Effects of cerebrovascular risk factors on gray matter volume in adults aged 60-64 years: a voxel-based morphometric study

Association between Type 2 Diabetes Mellitus and Brain Atrophy: A Meta-Analysis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is known to be associated with cognitive decline and brain structural changes. This study systematically reviews and estimates human brain volumetric differences and atrophy associated with T2DM.

METHODS

PubMed, PsycInfo and Cochrane Library were searched for brain imaging studies reporting on brain volume differences between individuals with T2DM and healthy controls. Data were examined using meta-analysis, and association between age, sex, diabetes characteristics and brain volumes were tested using meta-regression.

RESULTS

A total of 14,605 entries were identified; after title, abstract and full-text screening applying inclusion and exclusion criteria, 64 studies were included and 42 studies with compatible data contributed to the meta-analysis (n=31,630; mean age 71.0 years; 44.4% male; 26,942 control; 4,688 diabetes). Individuals with T2DM had significantly smaller total brain volume, total grey matter volume, total white matter volume and hippocampal volume (approximately 1% to 4%); meta-analyses of smaller samples focusing on other brain regions and brain atrophy rate in longitudinal investigations also indicated smaller brain volumes and greater brain atrophy associated with T2DM. Meta-regression suggests that diabetes-related brain volume differences start occurring in early adulthood, decreases with age and increases with diabetes duration.

CONCLUSION

T2DM is associated with smaller total and regional brain volume and greater atrophy over time. These effects are substantial and highlight an urgent need to develop interventions to reduce the risk of T2DM for brain health.

A Metabolic Obesity Profile Is Associated With Decreased Gray Matter Volume in Cognitively Healthy Older Adults

Obesity is a risk factor for cognitive decline and gray matter volume loss in aging. Studies have shown that different metabolic factors, e.g., dysregulated glucose metabolism and systemic inflammation, might mediate this association. Yet, even though these risk factors tend to co-occur, they have mostly been investigated separately, making it difficult to establish their joint contribution to gray matter volume structure in aging. Here, we therefore aimed to determine a metabolic profile of obesity that takes into account different anthropometric and metabolic measures to explain differences in gray matter volume in aging. We included 748 elderly, cognitively healthy participants (age range: 60 - 79 years, BMI range: 17 - 42 kg/m2) of the LIFE-Adult Study. All participants had complete information on body mass index, waist-to-hip ratio, glycated hemoglobin, total blood cholesterol, high-density lipoprotein, interleukin-6, C-reactive protein, adiponectin and leptin. Voxelwise gray matter volume was extracted from T1-weighted images acquired on a 3T Siemens MRI scanner. We used partial least squares correlation to extract latent variables with maximal covariance between anthropometric, metabolic and gray matter volume and applied permutation/bootstrapping and cross-validation to test significance and reliability of the result. We further explored the association of the latent variables with cognitive performance. Permutation tests and cross-validation indicated that the first pair of latent variables was significant and reliable. The metabolic profile was driven by negative contributions from body mass index, waist-to-hip ratio, glycated hemoglobin, C-reactive protein and leptin and a positive contribution from adiponectin. It positively covaried with gray matter volume in temporal, frontal and occipital lobe as well as subcortical regions and cerebellum. This result shows that a metabolic profile characterized by high body fat, visceral adiposity and systemic inflammation is associated with reduced gray matter volume and potentially reduced executive function in older adults. We observed the highest contributions for body weight and fat mass, which indicates that factors underlying sustained energy imbalance, like sedentary lifestyle or intake of energy-dense food, might be important determinants of gray matter structure in aging.

Sex differences in brain aging and predictors of neurodegeneration in cognitively healthy older adults

We evaluated sex differences in MRI-based volume loss and differences in predictors of this neurodegeneration in cognitively healthy older adults. Mixed-effects regression was used to compare regional brain volume trajectories of 295 male and 328 female cognitively healthy Baltimore Longitudinal Study of Aging participants, aged 55-92 years, with up to 20 years of follow-up and to assess sex differences in the associations of age, hypertension, obesity, APOE e4 carrier status, and high-density lipoprotein cholesterol with regional brain volume trajectories. For both sexes, older age was associated with steeper volumetric declines in many brain regions, with sex differences in volume loss observed in frontal, temporal, and parietal regions. In males, hypertension and higher high-density lipoprotein cholesterol were protective against volume loss in the hippocampus, entorhinal cortex, and parahippocampal gyrus. In females, hypertension was associated with steeper volumetric decline in gray matter, and obesity was protective against volume loss in temporal gray matter. Predictors of volume change may affect annual rates of volume change differently between men and women.

