Sedentary Behavior and Incident Dementia Among Older Adults

Association of adherence to the EAT-Lancet diet with risk of dementia according to social economic status: a prospective cohort in UK Biobank

The EAT-Lancet Commission has proposed a reference diet aiming to promote human health and environmental sustainability. Socioeconomic disadvantage and poor diet are well-known risk factors for dementia; however, whether the effect of this reference diet on dementia varies by socioeconomic status has not been investigated. The dietary habits of 190,893 participants from UK-Biobank were assessed; the association of EAT-Lancet diet with incident dementia across socioeconomic status was determined by Cox models. One thousand seven hundred twenty-eight dementia cases were identified during a median of 12.24 years follow-up. An inverse association between adherence to EAT-Lancet diet and all-cause dementia (high vs. low; hazard ratio [HR], 95% confidence interval [CI]: 0.82, 0.72-0.94) or late-onset dementia (high vs. low; HR, 95% CI: 0.78, 0.68-0.91) was observed only in individuals with high socioeconomic status. On the contrary, no protective effects of EAT-Lancet diet on early-onset dementia were observed, regardless of the socioeconomic status. Our findings indicated that adherence to an environment-friendly diet helps attenuate risk of dementia only in individuals with high socioeconomic level.

Association between elevated blood-brain barrier permeability and the risk of progressive cognitive decline: A longitudinal study

BACKGROUND

The breakdown of the blood-brain barrier (BBB) is intricately linked to the onset and advancement of cognitive impairment and dementia. This investigation explores the correlation between blood-brain barrier permeability, assessed through the cerebrospinal fluid/serum albumin ratio (QAlb), in a clinical cohort and the evolution of cognitive decline.

METHODS

This prospective observational cohort study included 295 participants. Cognitive decline progression was characterized by an escalation in the overall deterioration scale and/or clinical dementia rating scores. The investigation delves into the correlation between blood-brain barrier permeability and the advancement of cognitive impairment among patients.

RESULTS

The APOE 4 allele and diabetes mellitus among individuals exhibited increased BBB permeability (P < 0.05). Moreover, AD patients exhibited the highest QAlb levels, signifying elevated BBB permeability compared to individuals with MCI and SCD (P < 0.05). After mean 17 months following up, 117 patients (51.31 %) were identified as experiencing cognitive decline progression, and we found that only AD diagnosis, CDR, and QAlb (All P < 0.05) were significant predictors of cognitive decline progression.

CONCLUSION

Our study emphasizes the clinical relevance of QAlb in detecting individuals with an elevated risk of cognitive decline. It suggests that heightened BBB permeability could contribute to clinical deterioration and serves as a plausible therapeutic target.

Hindlimb immobilization induces insulin resistance and elevates mitochondrial ROS production in the hippocampus of female rats

Alzheimer's disease (AD) is the fifth leading cause of death in older adults, and treatment options are severely lacking. Recent findings demonstrate a strong relationship between skeletal muscle and cognitive function, with evidence supporting that muscle quality and cognitive function are positively correlated in older adults. Conversely, decreased muscle function is associated with a threefold increased risk of cognitive decline. Based on these observations, the purpose of this study was to investigate the negative effects of muscle disuse [via a model of hindlimb immobilization (HLI)] on hippocampal insulin sensitivity and mitochondrial function and identify the potential mechanisms involved. HLI for 10 days in 4-mo-old female Wistar rats resulted in the following novel findings: 1) hippocampal insulin resistance and deficits in whole body glucose homeostasis, 2) dramatically increased mitochondrial reactive oxygen species (ROS) production in the hippocampus, 3) elevated markers for amyloidogenic cleavage of amyloid precursor protein (APP) and tau protein in the hippocampus, 4) and reduced brain-derived neurotrophic factor (BDNF) expression. These findings were associated with global changes in iron homeostasis, with muscle disuse producing muscle iron accumulation in association with decreased serum and whole brain iron levels. We report the novel finding that muscle disuse alters brain iron homeostasis and reveal a strong negative correlation between muscle and brain iron content. Overall, HLI-induced muscle disuse has robust negative effects on hippocampal insulin sensitivity and ROS production in association with altered brain iron homeostasis. This work provides potential novel mechanisms that may help explain how loss of muscle function contributes to cognitive decline and AD risk.NEW & NOTEWORTHY Muscle disuse via hindlimb immobilization increased oxidative stress and insulin resistance in the hippocampus. These findings were in association with muscle iron overload in connection with iron dysregulation in the brain. Overall, our work identifies muscle disuse as a contributor to hippocampal dysfunction, potentially through an iron-based muscle-brain axis, highlighting iron dysregulation as a potential novel mechanism in the relationship between muscle health, cognitive function, and Alzheimer's disease risk.

