The short-term effects of sedentary behaviour on cerebral hemodynamics and cognitive performance in older adults: a cross-over design on the potential impact of mental and/or physical activity

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.

Association of 24-Hour movement behavior and cognitive function in older Taiwanese adults

OBJECTIVES

This study investigates how 24-hour movement behaviors (physical activity, sedentary time, sleep) relate to cognitive performance in older adults.

METHODS

213 adults (aged 65+) wore accelerometers to track activity. Cognitive function was assessed using the Mini-Mental State Examination (MMSE). Isotemporal substitution analysis examined how replacing one behavior with another affected cognition.

RESULTS

Increased light physical activity was linked to better cognitive function, whereas longer sleep had a negative impact. Replacing 30 min of sedentary behavior or sleep with light physical activity improved orientation, attention, language, and short-term memory. Substituting moderate-to-vigorous physical activity did not have the same cognitive benefit.

CONCLUSION

Encouraging older adults to replace sedentary time or excess sleep with light physical activity could support cognitive health and potentially help prevent dementia. These findings have implications for public health strategies promoting cognitive well-being in aging populations.

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.

Effects of Physical Exercise on Cerebral Blood Velocity in Older Adults: A Systematic Review and Meta-Analysis

As the older population grows, there is an increasing interest in understanding how physical exercise can counteract the changes seen with aging. The benefits of exercise to general health, and especially to the cardiovascular system, have been a topic of discussion for decades. However, there is still a need to elucidate the effects of training programs on the cerebrovascular blood velocity in older people. This systematic review and meta-analysis aimed to investigate the effect of physical exercise on the cerebral blood velocity in older people (PROSPERO CRD42019136305). A search was performed on PubMed, Web of Science, EBSCO, ScienceDirect, and Scopus from the inception of this study to October 2023, retrieving 493 results, of which 26 were included, analyzing more than 1000 participants. An overall moderate risk of bias was found for the studies using the Cochrane risk-of-bias tools for randomized and non-randomized clinical trials. The pooled results of randomized trials showed that older people who underwent physical exercise presented a statistically significant increase in cerebral blood velocity (3.58; 95%CI = 0.51, 6.65; p = 0.02). This result indicates that physical exercise is important to help maintain cerebral health in older adults.

Physiology of sedentary behavior

Sedentary behaviors (SB) are characterized by low energy expenditure while in a sitting or reclining posture. Evidence relevant to understanding the physiology of SB can be derived from studies employing several experimental models: bed rest, immobilization, reduced step count, and reducing/interrupting prolonged SB. We examine the relevant physiological evidence relating to body weight and energy balance, intermediary metabolism, cardiovascular and respiratory systems, the musculoskeletal system, the central nervous system, and immunity and inflammatory responses. Excessive and prolonged SB can lead to insulin resistance, vascular dysfunction, shift in substrate use toward carbohydrate oxidation, shift in muscle fiber from oxidative to glycolytic type, reduced cardiorespiratory fitness, loss of muscle mass and strength and bone mass, and increased total body fat mass and visceral fat depot, blood lipid concentrations, and inflammation. Despite marked differences across individual studies, longer term interventions aimed at reducing/interrupting SB have resulted in small, albeit marginally clinically meaningful, benefits on body weight, waist circumference, percent body fat, fasting glucose, insulin, HbA1c and HDL concentrations, systolic blood pressure, and vascular function in adults and older adults. There is more limited evidence for other health-related outcomes and physiological systems and for children and adolescents. Future research should focus on the investigation of molecular and cellular mechanisms underpinning adaptations to increasing and reducing/interrupting SB and the necessary changes in SB and physical activity to impact physiological systems and overall health in diverse population groups.

Variety and Duration of Different Sedentary Behaviors, Inflammation, Genetic Susceptibility, and New-Onset Dementia in the Older Population

OBJECTIVES

We aimed to evaluate the relationship of the variety and duration of different sedentary behaviors (TV-watching, driving, and nonoccupational computer use) with the risk of dementia in older participants, and examine whether inflammation and genetic susceptibility may modify the relationship.

DESIGN

A prospective cohort study.

SETTING AND PARTICIPANTS

173,829 older participants (≥60 years) without prior dementia in the UK Biobank were enrolled.

METHODS

A healthy sedentary behavior score was calculated as the number of the 3 major sedentary behaviors with a duration associated with the lowest risk of dementia. The primary outcome was new-onset all-cause dementia.

RESULTS

During a median follow-up of 12.4 years, 4965 (2.9%) participants developed new-onset dementia. There were U-shaped associations for TV-watching and driving time, and a reversed J-shaped association for nonoccupational computer use time with new-onset all-cause dementia, with the lowest dementia risk at >0-<2 hours/day for all the 3 sedentary behaviors. Moreover, a higher healthy sedentary behavior score was significantly associated with a lower risk of all-cause dementia (per 1 score increment: hazard ratio 0.78, 95% CI 0.75-0.81), with a stronger inverse association in those with higher levels of high-sensitivity C-reactive protein and monocytes (both P-interactions <.05). Genetic risks of dementia did not significantly modify the association. Similar trends were found for new-onset Alzheimer's disease and vascular dementia.

