Leisure-time physical activity from mid- to late life, body mass index, and risk of dementia

Population-Based Approaches to Alzheimer's Disease Prevention

Progress in prevention and treatment of Alzheimer's disease (AD) and dementia is hampered by the restricted understanding of the biological and environmental causes underlying pathophysiology. It is widely accepted that certain genetic factors are associated with AD and a number of lifestyle and other environmental characteristics have also been linked to dementia risk. However, interactions between genes and the environment are not yet well understood, and coordinated global action is required to utilize existing cohorts and other resources effectively and efficiently to identify new avenues for dementia prevention. This chapter provides a brief summary of current research on risk and protective factors and opportunities and challenges in relation to population-based approaches are discussed.

Systems healthcare: a holistic paradigm for tomorrow

Systems healthcare is a holistic approach to health premised on systems biology and medicine. The approach integrates data from molecules, cells, organs, the individual, families, communities, and the natural and man-made environment. Both extrinsic and intrinsic influences constantly challenge the biological networks associated with wellness. Such influences may dysregulate networks and allow pathobiology to evolve, resulting in early clinical presentation that requires astute assessment and timely intervention for successful mitigation. Herein, we describe the components of relevant biological systems and the nature of progression from at-risk to manifest disease. We illustrate the systems approach by examining two relevant clinical examples: Alzheimer's and cardiovascular diseases. The implications of systems healthcare management are examined through the lens of economics, ethics, policy and the law. Finally, we propose the need to develop new educational paradigms to enhance the training of the health professional in an era of systems medicine.

Leisure time physical activity and dementia risk: a dose-response meta-analysis of prospective studies

BACKGROUND

There is considerable evidence of the favourable role of more physical activity (PA) in fighting against dementia. However, the shape of the dose-response relationship is still unclear.

OBJECTIVE

To quantitatively investigate the relationship between dementia and PA.

DESIGN

PubMed, EMBASE, Ovid and the Cochrane Library were searched for prospective studies published from 1 January 1995 to 15 October 2016. Two types of meta-analyses were performed with a focus on the dose-response relationship using two stage generalised least squares regression.

RESULTS

The primary analysis exhibited a dose-response trend for all-cause dementia (ACD), Alzheimer's disease (AD) but not for vascular dementia (VD). In the dose-response analysis, either ACD (p_trend <0.005; p_{non-linearity}=0.87) or AD (p _trend <0.005; p_{non-linearity}=0.10) exhibited a linear relationship with leisure time PA (LTPA) over the observed range (0-2000 kcal/week or 0-45 metabolic equivalent of task hours per week (MET-h/week)). Specifically, for every 500 kcal or 10 MET-h increase per week, there was, on average, 10% and 13% decrease in the risk of ACD and AD, respectively.

CONCLUSIONS

We have reported, for the first time, the dose-response relationship between LTPA and dementia, further supporting the international PA guideline from the standpoint of dementia prevention.

The impact of physical activity and sex differences on intraindividual variability in inhibitory performance in older adults

It is well-known that processing speed and executive functions decline with advancing age. However, physical activity (PA) has a positive impact on cognitive performances in aging, specifically for inhibition. Less is known concerning intraindividual variability (iiV) in reaction times. This study aims to investigate the influence of PA and sex differences on iiV in inhibitory performance during aging. Healthy adults were divided into active and sedentary groups according to PA level. To analyse iiV in reaction times, individual mean, standard deviation and the ex-Gaussian parameters were considered. An interaction between activity level and sex was revealed, sedentary females being slower and more variable than sedentary men. No sex differences were found in the active groups. These results indicate that the negative impact of sedentariness on cognitive performance in older age is stronger for females. The present findings underline the need to consider sex differences in active aging approaches.

EFAD transgenic mice as a human APOE relevant preclinical model of Alzheimer's disease

Identified in 1993, APOE4 is the greatest genetic risk factor for sporadic Alzheimer's disease (AD), increasing risk up to 15-fold compared with APOE3, with APOE2 decreasing AD risk. However, the functional effects of APOE4 on AD pathology remain unclear and, in some cases, controversial. In vivo progress to understand how the human (h)-APOE genotypes affect AD pathology has been limited by the lack of a tractable familial AD-transgenic (FAD-Tg) mouse model expressing h-APOE rather than mouse (m)-APOE. The disparity between m- and h-apoE is relevant for virtually every AD-relevant pathway, including amyloid-β (Aβ) deposition and clearance, neuroinflammation, tau pathology, neural plasticity and cerebrovascular deficits. EFAD mice were designed as a temporally useful preclinical FAD-Tg-mouse model expressing the h-APOE genotypes for identifying mechanisms underlying APOE-modulated symptoms of AD pathology. From their first description in 2012, EFAD mice have enabled critical basic and therapeutic research. Here we review insights gleaned from the EFAD mice and summarize future directions.

Physical Activity and Alzheimer's Disease: A Systematic Review

The current literature includes several studies investigating the association between physical activity and risk of Alzheimer's disease (AD). The aim of this review was to systematically evaluate available evidence on this association. Medline via PubMed and CINAHL databases were searched for original English language research articles assessing the relationship between physical activity and incident AD. The review was limited to prospective observational and intervention studies. Criteria for exclusion were studies focusing on individuals with dementia, cross-sectional study design, and case reports. The quality of included studies was assessed in 5 domains of bias. Twenty-four studies met the inclusion criteria. The number of participants ranged from 176 to 5,698. Follow-up time varied from 1 to 34 years. Physical activity was inversely associated with risk of AD in most studies (n = 18). Leisure-time physical activity was particularly protective against AD, but not work-related physical activity. The risk of bias assessment showed that overall quality of evidence was moderate for 16 and low for 8 studies. Beyond all the available general recommendations for health promotion, current evidence does not allow to draw specific practical recommendations concerning the types, frequency, intensity, or duration of physical activity that may be protective against AD.

