Search

Cerebral white matter (WM) represents the structural substrate of neuronal communications which is damaged by Alzheimer's disease (AD). Aerobic exercise training (AET) may improve WM integrity in cognitively normal older adults, but its efficacy remains unknown in patients with amnestic mild cognitive impairment (MCI), a prodromal phase of AD dementia. Therefore, we conducted a proof-of-concept study that randomized 70 amnestic MCI patients to a 1-year program of AET or a non-aerobic stretching and toning (SAT), active control group. Thirty-six patients completed both baseline and follow-up MRI scans, and cerebral WM integrity was measured by WM lesion volume and diffusion characteristics using fluid-attenuated-inversion-recovery and diffusion tensor imaging respectively. Peak oxygen uptake (VO2peak) and neuropsychological function were also measured. At baseline and 1-year follow-up, WM lesion volume and diffusion characteristics were similar between the AET and SAT groups, although VO2peak significantly improved after AET. The AET group showed slight improvement in neuropsychological performance. When analyzing individual data, tract-based spatial statistics demonstrated that VO2peak improvements are associated with attenuated elevations in mean and axial diffusivities, particularly the anterior WM fiber tracts (e.g., genu of corpus callosum). In patients with amnestic MCI, we found that although AET intervention did not improve WM integrity at group level analysis, individual cardiorespiratory fitness gains were associated with improved WM tract integrity of the prefrontal cortex.

Background: Central arterial stiffness and brain hypoperfusion are emerging risk factors of Alzheimer’s disease (AD). Aerobic exercise training (AET) may improve central arterial stiffness and brain perfusion. Objective: To investigate the effects of AET on central arterial stiffness and cerebral blood flow (CBF) in patients with amnestic mild cognitive impairment (MCI), a prodromal stage of AD. Methods: This is a proof-of-concept, randomized controlled trial that assigned 70 amnestic MCI patients into a 12-month program of moderate-to-vigorous AET or stretching-and-toning (SAT) intervention. Carotid β-stiffness index and CBF were measured by color-coded duplex ultrasonography and applanation tonometry. Total CBF was measured as the sum of CBF from both the internal carotid and vertebral arteries, and divided by total brain tissue mass assessed with MRI to obtain normalized CBF (nCBF). Episodic memory and executive function were assessed using standard neuropsychological tests (CVLT-II and D-KEFS). Changes in cardiorespiratory fitness were measured by peak oxygen uptake (VO2peak). Results: Total 48 patients (29 in SAT and 19 in AET) were completed one-year training. AET improved VO2peak, decreased carotid β-stiffness index and CBF pulsatility, and increased nCBF. Changes in VO2peak were associated positively with changes in nCBF (r = 0.388, p = 0.034) and negatively with carotid β-stiffness index (r = –0.418, p = 0.007) and CBF pulsatility (r = –0.400, p = 0.014). Decreases in carotid β-stiffness were associated with increases in cerebral perfusion (r = –0.494, p = 0.003). AET effects on cognitive performance were minimal compared with SAT. Conclusion: AET reduced central arterial stiffness and increased CBF which may precede its effects on neurocognitive function in patients with MCI.

BACKGROUND: Mounting evidence showed the self-reported levels of physical activity are positively associated with white matter (WM) integrity and cognitive performance in normal adults and patients with mild cognitive impairment (MCI). However, the objective measure of cardiorespiratory fitness (CRF) was not used in these studies. OBJECTIVE: To determine the associations of CRF measured by maximal oxygen uptake (VO(2)max) with WM fiber integrity and neurocognitive performance in older adults with MCI. METHODS: Eighty-one participants (age = 65 ± 7 years, 43 women), including 26 cognitively normal older adults and 55 amnestic MCI patients, underwent VO(2)max test to measure CRF, diffusion tensor imaging (DTI) to assess WM fiber integrity, and neurocognitive assessment focused on memory and executive function. DTI data were analyzed by the tract-based spatial statistics and region-of-interest approach. RESULTS: Cognitively normal older adults and MCI patients were not different in global WM fiber integrity and VO(2)max. VO(2)max was associated positively with DTI metrics of fractional anisotropy in ~54% WM fiber tracts, and negatively with mean and radial diffusivities in ~46% and ~56 of the WM fiber tracts. The associations of VO(2)max with DTI metrics remained statistically significant after adjustment of age, sex, body mass index, WM lesion burden, and MCI status. The DTI metrics obtained from the area that correlated to VO(2)max were associated with executive function performance in MCI patients. CONCLUSIONS: Higher levels of CRF are associated with better WM fiber integrity, which in turn is correlated with better executive function performance in MCI patients.