Aging and Hypertension - Independent or Intertwined White Matter Impairing Factors? Insights From the Quantitative Diffusion Tensor Imaging

Aging disrupts white matter integrity, and so does continuous elevated blood pressure that accompanies hypertension (HTN). Yet, our understanding of the interrelationship between these factors is still limited. The study aimed at evaluating patterns of changes in diffusion parameters (as assessed by quantitative diffusion fiber tracking - qDTI) following both aging, and hypertension, as well as the nature of their linkage. 146 participants took part in the study: the control group (N = 61) and the patients with hypertension (N = 85), and were divided into three age subgroups (25-47, 48-56, 57-71 years). qDTI was used to calculate the values of fractional anisotropy, mean, radial and axial diffusivity in 20 main tracts of the brain. The effects of factors (aging and hypertension) on diffusion parameters of tracts were tested with a two-way ANOVA. In the right hemisphere there was no clear effect of the HTN, nor an interaction between the factors, though some age-related effects were observed. Contrary, in the left hemisphere both aging and hypertension contributed to the white matter decline, following a functional pattern. In the projection pathways and the fornix, HTN and aging played part independent of each other, whereas in association fibers and the corpus callosum if the hypertension effect was significant, an interaction was observed. HTN patients manifested faster decline of diffusion parameters but also reached a plateau earlier, with highest between-group differences noted in the middle-aged subgroup. Healthy and hypertensive participants have different brain aging patterns. The HTN is associated with acceleration of white matter integrity decline, observed mainly in association fibers of the left hemisphere.

Body mass index and its relation to neuropsychological functioning and brain volume in healthy older adults

Obesity is a growing concern worldwide because of its adverse health effects, including its negative impact on cognitive functioning. This concern is especially relevant for older adults, who are already likely to experience some cognitive decline and loss of brain volume due to aging, (Gea et al., 2002). However, there is some evidence that higher body mass index (BMI) may actually be protective in later life (Hughes et al., 2009; Luchsinger et al., 2007; Nilsson and Nilsson, 2009; Sturman et al., 2008). Therefore, the purpose of the current study was to assess the relationship between BMI and neuropsychological functioning in older adults, and concurrently the relationship between BMI and brain volume. Older adults (N = 88) reported height and weight to determine BMI (M = 26.5) based on Centers for Disease Control and Prevention (CDC) guidelines. Cognitive function was assessed with the Repeatable Battery for Assessment of Neuropsychological Status (RBANS). Brain volume measurements were evaluated via structural MRI. Results indicated no association between BMI and neuropsychological functioning. There was a significant association between BMI and total grey matter volume while controlling for age and years of education (β = 0.208, p = .026, ΔR² = 0.043), indicating that as BMI increased, brain volume in these areas modestly increased. However, these results did not survive multiple comparison corrections and were further attenuated to near significance when sex was explicitly added as an additional covariate. Nevertheless, while replication is clearly needed, these results suggest that moderately greater BMI in later life may modestly attenuate concomitant grey matter volume decline.