Physical activity domains and cognitive function over three years in older adults with subjective memory complaints: Secondary analysis from the MAPT trial

OBJECTIVES

We aimed to examine the associations of physical activity (PA) domains (i.e., PA in leisure-time (LTPA), for housework (HPA), or for gardening (GPA)) with cognitive function in older adults with subjective memory complaints (no-dementia) and to investigate if those associations were dependent on the status of apolipoprotein E allele 4 (APOE4), omega-3 levels and mild cognitive impairment (MCI).

DESIGN

Observational prospective secondary analysis using longitudinal data from a randomized controlled trial.

METHODS

Participants were 420 French community-dwelling people (aged 75.6±4.4; 66.4% women) randomized into the placebo group. They were assessed at baseline, 6-, 12-, 24- and 36-month using a battery of neuropsychological tests; a composite cognitive Z score was elaborated for all time points. Data on PA come from baseline and was obtained using a self-reported questionnaire.

RESULTS

In time-adjusted analysis, LTPA significantly predicted cognitive function over three years for almost all tests and the composite Z score, with higher LTPA associated with better function; multivariate analysis showed a significant association only for verbal fluency. HPA was not associated to cognitive function, whereas GPA had mixed results. The magnitude of the PA-cognition associations was very weak, being the strongest for LTPA. Stratified analyses showed that the associations between PA and cognitive function were stronger for MCI, people with normal omega-3 index levels, and APOE4 non-carriers.

CONCLUSIONS

PA domain is an important aspect to take into account when examining the associations between PA and cognitive function. Biomarkers of cognitive function may modulate the PA-cognition associations.

Physical activity, cognitive decline, and risk of dementia: 28 year follow-up of Whitehall II cohort study

Objective To test the hypotheses that physical activity in midlife is not associated with a reduced risk of dementia and that the preclinical phase of dementia is characterised by a decline in physical activity.Design Prospective cohort study with a mean follow-up of 27 years.Setting Civil service departments in London (Whitehall II study).Participants 10 308 participants aged 35-55 years at study inception (1985-88). Exposures included time spent in mild, moderate to vigorous, and total physical activity assessed seven times between 1985 and 2013 and categorised as "recommended" if duration of moderate to vigorous physical activity was 2.5 hours/week or more.Main outcome measures A battery of cognitive tests was administered up to four times from 1997 to 2013, and incident dementia cases (n=329) were identified through linkage to hospital, mental health services, and mortality registers until 2015.Results Mixed effects models showed no association between physical activity and subsequent 15 year cognitive decline. Similarly, Cox regression showed no association between physical activity and risk of dementia over an average 27 year follow-up (hazard ratio in the "recommended" physical activity category 1.00, 95% confidence interval 0.80 to 1.24). For trajectories of hours/week of total, mild, and moderate to vigorous physical activity in people with dementia compared with those without dementia (all others), no differences were observed between 28 and 10 years before diagnosis of dementia. However, physical activity in people with dementia began to decline up to nine years before diagnosis (difference in moderate to vigorous physical activity -0.39 hours/week; P=0.05), and the difference became more pronounced (-1.03 hours/week; P=0.005) at diagnosis.Conclusion This study found no evidence of a neuroprotective effect of physical activity. Previous findings showing a lower risk of dementia in physically active people may be attributable to reverse causation-that is, due to a decline in physical activity levels in the preclinical phase of dementia.

A Life-Long Approach to Physical Activity for Brain Health

It is well established that engaging in lifelong Physical activity (PA) can help delay the onset of many chronic lifestyle related and non-communicable diseases such as cardiovascular disease, type two diabetes, cancer and chronic respiratory diseases. Additionally, growing evidence also documents the importance of PA for brain health, with numerous studies indicating regular engagement in physical activities may be protective against cognitive decline and dementia in late life. Indeed, the link between PA and brain health may be different at each stage of life from childhood, mid-life and late life. Building on this emerging body of multidisciplinary research, this review aims to summarize the current body of evidence linking regular PA and brain health across the lifespan. Specifically, we will focus on the relationship between PA and brain health at three distinct stages of life: childhood and adolescence, mid-life, late life in cognitively healthy adults and later life in adults living with age-related neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer's disease (AD).

Cerebrospinal Fluid Clearance in Alzheimer Disease Measured with Dynamic PET

Evidence supporting the hypothesis that reduced cerebrospinal fluid (CSF) clearance is involved in the pathophysiology of Alzheimer disease (AD) comes primarily from rodent models. However, unlike rodents, in which predominant extracranial CSF egress is via olfactory nerves traversing the cribriform plate, human CSF clearance pathways are not well characterized. Dynamic PET with ¹⁸F-THK5117, a tracer for tau pathology, was used to estimate the ventricular CSF time-activity as a biomarker for CSF clearance. We tested 3 hypotheses: extracranial CSF is detected at the superior turbinates; CSF clearance is reduced in AD; and CSF clearance is inversely associated with amyloid deposition. Methods: Fifteen subjects, 8 with AD and 7 normal control volunteers, were examined with ¹⁸F-THK5117. Ten subjects additionally underwent ¹¹C-Pittsburgh compound B (¹¹C-PiB) PET scanning, and 8 were ¹¹C-PiB-positive. Ventricular time-activity curves of ¹⁸F-THK5117 were used to identify highly correlated time-activity curves from extracranial voxels. Results: For all subjects, the greatest density of CSF-positive extracranial voxels was in the nasal turbinates. Tracer concentration analyses validated the superior nasal turbinate CSF signal intensity. AD patients showed ventricular tracer clearance reduced by 23% and 66% fewer superior turbinate CSF egress sites. Ventricular CSF clearance was inversely associated with amyloid deposition. Conclusion: The human nasal turbinate is part of the CSF clearance system. Lateral ventricle and superior nasal turbinate CSF clearance abnormalities are found in AD. Ventricular CSF clearance reductions are associated with increased brain amyloid depositions. These data suggest that PET-measured CSF clearance is a biomarker of potential interest in AD and other neurodegenerative diseases.