Aerobic exercise (AE) has recently received increasing attention in the prevention of Alzheimer's disease (AD). There is some evidence that it can improve neurocognitive function in elderly individuals. However, the mechanism of these improvements is not completely understood. In this prospective clinical trial, thirty amnestic mild cognitive impairment participants were enrolled into two groups and underwent 12 months of intervention. One group (n = 15) performed AE training (8M/7F, age = 66.4 years), whereas the other (n = 15) performed stretch training (8M/7F, age = 66.1 years) as a control intervention. Both groups performed 25-30 minutes training, 3 times per week. Frequency and duration were gradually increased over time. Twelve-month AE training improved cardiorespiratory fitness (p = 0.04) and memory function (p = 0.004). Cerebral blood flow (CBF) was measured at pre- and post-training using pseudo-continuous-arterial-spin-labeling MRI. Relative to the stretch group, the AE group displayed a training-related increase in CBF in the anterior cingulate cortex (p = 0.016). Furthermore, across individuals, the extent of memory improvement was associated with CBF increases in anterior cingulate cortex and adjacent prefrontal cortex (voxel-wise p < 0.05). In contrast, AE resulted in a decrease in CBF of the posterior cingulate cortex, when compared to the stretch group (p = 0.01). These results suggest that salutary effects of AE in AD may be mediated by redistribution of blood flow and neural activity in AD-sensitive regions of brain.

BACKGROUND The current evidence is inconclusive to support the benefits of aerobic exercise training (AET) for preventing neurocognitive decline in patients with amnestic mild cognitive impairment (aMCI). OBJECTIVE To examine the effect of a progressive, moderate-to-high intensity AET program on memory and executive function, brain volume, and cortical amyloid-β (Aβ) plaque deposition in aMCI patients. METHODS This is a proof-of-concept trial that randomized 70 aMCI patients to 12 months of AET or stretching and toning (SAT, active control) interventions. Primary neuropsychological outcomes were assessed by using the California Verbal Learning Test-second edition (CVLT-II) and the Delis-Kaplan Executive Function System (D-KEFS). Secondary outcomes were the global and hippocampal brain volumes and the mean cortical and precuneus Aβ deposition. RESULTS Baseline cognitive scores were similar between the groups. Memory and executive function performance improved over time but did not differ between the AET and SAT groups. Brain volume decreased and precuneus Aβ plaque deposition increased over time but did not differ between the groups. Cardiorespiratory fitness was significantly improved in the AET compared with SAT group. In amyloid positive patients, AET was associated with reduced hippocampal atrophy when compared with the SAT group. CONCLUSION The AET and SAT groups both showed evidence of slightly improved neuropsychological scores in previously sedentary aMCI patients. However, these interventions did not prevent brain atrophy or increases in cortical Aβ deposition over 12 months. In amyloid positive patients, AET reduced hippocampal atrophy when compared with the SAT group.

