Being overweight in midlife is associated with lower cognitive ability and steeper cognitive decline in late life

Weight Gain in Midlife Women

PURPOSE OF REVIEW

To summarize the evidence and clinical implications of weight and body composition changes during midlife in women and provide an overview of weight gain prevention and management in this population.

RECENT FINDINGS

Aging-related changes such as decreased energy expenditure and physical activity are important culprits for weight gain in midlife women. The hormonal changes of menopause also influence body adiposity distribution and increase central adiposity. These body changes can have health consequences including the development of cardiometabolic diseases, osteoarthritis, cancer, worsening in cognition, mental health, and menopause symptoms. Midlife women experience changes related to aging, menopause, and lifestyle which favor weight gain. Clinical practice should focus on early counseling and anticipatory guidance on the importance of dietary changes and physical activity to attenuate this phenomenon. Future research should focus on the longitudinal relationship between weight trends in midlife and health consequences and mortality.

Unlocking Cognitive Potential: Association of Sarcopenia and Mediterranean Diet on Cognitive Function in Community-Dwelling Elderly of the Dalmatian Region

The aim of this study was to determine the association between muscle strength, adherence to the Mediterranean diet (MeDi) and cognitive function in community-dwelling elderly. General data, data of body composition and anthropometric parameters, clinical and laboratory findings, cognitive test questionnaires (Mini-Mental State Examination-MMSE, Trail Making Test-TMT, Symbol Digit Modalities Test-SDMT), and nutritional assessments (Mini Nutritional Assessment-MNA, Mediterranean Diet Serving Score-MDSS) were obtained for each study participant. Handgrip strength (HS) was used as one of the key parameters for defining probable sarcopenia, among the Short Physical Performance Battery test (SPPB) (for defining physical activity) and the strength, assistance with walking, rising from a chair, climbing stairs, and falls questionnaire (SARC-F). Our cross-sectional study involved 114 participants aged ≥ 60 years, and two-thirds of the participants were female (76.3% vs. 23.7%). Probable sarcopenia was found in 34.7% of them. Using bivariate regression analysis, cognitive deficit among the sarcopenic population was associated with the following groups of collected data: (a) sociodemographic-associated factors-advanced age (OR: 1.07; p = 0.004), single marital status (OR: 3.25; p = 0.03), and low level of education (OR: 0.22; p < 0.003); (b) behavioral-associated factors-duration of institutionalization (OR: 1.05; p = 0.007), performance of heavy physical work (OR: 6.26; p = 0.001), low physical activity (OR: 0.08; p = 0.002), and risk of malnutrition (OR: 3.87; p = 0.005); (c) disease-related factors-loss of appetite (OR: 2.24; p = 0.04), information processing speed (OR: 0.88; p < 0.001), blood pressure systolic/diastolic variables (OR: 0.96/0.96; p = 0.002/0.02), medications (OR: 1.19; p = 0.005), predictive sarcopenia score ≥ 4 (OR: 3.1; p = 0.003), and low muscle strength (OR: 0.92; p = 0.002). Cognitive preservation among the sarcopenic population was associated with married status (OR: 0.23; p = 0.20), a high level of education (OR: 0.18; p = 0.002), smoking (OR: 0.33; p = 0.02), high physical activity (OR: 0.07; p < 0.001), and dietary habits using poultry (OR: 0.12; p = 0.004). The results suggest a significant association between sarcopenia and cognitive function in community-dwelling elderly, highlighting the need for regular nutritional interventions in this special population.

Early-life cumulative exposure to excess bodyweight and midlife cognitive function: longitudinal analysis in three British birth cohorts

BACKGROUND

Excess bodyweight (BMI >25 kg/m2) in midlife (age 40-65 years) has been linked to future cognitive decline and an increased risk of dementia. Whether chronic exposure to excess bodyweight in the early decades of life (<40 years) is associated with compromised cognitive function by midlife, however, remains unclear. This study therefore aimed to test potential bidirectional direct and indirect pathways linking cumulative exposure to excess bodyweight and cognitive function in the early decades of life.

METHODS

In this longitudinal analysis, harmonised measures of BMI and cognitive function were available in 19 742 participants aged 47-53 years recruited to the 1946 National Survey of Health and Development (n=2131), the 1958 National Child Development Study (n=9385), and the 1970 British Cohort Study (n=8226). Individual BMI trajectories spanning three decades from age 10-40 years were created for each participant and excess bodyweight duration, BMI change between ages, and cumulative excess bodyweight exposure were calculated. Harmonised measures of verbal and non-verbal ability, mathematical ability, and reading ability were used to create a latent factor for childhood cognitive function, and immediate and delayed recall, animal naming, and letter-search speed tests were used for midlife cognitive function. Multivariable linear regression and structural equation models (SEM) were used to test for potential bidirectional relationships between cognition and excess bodyweight in both individual cohorts and pooled datasets while accounting for other potential early-life confounders.

FINDINGS

Increases in BMI during adolescence and greater cumulative exposure to excess bodyweight across early life were associated with lower midlife cognitive function in all cohorts (eg, pooled difference in cognitive function per 10 years excess bodyweight duration -0·10; 95% CI -0·12 to -0·08; p<0·001). Further adjustment for childhood cognitive function attenuated many of these associations towards the null (eg, pooled difference in cognitive function per 10 years excess bodyweight duration -0·04; 95% CI -0·06 to -0·02; p=0·001), however, with any remaining associations then fully attenuating once further adjusted for other early-life factors (eg, pooled difference in cognitive function per 10 years excess bodyweight duration 0, -0·03 to 0·01; p=0·38). In the reverse direction, low childhood cognition was associated with greater cumulative exposure to excess bodyweight over the next four decades, although much of this relationship was found to probably be explained via other potentially modifiable upstream early-life factors such as childhood disadvantage. SEM in all cohorts suggested the presence of modest direct and indirect pathways connecting earlier cognitive function to later excess bodyweight, but scarce evidence for an effect of early-life excess bodyweight on cognitive function by midlife.

INTERPRETATION

The association between cumulative exposure to excess bodyweight in early life and lower cognitive function in midlife is probably confounded by a persistently lower cognitive function from childhood. Initiatives to improve early-life factors such as childhood disadvantage and education, however, might exert dual but independent benefits on both of these factors before old age.

FUNDING

Alzheimer's Research UK, Diabetes Research and Wellness Foundation, Diabetes UK, British Heart Foundation, and Medical Research Council.

Long-Term Brain Structure and Cognition Following Bariatric Surgery

Importance

Weight loss induced by bariatric surgery (BS) is associated with improved cognition and changed brain structure; however, previous studies on the association have used small cohorts and short follow-up periods, making it difficult to determine long-term neurological outcomes associated with BS.

Objective

To investigate long-term associations of weight loss after BS with cognition and brain structure and perfusion.

Design, Setting, and Participants

This cohort study included participants from the Bariatric Surgery Rijnstate and Radboudumc Neuroimaging and Cognition in Obesity study. Data from participants with severe obesity (body mass index [BMI; calculated as weight in kilograms divided by height in meters squared] >40, or BMI >35 with comorbidities) eligible for Roux-en-Y gastric bypass and aged 35 to 55 years were enrolled from a hospital specialized in BS (Rijnstate Hospital, Arnhem, the Netherlands). Participants were recruited between September 2018 and December 2020 with follow-up till March 2023. Data were collected before BS and at 6 and 24 months after BS. Data were analyzed from March to November 2023.

Exposure

Roux-en-Y gastric bypass.

Main Outcomes and Measures

Primary outcomes included body weight, BMI, waist circumference, blood pressure, medication use, cognitive performance (20% change index of compound z-score), brain volumes, cortical thickness, cerebral blood flow (CBF), and spatial coefficient of variation (sCOV). Secondary outcomes include cytokines, adipokines, depressive symptoms (assessed using the Beck Depression Inventory), and physical activity (assessed using the Baecke Questionnaire).

