Slow gait speed - an indicator of lower cerebral vasoreactivity in type 2 diabetes mellitus

Cerebral Blood Flow Alterations in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Arterial Spin Labeling Studies

Objective

Arterial spin labeling (ASL) studies have revealed inconsistent regional cerebral blood flow (CBF) alterations in patients with type 2 diabetes mellitus (T2DM). The aim of this systematic review and meta-analysis was to identify concordant regional CBF alterations in T2DM.

Methods

A systematic review was conducted to the published literatures comparing cerebral perfusion between patients with T2DM and healthy controls using ASL. The seed-based d mapping (SDM) was further used to perform quantitative meta-analysis on voxel-based literatures and to estimate the regional CBF alterations in patients with T2DM. Metaregression was performed to explore the associations between clinical characteristics and cerebral perfusion alterations.

Results

A total of 13 studies with 14 reports were included in the systematic review and 7 studies with 7 reports were included in the quantitative meta-analysis. The qualitative review found widespread CBF reduction in cerebral lobes in T2DM. The meta-analysis found increased regional CBF in right supplementary motor area and decreased regional CBF in bilateral middle occipital gyrus, left caudate nucleus, right superior parietal gyrus, and left calcarine fissure/surrounding cortex in T2DM.

Conclusion

The patterns of cerebral perfusion alterations, characterized by the decreased CBF in occipital and parietal lobes, might be the neuropathology of visual impairment and cognitive aging in T2DM.

Functional tests in patients with ischemic heart disease

Lately, easier and shorter tests have been used in the functional evaluation of cardiac patients. Among these, walking speed (WS) and Timed Up and Go (TUG) tests are associated with all-cause mortality, mainly cardiovascular and the rate of re-hospitalization, especially in the elderly population. We prospectively analyzed a group of 38 patients admitted to the Cardiology Clinic from Elias Hospital, Romania, with chronic coronary syndrome (CCS) (n=22) and STEMI (n=16). We assessed the patients immediately after admission and before discharge with G-WALK between the 1^st and 30^th of September 2019. Our study group had a mean age of 62.7±12.1 years. Patients with a low WS were older (69.90±12.84 vs. 59.90±10.32 years, p=0.02) and had a lower serum hemoglobin (12.38±1.20 vs. 13.72±2.07 g/dl, p=0.02). The WS significantly improved during hospitalization (p=0.03) after optimal treatment. The TUG test performed at the time of admission had a longer duration in patients with heart failure (14.05 vs. 10.80 sec, p=0.02) and was influenced by patients' age (r=0.567, p=0.02), serum creatinine (r=0.409, p=0.03) and dilation of right heart chambers (r=0.399, p=0.03). WS and TUG tests can be used in patients with CCS and STEMI, and are mainly influenced by age, thus having a greater value among the elderly.

Asymptomatic carotid artery stenosis is associated with cerebral hypoperfusion

OBJECTIVE

We have shown that almost 50% of patients with asymptomatic carotid stenosis (ACS) will demonstrate cognitive impairment. Recent evidence has suggested that cerebral hypoperfusion is an important cause of cognitive impairment. Carotid stenosis can restrict blood flow to the brain, with consequent cerebral hypoperfusion. In contrast, cross-hemispheric collateral compensation through the Circle of Willis, and cerebrovascular vasodilation can also mitigate the effects of flow restriction. It is, therefore, critical to develop a clinically relevant measure of net brain perfusion in patients with ACS that could help in risk stratification and in determining the appropriate treatment. To determine whether ACS results in cerebral hypoperfusion, we developed a novel approach to quantify interhemispheric cerebral perfusion differences, measured as the time to peak (TTP) and mean transit time (MTT) delays using perfusion-weighted magnetic resonance imaging (PWI) of the whole brain. To evaluate the utility of using clinical duplex ultrasonography (DUS) to infer brain perfusion, we also assessed the relationship between the PWI findings and ultrasound-based peak systolic velocity (PSV).

METHODS

Structural and PWI of the brain and magnetic resonance angiography of the carotid arteries were performed in 20 patients with ≥70% ACS. DUS provided the PSV, and magnetic resonance angiography provided plaque geometric measures at the stenosis. Volumetric perfusion maps of the entire brain from PWI were analyzed to obtain the mean interhemispheric differences for the TTP and MTT delays. In addition, the proportion of brain volume that demonstrated a delay in TTP and MTT was also measured. These proportions were measured for increasing severity of perfusion delays (0.5, 1.0, and 2.0 seconds). Finally, perfusion asymmetries on PWI were correlated with the PSV and stenosis features on DUS using Pearson's correlation coefficients.