Effects of reducing sedentary behaviour by increasing physical activity, on cognitive function, brain function and structure across the lifespan: a systematic review and meta-analysis

OBJECTIVE

To examine the acute and chronic effects of reducing prolonged sedentary time (ST) with physical activity (PA) on cognitive and brain health.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed, Scopus, CINAHL, PsycINFO, SPORTDiscus, Web of Science, and ProQuest Dissertation and Theses.

ELIGIBILITY CRITERIA

Randomised controlled trials (RCTs) published from inception to 17 June 2024, with healthy participants without cognitive impairment or neurological conditions that affect cognitive functioning, aged ≥4 years, testing acute and chronic effects of reducing ST and/or prolonged ST by reallocating ST to PA on cognitive function, brain function, and structure.

RESULTS

We included 25 RCTs (n=1289) investigating acute (21 studies) and chronic (4 studies) effects on cognitive function (acute: n=20, chronic: n=4) and brain function (acute: n=7, chronic: n=1); there were no studies on brain structure. Acutely interrupting continuous ST with either multiple or a single PA bout improved cognitive function measured from 3 hours to three consecutive days based on 91 effect sizes (g=0.17, 95% CI: 0.05 to 0.29, p=0.005, I 2=45.5%). When comparing single versus multiple PA bouts, only multiple PA bouts yielded a positive effect on cognitive function based on 72 effect sizes (g=0.20, 95% CI: 0.06 to 0.35, p=0.006; I 2=48.8%). Chronic studies reported null findings on cognitive function (n=4), with some evidence of improved neural efficiency of the hippocampus (n=1).

CONCLUSION

Interrupting ST with PA acutely improves cognitive function. The evidence from chronic studies remains inconclusive.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020200998.

Factors Affecting Resilience and Prevention of Alzheimer's Disease and Related Dementias

Alzheimer's disease (AD) is a devastating, age-associated neurodegenerative disorder and the most common cause of dementia. The clinical continuum of AD spans from preclinical disease to subjective cognitive decline, mild cognitive impairment, and dementia stages (mild, moderate, and severe). Neuropathologically, AD is defined by the accumulation of amyloid β (Aβ) into extracellular plaques in the brain parenchyma and in the cerebral vasculature, and by abnormally phosphorylated tau that accumulates intraneuronally forming neurofibrillary tangles (NFTs). Development of treatment approaches that prevent or even reduce the cognitive decline because of AD has been slow compared to other major causes of death. Recently, the United States Food and Drug Administration gave full approval to 2 different Aβ-targeting monoclonal antibodies. However, this breakthrough disease modifying approach only applies to a limited subset of patients in the AD continuum and there are stringent eligibility criteria. Furthermore, these approaches do not prevent progression of disease, because other AD-related pathologies, such as NFTs, are not directly targeted. A non-mutually exclusive alternative is to address lifestyle interventions that can help reduce the risk of AD and AD-related dementias (ADRD). It is estimated that addressing such modifiable risk factors could potentially delay up to 40% of AD/ADRD cases. In this review, we discuss some of the many modifiable risk factors that may be associated with prevention of AD/ADRD and/or increasing brain resilience, as well as other factors that may interact with these modifiable risk factors to influence AD/ADRD progression. ANN NEUROL 2024.

Post-diagnosis smoking habit change and incident dementia in cancer survivors

INTRODUCTION

Many individuals change their smoking habits after cancer diagnosis. We aimed to evaluate the association of post-diagnosis smoking habit change with incident dementia in cancer survivors.