CONCLUSIONS AND IMPLICATIONS

The associations between the duration of different sedentary behaviors and new-onset dementia were different in the older population. Moreover, the variety of sedentary behavior was inversely associated with new-onset dementia, especially among those with higher levels of inflammation.

Differentiating the influence of sedentary behavior and physical activity on brain health in late adulthood

Public health messaging calls for individuals to be more physically active and less sedentary, yet these lifestyle behaviors have been historically studied independently. Both physical activity (PA) and sedentary behavior (SB) are linked through time-use in a 24-hour day and are related to health outcomes, such as neurocognition. While the benefits of PA on brain health in late adulthood have been well-documented, the influence of SB remains to be understood. The purpose of this paper was to critically review the evolving work on SB and brain health in late adulthood and emphasize key areas of consideration to inform potential research. Overall, the existing literature studying the impact of SB on the components and mechanisms of brain health are mixed and inconclusive, provided largely by cross-sectional and observational work employing a variety of measurement techniques of SB and brain health outcomes. Further, many studies did not conceptually or statistically account for the role of PA in the proposed relationships. Therefore, our understanding of the way in which SB may influence neurocognition in late adulthood is limited. Future efforts should include more prospective longitudinal and randomized clinical trials with intentional methodological approaches to better understand the relationships between SB and the brain in late adulthood, and how these potential links are differentiated from PA.

The Physiological and Molecular Links Between Physical Activity and Brain Health: A Review

There is currently an epidemic of sedentary behavior throughout the world, leading to negative impacts on physical health and contributing to both mortality and burden of disease. The consequences of this also impact the brain, where increased levels of cognitive decline are observed in individuals who are more sedentary. This review explores the physiological and molecular responses to our sedentary propensity, its contribution to several medical conditions and cognitive deficits, and the benefits of moderate levels of physical activity and exercise. Also presented is the recommended level of activity for overall physical health improvement.

The independent and joint association of accelerometer-measured physical activity and sedentary time with dementia: a cohort study in the UK Biobank

BACKGROUND

Research on the association of physical activity and sedentary time with dementia is accumulating, though elusive, and the interaction effects of the two remain unclear. We analysed the joint associations of accelerometer-measured physical activity and sedentary time with risk of incident dementia (all-cause dementia, Alzheimer's disease and vascular dementia).

METHODS

A total of 90,320 individuals from the UK Biobank were included. Accelerometer-measured total volume of physical activity (TPA) and sedentary time were measured at baseline and dichotomised by median (low TPA [< 27 milli-gravity (milli-g)], high TPA [≥ 27 milli-g]; low sedentary time [< 10.7 h/day], high sedentary time [≥ 10.7 h/day]). Cox proportional hazards models were used to evaluate the joint associations with incident dementia on both additive and multiplicative scales.

RESULTS

During a median follow-up of 6.9 years, 501 cases of all-cause dementia were identified. Higher TPA was associated with a lower risk of all-cause dementia, Alzheimer's disease and vascular dementia; the multivariate adjusted hazard ratios (HRs) (95% CI) per 10 milli-g increase were 0.63 (0.55-0.71), 0.74 (0.60-0.90) and 0.69 (0.51-0.93), respectively. Sedentary time was only found to be linked to all-cause dementia, and the HR for high sedentary time was 1.03 (1.01-1.06) compared with that for low sedentary time. No additive and multiplicative relationship of TPA and sedentary time to incident dementia was found (all P values > 0.05).

CONCLUSION

Higher TPA level was related to a lower risk of incident dementia irrespective of sedentary time, which highlighted the implication of promoting physical activity participation to counteract the potential detrimental effect of sedentary time on dementia.

Association between Physical Activity Levels and Brain Volumes in Adults Visiting Radio-Imaging Center of Tertiary Care Hospital

BACKGROUND AND AIM

There is evidence to support the favorable impact of physical activity (PA) on brain volume. However, the empirical evidence exploring the relationship between physical and sedentary behavior remains mixed. We aimed to explore the relationship between PA and sedentary behavior and brain volume.

METHODS

The study sample (n = 150, mean age = 39.7 years) included patients interviewed with the International Physical Activity Questionnaire (IPAQ) who underwent an MRI brain scan. From the images obtained, we measured total intracranial, gray matter, and white matter volume along with the hippocampus, amygdala, parahippocampal gyrus, and posterior cingulate cortex (PCC). Multivariable linear regression analysis was done.

RESULTS AND DISCUSSION

Left hippocampus and overall PA were positively and significantly associated (β = 0.71, p = 0.021) whereas time spent on vigorous physical activity showed a negative association (β = -0.328, p = 0.049) with left hippocampal volume.

CONCLUSION

We found a positive association between total PA and the left hippocampus, whereas vigorous PA showed a negative association with the left hippocampus.