Results

A total of 133 participants (mean [SD] age, 46.8 [5.7] years; 112 [84.2%] female) were included. Global cognition was at least 20% higher in 52 participants (42.9%) at 24 months after BS. Compared with baseline, at 24 months, inflammatory markers were lower (mean [SD] high-sensitivity C-reactive protein: 4.77 [5.80] μg/mL vs 0.80 [1.09] μg/mL; P < .001), fewer patients used antihypertensives (48 patients [36.1%] vs 22 patients [16.7%]), and patients had lower depressive symptoms (median [IQR] BDI score: 9.0 [5.0-13.0] vs 3.0 [1.0-6.0]; P < .001) and greater physical activity (mean [SD] Baecke score: 7.64 [1.29] vs 8.19 [1.35]; P < .001). After BS, brain structure and perfusion were lower in most brain regions, while hippocampal and white matter volume remained stable. CBF and sCOV did not change in nucleus accumbens and parietal cortex. The temporal cortex showed a greater thickness (mean [SD] thickness: 2.724 [0.101] mm vs 2.761 [0.007] mm; P = .007) and lower sCOV (median [IQR] sCOV: 4.41% [3.83%-5.18%] vs 3.97% [3.71%-4.59%]; P = .02) after BS.

Conclusions and Relevance

These findings suggest that BS was associated with health benefits 2 years after surgery. BS was associated with improved cognition and general health and changed blood vessel efficiency and cortical thickness of the temporal cortex. These results may improve treatment options for patients with obesity and dementia.

Cognition and obesity in adults with epilepsy

Introduction

Objective: to assess the occurrence of overweight/obesity in patient with epilepsy (PWEs) and to relate it to cognitive aspects and clinical variables. Methodology: the measurements of waist circumference, calf circumference, arm circumference, and the body mass index were related to the scores of the Mini-Mental State Examination and the Brief Cognitive Battery-Edu, as well as to the clinical variables of 164 PWEs, with a significance level of p < 0.05. Data were compared to a similar control group (CG) comprising 71 cases. Linear and multiple logistic regression models were used to assess factors related to cognitive aspects. Results: the mean age of the PWEs was 49.8 ± 16.6 years with a mean length of epilepsy of 22 ± 15.9 years. Overweight/obesity occurred in 106 (64.6 %) PWEs and in 42 (59.1 %) CG subjects. The PWEs had a worse performance in several cognitive functions when compared to CG subjects. In the PWEs, overweight/obesity was associated with lower educational level, older age, and cognitive impairment. Greater waist circumference, overweight, age at the first seizure, and use of polytherapy with antiseizure medications were predictive factors of memory impairment in multiple linear regression. Greater arm and calf circumference values were associated with better performance in several cognitive areas. Conclusion: the occurrence of overweight/obesity in PWEs and CG subjects was high. Cognitive impairment occurred in a high number of PWEs and was associated with overweight, greater waist circumference values, and clinical aspects of epilepsy. Better cognitive performance was associated with greater arm and calf circumference.

Hippocampal neurogenesis and Arc expression are enhanced in high-fat fed prepubertal female pigs by a diet including omega-3 fatty acids and Bifidobacterium breve CECT8242

PURPOSE

Obesity during childhood has become a pandemic disease, mainly caused by a diet rich in sugars and fatty acids. Among other negative effects, these diets can induce cognitive impairment and reduce neuroplasticity. It is well known that omega-3 and probiotics have a beneficial impact on health and cognition, and we have hypothesized that a diet enriched with Bifidobacterium breve and omega-3 could potentiate neuroplasticity in prepubertal pigs on a high-fat diet.

METHODS

Young female piglets were fed during 10 weeks with: standard diet (T1), high-fat (HF) diet (T2), HF diet including B. breve CECT8242 (T3) and HF diet including the probiotic and omega-3 fatty acids (T4). Using hippocampal sections, we analyzed by immunocytochemistry the levels of doublecortin (DCX) to study neurogenesis, and activity-regulated cytoskeleton-associated protein (Arc) as a synaptic plasticity related protein.

RESULTS

No effect of T2 or T3 was observed, whereas T4 increased both DCX+ cells and Arc expression. Therefore, a diet enriched with supplements of B. breve and omega-3 increases neurogenesis and synaptic plasticity in prepubertal females on a HF diet from nine weeks of age to sexual maturity. Furthermore, the analysis of serum cholesterol and HDL indicate that neurogenesis was related to lipidic demand in piglets fed with control or HF diets, but the neurogenic effect induced by the T4 diet was exerted by mechanisms independent of this lipidic demand.

CONCLUSION

Our results show that the T4 dietary treatment is effective in potentiating neural plasticity in the dorsal hippocampus of prepubertal females on a HF diet.

Habitual intake of fat and sugar is associated with poorer memory and greater impulsivity in humans

The vicious cycle model of obesity suggests that repeated habitual intake of a diet high in fat and sugar (HFS) results in impairment in hippocampal function which in turn increases impulsive behaviours, making it harder to resist unhealthy diet choices. Evidence from studies with rodents consistently show switching to a HFS diet impairs performance on hippocampally-sensitive memory tasks. The limited literature in humans also suggest impaired memory and increased impulsivity related to higher habitual HFS intake. However, these changes in memory and impulsivity have been looked at independently. To investigate how these effects are inter-related, three experiments were conducted where relative HFS intake was related to measures of memory and impulsivity. In Experiment 1 (90 female participants), HFS was associated with higher scores on the Everyday Memory Questionnaire-revised (EMQ), and higher scores on the total, Attention (BISatt) and Motor (BISmot) sub-scales of the Barratt Impulsiveness Scale (BIS11). Experiment 2 (84 women and 35 men), replicated the association between HFS and EMQ, and also found HFS related to poorer performance on the hippocampally-sensitive 4 mountain (4MT) memory task. The association between HFS intake and the BISatt replicated, but there were no significant associations with other BIS11 measures or delay-discounting for monetary rewards. Experiment 3 (199 women and 87 men) replicated the associations between DFS and 4MT and EMQ, and also found an association with overall recall, but not response inhibition, from a Remembering Causes Forgetting task: HFS was also significantly associated with BIS total, BISatt and BISmot. In all three studies these associations remained when potential confounds (BMI, age, gender, hunger state, restrained and disinhibited eating) were controlled for. Mediation analysis found that the effect of HFS on memory at least part mediated the relationship between HFS and impulsivity in Experiments 1 and 3, but not 2. Overall these data provide some support for the vicious cycle model, but also suggest that trait impulsivity may be a risk factor for poor dietary choice.

Obesity-Induced Brain Neuroinflammatory and Mitochondrial Changes

Obesity is defined as abnormal and excessive fat accumulation, and it is a risk factor for developing metabolic and neurodegenerative diseases and cognitive deficits. Obesity is caused by an imbalance in energy homeostasis resulting from increased caloric intake associated with a sedentary lifestyle. However, the entire physiopathology linking obesity with neurodegeneration and cognitive decline has not yet been elucidated. During the progression of obesity, adipose tissue undergoes immune, metabolic, and functional changes that induce chronic low-grade inflammation. It has been proposed that inflammatory processes may participate in both the peripheral disorders and brain disorders associated with obesity, including the development of cognitive deficits. In addition, mitochondrial dysfunction is related to inflammation and oxidative stress, causing cellular oxidative damage. Preclinical and clinical studies of obesity and metabolic disorders have demonstrated mitochondrial brain dysfunction. Since neuronal cells have a high energy demand and mitochondria play an important role in maintaining a constant energy supply, impairments in mitochondrial activity lead to neuronal damage and dysfunction and, consequently, to neurotoxicity. In this review, we highlight the effect of obesity and high-fat diet consumption on brain neuroinflammation and mitochondrial changes as a link between metabolic dysfunction and cognitive decline.

Ageing, Metabolic Dysfunction, and the Therapeutic Role of Antioxidants

The gradual ageing of the world population has been accompanied by a dramatic increase in the prevalence of obesity and metabolic diseases, especially type 2 diabetes. The adipose tissue dysfunction associated with ageing and obesity shares many common physiological features, including increased oxidative stress and inflammation. Understanding the mechanisms responsible for adipose tissue dysfunction in obesity may help elucidate the processes that contribute to the metabolic disturbances that occur with ageing. This, in turn, may help identify therapeutic targets for the treatment of obesity and age-related metabolic disorders. Because oxidative stress plays a critical role in these pathological processes, antioxidant dietary interventions could be of therapeutic value for the prevention and/or treatment of age-related diseases and obesity and their complications. In this chapter, we review the molecular and cellular mechanisms by which obesity predisposes individuals to accelerated ageing. Additionally, we critically review the potential of antioxidant dietary interventions to counteract obesity and ageing.