METHODS

We identified 558,127 individuals who were diagnosed with cancer at age ≥ 20 and survived for ≥ 3 years. Participants were classified into four groups: (1) sustained non-smokers, (2) initiators/relapsers, (3) quitters, and (4) continuing smokers. Dementia risk in each group was assessed using a cause-specific Cox model.

RESULTS

After cancer diagnosis, 2.3% of pre-diagnosis non-smokers initiated/relapsed into smoking, while 51.7% of pre-diagnosis smokers quit smoking. Compared to sustained non-smokers, multivariable-adjusted risk of dementia was 29% higher among initiators/relapsers, 11% higher among quitters, and 31% higher among continuing smokers. Compared to continuing smokers, the risk was 15% lower among quitters.

DISCUSSION

In cancer survivors, smoking initiation/relapse was associated with increased risk of dementia, whereas smoking cessation was associated with decreased risk of dementia.

HIGHLIGHTS

Approximately half of pre-diagnosis smokers quit smoking after a cancer diagnosis. Smoking cessation was associated with a 15% reduced risk of dementia. More than 2% of pre-diagnosis non-smokers initiated or relapsed into smoking after a cancer diagnosis. Smoking initiation/relapse was associated with a 29% elevated risk of dementia.

Modifiable risk factors for mild cognitive impairment among cognitively normal community-dwelling older adults: A systematic review and meta-analysis

Although numerous studies have investigated modifiable risk factors for mild cognitive impairment (MCI) among community-dwelling seniors, no meta-analysis has summarized these findings. Five databases were searched from January 1, 2000, to December 30, 2023. The protocol was registered with PROSPERO. Data were extracted and reported following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Relevant meta-analyses of modifiable risk factors were performed. The evidence of each factor was assessed by the GRADE for cohort studies. Of 16,651 citations, 87 studies involving 225,584 community-dwelling seniors were included. Fourteen meta-analyses involving 20 studies with 44,199 participants were performed. The analyses revealed low-to-moderate-quality evidence supporting that diabetes, 2 or more comorbidities, anxiety, apathy, depressive symptoms, and physical frailty were risk factors for incident MCI in older adults. Conversely, hypertension, agitation, and irritability might not be risk factors. Additionally, moderate-quality evidence supports the protective effect of engaging in cognitive-demanding activities on the onset of MCI. Collectively, this study constitutes the first extensive compilation of evidence regarding the various risk factors for the development of MCI in older adults. Our findings hold significant potential to guide the formulation of prevention and management strategies to either prevent or potentially reverse the onset of MCI.

Crosstalk between bone and brain in Alzheimer's disease: Mechanisms, applications, and perspectives

Alzheimer's disease (AD) is a neurodegenerative disease that involves multiple systems in the body. Numerous recent studies have revealed bidirectional crosstalk between the brain and bone, but the interaction between bone and brain in AD remains unclear. In this review, we summarize human studies of the association between bone and brain and provide an overview of their interactions and the underlying mechanisms in AD. We review the effects of AD on bone from the aspects of AD pathogenic proteins, AD risk genes, neurohormones, neuropeptides, neurotransmitters, brain-derived extracellular vesicles (EVs), and the autonomic nervous system. Correspondingly, we elucidate the underlying mechanisms of the involvement of bone in the pathogenesis of AD, including bone-derived hormones, bone marrow-derived cells, bone-derived EVs, and inflammation. On the basis of the crosstalk between bone and the brain, we propose potential strategies for the management of AD with the hope of offering novel perspectives on its prevention and treatment. HIGHLIGHTS: The pathogenesis of AD, along with its consequent changes in the brain, may involve disturbing bone homeostasis. Degenerative bone disorders may influence the progression of AD through a series of pathophysiological mechanisms. Therefore, relevant bone intervention strategies may be beneficial for the comprehensive management of AD.

Physical Activity and Sedentary Behavior as Treatable Traits for Clinical Control in Moderate-to-Severe Asthma

BACKGROUND

Physical activity and sedentary behavior are treatable traits that may impact asthma control in distinct manners, but this impact remains poorly understood.

OBJECTIVE

To evaluate the influence of physical activity and sedentary behavior on clinical control in adults with moderate-to-severe asthma.