Total Sedentary Time and Cognitive Function in Middle-Aged and Older Adults: A Systematic Review and Meta-analysis

Background

An estimated 47 million people have dementia globally, and around 10 million new cases are diagnosed each year. Many lifestyle factors have been linked to cognitive impairment; one emerging modifiable lifestyle factor is sedentary time.

Objective

To conduct a systematic review and meta-analysis of peer-reviewed literature examining the association between total sedentary time with cognitive function in middle-aged and older adults under the moderating conditions of (a) type of sedentary time measurement; (b) the cognitive domain being assessed; (c) looking at sedentary time using categorical variables (i.e., high versus low sedentary time); and (d) the pattern of sedentary time accumulation (e.g., longer versus shorter bouts). We also aimed to examine the prevalence of sedentary time in healthy versus cognitively impaired populations and to explore how experimental studies reducing or breaking up sedentary time affect cognitive function. Lastly, we aimed to conduct a quantitative pooled analysis of all individual studies through meta-analysis procedures to derive conclusions about these relationships.

Methods

Eight electronic databases (EMBASE; Web of Science; PsycINFO; CINAHL; SciELO; SPORTDiscus; PubMed; and Scopus) were searched from inception to February 2021. Our search included terms related to the exposure (i.e., sedentary time), the population (i.e., middle-aged and older adults), and the outcome of interest (i.e., cognitive function). PICOS framework used middle-aged and older adults where there was an intervention or exposure of any sedentary time compared to any or no comparison, where cognitive function and/or cognitive impairment was measured, and all types of quantitative, empirical, observational data published in any year were included that were published in English. Risk of bias was assessed using QualSyst.

Results

Fifty-three studies including 83,137 participants met the inclusion criteria of which 23 studies had appropriate data for inclusion in the main meta-analysis. The overall meta-analysis suggested that total sedentary time has no association with cognitive function (r = −0.012 [95% CI − 0.035, 0.011], p = 0.296) with marked heterogeneity (I² = 89%). Subgroup analyses demonstrated a significant negative association for studies using a device to capture sedentary time r = −0.035 [95% CI − 0.063, − 0.008], p = 0.012). Specifically, the domains of global cognitive function (r = −0.061 [95% CI − 0.100, − 0.022], p = 0.002) and processing speed (r = −0.067, [95% CI − 0.103, − 0.030], p < 0.001). A significant positive association was found for studies using self-report (r = 0.037 [95% CI − 0.019, 0.054], p < 0.001). Specifically, the domain of processing speed showed a significant positive association (r = 0.057 [95% CI 0.045, 0.069], p < 0.001). For prevalence, populations diagnosed with cognitive impairment spent significantly more time sedentary compared to populations with no known cognitive impairments (standard difference in mean = −0.219 [95% CI − 0.310, − 0.128], p < 0.001).

Conclusions

The association of total sedentary time with cognitive function is weak and varies based on measurement of sedentary time and domain being assessed. Future research is needed to better categorize domains of sedentary behaviour with both a validated self-report and device-based measure in order to improve the strength of this relationship. PROSPERO registration number: CRD42018082384.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-022-00507-x.

Does physical activity moderate the association between device-measured sedentary time patterns and depressive symptoms in adults?

OBJECTIVES

To investigate the association between sedentary time (ST) patterns and depressive symptoms, and whether moderate-to-vigorous physical activity (MVPA) can moderate this association.

METHODS

This cross-sectional study included a representative sample of 243 adults (mean age 41.8±16.7 years, 56.4% women) from a city in Southeast Brazil. Depressive symptoms were estimated through the Hospital Anxiety and Depression Scale (HADS). ST patterns (i.e., number of breaks, mean length of sedentary bouts, and number of long sedentary bouts), total ST, and MVPA were assessed using accelerometers.

RESULTS

Poisson regression models revealed associations of total ST (ß = 0.063; 95%CI 0.011 to 0.116) and number of long bouts (0.108; 0.047 to 0.171) with depressive symptoms among men. MVPA moderated the associations of breaks and longer bouts of ST with depressive symptoms, with an increase of one break/hour, the increase of one long bout, and a decrease of 1 minute in mean bout length being associated with a reduction of 0.211 and increases of 0.081 and 0.166, respectively, in the number of depressive symptoms among men with physical inactivity (breaks = -0.211; -0.360 to -0.063; mean bout length = 0.081; 0.003 to 0.158; number of long bouts = 0.166; 0.090 to 0.242).

CONCLUSION

Interventions that encourage breaking up ST should be helpful to reduce depressive symptoms among people with physical inactivity.