Effects of Different Exercise Strategies and Intensities on Memory Performance and Neurogenesis

It is well established that physical exercise affects both hippocampal neurogenesis and memory functions. Until now, distinctive effects of controlled and voluntary training (VT) on behavior and neurogenesis as well as interactions between exercise intensity, neurogenesis and memory performance are still elusive. The present study tested the impact of moderate controlled and VT on memory formation and hippocampal neurogenesis and evaluated interactions between exercise performance, learning efficiency and proliferation of progenitor cells in the hippocampus. Our data show that both controlled and VT augmented spatial learning and promoted hippocampal neurogenesis. Regression analysis revealed a significant linear increase of the amount of new hippocampal neurons with increased exercise intensity. Regression analysis of exercise performance on retention memory performance revealed a quadratic, inverted u-shaped relationship between exercise performance and retention of spatial memory. No association was found between the amount of newborn neurons and memory performance. Our results demonstrate that controlled training (CT), if performed with an appropriate combination of speed and duration, improves memory performance and neurogenesis. Voluntary exercise elevates neurogenesis dose dependently to high levels. Best cognitive improvement was achieved with moderate exercise performance.

Aerobic exercise for Alzheimer's disease: A randomized controlled pilot trial

BACKGROUND

There is increasing interest in the role of physical exercise as a therapeutic strategy for individuals with Alzheimer's disease (AD). We assessed the effect of 26 weeks (6 months) of a supervised aerobic exercise program on memory, executive function, functional ability and depression in early AD.

METHODS AND FINDINGS

This study was a 26-week randomized controlled trial comparing the effects of 150 minutes per week of aerobic exercise vs. non-aerobic stretching and toning control intervention in individuals with early AD. A total of 76 well-characterized older adults with probable AD (mean age 72.9 [7.7]) were enrolled and 68 participants completed the study. Exercise was conducted with supervision and monitoring by trained exercise specialists. Neuropsychological tests and surveys were conducted at baseline,13, and 26 weeks to assess memory and executive function composite scores, functional ability (Disability Assessment for Dementia), and depressive symptoms (Cornell Scale for Depression in Dementia). Cardiorespiratory fitness testing and brain MRI was performed at baseline and 26 weeks. Aerobic exercise was associated with a modest gain in functional ability (Disability Assessment for Dementia) compared to individuals in the ST group (X2 = 8.2, p = 0.02). There was no clear effect of intervention on other primary outcome measures of Memory, Executive Function, or depressive symptoms. However, secondary analyses revealed that change in cardiorespiratory fitness was positively correlated with change in memory performance and bilateral hippocampal volume.

CONCLUSIONS

Aerobic exercise in early AD is associated with benefits in functional ability. Exercise-related gains in cardiorespiratory fitness were associated with improved memory performance and reduced hippocampal atrophy, suggesting cardiorespiratory fitness gains may be important in driving brain benefits.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01128361.

Impact of Physical Activity on Cognitive Decline, Dementia, and Its Subtypes: Meta-Analysis of Prospective Studies

The association of physical activity with dementia and its subtypes has remained controversial in the literature and has continued to be a subject of debate among researchers. A systematic review and meta-analysis of longitudinal studies on the relationship between physical activity and the risk of cognitive decline, all-cause dementia, Alzheimer's disease, and vascular dementia among nondemented subjects are considered. A comprehensive literature search in all available databases was conducted up until April 2016. Well-defined inclusion and exclusion criteria were developed with focus on prospective studies ≥ 12 months. The overall sample from all studies is 117410 with the highest follow-up of 28 years. The analyses are performed with both Bayesian parametric and nonparametric models. Our analysis reveals a protective effect for high physical activity on all-cause dementia, odds ratio of 0.79, 95% CI (0.69, 0.88), a higher and better protective effect for Alzheimer's disease, odds ratio of 0.62, 95% CI (0.49, 0.75), cognitive decline odds ratio of 0.67, 95% CI (0.55, 0.78), and a nonprotective effect for vascular dementia of 0.92, 95% CI (0.62, 1.30). Our findings suggest that physical activity is more protective against Alzheimer's disease than it is for all-cause dementia, vascular dementia, and cognitive decline.

Contribution of neuroinflammation and immunity to brain aging and the mitigating effects of physical and cognitive interventions

It is widely accepted that the brain and the immune system continuously interact during normal as well as pathological functioning. Human aging is commonly accompanied by low-grade inflammation in both the immune and central nervous systems, thought to contribute to many age-related diseases. This review of the current literature focuses first on the normal neuroimmune interactions occurring in the brain, which promote learning, memory and neuroplasticity. Further, we discuss the protective and dynamic role of barriers to neuroimmune interactions, which have become clearer with the recent discovery of the meningeal lymphatic system. Next, we consider age-related changes of the immune system and possible deleterious influences of immunosenescence and low-grade inflammation (inflammaging) on neurodegenerative processes in the normally aging brain. We survey the major immunomodulators and neuroregulators in the aging brain and their highly tuned dynamic and reciprocal interactions. Finally, we consider our current understanding of how physical activity, as well as a combination of physical and cognitive interventions, may mediate anti-inflammatory effects and thus positively impact brain aging.