Sex Differences in the Associations of Obesity with Tau, Amyloid PET, and Cognitive Outcomes in Preclinical Alzheimer's Disease: Cross-Sectional A4 Study

BACKGROUND

The association between obesity and Alzheimer's disease (AD) is complex. Recent studies indicated the relationships between obesity and AD may differ by sex, and women may benefit from being overweight in terms of AD risk.

OBJECTIVE

We investigated whether sex modifies the associations of obesity with tau positron emission tomography (PET), amyloid PET, and cognition in preclinical AD.

METHODS

We included 387 cognitively-unimpaired amyloid-positive participants (221 women, 166 men, 87.6% non-Hispanic White) with available 18F-flortaucipir PET, 18F-florbetapir PET, and completed the Preclinical Alzheimer Cognitive Composite (PACC) tests from the Anti-Amyloid Treatment in Asymptomatic Alzheimer's Disease (A4) study. Participants were categorized based on body mass index (BMI: kg/m2): normal-weight (BMI: 18.5-25), overweight (BMI: 25-30), and obese (BMI≥30).

RESULTS

Significant sex by BMI category interactions on PACC and its components: Mini-Mental State Examination (MMSE) and Reminding Test-Free+Total Recall (FCSRT96) revealed that overweight and obese women outperformed normal-weight women on FCSRT96, while obese men showed poorer MMSE performance than normal-weight men. These interactions were independent of APOE4. There were no significant interactions of sex by BMI category on tau and amyloid PET. However, sex-stratified analyses observed obesity was associated with less regional tau and mean cortical amyloid in women, not in men.

CONCLUSION

This study found that in preclinical AD, overweight and obesity were associated with better verbal memory in women, whereas obesity was associated with worse global cognition among men. Future studies focusing on the mechanism for this relationship may inform sex-specific interventions for AD prevention.

Learning Deficits Induced by High-Calorie Feeding in the Rat are Associated With Impaired Brain Kynurenine Pathway Metabolism

In addition to be a primary risk factor for type 2 diabetes and cardiovascular disease, obesity is associated with learning disabilities. Here we examined whether a dysregulation of the kynurenine pathway (KP) of tryptophan (Trp) metabolism might underlie the learning deficits exhibited by obese individuals. The KP is initiated by the enzymatic conversion of Trp into kynurenine (KYN) by indoleamine 2,3-dioxygenase (IDO). KYN is further converted to several signaling molecules including quinolinic acid (QA) which has a negative impact on learning. Wistar rats were fed either standard chow or made obese by exposure to a free choice high-fat high-sugar (fcHFHS) diet. Their learning capacities were evaluated using a combination of the novel object recognition and the novel object location tasks, and the concentrations of Trp and KYN-derived metabolites in several brain regions determined by ultra-performance liquid chromatography-tandem mass spectrometry. Male, but not female, obese rats exhibited reduced learning capacity characterized by impaired encoding along with increased hippocampal concentrations of QA, Xanthurenic acid (XA), Nicotinamide (Nam), and oxidized Nicotinamide Adenine Dinucleotide (NAD+). In contrast, no differences were detected in the serum levels of Trp or KP metabolites. Moreover, obesity enhanced the expression in the hippocampus and frontal cortex of kynurenine monooxygenase (KMO), an enzyme involved in the production of QA from kynurenine. QA stimulates the glutamatergic system and its increased production leads to cognitive impairment. These results suggest that the deleterious effects of obesity on cognition are sex dependent and that altered KP metabolism might contribute to obesity-associated learning disabilities.

Does sleep duration moderate genetic and environmental contributions to cognitive performance?

While prior research has demonstrated a relationship between sleep and cognitive performance, how sleep relates to underlying genetic and environmental etiologies contributing to cognitive functioning, regardless of the level of cognitive function, is unclear. The present study assessed whether the importance of genetic and environmental contributions to cognition vary depending on an individual's aging-related sleep characteristics. The large sample consisted of twins from six studies within the Interplay of Genes and Environment across Multiple Studies (IGEMS) consortium spanning mid- to late-life (Average age [Mage] = 57.6, range = 27-91 years, N = 7052, Female = 43.70%, 1525 complete monozygotic [MZ] pairs, 2001 complete dizygotic [DZ] pairs). Quantitative genetic twin models considered sleep duration as a primary moderator of genetic and environmental contributions to cognitive performance in four cognitive abilities (Semantic Fluency, Spatial-Visual Reasoning, Processing Speed, and Episodic Memory), while accounting for age moderation. Results suggested genetic and both shared and nonshared environmental contributions for Semantic Fluency and genetic and shared environmental contributions for Episodic Memory vary by sleep duration, while no significant moderation was observed for Spatial-Visual Reasoning or Processing Speed. Results for Semantic Fluency and Episodic Memory illustrated patterns of higher genetic influences on cognitive function at shorter sleep durations (i.e. 4 hours) and higher shared environmental contributions to cognitive function at longer sleep durations (i.e. 10 hours). Overall, these findings may align with associations of upregulation of neuroinflammatory processes and ineffective beta-amyloid clearance in short sleep contexts and common reporting of mental fatigue in long sleep contexts, both associated with poorer cognitive functioning.

Sex Differences in Cognition Across Aging

Sex and gender differences are seen in cognitive disturbances in a variety of neurological and psychiatry diseases. Men are more likely to have cognitive symptoms in schizophrenia whereas women are more likely to have more severe cognitive symptoms with major depressive disorder and Alzheimer's disease. Thus, it is important to understand sex and gender differences in underlying cognitive abilities with and without disease. Sex differences are noted in performance across various cognitive domains - with males typically outperforming females in spatial tasks and females typically outperforming males in verbal tasks. Furthermore, there are striking sex differences in brain networks that are activated during cognitive tasks and in learning strategies. Although rarely studied, there are also sex differences in the trajectory of cognitive aging. It is important to pay attention to these sex differences as they inform researchers of potential differences in resilience to age-related cognitive decline and underlying mechanisms for both healthy and pathological cognitive aging, depending on sex. We review literature on the progressive neurodegenerative disorder, Alzheimer's disease, as an example of pathological cognitive aging in which human females show greater lifetime risk, neuropathology, and cognitive impairment, compared to human males. Not surprisingly, the relationships between sex and cognition, cognitive aging, and Alzheimer's disease are nuanced and multifaceted. As such, this chapter will end with a discussion of lifestyle factors, like education and diet, as modifiable factors that can alter cognitive aging by sex. Understanding how cognition changes across age and contributing factors, like sex differences, will be essential to improving care for older adults.

Effect of the Intake of Brown Rice for Six Months on the Cognitive Function in Healthy Elderly Persons: A Study Protocol for a Pilot, Non-Randomized Controlled Trial

The nutritional components of brown rice have been reported to be effective against diabetes mellitus. Recent animal studies have suggested that it is also effective in maintaining cognitive function. Therefore, in this study, we examined the effect of a brown rice diet on cognitive function in individuals aged over 60 years. The study participants were recruited from a pool of individuals aged ≥60 years who were using elderly care facilities. The participants were provided with four servings of brown or white rice per week for 6 months, and their cognitive function was measured before and after the intervention period. Prior to the intervention, participants tasted the white and brown rice to determine which type they would like to be offered over the 6-month period. Since rice is the staple food of the participants in this study, they were allowed to decide whether they wanted to eat white or brown rice.

Cognitive impairments in patients with overweight and obesity

Background. In modern society, the growth of the overweight and obese population increase every year. This confirms the status assigned to the problem under consideration as a non-infectious epidemic of the 21st century. At the same time, the amount of scientific information about the influence of excess weight on various aspects of human life is actively increasing. This undoubtedly requires a systematic generalization of the available data.

Aims. The presented literature review is devoted to the analysis of modern scientific research on the specificity of cognitive impairment in overweight and obese people.

Materials and methods. Information search was carried out using Internet resources (PubMed, Web of Science, eLibrary.ru, frontiersin.org, sciencedirect. com, ncbi.nlm.nih.gov), literature sources were analyzed for the period from 2001 to 2020 for the following keywords: obesity, overweight, cognitive functions, cognitions, cognitive impairments.