Detrimental effects of physical inactivity on peripheral and brain vasculature in humans: Insights into mechanisms, long-term health consequences and protective strategies

The growing prevalence of physical inactivity in the population highlights the urgent need for a more comprehensive understanding of how sedentary behaviour affects health, the mechanisms involved and what strategies are effective in counteracting its negative effects. Physical inactivity is an independent risk factor for different pathologies including atherosclerosis, hypertension and cardiovascular disease. It is known to progressively lead to reduced life expectancy and quality of life, and it is the fourth leading risk factor for mortality worldwide. Recent evidence indicates that uninterrupted prolonged sitting and short-term inactivity periods impair endothelial function (measured by flow-mediated dilation) and induce arterial structural alterations, predominantly in the lower body vasculature. Similar effects may occur in the cerebral vasculature, with recent evidence showing impairments in cerebral blood flow following prolonged sitting. The precise molecular and physiological mechanisms underlying inactivity-induced vascular dysfunction in humans are yet to be fully established, although evidence to date indicates that it may involve modulation of shear stress, inflammatory and vascular biomarkers. Despite the steady increase in sedentarism in our societies, only a few intervention strategies have been investigated for their efficacy in counteracting the associated vascular impairments. The current review provides a comprehensive overview of the evidence linking acute and short-term physical inactivity to detrimental effects on peripheral, central and cerebral vascular health in humans. We further examine the underlying molecular and physiological mechanisms and attempt to link these to long-term consequences for cardiovascular health. Finally, we summarize and discuss the efficacy of lifestyle interventions in offsetting the negative consequences of physical inactivity.

Social Infrastructure and Street Networks as Critical Infrastructure for Aging Friendly Community Design: Mediating the Effect of Physical Activity

Establishing an age-friendly environment at the community level is essential for promoting healthy aging. This study focused on the relationship between older adults and the community environment through their levels of satisfaction within it. We measured their physical activity (PA) in the community environment and three variables of community-level satisfaction: community environment (SCE), community social infrastructure (SSI), and community street networks (SSN). We analyzed 108 older adult participants in Suzhou using mediation analysis and multiple linear regression to investigate the relationship between physical activity and the community environment. The results of the mediation effect model showed that SCE, SSI, and SSN all affected the physical functions of older adults via the total amount of physical activity (TPA); SSI and SSN affected older adults' physical functions by affecting the total duration of moderate-intensity physical activity (MPA) and vigorous-intensity physical activity (VPA). In addition, SSI and SSN are related to the types of community facilities, street space quality, and accessibility. Our study provides valuable insights into optimizing aging-friendly neighborhoods through moderate-to-vigorous-intensity PAs at both the facility and street space levels.

Sedentary behaviour and brain health in middle-aged and older adults: a systematic review

Sedentary behaviour may increase the risk of dementia. Studying physiological effects of sedentary behaviour on cerebral health may provide new insights into the nature of this association. Accordingly, we reviewed if and how acute and habitual sedentary behaviour relate to brain health factors in middle-aged and older adults (≥45 years). Four databases were searched. Twenty-nine studies were included, with mainly cross-sectional designs. Nine studies examined neurotrophic factors and six studied functional brain measures, with the majority of these studies finding no associations with sedentary behaviour. The results from studies on sedentary behaviour and cerebrovascular measures were inconclusive. There was a tentative association between habitual sedentary behaviour and structural white matter health. An explanatory pathway for this effect might relate to the immediate vascular effects of sitting, such as elevation of blood pressure. Nevertheless, due to the foremost cross-sectional nature of the available evidence, reverse causality could also be a possible explanation. More prospective studies are needed to understand the potential of sedentary behaviour as a target for brain health.

Effect of exercise on cognitive impairment in patients undergoing haemodialyses: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

The influence of exercise on cognition in patients undergoing haemodialysis has been examined. However, evidence elucidating the effects in this patient group is scarce.

OBJECTIVE

To examine the effect of exercise on cognitive impairment in patients undergoing haemodialysis and provide insight into the effects of various characteristics of exercise on cognitive impairment in this population.

DESIGN

A systematic review and meta-analysis, following the guidance of PRISMA was undertaken.

PARTICIPANTS

Adult patients undergoing haemodialysis.

RESULTS

This review found that exercise significantly improved cognitive impairment in patients undergoing haemodialysis (SMD = 0.37, 95% CI: 0.13, 0.60, p = 0.002). Subgroup analyses demonstrated that both intradialytic exercise (SMD = 0.82, 95% CI: 0.37, 1.26, p < 0.001) and interdialytic exercise (SMD = 0.24, 95% CI: 0.01, 0.47, p = 0.038), exercise for 16 weeks or over (SMD = 0.33, 95% CI: 0.07, 0.58, p = 0.012), and lasting for more than 30 minutes (SMD = 0.52, 95% CI: 0.17, 0.86, p = 0.004) significantly alleviated cognitive impairment. The effect of exercise on cognitive impairment in patients less than 65 years of age (SMD = 0.39, 95% CI: 0.10, 0.68, p = 0.009) was significantly better than those over 65.

CONCLUSION

Exercise significantly improves cognitive impairment in patients undergoing haemodialysis. Both Intradialytic and interdialytic exercise of at least 30 minutes duration, 3 times weekly, and at least for 16 weeks may play a significant role in alleviating cognitive impairment in patients under 65 years of age.

