Interactive effects of physical activity and APOE-ε4 on white matter tract diffusivity in healthy elders

Effects of Aging, Estimated Fitness, and Cerebrovascular Status on White Matter Microstructural Health

White matter (WM) microstructural health declines with increasing age, with evidence suggesting that improved cardiorespiratory fitness (CRF) may mitigate this decline. Specifically, higher fit older adults tend to show preserved WM microstructural integrity compared to their lower fit counterparts. However, the extent to which fitness and aging independently impact WM integrity across the adult lifespan is still an open question, as is the extent to which cerebrovascular health mediates these relationships. In a large sample (N = 125, aged 25-72), we assessed the impact of age and estimated cardiorespiratory fitness on fractional anisotropy (FA, derived using diffusion weighted imaging, dwMRI) and probed the mediating role of cerebrovascular health (derived using diffuse optical tomography of the cerebral arterial pulse, pulse-DOT) in these relationships. After orthogonalizing age and estimated fitness and computing a PCA on whole brain WM regions, we found several WM regions impacted by age that were independent from the regions impacted by estimated fitness (hindbrain areas, including brainstem and cerebellar tracts), whereas other areas showed interactive effects of age and estimated fitness (midline areas, including fornix and corpus callosum). Critically, cerebrovascular health mediated both relationships suggesting that vascular health plays a linking role between age, fitness, and brain health. Secondarily, we assessed potential sex differences in these relationships and found that, although females and males generally showed the same age-related FA declines, males exhibited somewhat steeper declines than females. Together, these results suggest that age and fitness impact specific WM regions and highlight the mediating role of cerebrovascular health in maintaining WM health across adulthood.

Associations between white matter hyperintensities and physical activity: A sectional study in UK Biobank participants

White matter hyperintensities (WMH) are key markers of cerebral small vessel disease (CSVD) linked to increased risks of stroke, dementia, and cognitive decline. Physical activity (PA) has been hypothesized to reduce WMH burden and preserve brain health, yet findings across studies remain mixed. This study examines the association between PA and WMH burden, as well as white matter integrity using diffusion tensor imaging (DTI) metrics, in a cohort of 10,868 participants from the UK Biobank. Participants were categorized into low, intermediate, and high PA tertiles based on accelerometer data. WMH volumes, normalized for head size, were classified into quintiles. Multilevel ordered logistic regression models revealed that high PA levels were significantly associated with reduced WMH burden (OR = 0.956, p = 0.026), while low PA levels increased the likelihood of higher WMH burden (OR = 1.148, p < 0.001). Subtype analyses indicated stronger associations between PA and periventricular WMH compared to deep WMH. Furthermore, DTI metrics demonstrated that higher PA levels were correlated with improved fractional anisotropy (FA) and reduced mean diffusivity (MD) in key white matter tracts, such as the corpus callosum and fornix, suggesting better white matter integrity. Our findings emphasize the potential neuroprotective effects of PA, particularly in mitigating WMH progression and preserving cognitive and motor functions. These results underscore the importance of promoting PA, especially in older adults, as a strategy to reduce the burden of CSVD and support brain health. Future longitudinal studies are needed to confirm causality and elucidate underlying mechanisms.

APOEε4 alters ApoE and Fabp7 in frontal cortex white matter in prodromal Alzheimer's disease

The ApoE ε4 allele (APOEε4) is a major genetic risk factor for sporadic Alzheimer's disease (AD) and is linked to demyelination and cognitive decline. However, its effects on the lipid transporters apolipoprotein E (ApoE) and fatty acid-binding protein 7 (Fabp7), which are crucial for the maintenance of myelin in white matter (WM) during the progression of AD remain underexplored. To evaluate the effects of APOEε4 on ApoE, Fabp7 and myelin in the WM of the frontal cortex (FC), we examined individuals carrying one ε4 allele that came to autopsy with a premortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI) and mild to moderate AD compared with non-carrier counterparts. ApoE, Fabp7 and Olig2 immunostaining was used to visualize cells, whereas myelin basic protein (MBP) immunocytochemistry and luxol fast blue (LFB) histochemistry of myelin in the WM of the FC were combined with quantitative morphometry. We observed increased numbers of ApoE-positive astrocytes in the WM of both NCI and MCI APOEε4 carriers compared with non-carriers, whereas Fabp7-positive cells were elevated only in AD. Conversely, Olig2 cell counts and MBP immunostaining decreased in MCI APOEε4 carriers compared to non-carriers, while LFB levels were higher in NCI APOEε4 carriers compared to non-carriers. Although no correlations were found between ApoE, Fabp7, and cognitive status, LFB measurements were positively correlated with perceptual speed, global cognition, and visuospatial scores in APOEε4 carriers across clinical groups. The present findings suggest that the ε4 allele compromises FC myelin homeostasis by disrupting the lipid transporters ApoE, Fabp7 and myelination early in the onset of AD. These data support targeting cellular components related to WM integrity as possible treatments for AD.

APOE4 and sedentary lifestyle synergistically impair neurovascular function in the visual cortex of awake mice

Reduced cerebral blood flow occurs early in the development of Alzheimer's disease (AD), but the factors producing this reduction are unknown. Here, we ask whether genetic and lifestyle risk factors for AD-the ε4 allele of the Apolipoprotein (APOE) gene, and physical activity-can together produce this reduction in cerebral blood flow which leads eventually to AD. Using in vivo two-photon microscopy and haemodynamic measures, we record neurovascular function from the visual cortex of physically active or sedentary mice expressing APOE3 and APOE4 in place of murine APOE. Energy supply and demand are mismatched in APOE4 mice, with smaller increases in cerebral blood flow, blood volume and blood oxygenation occurring during neuronal activation as blood vessels frequently fail to dilate. Exercise dose-dependently overall improves neurovascular function, with an increased impact of exercise apparent after longer exposure times. Several haemodynamic measures show a larger beneficial effect of exercise in APOE4 vs. APOE3 mice. Thus, APOE4 genotype in conjunction with sedentary behaviour produces the worst neurovascular function. Promotion of physical activity may therefore be particularly important to improve cerebrovascular function and reduce dementia risk in APOE4 carriers.

Environmental enrichment is associated with favorable memory-related functional brain activity patterns in older adults

Background

In humans, environmental enrichment (EE), as measured by the engagement in a variety of leisure activities, has been associated with larger hippocampal structure and better memory function. The present cross-sectional study assessed whether EE during early life (13-30 years) and midlife (30-65 years) is associated with better preserved memory-related brain activity patterns in older age.

Methods

In total, 372 cognitively unimpaired older adults (aged ≥60 years old) of the DZNE-Longitudinal Study on Cognitive Impairment and Dementia (DELCODE; DRKS00007966) were investigated. EE was operationalized using items of the Lifetime of Experiences Questionnaire (LEQ), which measures the self-reported participation in a variety of leisure activities in early life and midlife. The preservation of memory-related functional brain activity was assessed using single-value scores, which relate older adults' brain activity patterns in the temporo-parieto-occipital memory network to those of young adults during visual memory encoding (FADE and SAME scores).