Results. As a result of the literature review, the main directions of research on the relationship between cognitive impairment and overweight, as well as the relationship between cognitive dysfunction and obesity, were identified. The specificity of diametrically opposed opinions within the framework of each consecrated trend is presented. According to the results of the analysis of the identified areas, in the scientific community the most common point of view is the presence of a connection between obesity and cognitive impairment. In this connection, the authors identified the main cognitive impairments associated with excess weight and their mediating mechanisms. And also the age specificity of the problem under study is indicated.

Conclusions. Despite the fact that the problem of the relationship between obesity, overweight and cognitive functions is comprehensively studied, there is a shortage of data on the state of thinking, attention, praxis, gnosis, and speech in overweight people.

Inflammation and Insulin Resistance as Risk Factors and Potential Therapeutic Targets for Alzheimer's Disease

Overnutrition and modern diets containing high proportions of saturated fat are among the major factors contributing to a low-grade state of inflammation, hyperglycemia and dyslipidemia. In the last decades, the global rise of type 2 diabetes and obesity prevalence has elicited a great interest in understanding how changes in metabolic function lead to an increased risk for premature brain aging and the development of neurodegenerative disorders such as Alzheimer's disease (AD). Cognitive impairment and decreased neurogenic capacity could be a consequence of metabolic disturbances. In these scenarios, the interplay between inflammation and insulin resistance could represent a potential therapeutic target to prevent or ameliorate neurodegeneration and cognitive impairment. The present review aims to provide an update on the impact of metabolic stress pathways on AD with a focus on inflammation and insulin resistance as risk factors and therapeutic targets.

The relationship of obesity predicting decline in executive functioning is attenuated with greater leisure activities in old age

Objectives: We investigated the longitudinal relationship between obesity and subsequent decline in executive functioning over six years as measured through performance changes in the Trail Making Test (TMT). We also examined whether this longitudinal relationship differed by key markers of cognitive reserve (education, occupation, and leisure activities), taking into account age, sex, and chronic diseases as covariates.Method: We used latent change score modeling based on longitudinal data from 897 older adults tested on TMT parts A and B in two waves six years apart. Mean age in the first wave was 74.33 years. Participants reported their weight and height (to calculate BMI), education, occupation, leisure activities, and chronic diseases.Results: There was a significant interaction of obesity in the first wave of data collection with leisure activities in the first wave on subsequent latent change. Specifically, obesity in the first wave significantly predicted a steeper subsequent decline in executive functioning over six years in individuals with a low frequency of leisure activities in the first wave. In contrast, in individuals with a high frequency of leisure activities in the first wave, this longitudinal relationship between obesity and subsequent decline in executive functioning was not significant.Conclusion: The longitudinal relationship between obesity and subsequent decline in executive functioning may be attenuated in individuals who have accumulated greater cognitive reserve through an engaged lifestyle in old age. Implications for current cognitive reserve and gerontological research are discussed.

A critical review of the epidemiological evidence of effects of air pollution on dementia, cognitive function and cognitive decline in adult population

Dementia is arguably the most pressing public health challenge of our age. Since dementia does not have a cure, identifying risk factors that can be controlled has become paramount to reduce the personal, societal and economic burden of dementia. The relationship between exposure to air pollution and effects on cognitive function, cognitive decline and dementia has stimulated increasing scientific interest in the past few years. This review of the literature critically examines the available epidemiological evidence of associations between exposure to ambient air pollutants, cognitive performance, acceleration of cognitive decline, risk of developing dementia, neuroimaging and neurological biomarker studies, following Bradford Hill guidelines for causality. The evidence reviewed has been consistent in reporting associations between chronic exposure to air pollution and reduced global cognition, as well as impairment in specific cognitive domains including visuo-spatial abilities. Cognitive decline and dementia incidence have also been consistently associated with exposure to air pollution. The neuro-imaging studies reviewed report associations between exposure to air pollution and white matter volume reduction. Other reported effects include reduction in gray matter, larger ventricular volume, and smaller corpus callosum. Findings relating to ischemic (white matter hyperintensities/silent cerebral infarcts) and hemorrhagic (cerebral microbleeds) markers of cerebral small vessel disease have been heterogeneous, as have observations on hippocampal volume and air pollution. The few studies available on neuro-inflammation tend to report associations with exposure to air pollution. Several effect modifiers have been suggested in the literature, but more replication studies are required. Traditional confounding factors have been controlled or adjusted for in most of the reviewed studies. Additional confounding factors have also been considered, but the inclusion of these has varied among the different studies. Despite all the efforts to adjust for confounding factors, residual confounding cannot be completely ruled out, especially since the factors affecting cognition and dementia are not yet fully understood. The available evidence meets many of the Bradford Hill guidelines for causality. The reported associations between a range of air pollutants and effects on cognitive function in older people, including the acceleration of cognitive decline and the induction of dementia, are likely to be causal in nature. However, the diversity of study designs, air pollutants and endpoints examined precludes the attribution of these adverse effects to a single class of pollutant and makes meta-analysis inappropriate.

Obesity-induced cognitive impairment in older adults: a microvascular perspective

Over two-thirds of individuals aged 65 and older are obese or overweight in the United States. Epidemiological data show an association between the degree of adiposity and cognitive dysfunction in the elderly. In this review, the pathophysiological roles of microvascular mechanisms, including impaired endothelial function and neurovascular coupling responses, microvascular rarefaction, and blood-brain barrier disruption in the genesis of cognitive impairment in geriatric obesity are considered. The potential contribution of adipose-derived factors and fundamental cellular and molecular mechanisms of senescence to exacerbated obesity-induced cerebromicrovascular impairment and cognitive decline in aging are discussed.

Polycystic Ovary Syndrome and Brain: An Update on Structural and Functional Studies

CONTEXT

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder of women in reproductive age and is associated with reproductive, endocrine, metabolic, cardiovascular, and psychological outcomes. All these disorders are thought to be affected by central mechanisms which could be a major contributor in pathogenesis of PCOS.

EVIDENCE ACQUISITION

This mini-review discusses the relevance of central nervous system imaging modalities in understanding the neuroendocrine origins of PCOS as well as their relevance to understanding its comorbidities.

EVIDENCE SYNTHESIS

Current data suggest that central nervous system plays a key role in development of PCOS. Decreased global and regional brain volumes and altered white matter microstructure in women with PCOS is shown by structural imaging modalities. Functional studies show diminished reward response in corticolimbic areas, brain glucose hypometabolism, and greater opioid receptor availability in reward-related regions in insulin-resistant patients with PCOS. These structural and functional disturbances are associated with nonhomeostatic eating, diminished appetitive responses, as well as cognitive dysfunction and mood disorders in women with PCOS.

CONCLUSION

Structural and functional brain imaging is an emerging modality in understanding pathophysiology of metabolic disorders such as diabetes and obesity as well as PCOS. Neuroimaging can help researchers and clinicians for better understanding the pathophysiology of PCOS and related comorbidities as well as better phenotyping PCOS.

Association of anthropometric and nutrition status indicators with cognitive functions in centenarians

BACKGROUND & AIMS

How anthropometric and nutrition status indicators relate to cognitive function in the oldest old adults is an issue that needs to be explored. This study aimed to analyze the association of parameters and nutrition status indicators (waist circumference, BMI, calf circumference, and waist-calf circumference ratio [WCR]) with cognitive functions in centenarians.

METHODS

A cross-sectional observational study was conducted with the full sample of 1002 centenarians from Hainan. The mini-mental state examination (MMSE) was used to identify cognitive impairment. Multiple logistic regression analysis was used to examine the strength of association between each anthropometric index and the risk of cognitive impairment or severe cognitive impairment identified by MMSE. Locally Weighted Scatterplot Smoothing (LOWESS) curve was used to visualize the linear or non-linear relationship of each pair.

RESULTS

The risk of cognitive impairment identified by MMSE for centenarians was reduced by 12% for every 1 cm thickening of the calf circumference (OR = 0.88, 95% CI: 0.81-0.95) and the increase in each unit of WCR increased cognitive impairment the risk by 1.60 times (OR = 2.60, 95% CI: 1.31-5.13) after adjusting for demographic characteristics (i.e., gender, age, ethnicity, marital status, education level, and type of residence) and lifestyle (i.e., smoking, drinking, and exercise) related variables.