Integrative cerebral blood flow regulation in ischemic stroke

Optimizing cerebral perfusion is key to rescuing salvageable ischemic brain tissue. Despite being an important determinant of cerebral perfusion, there are no effective guidelines for blood pressure (BP) management in acute stroke. The control of cerebral blood flow (CBF) involves a myriad of complex pathways which are largely unaccounted for in stroke management. Due to its unique anatomy and physiology, the cerebrovascular circulation is often treated as a stand-alone system rather than an integral component of the cardiovascular system. In order to optimize the strategies for BP management in acute ischemic stroke, a critical reappraisal of the mechanisms involved in CBF control is needed. In this review, we highlight the important role of collateral circulation and re-examine the pathophysiology of CBF control, namely the determinants of cerebral perfusion pressure gradient and resistance, in the context of stroke. Finally, we summarize the state of our knowledge regarding cardiovascular and cerebrovascular interaction and explore some potential avenues for future research in ischemic stroke.

ABBaH teens: Activity Breaks for Brain Health in adolescents: study protocol for a randomized crossover trial

BACKGROUND

Physical activity breaks are widely being implemented in school settings as a solution to increase academic performance and reduce sitting time. However, the underlying physiological mechanisms suggested to improve cognitive function from physical activity and the frequency, intensity, and duration of the breaks remain unknown. This study will investigate the effects of frequent, short physical activity breaks during prolonged sitting on task-related prefrontal cerebral blood flow, cognitive performance, and psychological factors. Additionally, the moderating and mediating effects of arterial stiffness on changes in cerebral blood flow will be tested.

METHODS

This is a protocol for a randomized crossover study that will recruit 16 adolescents (13-14 years old). Participants will undergo three different conditions in a randomized order, on three separate days, involving sitting 80 min with a different type of break every 17 min for 3 min. The breaks will consist of (1) seated social breaks, (2) simple resistance activities, and (3) step-up activities. Before and after the 80-min conditions, prefrontal cerebral blood flow changes will be measured using functional near-infrared spectroscopy (primary outcome), while performing working memory tasks (1-, 2-, and 3-back tests). Arterial stiffness (augmentation index and pulse wave velocity) and psychological factors will also be assessed pre and post the 80-min interventions.

DISCUSSION

Publication of this protocol will help to increase rigor in science. The results will inform regarding the underlying mechanisms driving the association between physical activity breaks and cognitive performance. This information can be used for designing effective and feasible interventions to be implemented in schools.

TRIAL REGISTRATION

www.ClinicalTrials.gov , NCT04552626 . Retrospectively registered on September 21, 2020.

Regulation of cerebral blood flow in humans: physiology and clinical implications of autoregulation

Brain function critically depends on a close matching between metabolic demands, appropriate delivery of oxygen and nutrients, and removal of cellular waste. This matching requires continuous regulation of cerebral blood flow (CBF), which can be categorized into four broad topics: 1) autoregulation, which describes the response of the cerebrovasculature to changes in perfusion pressure; 2) vascular reactivity to vasoactive stimuli [including carbon dioxide (CO2)]; 3) neurovascular coupling (NVC), i.e., the CBF response to local changes in neural activity (often standardized cognitive stimuli in humans); and 4) endothelium-dependent responses. This review focuses primarily on autoregulation and its clinical implications. To place autoregulation in a more precise context, and to better understand integrated approaches in the cerebral circulation, we also briefly address reactivity to CO2 and NVC. In addition to our focus on effects of perfusion pressure (or blood pressure), we describe the impact of select stimuli on regulation of CBF (i.e., arterial blood gases, cerebral metabolism, neural mechanisms, and specific vascular cells), the interrelationships between these stimuli, and implications for regulation of CBF at the level of large arteries and the microcirculation. We review clinical implications of autoregulation in aging, hypertension, stroke, mild cognitive impairment, anesthesia, and dementias. Finally, we discuss autoregulation in the context of common daily physiological challenges, including changes in posture (e.g., orthostatic hypotension, syncope) and physical activity.

Frequent, Short Physical Activity Breaks Reduce Prefrontal Cortex Activation but Preserve Working Memory in Middle-Aged Adults: ABBaH Study

Prolonged sitting is increasingly common and may possibly be unfavorable for cognitive function and mood. In this randomized crossover study, the effects of frequent, short physical activity breaks during prolonged sitting on cognitive task-related activation of the prefrontal cortex were investigated. The effects on working memory, psychological factors, and blood glucose were also examined, and whether arterial stiffness moderated prefrontal cortex activation. Thirteen subjects (mean age 50.5 years; eight men) underwent three 3-h sitting conditions, interrupted every 30-min by a different 3-min break on separate, randomized-ordered days: seated social interactions (SOCIAL), walking (WALK), or simple resistance activities (SRA). Arterial stiffness was assessed at baseline. Before and after each 3-h condition, psychological factors (stress, mood, sleepiness, and alertness) were assessed through questionnaires and functional near-infrared spectroscopy (fNIRS) was used to measure changes in prefrontal oxygenated hemoglobin (Oxy-Hb), indicative of cortical activation, while performing working memory tasks [1- (baseline), 2-, and 3-back]. Blood glucose levels were continuously measured throughout the conditions. Results revealed no significant changes in Oxy-Hb during the 2-back compared with the 1-back test in any condition, and no time-by-condition interactions. During the 3-back test, there was a significant decrease in Oxy-Hb compared with the 1-back after the WALK condition in the right prefrontal cortex, but there were no time-by-condition interactions, although 3-back reaction time improved only in the WALK condition. Mood and alertness improved after the WALK condition, which was significantly different from the SOCIAL condition. Arterial stiffness moderated the effects, such that changes in Oxy-Hb were significantly different between WALK and SOCIAL conditions only among those with low arterial stiffness. Blood glucose during the interventions did not differ between conditions. Thus, breaking up prolonged sitting with frequent, short physical activity breaks may reduce right prefrontal cortex activation, with improvements in some aspects of working memory, mood, and alertness. Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT04137211.