Introduction: Atrial fibrillation (AF) is the leading cause of fatal ischemic stroke. Although stroke risk factors can be identified using available clinical assessment tools, current standard of care primarily relies on antithrombotic/anticoagulation therapy and fails to proactively modify the underlying risk factors contributing to stroke. The purpose of this study was to determine the effect of moderate-to-high intensity aerobic training in alleviating stroke risk by reducing arterial stiffness and AF burden in AF patients. Methods: Forty-two patients with clinically diagnosed AF between the ages of 65-75 were recruited and randomly assigned to either a 3-month aerobic training with moderate to high intensity (i.e. >80%MHR, 45 minutes, 3-4 days/week) or a health education group. Vascular integrity was evaluated by carotid-radial pulse-wave-velocity (PWVcr), carotid intima-media-thickness (cIMT) and end-diastolic velocity (EDV); AF burden was quantified using a 2-week continuous cardiac event monitor (ZioXT patch, iRhythm); stroke risk was assessed using the CHA 2 DS 2 -VASc scale. All measurements were assessed before and after training. Results: Thirty AF patients participated in the aerobic training group (f=18, age=70±3) and 12 participated in the health education group (f=8, age=69±4). After 3 months, the aerobic training group exhibited significant improvement in PWVcr (12.6±3.2m/s vs. 9.6±2.1m/s, p=0.001), EDV (14.3±2.5cm/s vs. 15.9±2.1cm/s, p=0.01), AF burden (84.3±12.3% vs. 66.6±1.3%, p=0.01), and CHA 2 DS 2 -VASc score (2.2±1.3 vs. 0.9±0.9, p=0.05). In addition, the change of EDV is predictive of the stroke risk (r 2 =0.32, p=0.01). No significant change was observed in the health education group. Conclusion: We found that 3 months of supervised aerobic training at moderate-to-high intensity level appeared to improve vascular integrity, alleviate AF burden, and reduce stroke risk in patients with AF. More importantly, the AF burden and stroke risk are modulated by improvements in vascular functions. This finding warrants future large-scale investigations to examine the dose-response relationship of exercise reducing ischemic stroke risk.

KEY POINTS Cerebral autoregulation (CA) is a key mechanism to protect brain perfusion in the face of changes in arterial blood pressure, but little is known about individual variability of CA and its relationship to the presence of brain white matter hyperintensity (WMH) in older adults, a type of white matter lesion related to cerebral small vessel disease (SVD). This study demonstrated the presence of large individual variability of CA in healthy older adults during vasoactive drug-induced changes in arterial pressure assessed at the internal carotid and vertebral arteries. We also observed, unexpectedly, that it was the 'over-' rather than the 'less-reactive' CA measured at the vertebral artery that was associated with WMH severity. These findings challenge the traditional concept of CA and suggest that the presence of cerebral SVD, manifested as WMH, is associated with posterior brain hypoperfusion during acute increase in arterial pressure. ABSTRACT This study measured the individual variability of static cerebral autoregulation (CA) and determined its associations with brain white matter hyperintensity (WMH) in older adults. Twenty-seven healthy older adults (13 females, 66 ± 6 years) underwent assessment of CA during steady-state changes in mean arterial pressure (MAP) induced by intravenous infusion of sodium nitroprusside (SNP) and phenylephrine. Cerebral blood flow (CBF) was measured using colour-coded duplex ultrasonography at the internal carotid (ICA) and vertebral arteries (VA). CA was quantified by a linear regression slope (CA slope) between percentage changes in cerebrovascular resistance (CVR = MAP/CBF) and MAP relative to baseline values. Periventricular and deep WMH volumes were measured with T2-weighted magnetic resonance imaging. MAP was reduced by -11 ± 7% during SNP, and increased by 21 ± 8% during phenylephrine infusion. CA demonstrated large individual variability with the CA slopes ranging from 0.37 to 2.20 at the ICA and from 0.17 to 3.18 at the VA; no differences in CA were found between the ICA and VA. CA slopes measured at the VA had positive correlations with the total and periventricular WMH volume (r = 0.55 and 0.59, P