Diabesity and Brain Energy Metabolism: The Case of Alzheimer's Disease

It is widely accepted that high calorie diets and a sedentary lifestyle sturdily influence the incidence and outcome of type 2 diabetes and obesity, which can occur simultaneously, a situation called diabesity. Tightly linked with metabolic and energy regulation, a close association between diabetes and Alzheimer's disease (AD) has been proposed. Among the common pathogenic mechanisms that underpin both conditions, insulin resistance, brain glucose hypometabolism, and metabolic dyshomeostasis appear to have a pivotal role. This century is an unprecedented diabetogenic period in human history, so therapeutic strategies and/or approaches to control and/or revert this evolving epidemic is of utmost importance. This chapter will make a brief contextualization about the impact that diabetes and obesity can exert in brain structure and function alongside with a brief survey about the role of insulin in normal brain function, exploring its roles in cognition and brain glucose metabolism. Later, attention will be given to the intricate relation of diabesity, insulin resistance, and AD. Finally, both pharmacological and lifestyle interventions will also be reviewed as strategies aimed at fighting diabesity and/or AD-related metabolic effects.

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.

Differences in Resting State Functional Connectivity between Young Adult Endurance Athletes and Healthy Controls

Expertise and training in fine motor skills has been associated with changes in brain structure, function, and connectivity. Fewer studies have explored the neural effects of athletic activities that do not seem to rely on precise fine motor control (e.g., distance running). Here, we compared resting-state functional connectivity in a sample of adult male collegiate distance runners (n = 11; age = 21.3 ± 2.5) and a group of healthy age-matched non-athlete male controls (n = 11; age = 20.6 ± 1.1), to test the hypothesis that expertise in sustained aerobic motor behaviors affects resting state functional connectivity in young adults. Although generally considered an automated repetitive task, locomotion, especially at an elite level, likely engages multiple cognitive actions including planning, inhibition, monitoring, attentional switching and multi-tasking, and motor control. Here, we examined connectivity in three resting-state networks that link such executive functions with motor control: the default mode network (DMN), the frontoparietal network (FPN), and the motor network (MN). We found two key patterns of significant between-group differences in connectivity that are consistent with the hypothesized cognitive demands of elite endurance running. First, enhanced connectivity between the FPN and brain regions often associated with aspects of working memory and other executive functions (frontal cortex), suggest endurance running may stress executive cognitive functions in ways that increase connectivity in associated networks. Second, we found significant anti-correlations between the DMN and regions associated with motor control (paracentral area), somatosensory functions (post-central region), and visual association abilities (occipital cortex). DMN deactivation with task-positive regions has been shown to be generally beneficial for cognitive performance, suggesting anti-correlated regions observed here are engaged during running. For all between-group differences, there were significant associations between connectivity, self-reported physical activity, and estimates of maximum aerobic capacity, suggesting a dose-response relationship between engagement in endurance running and connectivity strength. Together these results suggest that differences in experience with endurance running are associated with differences in functional brain connectivity. High intensity aerobic activity that requires sustained, repetitive locomotor and navigational skills may stress cognitive domains in ways that lead to altered brain connectivity, which in turn has implications for understanding the beneficial role of exercise for brain and cognitive function over the lifespan.

Investigating Discontinuity of Age Relations in Cognitive Functioning, General Health Status, Activity Participation, and Life Satisfaction between Young-Old and Old-Old Age

Health research suggests that findings on young-old adults cannot be generalized to old-old adults and thus that old-old age seems not a simple continuation of young-old age due to qualitative changes that result in a discontinuity in old age. Specifically, it would be of conceptual and methodological importance to inform research regarding estimates around which chronological age the beginning of old-old age could be placed at a population level, and whether this is universal or domain-specific. To derive such criteria, we investigated potential discontinuity of age relations between young-old and old-old age in a large population-based sample considering measures in different domains (processing speed, verbal abilities, general health status, activity participation, and life satisfaction). For processing speed, verbal abilities, general health status, and life satisfaction we observed some very small indication that there might be a discontinuity of age relations at the end of individuals' eighties, and for activity participation already at the beginning of individuals' eighties. In conclusion, models conceptualizing aging as a gradual development might not suffice to adequately represent the differences between the stages of young-old and old-old age due to some very small indication that there might be discontinuity in late adulthood.

Physical Activity and Cognitive Function in Middle-Aged and Older Adults: An Analysis of 104,909 People From 20 Countries

OBJECTIVE

To examine the associations of physical activity (PA) frequency (both moderate and vigorous intensity) and PA levels with cognitive function.

PATIENTS AND METHODS

Data of individuals 50 years or older, from 20 European countries (along with Israel), were collected from 2004 to November 2013 in the biannual Survey of Health, Ageing and Retirement in Europe. A total of 104,909 participants were assessed for cognitive function at least once (mean follow-up length, 29.5±35.7 months). Baseline moderate- and vigorous-intensity PA were reported by participants as more than once a week, once a week, one to three times a month, or hardly ever or never. With regard to PA frequency, participants were categorized as inactive, low active, intermediate active, or high active. The main outcome measure is a cognitive composite score created by summing the z scores of 4-item temporal orientation, 10-word list for delayed recall, and verbal fluency.