METHODS

This cross-sectional, multicentric study included 426 individuals with moderate-to-severe asthma. Assessments included physical activity and sedentary time (actigraphy), clinical asthma control (Asthma Control Questionnaire [ACQ]), quality of life (Asthma Quality of Life Questionnaire), anxiety and depression symptoms (Hospital Anxiety and Depression Scale), anthropometric data, and lung function. Participants were grouped according to physical activity levels and sedentary behavior.

RESULTS

Participants who walked ≥7500 steps/day presented better ACQ scores than those who walked <7500 steps/day (P < .05), independent of sedentary status. The percentage of patients with controlled asthma was higher in the active/sedentary (43.9%) and active/nonsedentary (43.8%) groups than in the inactive/sedentary (25.4%) and inactive/nonsedentary (23.9%) groups (P < .02). The likelihood of having uncontrolled asthma according to the treatable traits of physical inactivity (odds ratio [95% confidence interval]: 2.36 [1.55-3.59]), higher anxiety (2.26 [1.49-3.42]), and depression symptoms (1.95 [1.28-2.95]) was significant (P ≤ .002). Obesity and sedentary time were not associated with asthma control.

CONCLUSIONS

Our results show that ≥7500 steps/day is associated with better asthma control independent of sedentary time in adults with moderate-to-severe asthma. Physical inactivity, anxiety, and depression symptoms are associated with higher odds of uncontrolled asthma. These results suggest that interventions should mainly focus on increasing physical activity rather than reducing sedentary time.

Sedentary behavior from television watching elevates GlycA levels: A bidirectional Mendelian randomization study

BACKGROUND

Current evidence linking sedentary behavior (SB), physical activity (PA), and inflammation raises questions about their causal relationships, prompting concerns about potential residual confounding or reverse causation.

METHODS

A bidirectional Mendelian randomization (MR) analysis was conducted. SB data (n = 408,815) from "computer use," "television watching," and "driving" were included. The PA data encompassed nine types of PA (n = 460,376) over the last four weeks and included data on the frequency of vigorous PA (n = 440,512) and moderate PA (n = 440,266) for over 10 min. Additionally, three genome-wide association study datasets (n = 64,949) on light, moderate, and vigorous exercise were included to minimize potential bias from changes in exercise intensity. Inflammation data included levels of C-reactive protein (CRP) (n = 575,531), glycoprotein acetyl (GlycA) (n = 115,082), interleukin (IL)-8, IL-6, IL-6 receptor (IL-6R), and soluble IL-6R (sIL-6R) (n = 35,278). All datasets represented participants of European ancestry.

RESULTS

Television watching as an SB showed significant positive causal effects on GlycA and CRP (inverse variance weighted (IVW), odds ratios (OR): 1.34, 95% confidence intervals (CI): 1.25-1.44, p = 3.570 × 10-17; IVW, OR: 1.21, 95% CI: 1.16-1.26, p = 1.500 × 10-19, respectively), with more robust evidence for GlycA. In the direction from inflammation to PA, a negative causal relationship between CRP and"number of days/week of moderate PA 10+ minutes"was observed (IVW, OR: 0.92, 95% CI: 0.89-0.96, p = 3.260 × 10-5). Sensitivity analyses were used to verify the robustness and reliability of the results. However, other initially observed associations ceased to be significant after controlling for obesity-related confounders.

CONCLUSION

Our MR analysis suggested a potential causal relationship between television watching and chronic low-grade inflammation, with more substantial evidence for GlycA. Additionally, different types of SB may have varying effects on inflammation. Obesity-related traits could partly or entirely influence the relationship between SB, PA, and inflammatory markers. Furthermore, Our findings indicate that SB is an independent risk factor for inflammation, separate from PA, and highlight the different mechanisms by which SB and PA affect disease.

Associations between accelerometer-derived sedentary behavior and physical activity with white matter hyperintensities in middle-aged to older adults

INTRODUCTION

We examined the relationship between sedentary behavior (SB), moderate-to-vigorous physical activity (MVPA), and white matter hyperintensity (WMH) volumes, a common magnetic resonance imaging (MRI) marker associated with risk of neurodegenerative disease in middle-aged to older adults.

METHODS

We used data from the UK Biobank (n = 14,415; 45 to 81 years) that included accelerometer-derived measures of SB and MVPA, and WMH volumes from MRI.