Differential associations between systemic markers of disease and cortical thickness in healthy middle-aged and older adults

Aside from cortical damage associated with age, cerebrovascular and neurodegenerative diseases, it's an outstanding question if factors of global health, including normal variation in blood markers of metabolic and systemic function, may also be associated with individual variation in brain structure. This cross-sectional study included 138 individuals between 40 to 86 years old who were physically healthy and cognitively intact. Eleven markers (total cholesterol, HDL, LDL, triglycerides, insulin, fasting glucose, glycated hemoglobin, creatinine, blood urea nitrogen, albumin, total protein) and five derived indicators (estimated glomerular filtration rate, creatinine clearance rate, insulin-resistance, average glucose, and cholesterol/HDL ratio) were obtained from blood sampling of all participants. T1-weighted 3T MRI scans were used to evaluate gray matter cortical thickness. The markers were clustered into five factors, and factor scores were related to cortical thickness by general linear model. Two factors, one linked to insulin/metabolic health and the other to kidney function (KFF) showed regionally selective associations with cortical thickness including lateral and medial temporal, temporoparietal, and superior parietal regions for both factors and frontoparietal regions for KFF. An association between the increasing cholesterol and greater thickness in frontoparietal and occipital areas was also noted. Associations persisted independently of age, presence of cardiovascular risk factors and ApoE gene status. These findings may provide information on distinct mechanisms of inter-individual cortical variation as well as factors contributing to trajectories of cortical thinning with advancing age.

Chronic cigarette smoking is linked with structural alterations in brain regions showing acute nicotinic drug-induced functional modulations

Background

Whereas acute nicotine administration alters brain function which may, in turn, contribute to enhanced attention and performance, chronic cigarette smoking is linked with regional brain atrophy and poorer cognition. However, results from structural magnetic resonance imaging (MRI) studies comparing smokers versus nonsmokers have been inconsistent and measures of gray matter possess limited ability to inform functional relations or behavioral implications. The purpose of this study was to address these interpretational challenges through meta-analytic techniques in the service of clarifying the impact of chronic smoking on gray matter integrity and more fully contextualizing such structural alterations.

Methods

We first conducted a coordinate-based meta-analysis of structural MRI studies to identify consistent structural alterations associated with chronic smoking. Subsequently, we conducted two additional meta-analytic assessments to enhance insight into potential functional and behavioral relations. Specifically, we performed a multimodal meta-analytic assessment to test the structural–functional hypothesis that smoking-related structural alterations overlapped those same regions showing acute nicotinic drug-induced functional modulations. Finally, we employed database driven tools to identify pairs of structurally impacted regions that were also functionally related via meta-analytic connectivity modeling, and then delineated behavioral phenomena associated with such functional interactions via behavioral decoding.

Results

Across studies, smoking was associated with convergent structural decreases in the left insula, right cerebellum, parahippocampus, multiple prefrontal cortex (PFC) regions, and the thalamus. Indicating a structural–functional relation, we observed that smoking-related gray matter decreases overlapped with the acute functional effects of nicotinic agonist administration in the left insula, ventromedial PFC, and mediodorsal thalamus. Suggesting structural-behavioral implications, we observed that the left insula’s task-based, functional interactions with multiple other structurally impacted regions were linked with pain perception, the right cerebellum’s interactions with other regions were associated with overt body movements, interactions between the parahippocampus and thalamus were linked with memory processes, and interactions between medial PFC regions were associated with face processing.

Conclusions

Collectively, these findings emphasize brain regions (e.g., ventromedial PFC, insula, thalamus) critically linked with cigarette smoking, suggest neuroimaging paradigms warranting additional consideration among smokers (e.g., pain processing), and highlight regions in need of further elucidation in addiction (e.g., cerebellum).

Electronic supplementary material

The online version of this article (doi:10.1186/s12993-016-0100-5) contains supplementary material, which is available to authorized users.

Voxelwise meta-analysis of gray matter anomalies in chronic cigarette smokers

BACKGROUND

Evidence from previous voxel-based morphometry (VBM) studies revealed that widespread brain regions are involved in chronic smoking. However, the spatial localization reported for gray matter (GM) abnormalities is heterogeneous. The aim of the present study was quantitatively to integrate studies on GM abnormalities observed in chronic smokers.

METHODS

A systematic search of the PubMed, Web of Knowledge and Science Direct databases from January 1, 2000 to July 31, 2015 was performed to identify eligible whole-brain VBM studies. Comprehensive meta-analyses to investigate regional GM abnormalities in chronic smokers were conducted with the Seed-based d Mapping software package.