Results

EE during early life and midlife was significantly associated with higher SAME scores during novelty processing (n = 372, β = 0.13, p = 0.011). Thus, older participants with higher EE showed greater similarity of functional brain activity patterns during novelty processing with young adults. This positive association was observed most strongly in participants with subjective cognitive decline (SCD, n = 199, β = 0.20, p = 0.006).

Conclusion

More frequent participation in a variety of leisure activities in early life and midlife is associated with more successful aging of functional brain activity patterns in the memory network of older adults, including participants at increased risk for dementia. Longitudinal studies are needed to clarify whether higher EE during life could help preserve memory network function in later life.

Adherence to Life's Essential 8 is associated with delayed white matter aging

Importance

The American Heart Association introduced Life's Essential 8 (LE8) as a checklist of healthy lifestyle factors to help older individuals maintain and improve cardiovascular health and live longer. How LE8 can foster healthy brain aging and interact with genetic risk factors to render the aging brain less vulnerable to dementia is not well understood.

Objective

To investigate the impact of LE8 on the white matter brain aging and the moderating effects of the APOE4 allele.

Design Setting and Participants

This cross-sectional study uses genetic, imaging, and other health-related data collected in the UK Biobank cohort. Participants included non-pregnant whites with LE8 variables, diffusion tensor imaging data, and genetic data on APOE4 available, and excluded the extreme white matter hyperintensities. The baseline assessment was performed from 2006 to 2010. The diffusion tensor imaging data were collected since 2014.

Exposures

LE8 variables, encompassing diet, physical activity, smoking, sleep, body mass index, lipids, hemoglobin, and blood pressure.

Main Outcomes and Measures

The white matter brain age was predicted from regional fractional anisotropy measures derived from diffusion tensor imaging data using the random forest regression method. The outcome white matter brain age gap was calculated by subtracting individuals' chronological age from their predicted brain age.

Results

The analysis included 9,430 women and 9,387 men (mean age 55.45 [SD: 7.46] years). Higher LE8 scores were associated with lower white matter brain age gap, indicating delayed brain aging. The findings are consistent for each of the individual LE8 variables. The effect was stronger among non- APOE4 carriers (124 days younger per 10-point increase, 95% CI, 102 to 146 days; P<0.001) than APOE4 carriers (84 days younger per 10-point increase, 95% CI, 47 to 120 days; P<0.001). Notably, early middle-aged women with APOE4 showed significant interactions between LE8 scores and brain aging (P interaction = 0.048), not observed in men.

Conclusions and Relevance

Adherence to LE8 is associated with delayed brain aging, moderated by genetic factors such as APOE4 . These findings highlight the potential of behavioral and lifestyle interventions in reducing dementia risk, emphasizing tailored prevention plans for those with different genetic predispositions to dementia and sex.

Physical Exercise Counteracts Aging-Associated White Matter Demyelination Causing Cognitive Decline

In the central nervous system, oligodendrocytes wrap around neuronal axons to form myelin, an insulating layer or sheath that allows for the efficient conductance of action potentials. In addition to structural insulation, myelin provides encased axons with nutrient, metabolic and defensive support. Demyelination, or myelin loss, can therefore cause axonal dysfunction, leading to neurological impairment and disease. In Alzheimer's disease (AD), progressive white matter demyelination is acknowledged as one of the earliest pathologies preceding symptom onset. Unfortunately, current pharmacotherapy for slowing demyelination or promoting remyelination in AD is nonexistent. Exercise is recognized for its wide-ranging benefits to human health, including improved mental health and the prevention of lifestyle-related diseases. Mounting evidence suggests the contribution of physical activity in delaying the progression of dementia in elderly populations. Recent mechanistic studies have shown that exercise facilitates myelination in the brain through the vitalization of intrinsic pro-myelination cues, such as increased neurotrophic factors and electrical activity. In this review, we summarize and discuss the potential of physical exercise on counteracting aging-associated white matter demyelination, which causes cognitive decline in AD. We highlight the need of further basic and clinical research investigations on this topic to establish novel approaches for healthy and improved brain aging.

Effects of Aging, Fitness, and Cerebrovascular Status on White Matter Microstructural Health

White matter (WM) microstructural health declines with increasing age, with evidence suggesting that improved cardiorespiratory fitness (CRF) may mitigate this decline. Specifically, higher fit older adults tend to show preserved WM microstructural integrity compared to their lower fit counterparts. However, the extent to which fitness and aging independently impact WM integrity across the adult lifespan is still an open question, as is the extent to which cerebrovascular health mediates these relationships. In a large sample (N = 125, aged 25-72), we assessed the impact of age and fitness on fractional anisotropy (FA, derived using diffusion weighted imaging, DWI) and probed the mediating role of cerebrovascular health (derived using diffuse optical tomography of the cerebral arterial pulse, pulse-DOT) in these relationships. After orthogonalizing age and fitness and computing a PCA on whole brain WM regions, we found several WM regions impacted by age that were independent from the regions impacted by fitness (hindbrain areas, including brainstem and cerebellar tracts), whereas other areas showed interactive effects of age and fitness (midline areas, including fornix and corpus callosum). Critically, cerebrovascular health mediated both relationships suggesting that vascular health plays a linking role between age, fitness, and brain health. Secondarily, we assessed potential sex differences in these relationships and found that, although females and males generally showed the same age-related FA declines, males exhibited somewhat steeper declines than females. Together, these results suggest that age and fitness impact specific WM regions and highlight the mediating role of cerebrovascular health in maintaining WM health across adulthood.

Estimating the effect of physical activity on cognitive function within the UK Biobank cohort

BACKGROUND

Physical activity (PA) has been associated with benefits for cognitive function (CF), but previous estimates of the strength of this relationship may have been biased due to limitations in statistical modelling practices that are common among observational studies. We aimed to address this by using a rigorously constructed conceptual causal model to guide an empirical analysis estimating the effect of PA on CF in the UK Biobank cohort of middle-aged and older adults.

METHODS

This study analysed a subsample of 334 227 adults from the UK Biobank prospective cohort study. PA was measured subjectively by self-report and by device using accelerometry, and CF was measured using objective cognitive tests. Composite CF measures were derived to represent general and domain-specific performance. Effect coefficients were estimated using regression models, adjusting for a wide range of confounders specified by the assumed causal model, including genetic risk factors, and relevant health, sociodemographic and behavioural variables from across the lifespan.

RESULTS

Results indicated very small effect sizes (standardized mean difference estimates all <0.01) of inconsistent direction, for both cross-sectional and longitudinal analyses.

CONCLUSIONS

The expected protective effect of PA on CF was not observed. This may reflect selection bias within UK Biobank, or the relatively young age of the sample at follow-up.