RESULTS

Of the 20 patients, 18 had unilateral stenosis (8 right and 10 left) and 2 had bilateral stenoses. The interhemispheric (left-right) TTP delays measured for the whole brain volume identified impaired perfusion in the hemisphere ipsilateral to the stenosis in 16 of the 18 patients. More than 45% of the patients had had ischemia in at least one half of their brain volume, with a TTP delay >0.5 second. The TTP and MTT delays showed strong correlations with PSV. In contrast, the correlations with the percentage of stenosis were weaker. The correlations for the PSV were strongest with the perfusion deficits (TTP and MTT delays) measured for the whole brain using our proposed algorithm (r = 0.80 and r = 0.74, respectively) rather than when measured on a single magnetic resonance angiography slice as performed in current clinical protocols (r = 0.31 and r = 0.58, respectively).

CONCLUSIONS

Interhemispheric TTP and MTT delay measured for the whole brain using PWI has provided a new tool for assessing cerebral perfusion deficits in patients with ACS. Carotid stenosis was associated with a detectable reduction in ipsilateral brain perfusion compared with the opposite hemisphere in >80% of patients. The PSV measured at the carotid stenosis using ultrasonography correlated with TTP and MTT delays and might serve as a clinically useful surrogate to brain hypoperfusion in these patients.

Quantitative Cerebrovascular Reactivity in Normal Aging: Comparison Between Phase-Contrast and Arterial Spin Labeling MRI

Purpose: Cerebrovascular reactivity (CVR) is an index of the dilatory function of cerebral blood vessels and has shown great promise in the diagnosis of risk factors in cerebrovascular disease. Aging is one such risk factor; thus, it is important to characterize age-related differences in CVR. CVR can be measured by BOLD MRI but few studies have measured quantitative cerebral blood flow (CBF)-based CVR in the context of aging. This study aims to determine the age effect on CVR using two quantitative CBF techniques, phase-contrast (PC), and arterial spin labeling (ASL) MRI.

Methods: In 49 participants (32 younger and 17 older), CVR was measured with PC, ASL, and BOLD MRI. These CVR methods were compared across young and older groups to determine their dependence on age. PC and ASL CVR were also studied for inter-correlation and mean differences. Gray and white matter CVR values were also studied.

Results: PC CVR was higher in younger participants than older participants (by 17%, p = 0.046). However, there were no age differences in ASL or BOLD CVR. ASL CVR was significantly correlated with PC CVR (p = 0.042) and BOLD CVR (p = 0.016), but its values were underestimated compared to PC CVR (p = 0.045). ASL CVR map revealed no difference between gray matter and white matter tissue types, whereas gray matter was significantly higher than white matter in the BOLD CVR map.

Conclusion: This study compared two quantitative CVR techniques in the context of brain aging and revealed that PC CVR is a more sensitive method for detection of age differences, despite the absence of spatial information. The ASL method showed a significant correlation with PC and BOLD, but it tends to underestimate CVR due to confounding factors associated with this technique. Importantly, our data suggest that there is not a difference in CBF-based CVR between the gray and white matter, in contrast to previous observation using BOLD MRI.

Asymptomatic carotid stenosis is associated with mobility and cognitive dysfunction and heightens falls in older adults

BACKGROUND

Atherosclerosis of the carotid bifurcation with plaque formation causes asymptomatic carotid artery stenosis (ACAS), which may also be associated with cerebral hypoperfusion. Cerebral hypoperfusion adversely affects multiple aspects of mobility and cognition. This study tests the hypothesis that community-dwelling older adults with a 50% or greater diameter-reducing ACAS will have mobility and cognitive impairments that heighten their risk for falls.

METHODS

Eighty community-dwelling adults completed a mobility assessment (Short Physical Performance Battery, Berg Balance Scale, Four Square Step Test, Dynamic Gait Index, Timed Up and Go, and gait speed), self-reported physical function (Activities-Specific Balance Confidence, SF-12 Physical Function Component), and cognitive tests (Mini-Mental State Examination). Falls were recorded for the past 6 months. Standardized carotid ultrasound examination classified participants into no stenosis (<50% diameter reduction) (n = 54), moderate stenosis (50%-69%) (n = 17), and high-grade stenosis (70%-99%) (n = 9) groups. Linear and logistic regression analyses determined the associations between these measures and the degree of stenosis (three groups).

RESULTS

Logistic regression analysis showed their degree of stenosis was associated with reductions in mobility (Short Physical Performance Battery [P = .008], Berg Balance Scale [P = .0008], Four Square Step Test [P = .005], DGI [P = .0001], TUG [P = .0004], gait speed [P = .02]), perceived physical function (ABC [P < .0001], SF-12 Physical Function Component [P < .0001]), and cognition (MMSE [P = .003]). Adults with moderate- and high-grade stenosis had a greater incidence of falls compared with those without stenosis (relative risk, 2.86; P = .01). Results remained unchanged after adjustment for age, sex and cardiovascular risk factors.