OBJECTIVE: The prevalence of post-stroke fatigue differs widely across studies, and reasons for such divergence are unclear. We aimed to collate individual data on post-stroke fatigue from multiple studies to facilitate high-powered meta-analysis, thus increasing our understanding of this complex phenomenon.METHODS: We conducted an Individual Participant Data (IPD) meta-analysis on post-stroke fatigue and its associated factors. The starting point was our 2016 systematic review and meta-analysis of post-stroke fatigue prevalence, which included 24 studies that used the Fatigue Severity Scale (FSS). Study authors were asked to provide anonymised raw data on the following pre-identified variables: (i) FSS score, (ii) age, (iii) sex, (iv) time post-stroke, (v) depressive symptoms, (vi) stroke severity, (vii) disability, and (viii) stroke type. Linear regression analyses with FSS total score as the dependent variable, clustered by study, were conducted.RESULTS: We obtained data from 14 of the 24 studies, and 12 datasets were suitable for IPD meta-analysis (total n = 2102). Higher levels of fatigue were independently associated with female sex (coeff. = 2.13, 95% CI 0.44-3.82, p = 0.023), depressive symptoms (coeff. = 7.90, 95% CI 1.76-14.04, p = 0.021), longer time since stroke (coeff. = 10.38, 95% CI 4.35-16.41, p = 0.007) and greater disability (coeff. = 4.16, 95% CI 1.52-6.81, p = 0.010). While there was no linear association between fatigue and age, a cubic relationship was identified (p CONCLUSION: Use of IPD meta-analysis gave us the power to identify novel factors associated with fatigue, such as longer time since stroke, as well as a non-linear relationship with age.

Purpose To examine the potential benefits of life-long aerobic exercise on brain health, in particular cerebrovascular function.

Purpose To investigate differences in the age-related decline in brain tissue concentration between Masters athletes and sedentary older adults. Materials and Methods Twelve Masters athletes (MA) (three females, age = 72.4 ± 5.6 years, endurance training >15 years), 12 sedentary elderly (SE) similar in age and educational level (four females, age = 74.6 ± 4.3 years), and nine young controls (YC) (four females, age = 27.2 ± 3.6 years) participated. T1-weighted high-resolution (1 × 1 × 1mm3) images were acquired. Voxel-based analysis was conducted to identify clusters showing tissue concentration differences with t-tests. Cognitive function was assessed using a standard clinical battery focused on executive function and memory. Results Two MA and two SE were unable to complete the magnetic resonance imaging (MRI) study. Both SE and MA showed lower gray matter (GM) concentrations than YC in the superior, inferior and middle frontal gyrus, superior temporal gyrus, postcentral gyrus, and the cingulate gyrus (PFDR-corrected < 0.001) and lower white matter (WM) concentrations in the inferior frontal gyrus and precentral gyrus (PFDR-corrected < 0.005). Notably, MA showed higher GM and WM concentrations than SE in the subgyral, cuneus, and precuneus regions related to visuospatial function, motor control, and working memory (PFDR-corrected < 0.005). After controlling for estimated intelligence, MA outperformed SE on tasks of letter (P < 0.01) and category (P < 0.05) fluency. Conclusion Life-long exercise may confer benefits to some aspects of executive function and age-related brain tissue loss in the regions related to visuospatial function, motor control, and working memory in older adults. J. Magn. Reson. Imaging 2013;38:1169–1176. © 2013 Wiley Periodicals, Inc.

Amnestic mild cognitive impairment represents an early stage of Alzheimer’s disease, and characterization of physiological alterations in mild cognitive impairment is an important step toward accurate diagnosis and intervention of this condition. To investigate the extent of neurodegeneration in patients with mild cognitive impairment, whole-brain cerebral metabolic rate of oxygen in absolute units of µmol O2/min/100 g was quantified in 44 amnestic mild cognitive impairment and 28 elderly controls using a novel, non-invasive magnetic resonance imaging method. We found a 12.9% reduction ( p = 0.004) in cerebral metabolic rate of oxygen in mild cognitive impairment, which was primarily attributed to a reduction in the oxygen extraction fraction, by 10% ( p = 0.016). Global cerebral blood flow was not found to be different between groups. Another aspect of vascular function, cerebrovascular reactivity, was measured by CO2-inhalation magnetic resonance imaging and was found to be equivalent between groups. Therefore, there seems to be a global, diffuse diminishment in neural function in mild cognitive impairment, while their vascular function did not show a significant reduction.