Associations of cardiorespiratory fitness and exercise with brain white matter in healthy adults: A systematic review and meta-analysis

Magnetic resonance imaging (MRI) studies have revealed positive associations between brain structure and physical activity, cardiorespiratory fitness, and exercise (referred to here as PACE). While a considerable body of research has investigated the effects of PACE on grey matter, much less is known about effects on white matter (WM). Hence, we conducted a systematic review of peer-reviewed literature published prior to 5^th July 2021 using online databases (PubMed and Scopus) and PRISMA guidelines to synthesise what is currently known about the relationship between PACE and WM in healthy adults. A total of 60 studies met inclusion criteria and were included in the review. Heterogeneity across studies was calculated using Qochran's q test, and publication bias was assessed for each meta-analysis using Begg and Mazumdar rank correlation test. A meta-regression was also conducted to explore factors contributing to any observed heterogeneity. Overall, we observed evidence of positive associations between PACE and global WM volume (effect size (Hedges's g) = 0.137, p < 0.001), global WM anomalies (effect size = 0.182, p < 0.001), and local microstructure integrity (i.e., corpus callosum: effect size = 0.345, p < 0.001, and anterior limb of internal capsule: effect size = 0.198, p < 0.001). These findings suggest that higher levels of PACE are associated with improved global WM volume and local integrity. We appraise the quality of evidence, and discuss the implications of these findings for the preservation of WM across the lifespan. We conclude by providing recommendations for future research in order to advance our understanding of the specific PACE parameters and neurobiological mechanisms underlying these effects.

Gradient Patterns of Age-Related Diffusivity Changes in Cerebral White Matter

The current concept of brain aging proposes three gradient patterns of changes in white matter that occur during healthy brain aging: antero-posterior, supero-inferior, and the myelodegeneration-retrogenesis (or the “last-in-first-out”) concept. The aim of this study was to correlate white matter diffusivity measures (fractional anisotropy-FA, mean diffusivity-MD, radial diffusivity-RD, and axial diffusivity-AD) in healthy volunteers with chronological age and education level, in order to potentially incorporate the findings with proposed patterns of physiological brain aging. The study was performed on 75 healthy participants of both sexes, with an average age of 37.32 ± 11.91 years underwent brain magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI). DTI was performed using tract-based spatial statistics (TBSS), with the analysis of four parameters: FA, MD, RD, and AD. Skeletonized measures were averaged in 29 regions of interest in white matter. Correlations between age and DTI measures and between education-level and DTI measures were performed using Pearson's correlation test. To correct for multiple comparisons, we applied a Bonferroni correction to the p-values. Significance was set at p ≤ 0.001. A significant negative correlation of FA with age was observed in posterior thalamic radiation (PTR) (p< 0.001). A significant positive correlation between age and MD was observed in sagittal stratum (SS) (p< 0.001), between age and RD in PTR, SS, and retrolenticular internal capsule (p< 0.001), and between age and AD in the body of the corpus callosum (p< 0.001). There were no significant correlations of DTI parameters with educational level. According to our study, RD showed the richest correlations with age, out of all DTI metrics. FA, MD, and RD showed significant changes in the diffusivity of projection fibers, while AD presented diffusivity changes in the commissural fibers. The observed heterogeneity in diffusivity changes across the brain cannot be explained by a single aging gradient pattern, since it seems that different patterns of degradation are true for different fiber tracts that no currently available theory can globally explain age-related changes in the brain. Additional factors, such as the effect of somatosensory decline, should be included as one of the important covariables to the existing patterns.

Neurite dispersion and density mediates the relationship between cardiorespiratory fitness and cognition in healthy younger adults

Growing evidence suggests physical activity and cardiorespiratory fitness are associated with better cognition across the lifespan. However, the neurobiological underpinnings relating fitness and cognition remain unclear, particularly in healthy younger adults. Using a well-established and popular multi-compartment diffusion modeling approach, called Neurite Orientation and Dispersion and Density Imaging (NODDI), we investigated the relationship between physical fitness (measured via a 2-min walk test), cognition (fluid and crystallized), and gray and white matter microstructure, in a large sample (n = 816) of healthy younger adults (ages 22-35 years) from the human connectome project (HCP). Concurrent with previous literature, we found that fitness was positively associated with both fluid and crystallized cognition. Furthermore, we found that physical fitness was negatively associated with white matter orientation dispersion index (ODIWM) around the cerebellar peduncle and was negatively associated with widespread cortical and subcortical gray matter neurite density index (NDIGM). Lower ODIWM of the cerebral peduncle was associated with better fluid cognitive performance, while lower NDIGM was associated with better crystallized cognition. Finally, we found that while ODIWM partially mediated the relationship between fitness and fluid cognition, NDIGM partially mediated the relationship between fitness and crystallized cognition. This study is the first to explore the relationship between physical fitness and white and gray matter microstructure measures using NODDI. Our findings suggest that in addition to improved cognitive performance, higher physical fitness may be associated with lower white matter tract dispersion and lower neurite density in the cortical and subcortical gray matter of healthy younger adults.

Vigorous Physical Activity and Cognitive Trajectory Later in Life: Prospective Association and Interaction by Apolipoprotein E e4 in the Nurses' Health Study

BACKGROUND

The apolipoprotein E (APOE) e4 allele is a well-established genetic risk factor of brain aging. Vigorous physical activity may be particularly important in APOE-e4 carriers, but data have been inconsistent, likely due to differences in the timing of the physical activity assessment, definition of cognitive decline, and/or sample size.

METHODS

We prospectively evaluated the association between vigorous physical activity and cognition assessed at least 9 years later, according to APOE-e4 carrier status. Biennially from 1986, Nurses' Health Study participants reported their leisure-time physical activities. Starting in 1995-2001 and through 2008, participants (aged 70+ years) underwent up to 4 repeated cognitive telephone assessments (6 tasks averaged together using z-scores).

RESULTS

Among 7252 women, latent process mixed models identified 3 major patterns of cognitive change over 6 years: high-stable, medium-stable, and decline. Taking the high-stable cognitive trajectory as the outcome reference in multinomial logistic regressions, highest tertile of vigorous physical activity (≥5.9 metabolic-equivalent [MET]-hours/wk) compared to lowest tertile (≤0.9 MET-hours/wk) was significantly associated with subsequent lower likelihood of the medium-stable trajectory in the global score (odds ratio [OR] [95% CI] = 0.72 [0.63, 0.82]), verbal memory (OR [95% CI] = 0.78 [0.68-0.89]), and telephone interview of cognitive status score (OR [95% CI] = 0.81 [0.70-0.94]). Vigorous physical activity was also associated with lower likelihood of decline in category fluency (OR [95% CI] = 0.72 [0.56, 0.92]). We observed some evidence (p-interaction = .07 for the global score) that the association was stronger among APOE-e4 carriers than noncarriers (OR [95% CI] = 0.60 [0.39, 0.92] vs 0.82 [0.59, 1.16]).

CONCLUSION

Midlife vigorous physical activity was associated with better cognitive trajectories in women in their seventies, with suggestions of stronger associations among APOE-e4 carriers.

Apolipoprotein E Genotype Moderation of the Association Between Physical Activity and Brain Health. A Systematic Review and Meta-Analysis

Introduction

Possession of one or two e4 alleles of the apolipoprotein E (APOE) gene is associated with cognitive decline and dementia risk. Some evidence suggests that physical activity may benefit carriers of the e4 allele differently.