Sit less and move more for cardiovascular health: emerging insights and opportunities

Sedentary behaviour - put simply, too much sitting, as a distinct concept from too little exercise - is a novel determinant of cardiovascular risk. This definition provides a perspective that is complementary to the well-understood detrimental effects of physical inactivity. Sitting occupies the majority of the daily waking hours in most adults and has become even more pervasive owing to the COVID-19 pandemic. The potential for a broad cardiovascular health benefit exists through an integrated approach that involves 'sitting less and moving more'. In this Review, we first consider observational and experimental evidence on the adverse effects of prolonged, uninterrupted sitting and the evidence identifying the possible mechanisms underlying the associated risk. We summarize the results of randomized controlled trials demonstrating the feasibility of changing sedentary behaviour. We also highlight evidence on the deleterious synergies between sedentary behaviour and physical inactivity as the underpinnings of our case for addressing them jointly in mitigating cardiovascular risk. This integrated approach should not only reduce the specific risks of too much sitting but also have a positive effect on the total amount of physical activity, with the potential to more broadly benefit the health of individuals living with or at risk of developing cardiovascular disease.

Sedentary Lifestyle Matters as Past Sedentariness, Not Current Sedentariness, Predicts Cognitive Inhibition Performance among College Students: An Exploratory Study

Background: Currently, sedentariness is assessed over a short period of time, thus it is difficult to study its cognitive implications. To investigate the cognitive consequences of a sedentary lifestyle, the past level (i.e., the sedentary time accumulated over the years) and current level of sedentariness should be considered. This pilot study aimed to investigate the negative association between a sedentary lifestyle and cognition by considering both the current and past sedentariness. It was expected that the physical activity level moderates the potential negative association between sedentariness and cognition. Methods: 52 college students (M_age = 20.19, SD_age = 2; 36 women) participated in the study. Current sedentariness (ratio of sedentary time in the last year), past sedentariness (ratio of sedentary time accumulated in previous years), and physical activity (ratio of time spent in physical activity in years) were assessed using a questionnaire. Cognitive inhibition, cognitive flexibility, and working memory updating were measured through three specific tests. Results: Past sedentariness significantly explained the inhibition performance when controlled for physical activity, whereas current sedentariness did not. More precisely, past sedentariness only negatively predicted cognitive inhibition when the physical activity level was low (β = -3.15, z(48) = -2.62, p = 0.01). Conclusions: The impact of sedentariness on cognitive functioning might only be revealed when past sedentariness and physical activity are controlled.

Objectively assessed physical activity and sedentary behavior and global cognitive function in older adults: a systematic review

BACKGROUND

Both physical activity (PA) and sedentary behavior (SB) are important factors for healthy ageing. This systematic review aimed to determine the association of objectively assessed (instrumented) PA and SB with global cognitive function in older adults.

METHODS

PubMed, Embase, the Cochrane Library (via Wiley), CINAHL, PsychINFO, and SPORTDiscus (via EBSCO) were searched from inception to June 21, 2020 for articles that described associations of objectively assessed PA/SB with global cognitive function in older adults aged 60 years and older. Results were synthesized using an effect direction heat map and albatross plots portrayed estimated effect sizes (standardized regression coefficients (βs)), which were summarized in boxplots.

RESULTS

In total, 45 articles were included representing a total of 15,817 older adults (mean/median age ranged from 65 to 88 years; 49.5% female). Longitudinal studies (n = 7) showed that higher moderate-to-vigorous and light PA (MVPA and LPA, respectively) and lower SB were associated with better global cognitive function. Standardized βs of cross-sectional studies (n = 38) showed that lower SB (median [IQR], β = 0.078 [0.004-0.184] and higher LPA (β = 0.096 [0.046-0.188]), activity counts (β = 0.131 [0.049-0.224]), number of steps (β = 0.155 [0.096-0.246]), MVPA (β = 0.163 [0.069-0.285]) and total PA (TPA) (β = 0.174 [0.147-0.255]) were associated with better global cognitive function.

CONCLUSIONS

Higher PA and lower SB are associated with better global cognitive function in older adults. The greatest estimated effect sizes were found for moderate-to-vigorous and TPA, suggesting that greater duration of any PA, and high intensity PA could be most beneficial for global cognitive function.