RESULTS

Eleven studies comprising 686 chronic cigarette smokers and 1024 nonsmokers were included in the meta-analyses. Consistently across studies, the chronic smokers showed a robust GM decrease in the bilateral prefrontal cortex and a GM increase in the right lingual cortex. Moreover, meta-regression demonstrated that smoking years and cigarettes per day were partly correlated with GM anomalies in chronic cigarette smokers.

CONCLUSIONS

The convergent findings of this quantitative meta-analysis reveal a characteristic neuroanatomical pattern in chronic smokers. Future longitudinal studies should investigate whether this brain morphometric pattern can serve as a useful target and a prognostic marker for smoking intervention.

Genetic and environmental contributions to the relationships between brain structure and average lifetime cigarette use

Chronic cigarette use has been consistently associated with differences in the neuroanatomy of smokers relative to nonsmokers in case-control studies. However, the etiology underlying the relationships between brain structure and cigarette use is unclear. A community-based sample of male twin pairs ages 51-59 (110 monozygotic pairs, 92 dizygotic pairs) was used to determine the extent to which there are common genetic and environmental influences between brain structure and average lifetime cigarette use. Brain structure was measured by high-resolution structural magnetic resonance imaging, from which subcortical volume and cortical volume, thickness and surface area were derived. Bivariate genetic models were fitted between these measures and average lifetime cigarette use measured as cigarette pack-years. Widespread, negative phenotypic correlations were detected between cigarette pack-years and several cortical as well as subcortical structures. Shared genetic and unique environmental factors contributed to the phenotypic correlations shared between cigarette pack-years and subcortical volume as well as cortical volume and surface area. Brain structures involved in many of the correlations were previously reported to play a role in specific aspects of networks of smoking-related behaviors. These results provide evidence for conducting future research on the etiology of smoking-related behaviors using measures of brain morphology.

Framingham Coronary Heart Disease Risk Score Can be Predicted from Structural Brain Images in Elderly Subjects

Recent literature has presented evidence that cardiovascular risk factors (CVRF) play an important role on cognitive performance in elderly individuals, both those who are asymptomatic and those who suffer from symptoms of neurodegenerative disorders. Findings from studies applying neuroimaging methods have increasingly reinforced such notion. Studies addressing the impact of CVRF on brain anatomy changes have gained increasing importance, as recent papers have reported gray matter loss predominantly in regions traditionally affected in Alzheimer's disease (AD) and vascular dementia in the presence of a high degree of cardiovascular risk. In the present paper, we explore the association between CVRF and brain changes using pattern recognition techniques applied to structural MRI and the Framingham score (a composite measure of cardiovascular risk largely used in epidemiological studies) in a sample of healthy elderly individuals. We aim to answer the following questions: is it possible to decode (i.e., to learn information regarding cardiovascular risk from structural brain images) enabling individual predictions? Among clinical measures comprising the Framingham score, are there particular risk factors that stand as more predictable from patterns of brain changes? Our main findings are threefold: (i) we verified that structural changes in spatially distributed patterns in the brain enable statistically significant prediction of Framingham scores. This result is still significant when controlling for the presence of the APOE 4 allele (an important genetic risk factor for both AD and cardiovascular disease). (ii) When considering each risk factor singly, we found different levels of correlation between real and predicted factors; however, single factors were not significantly predictable from brain images when considering APOE4 allele presence as covariate. (iii) We found important gender differences, and the possible causes of that finding are discussed.

Hypertension, brain damage and cognitive decline

Loss of cognitive function is one the most devastating manifestations of ageing and vascular disease. Cognitive decline is rapidly becoming an important cause of disability worldwide and contributes significantly to increased mortality. There is growing evidence that hypertension is the most important modifiable vascular risk factor for development and progression of both cognitive decline and dementia. High blood pressure contributes to cerebral small and large vessel disease resulting in brain damage and dementia. A decline in cerebrovascular reserve capacity and emerging degenerative vascular wall changes underlie complete and incomplete brain infarcts, haemorrhages and white matter hyperintensities. This review discusses the complexity of factors linking hypertension to brain functional and structural changes, and to cognitive decline and dementia. The evidence for possible clinical markers useful for prevention of decreased cognitive ability, as well as recent data on vascular mechanism in the pathogenesis of cognitive decline, and the role of antihypertensive therapies in long-term prevention of late-life cognitive decline will be reviewed.