Method

We conducted a systematic review and meta-analysis of studies which assessed APOE differences in the association between physical activity and: lipid profile, Alzheimer's disease pathology, brain structure and brain function in healthy adults. Searches were carried out in PubMed, SCOPUS, Web of Science and PsycInfo.

Results

Thirty studies were included from 4,896 papers screened. Carriers of the e4 allele gained the same benefit from physical activity as non-carriers on most outcomes. For brain activation, e4 carriers appeared to gain a greater benefit from physical activity on task-related and resting-state activation and resting-state functional connectivity compared to non-carriers. Post-hoc analysis identified possible compensatory mechanisms allowing e4 carriers to maintain cognitive function.

Discussion

Though there is evidence suggesting physical activity may benefit e4 carriers differently compared to non-carriers, this may vary by the specific brain health outcome, perhaps limited to brain activation. Further research is required to confirm these findings and elucidate the mechanisms.

Sex-Specific Patterns of Body Mass Index Relationship with White Matter Connectivity

BACKGROUND

Obesity is an increasingly recognized modifiable risk factor for Alzheimer's disease (AD). Increased body mass index (BMI) is related to distinct changes in white matter (WM) fiber density and connectivity.

OBJECTIVE

We investigated whether sex differentially affects the relationship between BMI and WM structural connectivity.

METHODS

A cross-sectional sample of 231 cognitively normal participants were enrolled from the Knight Alzheimer Disease Research Center. Connectome analyses were done with diffusion data reconstructed using q-space diffeomorphic reconstruction to obtain the spin distribution function and tracts were selected using a deterministic fiber tracking algorithm.

RESULTS

We identified an inverse relationship between higher BMI and lower connectivity in the associational fibers of the temporal lobe in overweight and obese men. Normal to overweight women showed a significant positive association between BMI and connectivity in a wide array of WM fibers, an association that reversed in obese and morbidly obese women. Interaction analyses revealed that with increasing BMI, women showed higher WM connectivity in the bilateral frontoparietal and parahippocampal parts of the cingulum, while men showed lower connectivity in right sided corticostriatal and corticopontine tracts. Subgroup analyses demonstrated comparable results in participants with and without positron emission tomography or cerebrospinal fluid evidence of brain amyloidosis, indicating that the relationship between BMI and structural connectivity in men and women is independent of AD biomarker status.

CONCLUSION

BMI influences structural connectivity of WM differently in men and women across BMI categories and this relationship does not vary as a function of preclinical AD.

Evidence for exercise-related plasticity in functional and structural neural network connectivity

The number of studies investigating exercise and cardiorespiratory fitness (CRF)-related changes in the functional and structural organization of brain networks continues to rise. Functional and structural connectivity are critical biomarkers for brain health and many exercise-related benefits on the brain are better represented by network dynamics. Here, we reviewed the neuroimaging literature to better understand how exercise or CRF may facilitate and maintain the efficiency and integrity of functional and structural aspects of brain networks in both younger and older adults. Converging evidence suggests that increased exercise performance and CRF modulate functional connectivity of the brain in a way that corresponds to behavioral changes such as cognitive and motor performance improvements. Similarly, greater physical activity levels and CRF are associated with better cognitive and motor function, which may be brought about by enhanced structural network integrity. This review will provide a comprehensive understanding of trends in exercise-network studies as well as future directions based on the gaps in knowledge that are currently present in the literature.

Cross-sectional and longitudinal interaction effects of physical activity and APOE-ε4 on white matter integrity in older adults: The MAPT study

BACKGROUND

Physical activity (PA) has been shown to modulate the detrimental effect of carrying the apolipoprotein-E epsilon 4 (APOE-ɛ4) allele on brain structure. However, the current literature mainly provides cross-sectional data, and longitudinal studies investigating the interaction between genotype and PA on white matter (WM) integrity are lacking.

OBJECTIVES

We investigated both the cross-sectional and the longitudinal interactive effects of APOE-ɛ4 and PA on WM integrity in older adults.

METHODS

Fractional anisotropy, as well as axial, radial, and mean diffusivity, extracted from brain diffusion tensor imaging (DTI) were used to assess WM integrity in non-demented older adults. They were categorized according to their APOE-ɛ4 status (carriers vs. non-carriers), and their level of total (TPA), moderate to vigorous (MVPA) and light (LPA) PA were assessed using a questionnaire. Mixed model regressions were performed to test the interactive effects of APOE-ɛ4 status and PA on WM integrity at baseline and over a 3-year follow-up.

RESULTS

190 subjects with a mean age 74.5 years (SD = 3.9) were examined. Despite a lack of cross-sectional associations, sensitivity analyses revealed that, in the carrier group only, higher levels of LPA, but not MVPA, were mainly associated with higher axial and mean diffusivity values over time.

CONCLUSIONS

This study partially confirms the previously reported interactive associations between PA, APOE-ɛ4 genotype and WM integrity, supporting the hypothesis that PA may protect against fiber loss in WM tracts containing crossing fibers. Future studies assessing sedentary behaviors in addition to PA could bring relevant contributions to the field. CLINICAL TRIAL REGISTRATION NUMBER FROM CLINICALTRIALS.GOV: NCT00672685.

APOE Genotype and Alzheimer's Disease: The Influence of Lifestyle and Environmental Factors

Alzheimer's disease (AD) is the most common neurodegenerative disorder with obscure pathogenesis and no disease-modifying therapy to date. AD is multifactorial disease that develops from the complex interplay of genetic factors and environmental exposures. The E4 allele of the gene encoding apolipoprotein E (APOE) is the most common genetic risk factor for AD, whereas the E2 allele acts in a protective manner. A growing amount of epidemiological evidence suggests that several lifestyle habits and environmental factors may interact with APOE alleles to synergistically affect the risk of AD development. Among them, physical exercise, dietary habits including fat intake and ketogenic diet, higher education, traumatic brain injury, cigarette smoking, coffee consumption, alcohol intake, and exposure to pesticides and sunlight have gained increasing attention. Although the current evidence is inconsistent, it seems that younger APOE4 carriers in preclinical stages may benefit mostly from preventive lifestyle interventions, whereas older APOE4 noncarriers with dementia may show the most pronounced effects. The large discrepancies between the epidemiological studies may be attributed to differences in the sample sizes, the demographic characteristics of the participants, including age and sex, the methodological design, and potential related exposures and comorbidities as possible cofounding factors. In this Review, we aim to discuss available evidence of the prominent APOE genotype-environment interactions in regard to cognitive decline with a focus on AD, providing an overview of the current landscape in this field and suggesting future directions.

Effects of physical activity on brain function and structure in older adults: A systematic review

Despite increasing evidence that physical activity (PA) contributes to brain health in older individuals, both at the level of brain structure and function, this relationship is not yet well established. To explore this potential association, a systematic literature search was performed using PubMed, Scopus, and Web of Science, adhering to PRISMA guidelines. A total of 32 studies met the eligibility criteria: 24 cross-sectional and 8 longitudinal. Results from structural Magnetic Resonance Imaging (MRI) showed that PA associated with larger brain volumes (less brain atrophy) specifically in brain regions vulnerable to dementia, comprising the hippocampus, temporal, and frontal regions. Furthermore, functional MRI (fMRI) showed greater task-relevant activity in brain areas recruited in executive function and memory tasks. However, the dose-response relationship is unclear due to the high variability in PA measures. Further research using objective measures is needed to better understand which PA type, intensity, frequency, and duration, has the greatest protective effect on brain health. Findings highlight the importance of PA in both cognitive decline and dementia prevention.