A Proposed Hypothesis on Dementia: Inflammation, Small Vessel Disease, and Hypoperfusion Is the Sequence That Links All Harmful Lifestyles to Cognitive Impairment

There is growing consensus that certain lifestyles can contribute to cognitive impairment and dementia, but the physiological steps that link a harmful lifestyle to its negative impact are not always evident. It is also unclear whether all lifestyles that contribute to dementia do so through the same intermediary steps. This article will focus on three lifestyles known to be risk factors for dementia, namely obesity, sedentary behavior, and insufficient sleep, and offer a unifying hypothesis proposing that lifestyles that negatively impact cognition do so through the same sequence of events: inflammation, small vessel disease, decline in cerebral perfusion, and brain atrophy. The hypothesis will then be tested in a recently identified risk factor for dementia, namely hearing deficit. If further studies confirm this sequence of events leading to dementia, a significant change in our approach to this debilitating and costly condition may be necessary, possible, and beneficial.

Does breaking up prolonged sitting improve cognitive functions in sedentary adults? A mapping review and hypothesis formulation on the potential physiological mechanisms

Background

Prolonged (excessive) sitting is detrimentally associated with cardiovascular, metabolic and mental health. Moreover, prolonged sitting has been associated with poor executive function, memory, attention and visuospatial skills, which are important cognitive aspects of work performance. Breaking up prolonged sitting with standing or light-intensity exercises at the workplace is recognized as a potential measure in improving cognition. However, preliminary evidence, primarily from acute laboratory experiments, has enabled formulating hypothesis on the possible mechanistic pathways. Hence, the aim of this mapping review is to gather preliminary evidence and substantiate possible physiological mechanisms underpinning the putative effects of breaking prolonged sitting on improving cognitive function among sedentary office workers.

Mapping method

We searched four databases to identify relevant studies that explored the effects of uninterrupted sitting on cognitive function. First, we introduce how prolonged sitting increases the risks of hyperglycemia, autonomic stability, inflammation, adverse hormonal changes and restrictions in cerebral blood flow (CBF) and alters cognitive function. Second, we elucidate the direct and indirect effects of breaking up prolonged sitting time that may prevent a decline in cognitive performance by influencing glycaemic variability, autonomic stability, hormones (brain derived neurotrophic factor, dopamine, serotonin), vascular functions, and CBF. We highlight the importance of breaking up prolonged sitting on metabolic, vascular and endocrine functions, which in turn may improve cognitive functions and eventually foster work productivity. Improved synaptic transmission or neuroplasticity due to increased brain glucose and mitochondrial metabolism, increased endothelial shear and CBF, increased brain neurotrophic factors (dopamine) and accelerated anti-inflammatory functions are some of the hypothetical mechanisms underpinning improved cognitive functions.

Conclusion

We postulate that improving cognitive function by breaking up prolonged sitting periods is biologically plausible with the myriad of (suggested) physiological mechanisms. Future experimental studies to ascertain the aforementioned hypothetical mechanisms and clinical trials to break sedentary behavior and improve cognitive functions in sedentary office workers are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04136-5.

Life-Space Mobility and Active Aging as Factors Underlying Quality of Life Among Older People Before and During COVID-19 Lockdown in Finland-A Longitudinal Study

Background

Social distancing, i.e. avoiding places with other people and staying at home, was recommended to prevent viral transmission during the COVID-19 pandemic. Potentially, reduced out-of-home mobility and lower activity levels among older people may lower their quality of life (QOL). We studied cross-sectional and longitudinal associations of and changes in life-space mobility, active ageing and QOL during COVID-19 social distancing compared to two years before.

Methods

Altogether 809 community-living participants initially aged 75, 80 or 85 years of our active aging study (AGNES) conducted in 2017-2018 took part in the current AGNES-COVID-19 survey in May and June 2020. Outdoor mobility was assessed with the Life-Space Assessment (range 0-120). Active approach to life was assessed with the University of Jyväskylä Active Aging Scale (range 0–272), and QOL with the shortened Older People’s Quality of Life Questionnaire (range13-65; higher scores better for all). Data were analyzed with General Estimating Equations, General Linear Models, and Oneway-ANOVA.

Results

Life-space mobility (B -10.8, SE 0.75, p<0.001), the active ageing score (B -24.1, SE 0.88, p<0.001) and the QOL score (B -1.65, SE 0.21, p<0.001) were lower during COVID-19 social distancing vs. two years before. Concurrent life-space mobility and active ageing scores, age and sex explained 48% of QOL at the baseline and 42% during social distancing. Longitudinally, steeper declines in all three variables coincided.

Conclusions

The observed declines indicate compliance with social distancing recommendation, but underline the importance of participation in meaningful life situations as a factor underlying good QOL also during COVID-19 pandemic.

