American populations. However, the biological mechanisms underlying these associations remain unclear. C-reactive protein (CRP), a marker of inflammation, is a known correlate of cardiovascular and other health outcomes and has also been linked to several psychosocial processes. To our knowledge, no studies have examined the association between experiences of discrimination and CRP. We examined the cross-sectional association between self-reported experiences of discrimination and CRP in a sample of 296 older African-American adults (70% female, mean age=73.1). Experiences of discrimination were assessed with the 9-item everyday discrimination scale and CRP was assayed from blood samples. In linear regression models adjusted for age, sex and education, experiences of discrimination were associated with higher levels of CRP (B=.10, p=.03). This association remained significant after additional adjustments for depressive symptoms (B=.10, p=.04), smoking, and chronic health conditions (heart disease, diabetes, hypertension) that might influence inflammation (B=.11, p=.02). However, results were attenuated when body mass index (BMI) was added to the model (B=.09, p=.07). In conclusion, self-reported experiences of everyday discrimination are associated with higher levels of CRP in older African-American adults, although this association is not completely independent of BMI.