CONCLUSIONS

Results suggest that calf circumference is negatively associated with the risk of cognitive impairment identified by MMSE in centenarians. Older adults with lower calf circumference should pay attention to their cognitive function.

Environment and Gene Association With Obesity and Their Impact on Neurodegenerative and Neurodevelopmental Diseases

Obesity is a multifactorial disease in which environmental conditions and several genes play an important role in the development of this disease. Obesity is associated with neurodegenerative diseases (Alzheimer, Parkinson, and Huntington diseases) and with neurodevelopmental diseases (autism disorder, schizophrenia, and fragile X syndrome). Some of the environmental conditions that lead to obesity are physical activity, alcohol consumption, socioeconomic status, parent feeding behavior, and diet. Interestingly, some of these environmental conditions are shared with neurodegenerative and neurodevelopmental diseases. Obesity impairs neurodevelopment abilities as memory and fine-motor skills. Moreover, maternal obesity affects the cognitive function and mental health of the offspring. The common biological mechanisms involved in obesity and neurodegenerative/neurodevelopmental diseases are insulin resistance, pro-inflammatory cytokines, and oxidative damage, among others, leading to impaired brain development or cell death. Obesogenic environmental conditions are not the only factors that influence neurodegenerative and neurodevelopmental diseases. In fact, several genes implicated in the leptin–melanocortin pathway (LEP, LEPR, POMC, BDNF, MC4R, PCSK1, SIM1, BDNF, TrkB, etc.) are associated with obesity and neurodegenerative and neurodevelopmental diseases. Moreover, in the last decades, the discovery of new genes associated with obesity (FTO, NRXN3, NPC1, NEGR1, MTCH2, GNPDA2, among others) and with neurodegenerative or neurodevelopmental diseases (APOE, CD38, SIRT1, TNFα, PAI-1, TREM2, SYT4, FMR1, TET3, among others) had opened new pathways to comprehend the common mechanisms involved in these diseases. In conclusion, the obesogenic environmental conditions, the genes, and the interaction gene–environment would lead to a better understanding of the etiology of these diseases.

Genetic Underpinnings of Increased BMI and Its Association With Late Midlife Cognitive Abilities

Objectives: First, we test for differences in various cognitive abilities across trajectories of body mass index (BMI) over the later life course. Second, we examine whether genetic risk factors for unhealthy BMIs—assessed via polygenic risk scores (PRS)—predict cognitive abilities in late-life. Methods: The study used a longitudinal sample of Vietnam veteran males to explore the associations between BMI trajectories, measured across four time points, and later cognitive abilities. The sample of 977 individuals was drawn from the Vietnam Era Twin Study of Aging. Cognitive abilities evaluated included executive function, abstract reasoning, episodic memory, processing speed, verbal fluency, and visual spatial ability. Multilevel linear regression models were used to estimate the associations between BMI trajectories and cognitive abilities. Then, BMI PRS was added to the models to evaluate polygenic associations with cognitive abilities. Results: There were no significant differences in cognitive ability between any of the BMI trajectory groups. There was a significant inverse relationship between BMI-PRS and several cognitive ability measures. Discussion: While no associations emerged for BMI trajectories and cognitive abilities at the phenotypic levels, BMI PRS measures did correlate with key cognitive domains. Our results suggest possible polygenic linkages cutting across key components of the central and peripheral nervous system.

Time for a Systems Biological Approach to Cognitive Aging?-A Critical Review

The underlying premise of current theories of cognitive decline with age tend to be primarily cognitive or biological explanations, with relatively few theories adequately integrating both aspects. Though literature has also emphasized the importance of several factors that contribute to cognitive aging including: (a) decline in sensory abilities; (b) the effect of motor speed on paper-pencil measures of cognitive speed; (c) the impact of level of education and physical activity; and (d) molecular biological changes that occur with age, these factors have seldom been implicated into any single theoretical model of cognitive aging. Indeed, such an integrated bio-cognitive model of aging has the potential to provide a more comprehensive understanding of attention, perception, learning, and memory across the lifespan. Thus, the aim of this review was to critically evaluate common theories of age-related cognitive decline and highlight the need for a more comprehensive systems neuroscience approach to cognitive aging.

Food Insecurity and Cognitive Function in Middle to Older Adulthood: A Systematic Review

Food insecurity (FI) may limit cognitive functioning during aging. The goal of this systematic review was to summarize existing evidence linking FI and general or specific cognitive functions in middle and older adulthood. A systematic search of human studies published between 1 January 2000 and 30 April 2018 was conducted in PubMed, PsycINFO, and CAB Direct. Four independent reviewers assessed the eligibility of identified articles and conducted data extraction and data quality assessment. Ten studies were included in the review, including 1 cluster-randomized controlled trial, 2 longitudinal studies, and 7 cross-sectional studies. Three studies reported the association between early-life FI experience and a global cognitive function measure. Nine studies reported later-life FI experience in relation to global or specific cognitive functions. The results suggest an adverse association between FI experienced in early or later life and global cognitive function; and between later-life FI and executive function and memory. Findings from the review are preliminary because of sparse data, heterogeneity across study populations, exposure and outcome assessments, and potential risk of bias across studies. Future studies are recommended to better understand the role of FI in cognitive function, with the goal of identifying possible critical windows for correction of FI in vulnerable subpopulations to prevent neurocognitive deficit in adulthood.

Body mass index and trajectories of cognitive decline among older Korean adults

Objectives: This study examined the relationship between body mass index (BMI) and trajectories of cognitive decline among older Korean adults.Methods: Participants were a nationally representative sample of 5126 Korean adults aged 60 or older from the Korean Longitudinal Study of Aging (KLoSA: 2006-2014). The main outcome variable, cognitive function, was measured with the Korean Mini-Mental State Examination (K-MMSE). According to the BMI values, respondents were divided into four groups at each wave: underweight (<18.5 kg/m²), healthy weight (18.5-22.9 kg/m²), overweight (23.0-24.9 kg/m²), and obese (≥25.0 kg/m²). Growth curve modeling was used to analyze the relationship of interest.Results: The growth curve modeling revealed that, regardless of BMI values, cognitive functioning declined as participants aged, and the rate of cognitive decline accelerated with age. After adjusting for all covariates, older Korean adults who were underweight displayed steeper declines in cognitive functioning, compared to those with a healthy weight. Conversely, overweight or obese older adults showed a much slower cognitive decline as they aged, after adjusting for covariates.Conclusion: Compared to people with a healthy BMI, people with a low BMI may be at risk for cognitive dysfunction, whereas a high BMI could function as a protective factor for cognitive dysfunction in older adulthood. Future research examining the mechanism for these trajectories are needed. Implications for research and clinical practice are discussed.

Aging-related changes in fluid intelligence, muscle and adipose mass, and sex-specific immunologic mediation: A longitudinal UK Biobank study

BACKGROUND

Obesity in midlife and early late-life is associated with worse normal cognitive aging. Dual-energy X-ray absorptiometry (DEXA) suggests that visceral adipose mass (VAM) plays a predominant role, whereas non-visceral adipose mass (NVAM) and lean muscle mass (LMM) have shown conflicting relationships. It is unknown how longitudinal, cognitive changes in age-sensitive domains like fluid intelligence (FI) correspond to VAM, NVAM, and LMM in women and men. Furthermore, changes over time in blood leukocyte sub-populations may partially or fully account for sex-specific associations.

METHODS

Data on 4431 late middle-aged, cognitively unimpaired adults (mean = 64.5 y) was obtained from the UK Biobank prospective cohort across 22 centers. FI scores, blood leukocyte counts, and covariates (age, social class, education) were measured at three 2-year intervals over 6 years. DEXA collection overlapped with these intervals. Sex-stratified growth curves, structural equations, and Preacher-Hayes mediation were used to estimate direct and indirect effects. β-weights were standardized.

RESULTS

More LMM predicted gains in FI scores among women (β = 0.130, p < .001) and men (β = 0.089, p < .001). Conversely, more VAM and NVAM independently predicted FI decline equally among sexes (e.g., NVAM: women: β = -0.082, p < .001; men: β = -0.076, p < .001). Among women, FI associations were fully mediated by higher eosinophil counts via VAM (λ = 30.8%, p = .028) and lower lymphocyte counts via LMM (λ = 69.2%, p = .021). Among men, FI associations were partially mediated by lower basophils counts via LMM (λ = 4.5%, p = .042) and higher counts via VAM (λ = 50%, p = .037).