Relating education, brain structure, and cognition: the role of cardiovascular disease risk factors

The protective effect of education on cognitive and brain health is well established. While the direct effects of individual cardiovascular disease (CVD) risk factors (i.e., hypertension, smoking, diabetes, and obesity) on cerebral structure have been investigated, little is understood about the possible interaction between the protective effect of education and the deleterious effects of CVD risk factors in predicting brain ageing and cognition. Using data from the PATH Through Life study (N = 266), we investigated the protective effect of education on cerebral structure and function and tested a possible mediating role of CVD risk factors. Higher education was associated with larger regional grey/white matter volumes in the prefrontal cortex in men only. The association between education and cognition was mediated by brain volumes but only for grey matter and only in relation to information processing speed. CVD risk factors did not mediate the association between regional volumes and cognition. This study provides additional evidence in support for a protective effect of education on cerebral structures and cognition. However, it does not provide support for a mediating role of CVD risk factors in these associations.

Cardiopulmonary fitness correlates with regional cerebral grey matter perfusion and density in men with coronary artery disease

Purpose

Physical activity is associated with positive effects on the brain but there is a paucity of clinical neuroimaging data in patients with coronary artery disease (CAD), a cardiovascular condition associated with grey matter loss. The purpose of this study was to determine which brain regions are impacted by cardiopulmonary fitness and with the change in fitness after 6 months of exercise-based cardiac rehabilitation.

Methods

CAD patients underwent magnetic resonance imaging at baseline, and peak volume of oxygen uptake during exercise testing (VO_2Peak) was measured at baseline and after 6 months of training. T1-weighted structural images were used to perform grey matter (GM) voxel-based morphometry (VBM). Pseudo-continuous arterial spin labeling (pcASL) was used to produce cerebral blood flow (CBF) images. VBM and CBF data were tested voxel-wise using VO_2Peak and age as explanatory variables.

Results

In 30 men with CAD (mean age 65±7 years), VBM and CBF identified 7 and 5 respective regions positively associated with baseline VO_2Peak. These included the pre- and post-central, paracingulate, caudate, hippocampal regions and converging findings in the putamen. VO_2Peak increased by 20% at follow-up in 29 patients (t = 9.6, df = 28, p<0.0001). Baseline CBF in the left post-central gyrus and baseline GM density in the right putamen predicted greater change in VO_2Peak.

Conclusion

Perfusion and GM density were associated with fitness at baseline and with greater fitness gains with exercise. This study identifies new neurobiological correlates of fitness and demonstrates the utility of multi-modal MRI to evaluate the effects of exercise in CAD patients.

Baseline cardiovascular risk predicts subsequent changes in resting brain function

BACKGROUND AND PURPOSE

The Framingham Heart Study group cardiovascular disease risk profile (FCRP) score was used to assess the relationship between baseline cardiovascular risk and subsequent changes in resting state cerebral blood flow (CBF) in cognitively normal older participants from the Baltimore Longitudinal Study of Aging.

METHODS

Ninty-seven cognitively normal participants underwent annual resting-state positron emission tomography scans at baseline and over a period of up to 8 years (mean interval, 7.4 years). Images quantifying voxel-wise longitudinal rates of CBF change were calculated and used to examine the relationship between baseline FCRP score and changes over time in regional CBF. Individual components of the FCRP score (age, cholesterol, blood pressure, smoking status, and type 2 diabetes) were also correlated with changes in regional CBF to examine the independent contributions of each component to the overall pattern of change.

RESULTS

Higher baseline FCRP scores were associated with accelerated longitudinal decline in CBF in orbitofrontal, medial frontal/anterior cingulate, insular, precuneus, and brain stem regions. Of the components that comprise the FCRP score, higher diastolic blood pressure and diabetes were associated independently with greater decline in the medial frontal/anterior cingulate and insular regions, respectively.