Interaction between physical exercise and APOE gene polymorphism on cognitive function in older people

We aimed to present an overview of the literature regarding the interaction between physical exercise and APOE gene polymorphism on cognitive function, particularly in patients with Alzheimer's disease (AD). Firstly, this review focused on the effect of the physical exercise on cognitive function, regardless of APOE gene polymorphism. Some studies have shown that a high level of cardiorespiratory fitness is associated with less neuronal damage with an improvement in memory score tests whereas other studies failed to detect any association between physical exercise and cognitive improvement either in healthy individuals or patients with AD. Taken together, standardized protocols and more longitudinal studies are required to provide a better insight into the effects of physical exercise on cognitive function. Although there is no agreement in the literature regarding the effects of physical exercise on cognitive function, it is well established that it improves social interaction and the feeling of well-being, thereby positively contributing to the quality of life of the elderly. Regarding the influence of physical exercise on cognitive function in APOE ε4 allele carriers, the data trend shows that the carriers of allele ε4 for APOE gene were more responsive to the beneficial effects of physical exercise on cognitive function compared with non-carriers. Nevertheless, studies with larger sample sizes will provide more accuracy about this relationship.

Does APOE genotype moderate the relationship between physical activity, brain health and dementia risk? A systematic review

INTRODUCTION

For decades, researchers have tried to understand the moderating effect of APOE ε4 carriage on the relationship between physical activity (PA), brain health and dementia risk. However, this field has produced inconsistent findings.

METHOD

We conducted a systematic review of the literature, searching for observational and interventional studies examining the effect of APOE ε4 carriage on the relationships between PA, dementia risk and different markers of brain health.

RESULTS

Observational studies using dementia risk as a primary outcome measure generally found that in shorter follow-up periods (up to 10 years) both APOE ε4 carriers and non-carriers benefit from PA, although longer follow-ups showed mixed results. In neuroimaging studies, mainly carriers or both groups showed benefits. Additionally, the association between PA and amyloid burden was more evident among carriers. Overall, studies with greater samples of active APOE ε4 carriers are more likely to report benefits within this group in terms of lower dementia risk and reduced brain pathology.

DISCUSSION

Although we have identified some patterns for the modulating effect of APOE ε4 on PA and dementia or brain pathology, the available data is, overall, inconclusive. Heterogeneity in study design, methodology, and outcomes blur the ability to detect clear associations.

Imaging Alzheimer's genetic risk using diffusion MRI: A systematic review

Diffusion magnetic resonance imaging (dMRI) is an imaging technique which probes the random motion of water molecules in tissues and has been widely applied to investigate changes in white matter microstructure in Alzheimer's Disease. This paper aims to systematically review studies that examined the effect of Alzheimer's risk genes on white matter microstructure. We assimilated findings from 37 studies and reviewed their diffusion pre-processing and analysis methods. Most studies estimate the diffusion tensor (DT) and compare derived quantitative measures such as fractional anisotropy and mean diffusivity between groups. Those with increased AD genetic risk are associated with reduced anisotropy and increased diffusivity across the brain, most notably the temporal and frontal lobes, cingulum and corpus callosum. Structural abnormalities are most evident amongst those with established Alzheimer's Disease. Recent studies employ signal representations and analysis frameworks beyond DT MRI but show that dMRI overall lacks specificity to disease pathology. However, as the field advances, these techniques may prove useful in pre-symptomatic diagnosis or staging of Alzheimer's disease.

Effects of Physical Activity on Brain Energy Biomarkers in Alzheimer's Diseases

The prevalence of dementia has substantially increased worldwide. Currently, there is no cure for dementia or Alzheimer’s disease (AD), and care for affected patients is financially and psychologically costly. Of late, more attention has been given to preventive interventions—in particular, physical activity/exercise. In this review, examine the risk factors associated with AD and the effects physical activity may play in the prevention of the degenerative process of this disease, loss of memory and cognitive performance in the elderly. To date, research has shown that physical activity, especially aerobic exercise, has a protective effect on cognitive function and memory in the elderly and Alzheimer’s patients. In comparison with aerobic exercise, several strength training studies have also shown positive effects, and the rare studies that compare the two different modalities show no difference.

White Matter Tract Integrity, Involvement in Sports, and Depressive Symptoms in Children

White matter tract integrity, measured via fractional anisotropy (FA), may serve as a mediating variable between exercise and depression. To study this, we examined data from 3973 children participating in the ABCD study. Parents of children completed the Sports and Activities questionnaire and the Child Behavior Checklist, and children completed a diffusion MRI scan, providing information about the FA of the parahippocampal cingulum and fornix. Results showed that involvement in sports was associated with reduced depression in boys. The number of activities and sports that a child was involved in was negatively related to FA of the left fornix but was unrelated to FA of other tracts. FA of these white matter tracts was also unrelated to depressive symptoms. This suggests that while white matter tract integrity is associated with exercise, it may not be part of a pathway linking exercise to depression levels in preadolescent boys.

Effects of low- and high-intensity physical exercise on physical and cognitive function in older persons with dementia: a randomized controlled trial

BACKGROUND

Potential moderators such as exercise intensity or apolipoprotein-E4 (ApoE4) carriership may determine the magnitude of exercise effects on physical and cognitive functions in patients with dementia (PwD). We determined the effects of a 24-week aerobic and strength training program with a low- and high-intensity phase on physical and cognitive function.

METHODS

In an assessor-blinded randomized trial, 91 PwD (all-cause dementia, recruited from daycare and residential care facilities, age 82.3 ± 7.0 years, 59 women, Mini-Mental State Examination 20.2 ± 4.4) were allocated to the exercise or control group. In the exercise group, PwD participated in a walking and lower limb strength training program with 12 weeks low- and 12 weeks high-intensity training offered three times/week. Attention-matched control participants performed flexibility exercises and recreational activities. We assessed adherence, compliance, and exercise intensity for each session. We assessed physical (endurance, gait speed, mobility, balance, leg strength) and cognitive (verbal memory, visual memory, executive function, inhibitory control, psychomotor speed) functions with performance-based tests at baseline and after 6, 12, 18, 24, and 36 weeks (follow-up). ApoE4 carriership was determined post-intervention.

RESULTS

Sixty-nine PwD were analyzed. Their mean attendance was ~ 60% during the study period. There were no significant effects of the exercise vs. control intervention on endurance, mobility, balance, and leg strength in favor of the exercise group (Cohen's d = 0.13-0.18). Gait speed significantly improved with ~ 0.05 m/s after the high-intensity phase for exercise participants (Cohen's d = 0.41) but declined at follow-up. There were no significant effects of the exercise vs. control intervention on any of the cognitive measures (Cohen's d ~ - 0.04). ApoE4 carriership did not significantly moderate exercise effects on physical or cognitive function.