Background Fatigue is a commonly neglected issue despite the high incidence rate reported in people post-stroke. Objective To explore the relationship between fatigue, aerobic fitness, and motor control in people with chronic stroke. Methods Nine people post-stroke participated in this cross-sectional study (7 females, mean age = 56.8 (11.8) years, range 47-73, time post-stroke = 47.6 (51.2) months, range 11-140). Participants performed a six-minute-walk exercise in order to induce fatigue, followed immediately by a Fatigue Index (FI) scale to report fatigue at the moment. The distance walked (6MWD) was documented. On a separate visit, aerobic fitness was characterized by VO(2Peak) using a cycle-ergometer. In addition, Fugl-Meyer (FM) test was administered to assess motor control of the hemiparetic side. Pearson Product Correlation Coefficient and multiple linear regression were used to analyze the relationships between FI, VO(2Peak) and FM. Results VO(2Peak) showed significant positive correlations with FM (r = .779, p = .013) and 6MWD (r = .726, p = .027). Fatigue index displayed significant negative correlations with VO(2Peak) (r = -.739, p = .023) and FM (r = -.873, p = .002), but not with 6MWD (r = -.620, p = .075). Using stepwise multiple regression, we found that that FM was an independent predictor of FI (p = .002) and explained 76.2% of variance in FI (R2 = .762). Conclusion Our data suggests that motor control capability may be a good predictor of fatigue in people post-stroke. Fatigue is a complex phenomenon; a quantifiable measure that is sensitive to multiple components is needed in order to distinguish the nature of fatigue and its contributing factors.

Measures are needed that identify persons that will develop Alzheimer's disease in order to target them for preventative interventions. There is evidence from animal, pathological and imaging studies that disruption of white matter occurs in the course of Alzheimer's disease and may be an early event. Prior studies have suggested that late-myelinating regions or white matter connecting limbic structures are particularly susceptible to degradation. Persons destined to develop the disease by virtue of fully penetrant genetic alterations (familial Alzheimer's disease or FAD) provide a model in which early and even presymptomatic changes of the disease may be identified. In this study we performed diffusion tensor imaging (DTI) on 2 demented and 21 subjects at-risk for inheriting an FAD mutation. We compared global and localized fractional anisotropy (FA) measures in white matter between FAD mutation carriers and non-carriers in the preclinical (clinical dementia rating1, n = 20) and presymptomatic (clinical dementia rating = 0, n = 15) stages of the disease. There were no significant differences between mutation carriers and non-carriers with regard to absolute age, age relative to the typical age of disease diagnosis in their family, gender or Mini-Mental Status Examination Score. Among preclinical FAD mutation carriers (n = 12), mean whole brain white-matter FA (P = 0.045), FA of the columns of the fornix (P = 0.012), area of the perforant pathways bilaterally (right side: P = 0.028, left side: P = 0.027) and left orbitofrontal lobe (P = 0.024) were decreased relative to that of non-carriers (n = 8). We also found that FA in the columns of the fornix (P = 0.008) and left orbitofrontal lobe white matter (P = 0.045) were decreased in the eight presymptomatic mutation carriers compared to seven non-carriers. Logistic regression demonstrated that FA of the columns of the fornix was a better predictor of mutation status than was cross-sectional area of the fornix, global mean white-matter FA and left frontal lobe white-matter FA. In a linear regression analysis, white-matter volume (P = 0.002), hippocampal volume (P = 0.023) and mutation status (P = 0.032) significantly predicted fornix FA. We conclude that FA is decreased in the white matter in preclinical and even presymptomatic FAD mutation carriers, particularly in the late-myelinating tracts connecting limbic structures. Decreased FA in of the columns of the fornix is particularly robust in early FAD and may provide a biomarker for early disease in sporadic Alzheimer's disease.