CONCLUSIONS

ACAS is associated with impaired mobility and cognition that are accompanied with increased fall risk. These impairments increased with worsening severity.

Rapid Systolic Blood Pressure Changes After Standing Up Associate With Impaired Physical Performance in Geriatric Outpatients

Background

Orthostatic hypotension is a prevalent condition in older adults and is associated with impaired physical performance and falls. The ability of older adults to compensate for rapid changes in systolic blood pressure (SBP; ie, SBP decline rate and SBP variability) may be important for physical performance. This study investigates the association of rapid SBP changes after standing up with physical performance.

Methods and Results

Consecutive patients who visited the Center of Geriatrics Amsterdam in 2014 and 2015 were included. The following SBP parameters were computed in 2 intervals (0–15 and 15–180 seconds) after standing up: steepness of steepest SBP decline; ratio of standing/supine SBP variability; and magnitude of largest SBP decline. Physical performance was assessed using the following measures: chair stand time, timed up and go time, walking speed, handgrip strength, and tandem stance performance. A total of 109 patients (45% men; age, mean, 81.7 years [standard deviation, 7.0 years]) were included. Steepness of steepest SBP decline (0–15 seconds) was associated with slower chair stand time (P<0.001), timed up and go time (P=0.022), and walking speed (P=0.024). Ratio of standing/supine SBP variability (0–15 seconds) was associated with slower chair stand time (P=0.005). Magnitude of largest SBP decline was not associated with physical performance.

Conclusions

SBP parameters reflecting rapid SBP changes were more strongly associated with physical performance compared with SBP decline magnitude in geriatric outpatients. These results support the hypothesis of an inadequate cerebral autoregulation during rapid SBP changes and advocate the use of continuous blood pressure measurements.

Lower cerebral vasoreactivity as a predictor of gait speed decline in type 2 diabetes mellitus

Gait speed is an indicator of overall functional health and is correlated with survival in older adults. We prospectively evaluated the long-term association between cerebral vasoreactivity and gait speed during normal walking (NW) and dual-task walking (DTW) in older adults with and without type 2 diabetes mellitus (T2DM). 40 participants (aged 67.3 ± 8.8 years, 20 with T2DM) completed a 2-year prospective study consisting of MRI, blood sampling, and gait assessments. The whole brain vasoreactivity was quantified using continuous arterial spin labeling MRI. Gait speed during DTW was assessed by subtracting serial sevens. Dual-task cost was calculated as the percent change in gait speed from NW to DTW. In the entire cohort, higher glycemic profiles were associated with a slower gait speed. In the diabetic group, lower vasoreactivity was associated with a slower gait speed during NW ([Formula: see text] = 0.30, p = 0.019) and DTW ([Formula: see text] = 0.35, p = 0.01) and a higher dual-task cost ([Formula: see text] = 0.69, p = 0.009) at 2-year follow-up. The participants with T2DM and lower cerebral vasoreactivity had a greater decrease in gait speed during NW and DTW after the 2-year follow-up ([Formula: see text] = 0.17, p = 0.04 and [Formula: see text] = 0.28, p = 0.03, respectively). Longer diabetes duration was associated with a higher dual-task cost ([Formula: see text] = 0.19, p = 0.04) and a greater decrease in gait speed during NW ([Formula: see text] = 0.17, p = 0.02). These findings indicate that in older adults with type 2 diabetes, gait performance is highly dependent on the integrity of cerebrovascular regulation.

Executive Network Activation is Linked to Walking Speed in Older Adults: Functional MRI and TCD Ultrasound Evidence From the MOBILIZE Boston Study

Background

Changes in cerebral blood flow velocity (CBF) in response to a cognitive task (task-related ΔCBF) have been shown by Transcranial Doppler ultrasonography (TCD) to be reduced in slow walkers. However, it is unknown whether reduced task-related ΔCBF is associated with reduced neural activity in specific brain regions, as measured by blood-oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI).

Methods

We assessed the regional changes in neural activity associated with reduced middle cerebral artery (MCA) task-related ΔCBF to an executive task and slow walking speed in 67 community-dwelling older adults from the MOBILIZE Boston Study. Participants underwent walking assessments and TCD ultrasonography measures of MCA ΔCBF during the n-back task of executive function. A subset of participants (n = 27) completed the same task during fMRI. Individual BOLD activation maps for the n-back task were correlated with TCD measures and network-level averages were associated with TCD and preferred walking speed.

Results

Participants with diminished task-related ΔCBF walked more slowly (β = .39, p = .001). fMRI revealed significant associations between task-related ΔCBF and regional BOLD activation in several brain regions/networks supplied by the MCA. Of these regions and networks, those within the executive network were most strongly associated with walking speed (β = .36, p = .01).

Conclusions

Task-related ΔCBF during an executive function task is related to activation in several neural networks and impairment in the ability to recruit the executive network in particular is associated with slow walking speed in older adults.