RESULTS

Adjusted, 2-level mixed-effect regressions found that compared with doing no PA, doing PA more than once a week, once a week, or one to three times a month was positively associated with the composite score (β coefficients varied from 0.52 to 0.75 for moderate-intensity PA and from 0.26 to 0.33 for vigorous-intensity PA). Similarly, compared with the inactive category, high-active, intermediate-active, and low-active categories had positive associations with the composite score (β varied from 0.77 to 1.10). Positive associations were also obtained between PA variables and the raw scores of cognitive tests.

CONCLUSION

Physical activity has dose-response associations with cognitive function, with even low PA frequencies (few times per month) being positively associated with cognitive function during aging.

Interactions between inflammation, sex steroids, and Alzheimer's disease risk factors

Alzheimer's disease (AD) is an age-related neurodegenerative disorder for which there are no effective strategies to prevent or slow its progression. Because AD is multifactorial, recent research has focused on understanding interactions among the numerous risk factors and mechanisms underlying the disease. One mechanism through which several risk factors may be acting is inflammation. AD is characterized by chronic inflammation that is observed before clinical onset of dementia. Several genetic and environmental risk factors for AD increase inflammation, including apolipoprotein E4, obesity, and air pollution. Additionally, sex steroid hormones appear to contribute to AD risk, with age-related losses of estrogens in women and androgens in men associated with increased risk. Importantly, sex steroid hormones have anti-inflammatory actions and can interact with several other AD risk factors. This review examines the individual and interactive roles of inflammation and sex steroid hormones in AD, as well as their relationships with the AD risk factors apolipoprotein E4, obesity, and air pollution.

Physical Activity and Alzheimer Disease: A Protective Association

OBJECTIVE

To explore whether being physically active can decrease Alzheimer disease (AD) risk.

PARTICIPANTS AND METHODS

We conducted a meta-analysis of prospective observational cohort studies reporting the association between physical activity (PA) and incident AD. Relevant articles were identified by title and abstract in the electronic databases PubMed, ScienceDirect, and Scopus using the keywords Alzheimer, Alzheimer disease, Alzheimer's, Alzheimer's disease, physical activity, sport, exercise, sedentary, fitness, and combinations thereof for articles published in any language up to February 15, 2016. Criteria for consideration included division of the study cohort by PA levels and sample size specification for each PA level group, quantification (number) of persons who had development of AD, and PA assessment during time off work (not just work time). We followed the MOOSE (Meta-analyses of Observational Studies in Epidemiology) recommendations and used the Newcastle-Ottawa scale for study quality assessment.

RESULTS

Ten high-quality studies were included in meta-analysis I (23,345 participants). Follow-up ranged from 3.9 to 31 years, and the participants' age ranged from 70 to 80 years. The pooled odds ratio for development of AD in participants who were more vs less physically active was 0.65 (95% CI, 0.56-0.74; P<.001; no publication bias [P=.24] but with heterogeneity among studies [I(2)=31.32%]). We could identify participants' adherence to international PA recommendations in 5 studies, which constituted meta-analysis II (10,615 participants). The pooled odds ratio for development of AD in participants who were active vs those who were inactive was 0.60 (95% CI, 0.51-0.71; P<.001; no publication bias [P=.34] and no heterogeneity [I(2)=5.63%]).

CONCLUSION

Although the limitations of self-reported PA data must be considered, regular PA performed by elderly people might play a certain protective role against AD.

Predicting dementia in primary care patients with a cardiovascular health metric: a prospective population-based study

Background

Improving cardiovascular health possibly decreases the risk of dementia. Primary care practices offer a suitable setting for monitoring and controlling cardiovascular risk factors in the older population. The purpose of the study is to examine the association of a cardiovascular health metric including six behaviors and blood parameters with the risk of dementia in primary care patients.

Methods

Participants (N = 3547) were insurants aged ≥55 of the largest German statutory health insurance company, who were enrolled in a six-year prospective population-based study. Smoking, physical activity, body mass index, blood pressure, total cholesterol, and fasting glucose were assessed by general practitioners at routine examinations. Using recommended cut-offs for each factor, the patients’ cardiovascular health was classified as ideal, moderate, or poor. Behaviors and blood parameters sub-scores, as well as a total score, were calculated. Dementia diagnoses were retrieved from health insurance claims data. Results are presented as hazard ratios (HRs) and 95 % confidence intervals (95 % CIs).

Results

Over the course of the study 296 new cases of dementia occurred. Adjusted for age, sex, and education, current smoking (HR = 1.77, 95 % CI 1.09–2.85), moderate (1.38, 1.05–1.81) or poor (1.81, 1.32–2.47) levels of physical activity, and poor fasting glucose levels (1.43, 1.02–2.02) were associated with an increased risk of dementia. Body mass index, blood pressure, and cholesterol were not associated with dementia. Separate summary scores for behaviors and blood values, as well as a total score showed no association with dementia. Sensitivity analyses with differently defined endpoints led to similar results.

Conclusions

Due to complex relationships of body-mass index and blood pressure with dementia individual components cancelled each other out and rendered the sum-scores meaningless for the prediction of dementia.

State of the Art Review: Physical Activity and Older Adults

Physical activity is an important component of a healthy lifestyle for all adults and especially for older adults. Using information from the updated 2008 Physical Activity Guidelines, 3 dimensions of physical activity are identified for older adults. These include increasing aerobic activity, increasing muscle-strengthening activity, and reducing sedentary or sitting behavior. Although the overall goal of the physical activity recommendations is to prevent chronic diseases and conditions from developing, many older adults are already affected. Therefore, suggested types of physical activity are described for specific diseases and conditions that are designed to mediate the condition or prevent additional disability. Finally, barriers to participation in physical activity specific to older adults are described, and possible solutions offered. Encouraging older adults to continue or even start a physical activity program can result in major health benefits for these individuals.