CONCLUSION

The proportion of LMM and VAM equally influenced male FI changes over 6 years, whereas higher LMM among women appeared to more strongly influence. FI changes. Leukocyte counts strongly mediated VAM- and LMM-related FI changes in a sex-specific manner, but not for NVAM. For clinical translation, exercise studies in older adults may benefit from assessing sex-specific values of DEXA-based tissue mass, FI, and leukocyte sub-populations to gauge potential cognitive benefits of less VAM and more LMM.

Inflammation Mediates Body Weight and Ageing Effects on Psychomotor Slowing

Inflammation (immune system activation) affects neuronal function and may have consequences for the efficiency and speed of functional brain processes. Indeed, unusually slow psychomotor speed, a measure predictive of behavioural performance and health outcomes, is found with obesity and ageing, two conditions also associated with chronic inflammation. Yet whether inflammation is the mediating factor remains unclear. Here, we assessed inflammation by indexing interleukin-6 level in blood and measured psychomotor speed as well as indices of selective visual attention in young (mean = 26 years) or old (mean = 71 years) adults (N = 83) who were either lean or currently significantly overweight (mean body mass index = 22.4 and 33.8, respectively). Inflammation was positively and significantly correlated with psychomotor speed, age, and body mass index but not with attention measures. Using mediation analyses we show for the first time that inflammation fully accounts for the significant psychomotor slowing found in those with high BMI. Moreover, we further show that age-related psychomotor slowing is partially mediated by inflammation. These findings support the proposal that reducing inflammation may mitigate weight- and age-related cognitive decline and thereby improve performance on daily tasks and health outcomes more generally.

Brief Report: Body Mass Index and Cognitive Function Among HIV-1-Infected Individuals in China, India, and Nigeria

BACKGROUND

Risk of cognitive impairment is increased among persons with high or low body mass index in HIV- and HIV+ populations in resource-rich settings. We examined this association among HIV+ patients in 3 resource-limited settings.

METHODS

This secondary analysis included data of 761 HIV+ volunteers pooled from 3 prospective cohort studies conducted in China (n = 404; 53%), India (n = 200; 26%), and Nigeria (n = 157; 21%). World Health Organization (WHO) weight classifications were based on body mass index. T scores, adjusted for demographics and practice effects, were derived from a 7-domain neuropsychological battery. Neurocognitive impairment (NCI) was defined as global deficit score of ≥0.5.

RESULTS

Overall, prevalence of NCI at baseline was 27.7% (similar across all cohorts). The overweight/obese and underweight constituted 37.3% and 15.5% of the total participants, respectively. In a multivariable logistic regression of pooled longitudinal data, adjusting for clinical and demographic variables, the odds of global NCI were 38% higher among the overweight/obese as compared to normal weight participants [odds ratio: 1.38 (95% confidence interval: 1.1 to 1.72); P = 0.005]. Similarly, the odds of global NCI were 39% higher among the underweight as compared to normal weight participants [odds ratio: 1.39 (95% confidence interval: 1.03 to 1.87); P = 0.029].

CONCLUSIONS

NCI among HIV-1-infected patients was more prevalent in both overweight/obese and underweight than normal weight individuals in 3 resource-limited settings, confirming observations in resource-rich settings. Mechanisms underlying these associations are unclear but likely differ for underweight and overweight persons.

Level of body fat relates to memory decline and interacts with age in its association with hippocampal and subcortical atrophy

Higher levels of body fat have shown adverse effects on multiple aspects of health, including cognitive and neuroanatomical changes. We tested the relationships of body fat levels and cholesterol to longitudinal age trajectories of subcortical gray matter volume (SCV), hippocampal volume (HCV), and episodic memory. Body fat was indexed by a concerted factor of BMI, visceral adipose tissue, percentage body fat, and total fat mass and was included in the analyses as a cross-sectional measure. We hypothesized that higher level of body fat would be related to steeper age trajectories of SCV, HCV, and memory. The sample consisted of 581 participants (20-83 years) with 942 magnetic resonance imaging and 945 memory examinations. Using generalized additive mixed models, a negative effect of body fat was found on SCV, HCV, and memory. Age and body fat interacted in their association with brain volume change. The results suggest that among cognitively healthy adults, there is a negative effect of higher body fat on SCV, HCV, and memory decline, an effect that increased with age for the neuroanatomical volumes.

Advanced glycation end products as biomarkers in systemic diseases: premises and perspectives of salivary advanced glycation end products

Advanced glycation end products (AGEs) are glycated proteins associated with high dry temperature food processing, coloring and flavor modification of food products. Previous studies on diet-related disease support the role of the glycation products as biomarkers in local and general proinflammatory response. Exogenous and endogenous AGEs are involved in chronic low-level inflammation, which underlies the onset of metabolic syndrome influenced by food intake, there by demonstrating their implication in diet-related pathologies. Although studies have revealed a strong association between the accumulation of AGEs and the occurrence/worsening of metabolic diseases, their routine use for the diagnosis or monitoring of local and general disease has not yet been reported.

[Long-term high-fat diet inhibits hippocampal expression of insulin receptor substrates and accelerates cognitive deterioration in obese rats]

OBJECTIVE

To assess the effect of long-term high-fat diet on the expressions of insulin receptor substrates in the hippocampus and spatial learning and memory ability of obese rats.

METHODS

A total of 100 4-week-old male SD rats were randomly divided into two groups and fed with common diet (CD group, n=40) or high-fat diet (HFD group, n=60) for 16 weeks. At 4, 8, 12, 16 and 20 weeks, 8 rats were randomly selected from each group for testing their spatial learning and memory function using Morris water maze. After the tests, the rats were sacrificed for measurement of the metabolic parameters and detection of the expressions of insulin receptor substrate-1 (IRS-1) and IRS-2 mRNAs in the CA1 region of the hippocampus.

RESULTS

Compared with those in CD group, the rats in HFD group showed a prolonged escape latency, longer swimming distance, faster average swimming speed, and shorter stay in the platformat 12 weeks. In HFD group, the serum levels of total cholesterol, triglyceride, low-density lipoprotein cholesterol, and fasting insulin were all significantly increased (P<0.05) and the level of high-density lipoprotein cholesterol decreased (P<0.01) in comparison with those in CD group at each of the time points. No significant difference was found in fast glucose levels between the two groups (P>0.05), but the expressions of IRS-1 and IRS-2 mRNAs were significantly decreased in HFD group at 12 weeks (P<0.05).

CONCLUSION

In obese rats, long-term feeding with high-fat diet leads to insulin resistance, which interferes with hippocampal expression of insulin receptor substrates and insulin metabolism to cause impairment of the cognitive function and accelerate cognitive deterioration.

[Long-term high-fat diet inhibits hippocampal expression of insulin receptor substrates and accelerates cognitive deterioration in obese rats]

OBJECTIVE

To assess the effect of long-term high-fat diet on the expressions of insulin receptor substrates in the hippocampus and spatial learning and memory ability of obese rats.

METHODS

A total of 100 4-week-old male SD rats were randomly divided into two groups and fed with common diet (CD group, n=40) or high-fat diet (HFD group, n=60) for 16 weeks. At 4, 8, 12, 16 and 20 weeks, 8 rats were randomly selected from each group for testing their spatial learning and memory function using Morris water maze. After the tests, the rats were sacrificed for measurement of the metabolic parameters and detection of the expressions of insulin receptor substrate-1 (IRS-1) and IRS-2 mRNAs in the CA1 region of the hippocampus.

RESULTS

Compared with those in CD group, the rats in HFD group showed a prolonged escape latency, longer swimming distance, faster average swimming speed, and shorter stay in the platformat 12 weeks. In HFD group, the serum levels of total cholesterol, triglyceride, low-density lipoprotein cholesterol, and fasting insulin were all significantly increased (P<0.05) and the level of high-density lipoprotein cholesterol decreased (P<0.01) in comparison with those in CD group at each of the time points. No significant difference was found in fast glucose levels between the two groups (P>0.05), but the expressions of IRS-1 and IRS-2 mRNAs were significantly decreased in HFD group at 12 weeks (P<0.05).

