Body mass index and brain structure in healthy children and adolescents.

Obesity is associated with cognitive dysfunction in children and adolescents, although the mechanisms underlying these deficits remain unclear. This study examined the associations between body mass index (BMI) and regional gray matter volume and white matter integrity in 120 healthy children and adolescents (6-18 years of age) who underwent magnetic resonance and diffusion tensor imaging. Bonferroni-corrected partial correlation analyses controlling for demographic and clinical characteristics revealed significant inverse associations between demographically standardized BMI values and gray matter volume of frontal (r = -0.31) and limbic (r = -0.35) brain regions. No such pattern emerged for fractional anisotropy of white matter tracts. Subsequent hierarchical regression analyses indicated that the relationship between standardized BMI and structural gray and white matter brain indices did not vary with age. These findings suggest that obesity in children and adolescents is associated with decreased volume of frontal and limbic cerebral gray matter regions. Further research is much needed to better elucidate possible brain-based mechanisms for cognitive dysfunction associated with obesity.

Body mass index and neurocognitive functioning across the adult lifespan.

OBJECTIVE: Cognitive dysfunction and structural brain abnormalities have been observed in obese versus lean individuals, but with variability across age and weight groups. The current study was designed to clarify the cognitive profile of obesity by examining performance across multiple cognitive domains in adults with wide-ranging age and weight status. METHOD: Participants (N = 732; 61% women; ages 18-88; BMI range 19-75) underwent assessment of cognitive functioning and relevant medical/demographic covariates. Neuropsychological tests were grouped by cognitive domain (via confirmatory factor analysis), and standardized scores were averaged into composite variables. RESULTS: Hierarchical linear regression analyses revealed main effects for BMI on motor (ΔR2 = .02, ß = -.15) and attention/processing speed (ΔR2 = .01, ß = -.07), whereas a significant interaction between BMI and age was observed (ΔR2 = .01, ß = -.08) for predicting executive functioning (p < .05). BMI was not independently associated with memory or language functioning and no interaction effects were observed for these variables. Although BMI was not independently related to executive dysfunction, a significant age × BMI interaction suggests that obesity-related executive deficits may increase with age. CONCLUSIONS: Overall, these findings may support an independent association between obesity and a frontal-subcortical pathology, though prospective studies are needed to further clarify this possibility.

Cognitive reserve preserves cognitive function in obese individuals.

Obesity is an established risk factor for cognitive impairment. Theories of cognitive reserve suggest that premorbid factors, such as intellectual ability, may attenuate the expression of cognitive impairment due to age or disease. The current study examined whether cognitive reserve, defined as estimated premorbid intellectual ability, moderates the relationship between obesity and cognitive function in obese adults. Participants without major medical or psychological conditions completed a computerized battery of neuropsychological tests. Hierarchical regression models found a significant interaction between BMI and cognitive reserve for attention/executive function and memory, suggesting that cognitive reserve attenuates the expression of obesity-related cognitive impairment.

Can bariatric surgery reduce risk of Alzheimer's disease?

Recent studies demonstrate that obesity is independently associated with poor neurocognitive outcomes, including cognitive impairment, increased risk for dementia, and regional alterations in brain structure. Bariatric surgery is an effective treatment for obesity and initial findings suggest that it may result in cognitive improvements. The current paper reviews and integrates recent research in this area, with a focus on potential mediators and moderators of neuropsychological outcome in bariatric surgery patients, including anesthetic and nutritional complications, and proposes novel avenues for continued study in this area.

Obesity is associated with reduced white matter integrity in otherwise healthy adults.

Existing work demonstrates that obesity is independently associated with cognitive dysfunction and macrostructural brain changes; however, little is known about the association between obesity and white matter (WM) integrity. We explore this relationship in a large cohort of otherwise healthy subjects. The present study classified 103 adult participants from the Brain Resource International Database between 21 and 86 years of age without history of neurological, medical, or psychiatric illness according to BMI (normal weight, overweight, obese) and subjected them to diffusion tensor imaging (DTI). Resulting fractional anisotropy (FA) indexes for the corpus callosum and fornix were examined in relation to BMI and age in a multiple regression framework. Results indicated that increasing BMI was independently associated with lower FA in the genu, splenium, and fornix, and a BMI × age interaction emerged for FA in the splenium and body of the corpus callosum. When categorized, obese persons demonstrated lower FA than normal and overweight persons for all WM indexes, but no FA differences emerged between overweight and normal persons. Results indicate both a direct association between obesity and reduced WM tract integrity and an interaction between obesity and aging processes on certain WM tracts in otherwise healthy adults. While such findings suggest a possible role for adiposity in WM dysfunction and associated cognitive deficits, prospective studies are needed to clarify the nature of these relationships and elucidate underlying mechanisms.