Alzheimer's disease due to loss of function: A new synthesis of the available data

Alzheimer's Disease (AD) is a highly complex disease involving a broad range of clinical, cellular, and biochemical manifestations that are currently not understood in combination. This has led to many views of AD, e.g. the amyloid, tau, presenilin, oxidative stress, and metal hypotheses. The amyloid hypothesis has dominated the field with its assumption that buildup of pathogenic β-amyloid (Aβ) peptide causes disease. This paradigm has been criticized, yet most data suggest that Aβ plays a key role in the disease. Here, a new loss-of-function hypothesis is synthesized that accounts for the anomalies of the amyloid hypothesis, e.g. the curious pathogenicity of the Aβ42/Aβ40 ratio, the loss of Aβ caused by presenilin mutation, the mixed phenotypes of APP mutations, the poor clinical-biochemical correlations for genetic variant carriers, and the failure of Aβ reducing drugs. The amyloid-loss view accounts for recent findings on the structure and chemical features of Aβ variants and their coupling to human patient data. The lost normal function of APP/Aβ is argued to be metal transport across neuronal membranes, a view with no apparent anomalies and substantially more explanatory power than the gain-of-function amyloid hypothesis. In the loss-of-function scenario, the central event of Aβ aggregation is interpreted as a loss of soluble, functional monomer Aβ rather than toxic overload of oligomers. Accordingly, new research models and treatment strategies should focus on remediation of the functional amyloid balance, rather than strict containment of Aβ, which, for reasons rationalized in this review, has failed clinically.

Association between Cognitive Status and Physical Activity: Study Profile on Baseline Survey of the My Mind Project

Background: The incidence of people with dementia is expected to increase significantly in the coming years, but it seems that there is a relationship between an active lifestyle and cognitive decline. The present study aimed to compare the characteristics and engagement in the physical activity (PA) of three groups of Italian elderly with different cognitive statuses at baseline phase. Methods: Data were examined using the results from the “My Mind Project” on 305 community-dwelling Italians. The sample was comprised of 93 subjects with Alzheimer’s disease (AD), 109 with mild cognitive impairment (MCI) and 103 healthy elderly (HE). Results: Classification of subjects on the basis of Physical Activity Scale for the Elderly (PASE) score showed that 47% of HE performed the highest level of physical activity while 40% of AD performed the lowest level. MCI subjects were distributed quite homogeneously across the levels (p < 0.001). Physical activity such as walking and light sports was carried out mainly and more frequently by HE as compared to the others (p < 0.05). As regards functional status, AD presented worse conditions in basic and instrumental activities of daily living than the other groups (p < 0.001). Conclusions: Our results evidenced that subjects with cognitive decline had the tendency to engage in PA less than HE. In particular, age and education negatively affected engagement in PA.

Physical activity delays hippocampal neurodegeneration and rescues memory deficits in an Alzheimer disease mouse model

The evidence for a protective role of physical activity on the risk and progression of Alzheimer's disease (AD) has been growing in the last years. Here we studied the influence of a prolonged physical and cognitive stimulation on neurodegeneration, with special emphasis on hippocampal neuron loss and associated behavioral impairment in the Tg4-42 mouse model of AD. Tg4-42 mice overexpress Aβ4-42 without any mutations, and develop an age-dependent hippocampal neuron loss associated with a severe memory decline. We demonstrate that long-term voluntary exercise diminishes CA1 neuron loss and completely rescues spatial memory deficits in different experimental settings. This was accompanied by changes in the gene expression profile of Tg4-42 mice. Deep sequencing analysis revealed an upregulation of chaperones involved in endoplasmatic reticulum protein processing, which might be intimately linked to the beneficial effects seen upon long-term exercise. We believe that we provide evidence for the first time that enhanced physical activity counteracts neuron loss and behavioral deficits in a transgenic AD mouse model. The present findings underscore the relevance of increased physical activity as a potential strategy in the prevention of dementia.

Can physical exercise in old age improve memory and hippocampal function?

Physical exercise can convey a protective effect against cognitive decline in ageing and Alzheimer's disease. While the long-term health-promoting and protective effects of exercise are encouraging, it's potential to induce neuronal and vascular plasticity in the ageing brain is still poorly understood. It remains unclear whether exercise slows the trajectory of normal ageing by modifying vascular and metabolic risk factors and/or consistently boosts brain function by inducing structural and neurochemical changes in the hippocampus and related medial temporal lobe circuitry-brain areas that are important for learning and memory. Hence, it remains to be established to what extent exercise interventions in old age can improve brain plasticity above and beyond preservation of function. Existing data suggest that exercise trials aiming for improvement and preservation may require different outcome measures and that the balance between the two may depend on exercise intensity and duration, the presence of preclinical Alzheimer's disease pathology, vascular and metabolic risk factors and genetic variability.