CONCLUSION

In obese rats, long-term feeding with high-fat diet leads to insulin resistance, which interferes with hippocampal expression of insulin receptor substrates and insulin metabolism to cause impairment of the cognitive function and accelerate cognitive deterioration.

The Relation of Obesity to Performance in Verbal Abilities, Processing Speed, and Cognitive Flexibility in Old Age: The Role of Cognitive Reserve

AIMS

The present study set out to investigate the relation of obesity to performance in verbal abilities, processing speed, and cognitive flexibility and its interplay with key correlates of cognitive reserve in a large sample of older adults.

METHODS

A total of 2,812 older adults served as a sample for the present study. Psychometric tests on verbal abilities, processing speed, and cognitive flexibility were administered. In addition, individuals were interviewed on their weight and height (to calculate body mass index; BMI), educational attainment, occupation, and engaging in different activities throughout adulthood.

RESULTS

Obesity (BMI ≥30) was significantly associated with a lower performance in verbal abilities, processing speed, and cognitive flexibility. Moderation analyses showed that obesity was related to lower processing speed and cognitive flexibility only in individuals with low engagement in activities and low education. Hierarchical regression analyses showed that obesity was not related to any of the three investigated cognitive performance measures when cognitive reserve in early and midlife was taken into account.

CONCLUSION

Present data suggest that cognitive reserve accumulated during the life course may reduce the detrimental influences of obesity on cognitive functioning in old age.

Higher Adiposity Is Associated With Slower Cognitive Decline in Hypertensive Patients: Secondary Analysis of the China Stroke Primary Prevention Trial

Background

Obesity is a risk factor for many diseases. However, the potential association between adiposity and cognitive decline in hypertensive patients is inconclusive. We performed a secondary data analysis of the CSPPT (China Stroke Primary Prevention Trial) to examine whether adiposity is correlated with longitudinal cognitive performance in hypertensive adults.

Methods and Results

The analysis included 16 791 patients in the CSPPT who received at least 2 cognitive assessments by the Mini‐Mental State Examination (MMSE) during the follow‐up (median, 4.5 years; interquartile range, 4.2–4.8 years). Outcomes included changes in MMSE scores and cognitive impairment (defined as MMSE score less than education‐specific cutoff point). A marked reduction in MMSE scores at the final (compared with at the 1‐year) follow‐up was apparent in both men (n=4838; mean [SD] score, 0.41 [3.62]) and women (n=7190; mean [SD] score, 1.07 [4.61]; both P<0.001). Analysis using a mixed‐effects model revealed an association between higher body mass index with less MMSE decline, even after controlling for demographics and comorbidities (men, β=0.0134 [SE, 0.0036]; women, β=0.0133 [SE, 0.0034]; both P<0.001). A total of 1037 men (15.3%) and 3317 women (33.1%) developed cognitive impairment. In multivariable Cox regression analyses, being obese in men (11.3% versus 18.0%; hazard ratio, 0.75; 95% confidence interval, 0.60–0.94) and women (30.1% versus 36.5%; hazard ratio, 0.82; 95% confidence interval, 0.74–0.91) was a protective factor against cognitive impairment compared with normal body mass index.

Conclusions

Higher adiposity is independently associated with slower cognitive decline in Chinese hypertensive adults.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00794885 CSPPT.

Blood-Brain Barriers in Obesity

After decades of rapid increase, the rate of obesity in adults in the USA is beginning to slow and the rate of childhood obesity is stabilizing. Despite these improvements, the obesity epidemic continues to be a major health and financial burden. Obesity is associated with serious negative health outcomes such as cardiovascular disease, type II diabetes, and, more recently, cognitive decline and various neurodegenerative dementias such as Alzheimer's disease. In the past decade, major advancements have contributed to the understanding of the role of the central nervous system (CNS) in the development of obesity and how peripheral hormonal signals modulate CNS regulation of energy homeostasis. In this article, we address how obesity affects the structure and function of the blood-brain barrier (BBB), the impact of obesity on Alzheimer's disease, the effects of obesity on circulating proteins and their transport into the brain, and how these changes can potentially be reversed by weight loss.

Cognitive ability and physical health: a Mendelian randomization study

Causes of the association between cognitive ability and health remain unknown, but may reflect a shared genetic aetiology. This study examines the causal genetic associations between cognitive ability and physical health. We carried out two-sample Mendelian randomization analyses using the inverse-variance weighted method to test for causality between later life cognitive ability, educational attainment (as a proxy for cognitive ability in youth), BMI, height, systolic blood pressure, coronary artery disease, and type 2 diabetes using data from six independent GWAS consortia and the UK Biobank sample (N = 112 151). BMI, systolic blood pressure, coronary artery disease and type 2 diabetes showed negative associations with cognitive ability; height was positively associated with cognitive ability. The analyses provided no evidence for casual associations from health to cognitive ability. In the other direction, higher educational attainment predicted lower BMI, systolic blood pressure, coronary artery disease, type 2 diabetes, and taller stature. The analyses indicated no causal association from educational attainment to physical health. The lack of evidence for causal associations between cognitive ability, educational attainment, and physical health could be explained by weak instrumental variables, poorly measured outcomes, or the small number of disease cases.

Genetic susceptibility to cardiovascular disease and risk of dementia

Several studies have shown cardiovascular disease (CVD) to be associated with dementia, but it is not clear whether CVD per se increases the risk of dementia or whether the association is due to shared risk factors. We tested how a genetic risk score (GRS) for coronary artery disease (CAD) affects dementia risk after CVD in 13 231 Swedish twins. We also utilized summarized genome-wide association data to study genetic overlap between CAD and Alzheimer´s disease (AD), and additionally between shared risk factors and each disease. There was no direct effect of a CAD GRS on dementia (hazard ratio 0.99, 95% confidence interval (CI): 0.98-1.01). However, the GRS for CAD modified the association between CVD and dementia within 3 years of CVD diagnosis, ranging from a hazard ratio of 1.59 (95% CI: 1.05-2.41) in the first GRS quartile to 1.91 (95% CI: 1.28-2.86) in the fourth GRS quartile. Using summary statistics, we found no genetic overlap between CAD and AD. We did, however, find that both AD and CAD share a significant genetic overlap with lipids, but that the overlap arose from clearly distinct gene clusters. In conclusion, genetic susceptibility to CAD was found to modify the association between CVD and dementia, most likely through associations with shared risk factors.

Body mass index, inflammatory biomarkers and neurocognitive impairment in HIV-infected persons

To determine the relationships among body mass index (BMI), and HIV-associated neurocognitive impairment and the potential mediating effects of inflammatory cytokines. Among the HIV-infected individuals (N = 90) included in this study, obesity was associated with slower processing speed (β = -.229, standard error (SE) = 2.15, p = .033), compared to participants with a normal BMI, after controlling for psychosocial and HIV clinical factors. Serum concentrations of the interleukin-16 (IL-16) cytokine were significantly associated with slowed processing speed (β = -.235, SE = 1.62, p = .033) but did not mediate the relationship between obesity and processing speed These findings suggest that obesity may contribute to cognitive processing speed deficits in HIV-infected adults. Elevated concentrations of IL-16 are also associated with slowing, though the results suggest that obesity and IL-16 may exert independent effects.

Obesity and Cognitive Decline in Adults: Effect of Methodological Choices and Confounding by Age in a Longitudinal Study

BACKGROUND AND OBJECTIVES

Obesity has been associated with increased risk of cognitive impairment or dementia, but recent findings are contradictory, possibly due to methodological differences. The present study tries to clarify these inconsistencies by following the cognitive trajectories of individuals with obesity over 12 years and studying the effect of obesity status (obesity at baseline versus incident obesity at follow-up), chronicity, definition, potential confounding (e.g. age, cardiovascular factors), and non-linear associations.

DESIGN

Longitudinal study with 12 years follow-up.

SETTING

Community based.

PARTICIPANTS

1,807 cognitively healthy individuals (aged 24-83) from the Maastricht Aging Study (1992-2004).

MEASUREMENTS

Memory, executive function and processing speed were assessed at baseline and at 6- and 12-year follow-up. Obesity was defined as having a body mass index (BMI) of ≥ 30.0 kg/m2 or waist circumference (WC) of > 102 cm for men and > 88 cm for women.