CONCLUSIONS

Baseline cardiovascular risk factors are associated with greater rates of decline in resting state regional brain function. The regions showing accelerated decline participate in higher-order cognitive processes and are also vulnerable to age-related neuropathology. These results, in conjunction with other studies, encourage early treatment of cardiovascular risk factors in older individuals.

Medial temporal lobe is vulnerable to vascular risk factors in men: a population-based study

BACKGROUND AND PURPOSE

Vascular risk factors (VRFs) are known to cause cerebral microvascular disease, but evidence supporting an effect of VRFs on regional brain atrophy is mixed. We investigate whether an aggregation of VRFs is associated with volume of hippocampus and entorhinal cortex in elderly people living in the community.

METHODS

This cross-sectional study consists of 523 participants (age ≥60 years, 59.3% women) of the SNAC-K Study in central Stockholm, Sweden, who were free of clinical stroke and cognitive impairment. We collected data on VRFs through interviews, clinical examination and inpatient register system. Hippocampal and entorhinal cortex volume was manually measured on magnetic resonance images. Data were analysed with general linear regression models controlling for demographics and total intracranial volume.

RESULTS

  In men, high total cholesterol and diabetes were significantly or marginally associated with smaller hippocampus and entorhinal cortex; when current smoking, binge alcohol drinking, high cholesterol and diabetes were aggregated, an increasing number of VRFs were significantly associated with decreasing volume of hippocampus and entorhinal cortex (P for linear trend <0.01). In women, none of individual VRFs or their aggregation was significantly associated with the volume of these brain regions, except former smoking that was significantly associated with a larger volume of these regions.

CONCLUSIONS

Aggregation of VRFs is associated with reduced hippocampal and entorhinal cortex volume in apparently healthy elderly men, but not in women. This implies that in men, the medial temporal lobe is vulnerable to cardiovascular risk factors.

Regional grey matter shrinks in hypertensive individuals despite successful lowering of blood pressure

Objective

To determine whether reduction in brain grey matter volume associated with hypertension persisted or was remediated among hypertensive patients newly treated over the course of a year.

Methods

Forty-one hypertensive patients were assessed over the course of a one-year successful anti-hypertensive treatment. Brain areas identified previously in cross-sectional studies as differing in volume between hypertensive and normotensive individuals were examined with a semi-automated measurement technique (ALP, automated labeling pathway). Volumes of grey matter regions were computed at baseline and after a year of treatment and compared to archival data from normotensive individuals.

Results

Reductions in regional grey matter volume over the follow-up period were observed despite successful treatment of blood pressure. The comparison group of older, but normotensive individuals showed no significant changes over a year in the regions tested in the treated hypertensive group.

Conclusions

These novel results suggest that essential hypertension is associated with regional grey matter shrinkage and successful reduction of blood pressure may not completely counter that trend.

Thickness of the human cerebral cortex is associated with metrics of cerebrovascular health in a normative sample of community dwelling older adults

We examined how wide ranges in levels of risk factors for cerebrovascular disease are associated with thickness of the human cerebral cortex in 115 individuals ages 43-83 with no cerebrovascular or neurologic history. Cerebrovascular risk factors included blood pressure, cholesterol, body mass index, creatinine, and diabetes-related factors. Variables were submitted into a principal components analysis that confirmed four orthogonal factors (blood pressure, cholesterol, cholesterol/metabolic and glucose). T1-weighted MRI was used to create models of the cortex for calculation of regional cortical thickness. Increasing blood pressure factor scores were associated with numerous regions of reduced thickness. Increasing glucose scores were modestly associated with areas of regionally decreased thickness. Increasing cholesterol scores, in contrast, were associated with thicker cortex across the whole brain. All findings were primarily independent of age. These results provide evidence that normal and moderately abnormal levels of parameters used to assess cerebrovascular health may impact brain structure, even in the absence of cerebrovascular disease. Our data have important implications for the clinical management of vascular health, as well as for what is currently conceptualized as "normal aging" as they suggest that subclinical levels of risk may impact cortical gray matter before a disease process is evident.