CONCLUSIONS

Exercise was superior to control activities for gait speed in our sample of PwD. However, the training effect provided no protection for mobility loss after detraining (follow-up). There were no beneficial effects of the exercise vs. control group on cognitive function. Exercise intensity moderated the effects of exercise on gait speed. ApoE4 carriership moderated the effect of exercise on global cognition only (trend level).

TRIAL REGISTRATION

Netherlands Trial Register, NTR5035. Registered on 2 March 2015.

Prevention of dementia presents a potentially critical platform for improvement of long-term public health

With the aging of the population, Alzheimer disease (AD) has become an epidemic and a major public health threat. Hundreds of molecules tested in clinical trials in the last decade to treat AD have failed, moving the field to examine the clinical and neurobiological value of prevention of cognitive decline and AD. This short review describes recently finished or currently ongoing clinical trials for prevention of AD, both their main outcomes and secondary outcomes. In addition, the potential modifying effects of age and of genetics as important factors that may affect the design of future clinical trials is discussed. Finally, we discuss the development of new molecular imaging and of digital technologies as a means to disclosure of dementia-related risk and disease progress, and their potential importance as contributors to adherence to healthy lifestyle for the prevention or delay of AD onset.

Mid age APOE ε4 carriers show memory-related functional differences and disrupted structure-function relationships in hippocampal regions

Carriers of the APOE e4 allele are at higher risk of age-related cognitive decline and Alzheimer’s disease (AD). The underlying neural mechanisms are uncertain, but genotype differences in medial temporal lobe (MTL) functional activity and structure at mid-age might contribute. We tested 16 non-e4 and 16 e4 carriers (aged 45–55) on a subsequent memory task in conjunction with MRI to assess how hippocampal volume (from T1 structural) and microstructure (neurite orientation-dispersion, from NODDI) differs by genotype and in relation to memory encoding. No previous study has investigated APOE effects on hippocampal microstructure using NODDI. Recall performance did not differ by genotype. A genotype by condition interaction in left parahippocampus indicated that in e4 carriers activity did not differentiate subsequently remembered from forgotten words. Hippocampal volumes and microstructure also did not differ by genotype but hippocampal volumes correlated positively with recognition performance in non-e4 carriers only. Similarly, greater hippocampal neurite orientation-dispersion was linked to better recall but only in non-e4s. Thus, we suggest that mid-age e4 carriers show a breakdown of normal MTL activation and structure-performance relationships. This could reflect an inability to utilise compensatory mechanisms, and contribute to higher risk of cognitive decline and AD in later life.

The association between physical fitness parameters and white matter microstructure in older adults: A diffusion tensor imaging study

The present study was designed to examine whether different measures of physical fitness are differentially associated with white matter (WM) microstructure in older adults. Fifty-six healthy adults (mean age: 59.14 years) completed a standardized evaluation of physical fitness measurements (e.g., VO_2peak , push-ups, abdominal sit-ups, sit-and-reach, t test, and vertical jump). Fractional anisotropy (FA), an index of WM microstructure, was assessed using diffusion tensor imaging. The findings indicated that the cardiorespiratory fitness was positively associated with FA in the right cingulum hippocampus and the left cerebral peduncle. However, other physical fitness metrics were not significantly associated with FA in any region. These results suggest that cardiorespiratory fitness, but not other metrics of fitness, might be sensitive to WM microstructure.

Exercise ameliorates deficits in neural microstructure in a Disc1 model of psychiatric illness

Recent studies have investigated the effectiveness of aerobic exercise to improve physical and mental health outcomes in schizophrenia; however, few have explicitly explored the impact of aerobic exercise on neural microstructure, which is hypothesized to mediate the behavioral changes observed. Neural microstructure is influenced by numerous genetic factors including DISC1, which is a major molecular scaffold protein that interacts with partners like GSK3β, NDEL1, and PDE4. DISC1 has been shown to play a role in neurogenesis, neuronal migration, neuronal maturation, and synaptic signaling. As with other genetic variants that present an increased risk for disease, mutations of the DISC1 gene have been implicated in the molecular intersection of schizophrenia and numerous other major psychiatric illnesses. This study investigated whether short-term exercise recovers deficits in neural microstructure in a novel genetic Disc1 svΔ2 rat model. Disc1 svΔ2 animals and age- and sex-matched controls were subjected to a treadmill exercise protocol. Subsequent ex-vivo diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) compared neural microstructure in regions of interest (ROI) between sedentary and exercise wild-type animals and between sedentary and exercise Disc1 svΔ2 animals. Short-term exercise uncovered no significant differences in neural microstructure between sedentary and exercise control animals but did lead to significant differences between sedentary and exercise Disc1 svΔ2 animals in neocortex, basal ganglia, corpus callosum, and external capsule, suggesting a positive benefit derived from a short-term exercise regimen. Our findings suggest that Disc1 svΔ2 animals are more sensitive to the effects of short-term exercise and highlight the ameliorating potential of positive treatment interventions such as exercise on neural microstructure in genetic backgrounds of psychiatric disease susceptibility.

Associations between modifiable risk factors and white matter of the aging brain: insights from diffusion tensor imaging studies

There is increasing interest in factors that may modulate white matter (WM) breakdown and, consequentially, age-related cognitive and behavioral deficits. Recent diffusion tensor imaging studies have examined the relationship of such factors with WM microstructure. This review summarizes the evidence regarding the relationship between WM microstructure and recognized modifiable factors, including hearing loss, hypertension, diabetes, obesity, smoking, depressive symptoms, physical (in) activity, and social isolation, as well as sleep disturbances, diet, cognitive training, and meditation. Current cross-sectional evidence suggests a clear link between loss of WM integrity (lower fractional anisotropy and higher mean diffusivity) and hypertension, obesity, diabetes, and smoking; a relationship that seems to hold for hearing loss, social isolation, depressive symptoms, and sleep disturbances. Physical activity, cognitive training, diet, and meditation, on the other hand, may protect WM with aging. Preliminary evidence from cross-sectional studies of treated risk factors suggests that modification of factors could slow down negative effects on WM microstructure. Careful intervention studies are needed for this literature to contribute to public health initiatives going forward.

A prospective study of focal brain atrophy, mobility and fitness

BACKGROUND

The parallel decline of mobility and cognition with ageing is explained in part by shared brain structural changes that are related to fitness. However, the temporal sequence between fitness, brain structural changes and mobility loss has not been fully evaluated.

METHODS

Participants were from the Baltimore Longitudinal Study of Aging, aged 60 or older, initially free of cognitive and mobility impairments, with repeated measures of fitness (400-m time), mobility (6-m gait speed) and neuroimaging markers over 4 years (n = 332). Neuroimaging markers included volumes of total brain, ventricles, frontal, parietal, temporal and subcortical motor areas, and corpus callosum. Autoregressive models were used to examine the temporal sequence of each brain volume with mobility and fitness, adjusted for age, sex, race, body mass index, height, education, intracranial volume and APOE ɛ4 status.