Cerebral autoregulation (CA) is a key mechanism to protect brain perfusion in the face of changes in arterial blood pressure, but little is known about individual variability of CA and its relationship to the presence of brain white matter hyperintensity (WMH) in older adults, a type of white matter lesion related to cerebral small vessel disease (SVD). This study demonstrated the presence of large individual variability of CA in healthy older adults during vasoactive drug-induced changes in arterial pressure assessed at the internal carotid and vertebral arteries. We also observed, unexpectedly, that it was the 'over-' rather than the 'less-reactive' CA measured at the vertebral artery that was associated with WMH severity. These findings challenge the traditional concept of CA and suggest that the presence of cerebral SVD, manifested as WMH, is associated with posterior brain hypoperfusion during acute increase in arterial pressure.This study measured the individual variability of static cerebral autoregulation (CA) and determined its associations with brain white matter hyperintensity (WMH) in older adults. Twenty-seven healthy older adults (13 females, 66 ± 6 years) underwent assessment of CA during steady-state changes in mean arterial pressure (MAP) induced by intravenous infusion of sodium nitroprusside (SNP) and phenylephrine. Cerebral blood flow (CBF) was measured using colour-coded duplex ultrasonography at the internal carotid (ICA) and vertebral arteries (VA). CA was quantified by a linear regression slope (CA slope) between percentage changes in cerebrovascular resistance (CVR = MAP/CBF) and MAP relative to baseline values. Periventricular and deep WMH volumes were measured with T2-weighted magnetic resonance imaging. MAP was reduced by -11 ± 7% during SNP, and increased by 21 ± 8% during phenylephrine infusion. CA demonstrated large individual variability with the CA slopes ranging from 0.37 to 2.20 at the ICA and from 0.17 to 3.18 at the VA; no differences in CA were found between the ICA and VA. CA slopes measured at the VA had positive correlations with the total and periventricular WMH volume (r = 0.55 and 0.59, P 0.01). Collectively, these findings demonstrated the presence of large individual variability of CA in older adults, and that, when measured in the posterior cerebral circulation, it is the higher rather than lower CA reactivity that is associated with WMH severity.

Cerebral hypoperfusion elevates the risk of brain white matter (WM) lesions and cognitive impairment. Central artery stiffness impairs baroreflex, which controls systemic arterial perfusion, and may deteriorate neuronal fiber integrity of brain WM. The purpose of this study was to examine the associations among brain WM neuronal fiber integrity, baroreflex sensitivity (BRS), and central artery stiffness in older adults. Fifty-four adults (65 ± 6 years) with normal cognitive function or mild cognitive impairment (MCI) were tested. The neuronal fiber integrity of brain WM was assessed from diffusion metrics acquired by diffusion tensor imaging. BRS was measured in response to acute changes in blood pressure induced by bolus injections of vasoactive drugs. Central artery stiffness was measured by carotid-femoral pulse wave velocity (cfPWV). The WM diffusion metrics including fractional anisotropy (FA) and radial (RD) and axial (AD) diffusivities, BRS, and cfPWV were not different between the control and MCI groups. Thus, the data from both groups were combined for subsequent analyses. Across WM, fiber tracts with decreased FA and increased RD were associated with lower BRS and higher cfPWV, with many of the areas presenting spatial overlap. In particular, the BRS assessed during hypotension was strongly correlated with FA and RD when compared with hypertension. Executive function performance was associated with FA and RD in the areas that correlated with cfPWV and BRS. These findings suggest that baroreflex-mediated control of systemic arterial perfusion, especially during hypotension, may play a crucial role in maintaining neuronal fiber integrity of brain WM in older adults.

Purpose: To assess regional cerebral autoregulation (CA) and its association with white matter hyperintensities (WMH) in older adults. Methods: Twenty-seven healthy older subjects (13 females, 68 ±...

Background: With age, performance of motor tasks becomes more reliant on cognitive resources to compensate for the structural and functional declines in the motor control regions in the brain. We hypothesized that participants with amnestic mild cognitive impairment (aMCI) are more prone to motor dysfunctions than cognitively normal older adults under dual-task conditions where competitive demands challenge cognitive functions while performing a motor task simultaneously. Methods: Sixteen aMCI participants (females=9, age=64±5yrs, clinical dementia rating score=0.5) and 10 age- and education-matched cognitively normal adults (females=5, age=62±6yrs) participated. Using a 10-meter-walk test (10MW), gait velocity was recorded at baseline and under 4 different dual-task (DT) conditions designed to challenge working memory, executive function, and episodic memory. Specifically, DT1: verbal fluency; DT2: 5-digit backward span; DT3: serial-7 subtraction; and DT4: 3-item delayed recall. Physical function was measured by Timed Up-and-Go (TUG), simple reaction time (RT) to a free-falling yardstick, and functional reach (FR). Results: No difference was found in physical functions, aerobic fitness, and exercise cardiopulmonary responses between aMCI participants and controls. However, aMCI participants showed more pronounced gait slowing from baseline when compared to the controls (p