RESULTS

At baseline, 545 persons were obese (BMI: 329 (18%); WC: 494 (27%); both: 278 (15%). They showed faster decline in memory, executive function, and processing speed. Chronic obese showed less widespread impairment than those who regained normal weight. Associations across cognitive domains were weaker for obesity defined by BMI than for WC. At follow-up, 190 developed obesity, and they performed worse on executive function at baseline, but showed less decline compared with participants with normal weight. Yet, age-stratification and post-hoc analyses showed that most of these associations were confounded by age.

CONCLUSIONS

This study shows that the association between obesity and cognitive decline was confounded by the effect of age on rate of decline. Future studies should take this into account.

Effects of a multicomponent exercise program in institutionalized elders with Alzheimer's disease

This study examined the effect of a Multicomponent Training (MT) intervention on cognitive function, functional fitness and anthropometric variables in institutionalized patients with Alzheimer's disease (AD). Thirty-seven institutionalized elders (84.05 ± 5.58 years) clinically diagnosed with AD (mild and moderate stages) were divided into two groups: Experimental Group (EG, n = 19) and Control Group (CG, n = 18). The EG participated in a six-month supervised MT program (aerobic, muscular resistance, flexibility and postural exercises) of 45-55 minutes/session, twice/week. Cognitive function (MMSE), physical fitness (Senior Fitness Test) and anthropometric variables (Body Mass Index and Waist Circumference), were assessed before (M1), after three months (M2) and after six months (M3) of the experimental protocol. A two-way ANOVA, with repeated measures, revealed significant group and time interactions on cognitive function, chair stand, arm curl, 2-min step, 8-foot up-and-go (UG), chair sit-and-reach (CSR) and back scratch tests as well as waist circumference. Accordingly, for those variables a different response in each group was evident over the time, supported by a significantly better EG performance in chair stand, arm curl, 2-min step, UG, CSR and back scratch tests from M1 to M3, and a significant increase in MMSE from M1 to M2. The CG's performance decreased over time (M1 to M3) in chair stand, arm curl, 2-min step, UG, CSR, back scratch and MMSE. Results suggest that MT programs may be an important non-pharmacological strategy to improve physical and cognitive functions in institutionalized AD patients.

Grip Strength and Cognitive Abilities: Associations in Old Age

OBJECTIVES

Both physical functioning and cognitive abilities are important for well-being, not least in old age. Grip strength is often considered an indicator of general vitality and, as such, may predict cognitive functioning. Few longitudinal studies have examined the relationship between grip strength and cognition, especially where specific cognitive abilities have been targeted.

METHOD

Participants (n = 708, age range: 40-86 years at baseline) came from the population-based longitudinal Swedish Adoption/Twin Study of Aging. We used a longitudinal follow-up of 6 waves during 20 years. For the analyses, we used latent growth modeling, where latent growth trajectories were fitted to the cognitive traits (verbal ability, spatial ability, processing speed, and memory) or to the grip strength values and each, respectively, treated as time-varying covariates of the other trait.

RESULTS

Results supported a longitudinal influence of grip strength on changes in cognitive function. Grip strength performance was associated with change in the 4 cognitive abilities after age 65 years.

DISCUSSION

A rather stable connection was found between grip strength and cognitive abilities starting around 65 years of age. The starting period suggests that the association may be due to lifestyle changes, such as retirement, or to acceleration of the aging processes.

Obesity Reduces Cognitive and Motor Functions across the Lifespan

Due to a sedentary lifestyle, more and more people are becoming obese nowadays. In addition to health-related problems, obesity can also impair cognition and motor performance. Previous results have shown that obesity mainly affects cognition and motor behaviors through altering brain functions and musculoskeletal system, respectively. Many factors, such as insulin/leptin dysregulation and inflammation, mediate the effect of obesity and cognition and motor behaviors. Substantial evidence has suggested exercise to be an effective way to improve obesity and related cognitive and motor dysfunctions. This paper aims to discuss the association of obesity with cognition and motor behaviors and its underlying mechanisms. Following this, mechanisms of exercise to improve obesity-related dysfunctions are described. Finally, implications and future research direction are raised.

The interactive effects of age, education, and BMI on cognitive functioning

We examined the moderating effects of age and cognitive reserve on the relationship between body mass index (BMI) and processing speed, executive function, and working memory based on the literature suggesting that obese individuals perform more poorly on measures of these abilities. Fifty-six healthy, dementia-free community-dwelling older (mean age 65.72 ± 7.40) and younger (mean age 21.10 ± 2.33) adults completed a neuropsychological battery and reported height and weight. Mixed effects models were used to evaluate the interactive effects of age, education (a proxy for cognitive reserve), and BMI on cognitive scores. Higher education was protective for executive deficits in younger, but not older adults. Age differences in executive functions were reduced at higher education levels but increased in individuals with higher BMI. Results suggest the inter-relationships between cognitive reserve - as measured by education - and BMI differ across age, and that obesity may accelerate the cognitive aging process.

Body mass index and cognitive function: the potential for reverse causation

OBJECTIVE

Higher late life body mass index (BMI) is unrelated to or even predicts lower risk of dementia in late life, a phenomenon that may be explained by reverse causation due to weight loss during preclinical phases of dementia. We aim to investigate the association of baseline BMI and changes in BMI with dementia in a large prospective cohort, and to examine whether weight loss predicts cognitive function.

METHODS

Using a national cohort of adults average age 58 years at baseline in 1994 (n=7029), we investigated the associations between baseline BMI in 1994 and memory scores from 2000 to 2010. We also examined the association of BMI change from 1994 to 1998 with memory scores from 2000 to 2010. Last, to investigate reverse causation, we examined whether memory scores in 1996 predicted BMI trajectories from 2000 to 2010.

RESULTS

Baseline overweight predicted better memory scores 6 to 16 years later (β=0.012, 95% confidence interval (CI)=0.001; 0.023). Decline in BMI predicted lower memory scores over the subsequent 12 years (β=-0.026, 95% CI= -0.041; -0.011). Lower memory scores at mean age 60 years in 1996 predicted faster annual rate of BMI decline during follow-up (β=-0.158 kg m(-2) per year, 95% CI= -0.223; -0.094).

CONCLUSION

Consistent with reverse causation, greater decline in BMI over the first 4 years of the study was associated with lower memory scores over the next decade and lower memory scores was associated with a decline in BMI. These findings suggest that preclinical dementia predicts weight loss for people as early as their late 50s.

Diet-Induced Cognitive Deficits: The Role of Fat and Sugar, Potential Mechanisms and Nutritional Interventions

It is of vital importance to understand how the foods which are making us fat also act to impair cognition. In this review, we compare the effects of acute and chronic exposure to high-energy diets on cognition and examine the relative contributions of fat (saturated and polyunsaturated) and sugar to these deficits. Hippocampal-dependent memory appears to be particularly vulnerable to the effects of high-energy diets and these deficits can occur rapidly and prior to weight gain. More chronic diet exposure seems necessary however to impair other sorts of memory. Many potential mechanisms have been proposed to underlie diet-induced cognitive decline and we will focus on inflammation and the neurotrophic factor, brain-derived neurotrophic factor (BDNF). Finally, given supplementation of diets with omega-3 and curcumin has been shown to have positive effects on cognitive function in healthy ageing humans and in disease states, we will discuss how these nutritional interventions may attenuate diet-induced cognitive decline. We hope this approach will provide important insights into the causes of diet-induced cognitive deficits, and inform the development of novel therapeutics to prevent or ameliorate such memory impairments.

Testosterone deficiency, insulin-resistant obesity and cognitive function

Testosterone is an androgenic steroid hormone, which plays an important role in the regulation of male reproduction and behaviors, as well as in the maintenance of insulin sensitivity. Several studies showed that testosterone exerted beneficial effects in brain function, including preventing neuronal cell death, balancing brain oxidative stress and antioxidant activity, improving synaptic plasticity and involving cognitive formation. Although previous studies showed that testosterone deficiency is positively correlated with cognitive impairment and insulin-resistant obesity, several studies demonstrated contradictory findings. Thus, this review comprehensively summarizes the current evidence from in vitro, in vivo and clinical studies of the relationship between testosterone deficiency and insulin-resistant obesity as well as the correlation between either insulin-resistant obesity or testosterone deficiency and cognitive impairment. Controversial reports and the mechanistic insights regarding the roles of testosterone in insulin-resistant obesity and cognitive function are also presented and discussed.