RESULTS

After adjustment, greater volumes of total brain and selected frontal, parietal and temporal areas, and corpus callosum were unidirectionally associated with future faster gait speed over and beyond cross-sectional and autoregressive associations. There were trends towards faster gait speed being associated with future greater hippocampus and precuneus. Higher fitness was unidirectionally associated with future greater parahippocampal gyrus and not with volumes in other areas. Smaller ventricle predicted future higher fitness.

CONCLUSION

Specific regional brain volumes predict future mobility impairment. Impaired mobility is a risk factor for future atrophy of hippocampus and precuneus. Maintaining fitness preserves parahippocampal gyrus volume. Findings provide new insight into the complex and bidirectional relationship between the parallel decline of mobility and cognition often observed in older persons.

Physical activity mitigates adverse effect of metabolic syndrome on vessels and brain

Metabolic syndrome (MetS) adversely affects the vasculature and cerebral white matter (CWM) integrity. Arterial stiffening has been associated with diminished CWM integrity. Physical activity (PA) can ameliorate components of MetS and subsequently affect arterial stiffening and CWM integrity. Our aim was to determine the role of PA on mitigating the adverse influence of MetS on arterial stiffness and CWM integrity. In a cross-sectional study design, sixty-six middle-aged adults (40-62 years) composed of 18 sedentary MetS (Sed MetS), 21 physically active MetS (Active MetS), and 27 healthy individuals absent of MetS risk factors were studied. Carotid artery stiffness was assessed via simultaneous ultrasound and tonometry. CWM integrity was measured using diffusion tensor imaging (DTI) through metrics of fractional anisotropy (FA) and mean diffusivity (MD). Carotid β-stiffness index in Active MetS was lower than Sed MetS but was not different from Healthy controls (6.6 ± 1.5, 7.7 ± 2.1, and 5.6 ± 1.6 au, p = 0.001). CWM integrity was significantly greater in Active MetS subjects compared to Sed MetS subjects but statistically equal to Healthy controls in the anterior limb of the internal capsule, and splenium of the corpus callosum, uncinate fasciculus, and superior corona radiata (all p < 0.05). Middle-aged individuals with MetS who habitually perform PA demonstrated lower arterial stiffness and more favorable CWM integrity than their sedentary peers, indicating that PA may be effective in mitigating the adverse effects of MetS on the vasculature and brain at midlife.

Effects of Physical Exercise on Alzheimer's Disease Biomarkers: A Systematic Review of Intervention Studies

Physical exercise may be an important adjunct to pharmacological treatment of Alzheimer's disease (AD). Animal studies indicate that exercise may be disease modifying through several mechanisms including reduction of AD pathology. We carried out a systematic review of intervention studies of physical exercise with hippocampal volume (on MRI), amyloid-β, total tau, phosphorylated tau in cerebrospinal fluid (CSF), 18F-FDG-PET or amyloid PET as outcome measures in healthy subjects, patients with subjective memory complaints, mild cognitive impairment, or AD. We identified a total of 8 studies of which 6 investigated the effects of exercise on hippocampal volume in healthy subjects and 1 on CSF biomarkers and 1 on hippocampal volume in AD, and none investigating the remaining outcome measures or patient groups. Methodological quality of identified studies was generally low. One study found a detrimental effect on hippocampal volume and one found a positive effect, whereas the remaining studies did not find an effect of exercise on outcome measures. The present systematic study identified a relatively small number of studies, which did not support an effect of exercise on hippocampal volume. Methodological issues such small to moderate sample sizes and inadequate ramdomization procedures further limits conclusions. Our findings highlight the difficulties in conducting high quality studies of exercise and further studies are needed before definite conclusions may be reached.

Differential 5-year brain atrophy rates in cognitively declining and stable APOE-ε4 elders

OBJECTIVE

The apolipoprotein E (APOE) ε4 allele is the most important genetic risk factor for late-onset Alzheimer's disease. Many ε4 carriers, however, never develop Alzheimer's disease. The purpose of this study is to characterize the variability in phenotypic expression of the ε4 allele, as measured by the longitudinal trajectory of cognitive test scores and MRI brain volumes, in cognitively intact elders.

METHOD

Healthy older adults, ages 65-85, participated in a 5-year longitudinal study that included structural MRI and cognitive testing administered at baseline and at 1.5 and 5 years postenrollment. Participants included 22 ε4 noncarriers, 15 ε4 carriers who experienced a decline in cognition over the 5-year interval, and 11 ε4 carriers who remained cognitively stable.

RESULTS

No baseline cognitive or volumetric group differences were observed. Compared to noncarriers, declining ε4 carriers had significantly greater rates of atrophy in left (p = .001, Cohen's d = .691) and right (p = .003, d = .622) cortical gray matter, left (p = .003, d = .625) and right (p = .020, d = .492) hippocampi, and greater expansion of the right inferior lateral ventricle (p < .001, d = .751) over 5 years.

CONCLUSIONS

This study illustrates the variability in phenotypic expression of the ε4 allele related to neurodegeneration. Specifically, only those individuals who exhibited longitudinal declines in cognitive function experienced concomitant changes in brain volume. Future research is needed to better understand the biological and lifestyle factors that may influence the expression of the ε4 allele. (PsycINFO Database Record

Exercise as a Countermeasure to Declining Central Nervous System Function in Multiple Sclerosis

PURPOSE

The decline of central nervous system (CNS) function is a hallmark characteristic of multiple sclerosis (MS) that can manifest as cognitive impairment. We believe that exercise represents a potential behavioral approach for counteracting the declines in CNS structure and associated function among persons with MS (ie, exercise as a countermeasure of CNS decline). This theory is important because disease-modifying drugs represent a first-line approach for modifying the immune system and its effects on the CNS, but these drugs do not generally demonstrate robust improvements in cognitive performance.

METHODS

To the best of our knowledge, this article presents the first argument positioning exercise as a countermeasure for CNS decline in MS.

FINDING

The reviewed research indicates a proliferating body of evidence describing physical fitness, physical activity, and exercise effects on cognitive performance and neuroimaging outcomes (ie, CNS functioning) in MS, with the consistent and strong association between cognitive performance and neuroimaging outcomes in this population as a backdrop.

IMPLICATIONS

We further present a framework and future research directions for better positioning exercise as a possible neuroprotective behavior against declining CNS function in MS.

Exercise Training and Functional Connectivity Changes in Mild Cognitive Impairment and Healthy Elders

BACKGROUND

Effective interventions are needed to improve brain function in mild cognitive impairment (MCI), an early stage of Alzheimer's disease (AD). The posterior cingulate cortex (PCC)/precuneus is a hub of the default mode network (DMN) and is preferentially vulnerable to disruption of functional connectivity in MCI and AD.

OBJECTIVE

We investigated whether 12 weeks of aerobic exercise could enhance functional connectivity of the PCC/precuneus in MCI and healthy elders.

METHODS

Sixteen MCI and 16 healthy elders (age range = 60-88) engaged in a supervised 12-week walking exercise intervention. Functional MRI was acquired at rest; the PCC/precuneus was used as a seed for correlated brain activity maps.