Improvements in cognitive function following cardiac rehabilitation for older adults with cardiovascular disease.

Cognitive impairment is common in persons with cardiovascular disease (CVD). Cardiac rehabilitation (CR) improves many aspects of CVD linked to cognitive impairment. The current study explored whether CR may improve cognitive function. Potential mechanisms for cognitive changes were also examined through exploratory analyses, including changes in cardiovascular fitness and cerebral blood flow. Fifty-one older adults with CVD underwent neuropsychological assessment at baseline and discharge from a 12-week CR program. Cardiovascular fitness (i.e., metabolic equivalents [METs]) was estimated from a symptom-limited volitional stress test. Transcranial doppler quantified mean cerebral blood flow velocity and pulsatility indexes for the middle cerebral artery and anterior cerebral artery (ACA). Repeated measures ANOVA showed improvements in global cognition, attention-executive-psychomotor function, and memory. Exploratory analyses revealed improvement in METs and changes in ACA flow velocity, but only improvement in METs was related to improved verbal recall. CVD patients exhibited improvements in multiple cognitive domains following a 12-week CR program, suggesting that cognitive impairment is modifiable in this population. Although other studies are needed to elucidate underlying mechanisms, exploratory analyses suggest that cognitive improvements may be better explained by physiological processes other than improved cardiovascular fitness and cerebral blood flow.

Reduced executive functioning is associated with poorer outcome in cardiac rehabilitation.

Patients with cardiovascular disease and cognitive impairment show reduced adherence to treatment. No study has examined whether cognitive impairment may also predict reduced benefit from cardiac rehabilitation (CR). It appears that cognitively impaired patients may exhibit poorer adherence to CR and limited gains in cardiovascular fitness and/or quality of life (QOL). Forty-four older adults who enrolled in a CR program and completed measures at enrollment and discharge were included. Cognitive functioning was assessed using the Trail Making Test B. Estimated metabolic equivalents (METs) were derived from a treadmill stress test to provide a measure of cardiovascular fitness. QOL was measured with the Short Form-36 (SF-36) physical and mental component scales (PCS and MCS, respectively). Repeated measures analysis of variance showed improvements in METs [METs; F(1,36)=77.6, P<.001] and physical [SF-36 PCS; F(1,36)=14.14, P=.001)] and mental QOL [SF-36 MCS; F(1,36)=11.55, P=.002)]. Partial correlations indicated that poorer Trail Making Test B performance was associated with lower METs at discharge (r=-0.30, P<.05), but not PCS or MCS. Mini-Mental State Examination scores were not related to outcome variables. Current findings suggest that patients with poorer executive functioning derive reduced benefit from CR. CR programs may consider screening patients at baseline for low cognitive functioning to help identify those patients at greatest risk for poor outcome.

Longitudinal cognitive performance in older adults with cardiovascular disease: evidence for improvement in heart failure.

BACKGROUND: Cardiovascular disease (CVD) and particularly heart failure (HF) have been associated with cognitive impairment in cross-sectional studies, but it is unclear how cognitive impairment progresses over time in older adults with these conditions. OBJECTIVE: The aim of this study was to prospectively examine cognitive function in patients with HF versus other forms of CVD. METHOD: Seventy-five older adults (aged 53-84 years) with CVD underwent Doppler echocardiogram to evaluate cardiac status and 2 administrations of the Dementia Rating Scale (DRS), a test of global cognitive functioning, 12 months apart. RESULTS: Although DRS performance did not statistically differ between groups at either administration, a significant between-group difference in the rate of cognitive change emerged (lambda = 0.87; F = 10.50; P = .002; omega 2 = 0.11). Follow-up analyses revealed that patients with HF improved significantly on global DRS performance, whereas patients with other forms of CVD remained stable. More specifically, patients with HF showed improvement on subscales of attention, initiation/perseveration, and conceptualization. Exploratory analyses indicated that higher diastolic blood pressure at baseline was associated with improved DRS performance in patients with HF (r = 0.38; P = .02). CONCLUSIONS: Patients with HF exhibited modest cognitive improvements during 12 months, particularly in attention and executive functioning. Higher diastolic blood pressure at baseline was associated with improvement. These results suggest that cognitive impairment in patients with HF may be modifiable and that improved blood pressure control may be an important contributor to improved function. Further prospective studies are needed to replicate results and determine underlying mechanisms.