Vascular diseases and old age mental disorders: an update of neuroimaging findings

PURPOSE OF REVIEW

To review neuroimaging findings that have been reported in samples of patients with cardiovascular disorders and their association with the onset of Alzheimer's disease, vascular dementia, depression and bipolar disorder in the elderly and to highlight the implications of these findings to the knowledge about the pathophysiology of psychiatric disorders in old age, as well as their potential clinical implications.

RECENT FINDINGS

Vascular risk factors, such as hypertension, diabetes, dyslipidemia, smoking habits and heart failure, have all been associated with signs of cerebrovascular dysfunction, including structural MRI findings of signal hyperintensities, lacunes and stroke and functional imaging findings of brain regional hypoperfusion and hypometabolism. Such brain abnormalities have been found to increase the risk of onset of psychiatric disorder (depression, bipolar and dementia) in old age.

SUMMARY

As vascular risk factors are potentially modifiable when detected in midlife, the early characterization of brain changes associated with the presence of cardiovascular diseases holds promise to afford clinical applications in psychiatry, providing new perspectives for the prevention of old age psychiatric disorders.

Structural brain differences and cognitive functioning related to body mass index in older females

Little is known about the effect of obesity on brain structures and cognition in healthy older adults. This study examined the association between body mass index (BMI), regional volume differences in gray and white matter measured by magnetic resonance imaging (MRI), and cognitive functioning in older females. Participants included 95 community-dwelling older females (ages 52-92 years) who underwent extensive neuropsychological testing and high-resolution MRI scanning. Optimized voxel-based morphometry techniques were employed to determine the correlation between BMI and regional gray and white matter volumes. Volumes of significant regions were then correlated with cognitive functioning. Higher BMI was associated with decreased gray matter volumes in the left orbitofrontal, right inferior frontal, and right precentral gyri, a right posterior region including the parahippocampal, fusiform, and lingual gyri, and right cerebellar regions, as well as increased volumes of white matter in the frontal, temporal, and parietal lobes, even when hypertension was considered. Compared to normal weight women, obese women performed poorer on tests of executive functioning. Smaller gray matter volume in the left orbitofrontal region was associated with lower executive functioning. Additionally, despite the lack of significant group differences in memory and visuomotor speed, gray and white matter volumes predicted performance on these measures. The results provide additional evidence for a negative link between increased body fat and brain functioning in older females.

Age-related differences in regional brain volumes: a comparison of optimized voxel-based morphometry to manual volumetry

Regional manual volumetry is the gold standard of in vivo neuroanatomy, but is labor-intensive, can be imperfectly reliable, and allows for measuring limited number of regions. Voxel-based morphometry (VBM) has perfect repeatability and assesses local structure across the whole brain. However, its anatomic validity is unclear, and with its increasing popularity, a systematic comparison of VBM to manual volumetry is necessary. The few existing comparison studies are limited by small samples, qualitative comparisons, and limited selection and modest reliability of manual measures. Our goal was to overcome those limitations by quantitatively comparing optimized VBM findings with highly reliable multiple regional measures in a large sample (N=200) across a wide agespan (18-81). We report a complex pattern of similarities and differences. Peak values of VBM volume estimates (modulated density) produced stronger age differences and a different spatial distribution from manual measures. However, when we aggregated VBM-derived information across voxels contained in specific anatomically defined regions (masks), the patterns of age differences became more similar, although important discrepancies emerged. Notably, VBM revealed stronger age differences in the regions bordering CSF and white matter areas prone to leukoaraiosis, and VBM was more likely to report nonlinearities in age-volume relationships. In the white matter regions, manual measures showed stronger negative associations with age than the corresponding VBM-based masks. We conclude that VBM provides realistic estimates of age differences in the regional gray matter only when applied to anatomically defined regions, but overestimates effects when individual peaks are interpreted. It may be beneficial to use VBM as a first-pass strategy, followed by manual measurement of anatomically defined regions.

Total and regional gray matter volume is not related to APOE*E4 status in a community sample of middle-aged individuals

BACKGROUND

The APOE*E4 allele has been associated with greater gray matter atrophy and with Alzheimer's disease. The aim of this study was to investigate whether the relationship between cerebral gray matter atrophy and APOE*E4 genotype was also present in a community-dwelling, nondemented 60- to 64-year-old cohort.