RESULTS

A linear mixed effects model revealed a significant interaction in the right parietal lobe: the MCI group showed increased connectivity while the healthy elders showed decreased connectivity. In addition, both groups showed increased connectivity with the left postcentral gyrus. Comparing pre to post intervention changes within each group, the MCI group showed increased connectivity in 10 regions spanning frontal, parietal, temporal and insular lobes, and the cerebellum. Healthy elders did not demonstrate any significant connectivity changes.

CONCLUSION

The observed results show increased functional connectivity of the PCC/precuneus in individuals with MCI after 12 weeks of moderate intensity walking exercise training. The protective effects of exercise training on cognition may be realized through the enhancement of neural recruitment mechanisms, which may possibly increase cognitive reserve. Whether these effects of exercise training may delay further cognitive decline in patients diagnosed with MCI remains to be demonstrated.

Physical activity and beta-amyloid pathology in Alzheimer's disease: A sound mind in a sound body

Alzheimer's disease (AD) is the most common type of dementia worldwide. Since curative treatment has not been established for AD yet and due to heavy financial and psychological costs of patients' care, special attention has been paid to preventive interventions such as physical activity. Evidence shows that physical activity has protective effects on cognitive function and memory in AD patients. Several pathologic factors are involved in AD-associated cognitive impairment some of which are preventable by physical activity. Also, various experimental and clinical studies are in progress to prove exercise role in the beta-amyloid (Aβ) pathology as a most prevailing hypothesis explaining AD pathogenesis. This study aims to review the role of physical activity in Aβ-related pathophysiology in AD.

[Not Available]

Zusammenfassung. Unser Gehirn verändert sich mit zunehmendem Alter. Dieser physiologische Prozess kann mithilfe von Magnetresonanztomografie (MRT) beschrieben werden. Im Laufe des Lebens kommt es zu Atrophie (Schrumpfen von Hirnstrukturen) sowie Auftreten von charakteristischen MRT-Signal-Hyperintensitäten in der weissen Substanz. Eine besonders starke oder frühe Ausprägung dieser Veränderungen kann pathologisch sein. Die Abgrenzung zwischen gesundem Altern und Prozessen mit Krankheitswert ist dabei nicht einfach. In diesem Mini-Review sollen normale Alterungsprozesse des Gehirns beschrieben und krankhafte Veränderungen aufgezeigt werden, die weiterer Abklärung und Behandlung bedürfen.

Youthful Processing Speed in Older Adults: Genetic, Biological, and Behavioral Predictors of Cognitive Processing Speed Trajectories in Aging

Objective: To examine the impact of genetic, inflammatory, cardiovascular, lifestyle, and neuroanatomical factors on cognitive processing speed (CPS) change over time in functionally intact older adults.

Methods: This observational study conducted over two time points, included 120 community dwelling cognitively normal older adults between the ages of 60 and 80 from the University of California San Francisco Memory and Aging Center. Participants were followed with composite measures of CPS, calculated based on norms for 20–30 year-olds. Variables of interest were AD risk genes (APOE, CR1), markers of inflammation (interleukin 6) and cardiovascular health (BMI, LDL, HDL, mean arterial pressure, fasting insulin), self-reported physical activity, and corpus callosum (CC) volumes. The sample was divided into three groups: 17 “resilient-agers” with fast and stable processing speed; 56 “average-agers” with average and stable processing speed; and 47 “sub-agers” with average baseline speed who were slower at follow-up.

Results: Resilient-agers had larger baseline CC volumes than sub-agers (p < 0.05). Resilient-agers displayed lower levels of interleukin-6 (IL-6) and insulin (ps < 0.05) than sub-agers, and reported more physical activity than both average- and sub-agers (ps < 0.01). In a multinomial logistic regression, physical activity and IL-6 predicted average- and sub-ager groups. Resilient-agers displayed a higher frequency of APOE e4 and CR1 AA/AG alleles.

Conclusion: Robust and stable CPS is associated with larger baseline CC volumes, lower levels of inflammation and insulin, and greater self-reported physical activity. These findings highlight the relevance of neuroanatomical, biological, and lifestyle factors in the identification and prediction of heterogeneous cognitive aging change over time.

Mediators of Physical Activity on Neurocognitive Function: A Review at Multiple Levels of Analysis

Physical activity (PA) is known to maintain and improve neurocognitive health. However, there is still a poor understanding of the mechanisms by which PA exerts its effects on the brain and cognition in humans. Many of the most widely discussed mechanisms of PA are molecular and cellular and arise from animal models. While information about basic cellular and molecular mechanisms is an important foundation from which to build our understanding of how PA promotes cognitive health in humans, there are other pathways that could play a role in this relationship. For example, PA-induced changes to cellular and molecular pathways likely initiate changes to macroscopic properties of the brain and/or to behavior that in turn influence cognition. The present review uses a more macroscopic lens to identify potential brain and behavioral/socioemotional mediators of the association between PA and cognitive function. We first summarize what is known regarding cellular and molecular mechanisms, and then devote the remainder of the review to discussing evidence for brain systems and behavioral/socioemotional pathways by which PA influences cognition. It is our hope that discussing mechanisms at multiple levels of analysis will stimulate the field to examine both brain and behavioral mediators. Doing so is important, as it could lead to a more complete characterization of the processes by which PA influences neurocognitive function, as well as a greater variety of targets for modifying neurocognitive function in clinical contexts.

Timing of Physical Activity, Apolipoprotein E ε4 Genotype, and Risk of Incident Mild Cognitive Impairment

OBJECTIVES

To investigate the timing (mid- vs late life) of physical activity, apolipoprotein (APO)E ε4, and risk of incident mild cognitive impairment (MCI).

DESIGN

Prospective cohort study.

SETTING

Mayo Clinic Study of Aging (Olmsted County, MN).

PARTICIPANTS

Cognitively normal elderly adults (N = 1,830, median age 78, 50.2% female).

MEASUREMENTS

Light, moderate, and vigorous physical activities in mid- and late life were assessed using a validated questionnaire. An expert consensus panel measured MCI based on published criteria. Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) with age as a time scale after adjusting for sex, education, medical comorbidity, and depression.

RESULTS

Light (HR = 0.58, 95% CI = 0.43-0.79) and vigorous (HR = 0.78, 95% CI = 0.63-0.97) physical activity in midlife were associated with lower risk of incident MCI. The association between moderate activity and incident MCI was not significant (HR = 0.85, 95% CI = 0.67-1.09). In late life, light (HR = 0.75, 95% CI = 0.58-0.97) and moderate (HR = 0.81, 95% CI = 0.66-0.99) but not vigorous physical activity were associated with lower risk of incident MCI. A synergistic interaction was also observed between mid- and late-life activity in reducing risk of incident MCI. Furthermore, APOE ε4 carriers who did not exercise had a higher risk of incident MCI than noncarriers who reported physical activity.

CONCLUSION

Physical activity reduced the risk of incident MCI. Exercising in mid- and late life had an additive synergistic interaction in reducing the risk of MCI.