RESULTS

Both MVPA and SB were associated with WMH volumes (βMVPA = -0.03 [-0.04, -0.01], p < 0.001; βSB = 0.02 [0.01, 0.03], p = 0.007). There was a significant interaction between SB and MVPA on WMH volumes (βSB×MVPA = -0.015 [-0.028, -0.001], p SB×MVPA = 0.03) where SB was positively associated with WMHs at low MVPA, and MVPA was negatively associated with WMHs at high SB.

DISCUSSION

While this study cannot establish causality, the results highlight the potential importance of considering both MVPA and SB in strategies aimed at reducing the accumulation of WMH volumes in middle-aged to older adults.

Highlights

SB is associated with greater WMH volumes and MVPA is associated with lower WMH volumes.Relationships between SB and WMH are strongest at low levels of MVPA.Associations between MVPA and WMH are strongest at high levels of SB.Considering both SB and MVPA may be effective strategies for reducing WMHs.

Digital measures in epilepsy in low-resourced environments

INTRODUCTION

Digital measures and digital health-care delivery have been rarely implemented in lower-and-middle-income countries (LMICs), contributing to worsening global disparities and inequities. Sustainable ways to implement and use digital approaches will help to improve time to access, management, and quality of life in persons with epilepsy, goals that remain unreachable in under-resourced communities. As under-resourced environments differ in human and economic resources, no one approach will be appropriate to all LMICs.

AREAS COVERED

Digital health and tools to monitor and measure digital endpoints and metrics of quality of life will need to be developed or adapted to the specific needs of under-resourced areas. Portable technologies may partially address the urban-rural divide. Careful delineation of stakeholders and their engagement and alignment in all efforts is critically important if these initiatives are to be successfully sustained. Privacy issues, neglected in many regions globally, must be purposefully addressed.

EXPERT OPINION

Epilepsy care in under-resourced environments has been limited by the lack of relevant technologies for diagnosis and treatment. Digital biomarkers, and investigative technological advances, may finally make it feasible to sustainably improve care delivery and ultimately quality of life including personalized epilepsy care.

Historic Cognitive Function Trajectories as Predictors of Sedentary Behavior and Physical Activity in Older Adults

BACKGROUND

We examined whether trajectories of cognitive function over 10 years predict later-life physical activity (PA), sedentary time (ST), and sleep.

METHODS

Participants were from the Adult Changes in Thought (ACT) cohort study. We included 611 ACT participants who wore accelerometers and had 3+ measures of cognition in the 10 years prior to accelerometer wear. The Cognitive Assessment Screening Instrument (CASI) measured cognition and was scored using item-response theory (IRT). activPAL and ActiGraph accelerometers worn over 7 days measured ST and PA outcomes. Self-reported time in bed and sleep quality measured sleep outcomes. Analyses used growth mixture modeling to classify CASI-IRT scores into latent groups and examine associations with PA, ST, and sleep including demographic and health covariates.

RESULTS

Participants (Mean age = 80.3 (6.5) years, 90.3% White, 57.1% female, 29.3% had less than 16 years of education) fell into 3 latent trajectory groups: average stable CASI (56.1%), high stable CASI (34.0%), and declining CASI (9.8%). The declining group had 16 minutes less stepping time (95% confidence interval [95% CI]: 0.6, 31.4), 1 517 fewer steps per day (95% CI: 138, 2 896), and 16.3 minutes per day less moderate-to-vigorous PA (95% CI: 1.3, 31.3) compared to the average stable group. There were no associations between CASI trajectory and sedentary or sleep outcomes.

CONCLUSIONS

Declining cognition predicted lower PA providing some evidence of a reverse relationship between PA and cognition in older adults. However, this conclusion is limited by having outcomes at only one time point, a nonrepresentative sample, self-reported sleep outcomes, and using a global cognition measure.

Association between elevated systemic inflammatory markers and the risk of cognitive decline progression: a longitudinal study

BACKGROUND

Chronic systemic inflammation is linked to cognitive decline pathogenesis. This study investigates the association between systemic inflammation markers and cognitive decline progression in a clinical cohort.