METHODS

Hippocampal and amygdalar volumes were manually traced and analyzed on 331 cranial T1-weighted magnetic resonance imaging (MRI) scans to detect differences associated with APOE*E4 genotype. Voxel-based morphometric (VBM) analyses were applied to detect regional gray matter volume differences.

RESULTS

No total, hippocampal, or amygdalar gray matter volume difference was detected between APOE*E4 carriers and noncarriers.

CONCLUSIONS

In nondemented 60- to 64-year-olds, there was no association between APOE genotype and gray matter volume using both region-of-interest analysis and VBM.

Light to moderate alcohol use is associated with increased cortical gray matter in middle-aged men: a voxel-based morphometric study

We examined the associations of current alcohol consumption with brain morphometric measures in a healthy, community-dwelling cohort. Cranial T1-weighted 3D-structural MRI scans were obtain in 383 adults (men=211) aged 60-64 years, randomly selected form the larger PATH Through Life study. Voxel-based morphometric analyses were applied to detect regional gray matter and white matter volume changes related to reported weekly alcohol consumption (mean 7.04+/-8.15 drinks per week). Alcohol consumption in men had a linear association with greater gray matter in bilateral superior and medial frontal gyrus, bilateral middle occipital gyrus, right inferior parietal gyrus, bilateral precentral gyrus, left paracentral gyrus, left uncus and left inferior occipital gyrus, and with lesser white matter in bilateral superior temporal and left parahippocampal gyrus, after adjustment for age, education, total intracranial volume, smoking, hypertension, diabetes and hyperlipidemia. In women, there was no significant linear association between alcohol consumption and total or regional brain volumes. Our results showed a dose-related, sexually dimorphic impact of alcohol on brain tissue volumes independent of cerebrovascular risk factors. These findings are consistent with an inverse-U association between alcohol use and brain morphometry, while suggesting an increased vulnerability of white matter to alcohol-related brain damage.

Smoking is associated with reduced cortical regional gray matter density in brain regions associated with incipient Alzheimer disease

OBJECTIVES

The results of observational studies suggest that smoking increases the risk of Alzheimer disease (AD). The authors designed this study to determine if older people who smoke have decreased gray matter density in brain regions associated with incipient AD.

METHODS

The authors recruited 39 pairs (N = 78) of smokers/never-smokers 70 to 83 years of age who were matched for age, sex, education, and handedness. Participants were free of clinically significant cognitive impairment, depression, stroke, or other serious medical conditions. Gray matter density was determined by voxel-based morphometry using statistical parametric mapping of T1-weighted magnetic resonance images.

RESULTS

Smokers had decreased gray matter density in the posterior cingulum and precuneus (bilateral), right thalamus, and frontal cortex (bilateral) compared with never-smokers.

CONCLUSIONS

Smoking is associated with decreased gray matter density in brain regions previously associated with incipient AD. Longitudinal investigations are required to clarify whether these changes are progressive in nature.

Sex differences in regional gray matter in healthy individuals aged 44-48 years: a voxel-based morphometric study

The study examined sex-related differences in regional gray matter (GM) in 44-48 year old healthy individuals. T1-weighted MRI scans were acquired in 411 subjects aged 44-48 from a random community sample and optimized voxel-based morphometry was applied to detect regional GM difference between men and women, correcting for effects of age, years of education, handedness, and total intracranial volume (TIV). Men had larger brain volumes and higher white matter (WM) to TIV ratios compared with women. Women had higher GM to TIV ratios than men. After controlling for age, years of education, handedness, and TIV, there were no significant differences between men and women in the total GM volumes. Regional sex dimorphism was present, with men having more GM volume in midbrain, left inferior temporal gyrus, right occipital lingual gyrus, right middle temporal gyrus, and both cerebellar hemispheres. Women showed more GM in dorsal anterior, posterior and ventral cingulate cortices, and right inferior parietal lobule. Our results suggest sex dimorphism in GM in middle aged healthy individuals, which is not likely to be explained by brain pathology. These differences may provide the structural brain basis for sex differences in certain cognitive functions.