The physiological benefits of sitting less and moving more: Opportunities for future research

Sedentary behavior (SB) and physical activity (PA) are important risk factors of cardiovascular disease morbidity and mortality. In addition to increasing the amount of moderate-to-vigorous PA (MVPA), the current PA guidelines recommend that adults should reduce SB, or any waking activity performed while sitting, reclining, or lying, with low energy expenditure. While mounting evidence has emphasized the benefits of increasing MVPA, little has focused on the effect of SB on health. Therefore, this review discusses the pathophysiological effects of SB and the potential physiological benefits of reducing/breaking up SB at the levels below the current guidelines for PA. Such knowledge is important, given that the majority of the United States population performs insufficient or no MVPA and is at high risk of being negatively impacted by SB. Interventions targeting sedentary time, such as breaking up SB by standing and moving, may be safe, feasible, and applicable to execute daily for a wide range of the population. This review also discusses the importance of monitoring SB in the era of the coronavirus disease 2019 (COVID-19) pandemic and the clinical implications of sitting less and moving more.

Hourly staircase sprinting exercise "snacks" improve femoral artery shear patterns but not flow-mediated dilation or cerebrovascular regulation: a pilot study

Healthy males (n = 10; age: 24 ± 4 years; body mass index: 24 ± 2 kg·m^-2) completed 2 randomized conditions separated by ≥48 h involving 6-8.5 h of sitting with ("stair snacks") and without (sedentary) hourly staircase sprint interval exercise (∼14-20 s each). Resting blood flow and shear rates were measured in the femoral artery, internal carotid artery, and vertebral artery (Duplex ultrasound). Flow-mediated dilation (FMD) was quantified as an index of peripheral endothelial function in the femoral artery. Neurovascular coupling (NVC; regional blood flow response to local increases in cerebral metabolism) was assessed in the posterior cerebral artery (transcranial Doppler ultrasound). Femoral artery hemodynamics were higher following the active trial with no change in the sedentary trial, including blood flow (+32 ± 23% vs. -10 ± 28%; P = 0.015 and P = 0.253, respectively), vascular conductance (+32 ± 27% vs. -15 ± 26%; P = 0.012 and P = 0.098, respectively), and mean shear rate (+17 ± 8% vs. -8 ± 28%; P = 0.004 and P = 0.310, respectively). The change in FMD was not different within or between conditions (P = 0.184). Global cerebral blood flow (CBF), conductance, shear patterns, and NVC were not different within or between conditions (all P > 0.05). Overall, exercise "stair snacks" improve femoral artery blood flow and shear patterns but not peripheral (e.g., FMD) or cerebral (e.g., CBF and NVC) vascular function following prolonged sitting. The study was registered at ClinicalTrials.gov (NCT03374436). Novelty: Breaking up 8.5 h of sitting with hourly staircase sprinting exercise "snacks" improves resting femoral artery shear patterns but not FMD. Cerebral blood flow and neurovascular coupling were unaltered following 6 h of sitting with and without hourly exercise breaks.

Impact of prolonged sitting and physical activity breaks on cognitive performance, perceivable benefits, and cardiometabolic health in overweight/obese adults: The role of meal composition

BACKGROUND & AIMS

Physical activity (PA) breaks may effectively attenuate the detrimental impact of prolonged sitting on acute cognitive performance, perceivable benefits (e.g. mood), vascular function, and metabolic health. To date, the impact of meal composition on the effects of sedentary behavior and/or PA breaks on health has been scarcely studied. Therefore, our aim was to investigate whether meal composition alters how sedentary behavior and PA breaks affect these acute health outcomes.

METHODS

A total of 24 overweight and obese, sedentary adults completed four conditions in randomized order in a cross-over design: [a] high-protein, low-fat breakfast (HPLF) + 4hrs uninterrupted sitting (SIT), [b] HPLF + 4hrs interrupted sitting (ACT; 5-min cycling every 30 min), [c] Western breakfast (WEST; higher in fats/simple sugars, lower in protein/fiber) + SIT, [d] WEST + ACT. WEST and HPLF were isocaloric. Linear mixed models were used to examine changes in cognitive performance (Test of Attentional Performance), perceivable benefits (Likert-scales, Profile of Mood States questionnaire), vascular health (carotid artery reactivity, blood pressure), and metabolic health (post-breakfast glucose, insulin, lipids).

RESULTS

Independent of meal composition, we did not observe any effect of PA breaks on cognitive performance, vascular health and post-breakfast lipid responses. PA breaks delayed post-breakfast mood and vigor decrements, as well as increases in fatigue and sleepiness (all p < 0.05), but effects were independent of meal composition (p > 0.05). WEST resulted in higher post-breakfast glucose levels compared to HPLF (p < 0.05), while PA breaks did not impact this response (p > 0.05). PA breaks reduced post-breakfast insulin (p < 0.05), which did not differ between meals (p > 0.05).

CONCLUSIONS

The acute impact of PA breaks and/or prolonged sitting on cognitive performance, perceivable benefits, and vascular and metabolic health was not altered by the composition of a single meal in overweight/obese, sedentary adults. Possibly, breaking up prolonged sitting, rather than meal composition, is a more potent strategy to impact acute health outcomes, such as perceivable benefits and insulin levels.