METHODS

This prospective observational cohort study enrolled 295 participants. Cognitive decline progression was defined by an increase in clinical dementia rating (CDR) scores. The study examines the correlation between systemic inflammation markers, including systemic Inflammation Response Index (SIRI), systemic Immune-Inflammation Index (SII), prognostic Inflammatory and Nutritional Index (PIV), and cognitive impairment progression.

RESULTS

The presence of the APOE 4 allele and diabetes mellitus was associated with elevated PIV levels (P < 0.05). Additionally, AD patients had the highest SII levels, indicating increased inflammation compared to individuals with MCI and SCD (P < 0.05). After a mean follow-up of 17 months, 117 patients (51.31%) experienced cognitive decline progression. AD diagnosis, CDR, and SII were significant predictors of cognitive decline progression (All P < 0.05).

CONCLUSION

This study highlights the clinical significance of elevated systemic inflammation markers in identifying individuals at risk of cognitive decline. Addressing inflammation may offer a promising approach to improving cognitive health and mitigating age-related cognitive decline.

Changes in sedentary behavior in the chronic phase following stroke

BACKGROUND

Sedentary behavior increases risk for cardiovascular diseases. Little is known about sedentary behavior through the chronic phase after stroke. We aimed to describe how long and short bouts of sedentary behavior changed over the first three years after stroke and if cognition at baseline was an independent risk factor for sedentary behavior.

METHODS

This is a sub-study of the Norwegian cognitive impairment after stroke (Nor-COAST) study, a multicenter study recruiting patients with acute stroke. Sedentary behavior was monitored with a thigh-worn sensor (ActivPal3®), at three-, 18- and 36-months post stroke. Stroke severity was assessed by National Institutes of Health Stroke Scale (NIHSS) and cognition by Montreal cognitive assessment (MoCA). Mixed model analysis with mean number of sedentary minutes accumulated daily as the dependent variable was repeated for all four zones (<30min, 30-60min, 60-90min, >90min) and for total sedentary time.

RESULTS

The number of included participants was 528 (mean age 71.4, NIHSS on day 1, 2.7). The total amount of sedentary time accumulated between 08.00-22.00 increased significantly from about 9.8 hours at three months to 10.1 hours at 36 months post stroke (p=0.002). Patient characteristics associated with prolonged duration of the sedentary bouts and sedentary time were age, high BMI, comorbidities, and impaired physical function. No significant associations between MoCA score and sedentary time were found.

CONCLUSION

The participants became increasingly sedentary and had fewer breaks in sedentary time from three to 36 months after stroke. Baseline cognition was not related to later sedentary behavior.

Physical activity patterns and cognitive function in elderly women: a cross-sectional study from NHANES 2011-2014

Background

Amid the backdrop of global aging, the increasing prevalence of cognitive decline among the elderly, particularly within the female demographic, represents a considerable public health concern. Physical activity (PA) is recognized as an effective non-pharmacological intervention for mitigating cognitive decline in older adults. However, the relationship between different PA patterns and cognitive function (CF) in elderly women remains unclear.

Methods

This study utilized data from National Health and Nutrition Examination Survey (NHANES) 2011-2014 to investigate the relationships between PA, PA patterns [inactive, Weekend Warrior (WW), and Regular Exercise (RE)], and PA intensity with CF in elderly women. Multivariate regression analysis served as the primary analytical method.

Results

There was a significant positive correlation between PA and CF among elderly women (β-PA: 0.003, 95% CI: 0.000-0.006, P = 0.03143). Additionally, WW and RE activity patterns were associated with markedly better cognitive performance compared to the inactive group (β-WW: 0.451, 95% CI: 0.216-0.685, P = 0.00017; β-RE: 0.153, 95% CI: 0.085-0.221, P = 0.00001). Furthermore, our results indicate a progressive increase in CF with increasing PA intensity (β-MPA- dominated: 0.16, 95% CI: 0.02-0.09, P = 0.0208; β-VPA-dominated: 0.21, 95% CI: 0.09-0.34, P = 0.0011; β-Total VPA: 0.31, 95% CI: -0.01-0.63, P = 0.0566).

Conclusion

Our study confirms a positive association between PA and CF in elderly women, with even intermittent but intensive PA models like WW being correlated with improved CF. These findings underscore the significant role that varying intensities and patterns of PA play in promoting cognitive health among older age groups, highlighting the need for adaptable PA strategies in public health initiatives targeting this population.