Late-Life Risk Factors for All-Cause Dementia and Differential Dementia Diagnoses in Women: A Prospective Cohort Study

Since the first evidence of a decline in dementia incidence was reported in 2011, the focus on modifiable risk factors has increased. The possibility of risk factor intervention as a prevention strategy has been widely discussed; however, further evidence in relation to risk factors is still needed. The Prospective Epidemiologic Risk Factor (PERF I) study was an observational prospective study of postmenopausal Danish women who were initially examined between 1999 and 2001 (n = 5855). Follow-up data on diagnosis and survival as of December 31, 2014 was retrieved from the National Danish Patient Registry and the National Danish Causes of Death Registry. Cox proportional hazards regression model was applied to calculate adjusted hazard ratios (HR) for selected risk factors for dementia. Of 5512 eligible subjects, 592 developed dementia within the follow-up period of maximum 15 years. The independent factors associated with increased risk of all-cause dementia were depression (HR = 1.75 [95% CI 1.32-2.34]) and impaired fasting glucose levels. A dose-response relationship was observed between fasting glucose level and risk of dementia with HRs of 1.25 [1.05-1.49] and 1.45 [1.03-2.06] for impaired (5.6-6.9 mmol/L) and hyperglycemic (≥7.0 mmol/L) glucose levels, respectively. The factors associated with a decreased risk of dementia were overweight in late-life (HR = 0.75 [0. 62-0.89]) and physical activity at least once weekly (HR = 0.77 [0.61-0.96]). The identified risk factors for dementia in women in late-life are all considered modifiable. This supports the notion that prevention strategies may improve the poor future prospects for dementias in the ageing population.

Association of Long-Term Dietary Fat Intake, Exercise, and Weight with Later Cognitive Function in the Finnish Diabetes Prevention Study

OBJECTIVES

To investigate associations of long-term nutrient intake, physical activity and obesity with later cognitive function among the participants in the Finnish Diabetes Prevention Study, in which a lifestyle intervention was successful in diabetes prevention.

DESIGN

An active lifestyle intervention phase during middle age (mean duration 4 years) and extended follow-up (additional 9 years) with annual lifestyle measurements, followed by an ancillary cognition assessment.

SETTING

5 research centers in Finland.

PARTICIPANTS

Of the 522 middle-aged, overweight participants with impaired glucose tolerance recruited to the study, 364 (70%) participated in the cognition assessment (mean age 68 years).

MEASUREMENTS

A cognitive assessment was executed with the CERAD test battery and the Trail Making Test A on average 13 years after baseline. Lifestyle measurements included annual clinical measurements, food records, and exercise questionnaires during both the intervention and follow-up phase.

RESULTS

Lower intake of total fat (p=0.021) and saturated fatty acids (p=0.010), and frequent physical activity (p=0.040) during the whole study period were associated with better cognitive performance. Higher BMI (p=0.012) and waist circumference (p=0.012) were also associated with worse performance, but weight reduction prior to the cognition assessment predicted worse performance as well (decrease vs. increase, p=0.008 for BMI and p=0.002 for waist).

CONCLUSIONS

Long-term dietary fat intake, BMI, and waist circumference have an inverse association with cognitive function in later life among people with IGT. However, decreases in BMI and waist prior to cognitive assessment are associated with worse cognitive performance, which could be explained by reverse causality.

Cognitive Reserve and the Prevention of Dementia: the Role of Physical and Cognitive Activities

PURPOSE OF REVIEW

The article discusses the two most significant modifiable risk factors for dementia, namely, physical inactivity and lack of stimulating cognitive activity, and their effects on developing cognitive reserve.

RECENT FINDINGS

Both of these leisure-time activities were associated with significant reductions in the risk of dementia in longitudinal studies. In addition, physical activity, particularly aerobic exercise, is associated with less age-related gray and white matter loss and with less neurotoxic factors. On the other hand, cognitive training studies suggest that training for executive functions (e.g., working memory) improves prefrontal network efficiency, which provides support to brain functioning in the face of cognitive decline. While physical activity preserves neuronal structural integrity and brain volume (hardware), cognitive activity strengthens the functioning and plasticity of neural circuits (software), thus supporting cognitive reserve in different ways. Future research should examine whether lifestyle interventions incorporating these two domains can reduce incident dementia.

Efficacy of lifestyle interventions on clinical and neuroimaging outcomes in elderly

The prevalence of Alzheimer's disease (AD) is constantly growing worldwide in absence of any effective treatment. Methodology and technique advancements facilitated the early diagnosis of AD leading to a shift toward preclinical AD stages investigation in order to delay the disease onset in individuals at risk for AD. Recent evidence demonstrating the aging related multifactorial nature of AD supported the hypothesis that modifiable environmental factors can accelerate or delay the disease onset. In particular, healthy dietary habits, constant physical and cognitive activities are associated with reduced brain atrophy, amyloid load and incidence of AD cases. Due to these promising results, an emerging field of studies is currently investigating the efficacy of interventions addressing different lifestyle habits in cognitive intact elderly individuals as a potential preventive strategy against AD onset. We provide a critical overview of the current evidence on nonpharmacologic treatments in elderly individuals, discussing their efficacy on clinical and neuroimaging outcomes and identifying current methodological issues. Future perspectives, relevant for the scientific community and the worldwide public health institutes will be further discussed.

Obesity and sex interact in the regulation of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, for which a number of genetic, environmental, and lifestyle risk factors have been identified. A significant modifiable risk factor is obesity in mid-life. Interestingly, both obesity and AD exhibit sex differences and are regulated by sex steroid hormones. Accumulating evidence suggests interactions between obesity and sex in regulation of AD risk, although the pathways underlying this relationship are unclear. Inflammation and the E4 allele of apolipoprotein E have been identified as independent risk factors for AD and both interact with obesity and sex steroid hormones. We review the individual and cooperative effects of obesity and sex on development of AD and examine the potential contributions of apolipoprotein E, inflammation, and their interactions to this relationship.