Physical activity may influence cerebrovascular function. The objective of this study was to determine the impact of life-long aerobic exercise training on cerebral vasomotor reactivity (CVMR) to changes in end-tidal CO2 (EtCO2) in older adults. Eleven sedentary young (SY, 27 ± 5 years), 10 sedentary elderly (SE, 72 ± 4 years), and 11 Masters athletes (MA, 72 ± 6 years) underwent the measurements of cerebral blood flow velocity (CBFV), arterial blood pressure, and EtCO2 during hypocapnic hyperventilation and hypercapnic rebreathing. Baseline CBFV was lower in SE and MA than in SY while no difference was observed between SE and MA. During hypocapnia, CVMR was lower in SE and MA compared with SY (1.87 ± 0.42 and 1.47 ± 0.21 vs. 2.18 ± 0.28 CBFV%/mm Hg, P < 0.05) while being lowest in MA among all groups ( P < 0.05). In response to hypercapnia, SE and MA exhibited greater CVMR than SY (6.00 ± 0.94 and 6.67 ± 1.09 vs. 3.70 ± 1.08 CBFV1%/mm Hg, P < 0.05) while no difference was observed between SE and MA. A negative linear correlation between hypo- and hypercapnic CVMR ( R2 = 0.37, P < 0.001) was observed across all groups. Advanced age was associated with lower resting CBFV and lower hypocapnic but greater hypercapnic CVMR. However, life-long aerobic exercise training appears to have minimal effects on these age-related differences in cerebral hemodynamics.

To examine the potential benefits of life-long aerobic exercise on brain health, in particular cerebrovascular function.Ten Masters athletes (MA) (seven males, three females; 74.5 ± 5.8 years) and 10 sedentary elderly individuals (SE) (eight males, two females; 75.4 ± 5.6 years) were recruited and baseline cerebral blood flow (CBF) and cerebral vascular reactivity (CVR) to CO2 were measured on a 3T MRI scanner. Nine sedentary young subjects were also recruited to serve as a control group to verify the age effect.When compared to the SE group, MA showed higher CBF in posterior cingulate cortex/precuneus, which are key regions of the default-mode-network and are known to be highly sensitive to age and dementia. CVR in the MA brains were paradoxically lower than that in SE. This effect was present throughout the brain. Within the MA group, individuals with higher VO2max had an even lower CVR, suggesting a dose-response relationship.Life-long aerobic exercise preserved blood supply in the brain's default-mode-network against age-related degradation. On the other hand, its impact on the cerebral vascular system seems to be characterized by a dampening of CO2 reactivity, possibly because of desensitization effects due to a higher lifetime exposure.

Background and Purpose—Emerging evidence suggests that exercise may improve cognitive function in older adults. The purpose of this pilot research project was to describe changes in measures of cognition and executive function in individuals with chronic stroke following participation in aerobic and strengthening exercise. Methods—A single group pre-test post-test design was used. Nine individuals with chronic stroke (mean age 63.7±9.1, mean time since stroke 50.4±37.9 months) completed a 12-week program of aerobic and strengthening exercise, 3 days per week. The primary outcome measures examined executive function (digit span backwards and Flanker tests). Secondary measures examined various aspects of aerobic fitness (VO2peak, 6-minute walk distance) and function (Fugl-Meyer, 10-meter walk speed). Results—Following the intervention significant improvements were found in the digit span backwards test (mean change = 0.56±0.9 digits; p=0.05), Fugl-Meyer score (mean change = 3.6±5.7; p=0.05), and SIS total score (mean change = 33.8±38.5; p =0.02). A significant correlation was found between improved aerobic capacity and improved performance on the Flanker test (r=0.74; p=0.02). Discussion—The results of this pilot study indicate that a 12-week aerobic and strengthening exercise program improved selected measures of executive function and functional capacity in people with stroke. Limitations of this study include the small sample size and lack of a comparison group. Conclusions—This pilot study contributes to the emerging evidence that exercise is associated with improved cognition in people with stroke. These benefits indicate the need for future study with a larger group to have sufficient power to further explore these relationships. BACKGROUND AND PURPOSE