Does Physical Exercise Modify the Pathophysiology of Alzheimer's Disease in Older Persons?

Physical exercise is well known for its benefits on brain health. However, the mechanisms through which these benefits occur remain discussed, especially in the context of cognitive conditions such as Alzheimer's disease. The present short review summarizes the findings of interventional studies that examined the effects of exercise training on the specific and non-specific biomarkers of Alzheimer's disease. Controlled exercise intervention studies published in the English language were selected if they assessed the effects of a physical exercise intervention of at least 2 weeks in middle-aged or older adults on one of the following biomarkers measured either in the brain, the cerebrospinal fluid or the blood: beta-amyloid, tau, neurofilament light chain, and glial fibrillary acidic protein. Overall, there was no strong evidence of significant effects of exercise interventions on any of the selected biomarkers. However, in specific populations, such as women with obesity, pre-diabetes, or depression, favorable changes in blood beta-amyloid concentrations were reported. Further benefits on cerebrospinal fluid beta-amyloid were also demonstrated in APOE-ε4 allele carriers with Alzheimer's disease. In conclusion, the current evidence suggests that physical exercise does not modulate the pathophysiology of Alzheimer's disease in the overall population of middle-aged and older adults. Nonetheless, some specific populations, such as women with metabolic disorders and Alzheimer's disease patients with APOE-ε4 genotype, seem to be favorably affected. Further studies, including long follow-ups, large sample sizes, and concomitantly assessing the effects of other factors such as sedentary behavior and diet, are required to bring further evidence to the field.

Reversal of Soleus Muscle Atrophy in Older Adults: A Non-Volitional Exercise Intervention for a Changing Climate

The World Health Organization recommends that older adults undertake at least 150 minutes of moderate intensity physical activity over the course of each week in order to maintain physical, mental, and social health. This goal turns out to be very difficult for most community dwelling older adults to achieve, due to both actual and perceived barriers. These barriers include personal health limitations, confinement issues, and self-imposed restrictions such as fear of injury. Climate change exacerbates the confinement issues and injury fears among the elderly. To assist older adults in obtaining the benefits of increased physical activity under increasingly challenging climate conditions, we propose a targeted non-volitional intervention which could serve as a complement to volitional physical activity. Exogenous neuro-muscular stimulation of the soleus muscles is a non-invasive intervention capable of significantly increasing cardiac output in sedentary individuals. Long-term daily use has been shown to improve sleep, reduce bone loss, and reverse age-related cognitive decline, all of which are significant health concerns for older adults. These outcomes support the potential benefit of exogenous neuro-muscular stimulation as a complementary form of physical activity which older adults may find convenient to incorporate into their daily life when traditional forms of exercise are difficult to achieve due to barriers to completing traditional physical activities as a result of in-home or in-bed confinement, perceptual risks, or real environmental risks such as those arising from climate change.

Sedentary behavior and lifespan brain health

Higher levels of physical activity are known to benefit aspects of brain health across the lifespan. However, the role of sedentary behavior (SB) is less well understood. In this review we summarize and discuss evidence on the role of SB on brain health (including cognitive performance, structural or functional brain measures, and dementia risk) for different age groups, critically compare assessment approaches to capture SB, and offer insights into emerging opportunities to assess SB via digital technologies. Across the lifespan, specific characteristics of SB (particularly whether they are cognitively active or cognitively passive) potentially act as moderators influencing the associations between SB and specific brain health outcomes. We outline challenges and opportunities for future research aiming to provide more robust empirical evidence on these observations.

Oxygen imaging of hypoxic pockets in the mouse cerebral cortex

Consciousness is lost within seconds upon cessation of cerebral blood flow. The brain cannot store oxygen, and interruption of oxidative phosphorylation is fatal within minutes. Yet only rudimentary knowledge exists regarding cortical partial oxygen tension (Po2) dynamics under physiological conditions. Here we introduce Green enhanced Nano-lantern (GeNL), a genetically encoded bioluminescent oxygen indicator for Po2 imaging. In awake behaving mice, we uncover the existence of spontaneous, spatially defined "hypoxic pockets" and demonstrate their linkage to the abrogation of local capillary flow. Exercise reduced the burden of hypoxic pockets by 52% compared with rest. The study provides insight into cortical oxygen dynamics in awake behaving animals and concurrently establishes a tool to delineate the importance of oxygen tension in physiological processes and neurological diseases.