Association between Lifetime Physical Activity and Cognitive Functioning in Middle-Aged and Older Community Dwelling Adults: Results from the Brain in Motion Study

To determine if total lifetime physical activity (PA) is associated with better cognitive functioning with aging and if cerebrovascular function mediates this association. A sample of 226 (52.2% female) community dwelling middle-aged and older adults (66.5 ± 6.4 years) in the Brain in Motion Study, completed the Lifetime Total Physical Activity Questionnaire and underwent neuropsychological and cerebrovascular blood flow testing. Multiple robust linear regressions were used to model the associations between lifetime PA and global cognition after adjusting for age, sex, North American Adult Reading Test results (i.e., an estimate of premorbid intellectual ability), maximal aerobic capacity, body mass index and interactions between age, sex, and lifetime PA. Mediation analysis assessed the effect of cerebrovascular measures on the association between lifetime PA and global cognition. Post hoc analyses assessed past year PA and current fitness levels relation to global cognition and cerebrovascular measures. Better global cognitive performance was associated with higher lifetime PA (p=.045), recreational PA (p=.021), and vigorous intensity PA (p=.004), PA between the ages of 0 and 20 years (p=.036), and between the ages of 21 and 35 years (p.5), but partially mediated the relation between current fitness and global cognition. This study revealed significant associations between higher levels of PA (i.e., total lifetime, recreational, vigorous PA, and past year) and better cognitive function in later life. Current fitness levels relation to cognitive function may be partially mediated through current cerebrovascular function.

Strategies to support engagement and continuity of activity during mealtimes for families living with dementia; a qualitative study

BACKGROUND

Mealtimes are an essential part of living and quality of life for everyone, including persons living with dementia. A longitudinal qualitative study provided understanding of the meaning of mealtimes for persons with dementia and their family care partners. Strategies were specifically described by families to support meaningful mealtimes. The purpose of this manuscript is to describe the strategies devised and used by these families living with dementia.

METHODS

A longitudinal qualitative study was undertaken to explore the meaning and experience of mealtimes for families living with dementia over a three-year period. 27 families [older person with dementia and at least one family care partner] were originally recruited from the community of South-Western Ontario. Individual and dyad interviews were conducted each year. Digitally recorded transcripts were analyzed using grounded theory methodology. Strategies were identified and categorized.

RESULTS

Strategies to support quality mealtimes were devised by families as they adapted to their evolving lives. General strategies such as living in the moment, as well as strategies specific to maintaining social engagement and continuity of mealtime activities were reported.

CONCLUSIONS

In addition to nutritional benefit, family mealtimes provide important opportunities for persons with dementia and their family care partners to socially engage and continue meaningful roles. Strategies identified by participants provide a basis for further education and support to families living with dementia.

Comparison of physical activity questionnaires for the elderly with the International Classification of Functioning, Disability and Health (ICF)--an analysis of content

Background

Physical activity questionnaires (PAQ) have been extensively used to determine physical activity (PA) levels. Most PAQ are derived from an energy expenditure-based perspective and assess activities with a certain intensity level. Activities with a moderate or vigorous intensity level are predominantly used to determine a person’s PA level in terms of quantity. Studies show that the time spent engaging in moderate and vigorous intensity PA does not appropriately reflect the actual PA behavior of older people because they perform more functional, everyday activities. Those functional activities are more likely to be considered low-intense and represent an important qualitative health-promoting activity. For the elderly, functional, light intensity activities are of special interest but are assessed differently in terms of quantity and quality. The aim was to analyze the content of PAQ for the elderly.

Methods

N = 18 sufficiently validated PAQ applicable to adults (60+) were included. Each item (N = 414) was linked to the corresponding code of the International Classification of Functioning, Disability and Health (ICF) using established linking rules. Kappa statistics were calculated to determine rater agreement.

Results

Items were linked to 598 ICF codes and 62 different ICF categories. A total of 43.72% of the codes were for sports-related activities and 14.25% for walking-related activities. Only 9.18% of all codes were related to household tasks. Light intensity, functional activities are emphasized differently and are underrepresented in most cases. Additionally, sedentary activities are underrepresented (5.55%). κ coefficients were acceptable for n = 16 questionnaires (0.48-1.00).

Conclusions

There is a large inconsistency in the understandings of PA in elderly. Further research should focus (1) on a conceptual understanding of PA in terms of the behavior of the elderly and (2) on developing questionnaires that inquire functional, light intensity PA, as well as sedentary activities more explicitly.

Associations between Physical Activity in Old Age and Dementia-Related Mortality: A Population-Based Cohort Study

Background

Findings from the literature vary in relation to whether physical activity brings about less cognitive decline in old age. The present study investigated self-reported levels of physical activity in old age and its association with the risk of dementia-related mortality.

Methods

We included data from 31,086 subjects, between 65 and 80 years old, from the CONOR (Cohort of Norway) database. Cox regression analysis was used to estimate the risk of association.

Results

Taking part in ‘light’ (not causing perspiration or panting) activities of <3 h per week was associated with a decreased risk of dementia-related mortality, with a hazard ratio (HR) of 0.74 and a 95% confidence interval (CI) of 0.62-0.88, and of >3 h per week, with an HR of 0.61 and a 95% CI of 0.51-0.73. When taking part in ‘hard’ (causing perspiration or panting) activities, a similar risk (HR = 0.56; 95% CI 0.43-0.72) was observed for >3 h per week. Interestingly, the highest reduction in risk was seen for ‘hard’ activities of <3 h per week (HR = 0.50; 95% CI 0.41-0.61).

Conclusion

Physical activity during leisure time in old age was associated with a lower risk of dementia-related mortality when compared to inactive individuals.