Background and Purpose— Post-stroke fatigue is a common and neglected issue despite the fact that it impacts daily functions, quality of life, and has been linked with a higher mortality rate because of its association with a sedentary lifestyle. The purpose of this study was to identify the contributing factors of exertion fatigue and chronic fatigue in people post-stroke. Methods— Twenty-one post-stroke people (12 males, 9 females; 59.5±10.3 years of age; time after stroke 4.1±3.5 years) participated in the study. The response variables included exertion fatigue and chronic fatigue. Participants underwent a standardized fatigue-inducing exercise on a recumbent stepper. Exertion fatigue level was assessed at rest and immediately after exercise using the Visual Analog Fatigue Scale. Chronic fatigue was measured by the Fatigue Severity Scale. The explanatory variables included aerobic fitness, motor control, and depressive symptoms measured by peak oxygen uptake, Fugl-Meyer motor score, and the Geriatric Depression Scale, respectively. Results— Using forward stepwise regression, we found that peak oxygen uptake was an independent predictor of exertion fatigue ( P =0.006), whereas depression was an independent predictor of chronic fatigue ( P =0.002). Conclusion— Exertion fatigue and chronic fatigue are 2 distinct fatigue constructs, as identified by 2 different contributing factors.

Background Assessment of peak oxygen consumption (V̇o2peak) using traditional modes of testing such as treadmill or cycle ergometer can be difficult in individuals with stroke due to balance deficits, gait impairments, or decreased coordination. Objective The purpose of this study was to quantitatively assess the validity and feasibility of a modified exercise test using a total-body recumbent stepper (mTBRS-XT) in individuals after stroke. Design A within-subject design, with a sample of convenience, was used. Participants Eleven participants (7 male, 4 female) with a mean of 40.1 months (SD=32.7) after stroke, a mean age of 60.9 years (SD=12.0), and mild to severe lower-extremity Fugl-Myer test scores (range=13–34) completed the study. Methods Participants performed 2 maximal-effort graded exercise tests on separate days using the mTBRS-XT and a cycle ergometer exercise protocol to assess cardiorespiratory fitness. Measurements of V̇o2peak and peak heart rate (peak HR) were obtained during both tests. Results A strong relationship existed between the mTBRS-XT and the cycle ergometer exercise test for V̇o2peak and peak HR (r=.91 and .89, respectively). Mean V̇o2peak was significantly higher for the mTBRS-XT (16.6 mL×kg−1×min−1[SD=4.5]) compared with the cycle ergometer exercise protocol (15.4 mL×kg−1×min−1 [SD=4.5]). All participants performed the mTBRS-XT. One individual with severe stroke was unable to pedal the cycle ergometer. No significant adverse events occurred. Conclusion The mTBRS-XT may be a safe, feasible, and valid exercise test to obtain measurements of V̇o2peak in people with stroke. Health care professionals may use the mTBRS-XT to prescribe aerobic exercise based on V̇o2peak values for individuals with mild to severe deficits after stroke.

Most patients improve after stroke. But when dealing with individuals, clinicians are challenged to predict whether, how much, and how soon that particular patient will recover. The best predictive tool for at least 40 years has been the presenting clinical examination—the odds and the extent of recovery decrease roughly proportionally to the initial clinical severity.1,2 Newer technologies incorporated into the stroke workup have enabled neurologists to forecast more accurately individual stroke outcomes. Imaging and quantifying the “real estate factor”—infarct location and size—adds some confidence to stroke outcome prediction.3 But how much does this information really tell us that we do not already know from examining the patient? More importantly, can we develop algorithms that not only improve prognostication, but also inform treatment? Enter vascular- and flow-based imaging technologies. Visualizing acute large-vessel occlusion guides the use …