Dietary and Lifestyle Factors of Brain Iron Accumulation and Parkinson's Disease Risk

Purpose

Iron is an essential nutrient which can only be absorbed through an individual's diet. Excess iron accumulates in organs throughout the body including the brain. Iron dysregulation in the brain is commonly associated with neurodegenerative diseases like Alzheimer's disease and Parkinson's Disease (PD). Our previous research has shown that a pattern of iron accumulation in motor regions of the brain related to a genetic iron-storage disorder called hemochromatosis is associated with an increased risk of PD. To understand how diet and lifestyle factors relate to this brain endophenotype and risk of PD we analyzed the relationship between these measures, estimates of nutrient intake, and diet and lifestyle preference using data from UK Biobank.

Methods

Using distinct imaging and non-imaging samples (20,477 to 28,388 and 132,023 to 150,603 participants, respectively), we performed linear and logistic regression analyses using estimated dietary nutrient intake and food preferences to predict a) brain iron accumulation score (derived from T2-Weighted Magnetic Resonance Imaging) and b) PD risk. In addition, we performed a factor analysis of diet and lifestyle preferences to investigate if latent lifestyle factors explained significant associations. Finally, we performed an instrumental variable regression of our results related to iron accumulation and PD risk to identify if there were common dietary and lifestyle factors that were jointly associated with differences in brain iron accumulation and PD risk.

Results

We found multiple highly significant associations with measures of brain iron accumulation and preferences for alcohol (factor 7: t=4.02, pFDR=0.0003), exercise (factor 11: t=-4.31, pFDR=0.0001), and high-sugar foods (factor 2: t=-3.73, pFDR=0.0007). Preference for alcohol (factor 7: t=-5.83, pFDR<1×10-8), exercise (factor 11: t=-7.66, pFDR<1×10-13), and high sugar foods (factor 2: t=6.03, pFDR<1×10-8) were also associated with PD risk. Instrumental variable regression of individual preferences revealed a significant relationship in which dietary preferences associated with higher brain iron levels also appeared to be linked to a lower risk for PD (p=0.004). A similar relationship was observed for estimates of nutrient intake (p=0.0006). Voxel-wise analysis of i) high-sugar and ii) alcohol factors confirmed T2-weighted signal differences consistent with iron accumulation patterns in motor regions of the brain including the cerebellum and basal ganglia.

Conclusion

Dietary and lifestyle factors and preferences, especially those related to carbohydrates, alcohol, and exercise, are related to detectable differences in brain iron accumulation and alterations in risk of PD, suggesting a potential avenue for lifestyle interventions that could influence risk.

Physical inactivity causes exercise resistance of fat metabolism: harbinger or culprit of disease?

Physical inactivity is the fourth leading cause of death in the world. It is associated with myriad diseases and premature death. Two possible contributing factors are postprandial lipidaemia (PPL), which accelerates atherosclerosis, and impaired whole-body fat oxidation, which contributes to obesity. Acute exercise in physically active people is effective for increasing whole body fat oxidation and lowering PPL the next morning. However, in people who have low physical activity (<8000 steps/day), an acute bout of exercise (1 h at 62% maximal oxygen consumption) has no effect on increasing fat oxidation or reducing PPL ('exercise resistance'). The acute harms of inactivity are not due to the lack of exercise and are more powerful than the benefits of exercise, at least regarding fat metabolism. The increase in mortality with reduced daily steps is remarkably steep. Low background steps/day also impair the metabolic adaptations to short-term endurance training, suggesting that the ills of inactivity extend beyond fat metabolism. 'Exercise resistance' with inactivity could be a culprit, causing atherosclerosis, or maybe also a harbinger (impaired fat oxidation) of more widespread diseases. Recommendations regarding the amount of moderate to vigorous exercise needed for health should factor in the amount of background activity (i.e. ∼8000 steps/day) necessary to avoid 'exercise resistance'.