Pulse pressure is associated with walking impairment in multiple sclerosis

Pulse pressure is associated with decline in physical function in older adults

OBJECTIVES

This study examined the associations between pulse pressure, hypertension, and the decline in physical function in a prospective framework.

STUDY DESIGN

The Healthy Aging Longitudinal Study tracked a group of Taiwanese adults aged 55 or more over an average of 6.19 years to assess pulse pressure and decline in physical function, including in handgrip strength, gait speed, and 6-min walking distance, at baseline (2009-2013) and in the second phase of assessments (2013-2020).

MAIN OUTCOME MEASURES

Pulse pressure was calculated as the difference between systolic and diastolic blood pressure values. Weakness, slowness, and low endurance were defined as decreases of ≥0.23 m/s (one standard deviation) in gait speed, ≥5.08 kg in handgrip strength, and ≥ 57.73 m in a 6-min walk, as determined from baseline to the second phase of assessment. Linear and logistic regressions were employed to evaluate the associations between pulse pressure, hypertension, and decline in physical function.

RESULTS

Baseline pulse pressure was associated with future handgrip strength (beta = -0.017, p = 0.0362), gait speed (beta = -0.001, p < 0.0001), and 6-min walking distance (beta = -0.470, p < 0001). In multivariable models, only handgrip strength (beta = -0.016, p = 0.0135) and walking speed (beta = -0.001, p = 0.0042) remained significantly associated with future pulse pressure. Older adults with high systolic blood pressure (≥140 mmHg) and elevated pulse pressure (≥60 mmHg) exhibited a significantly increased risk of weakness (odds ratio: 1.30, 95 % confidence interval: 1.08-1.58), slowness (1.29, 1.04-1.59), and diminished endurance (1.25, 1.04-1.50) compared with the reference group, who exhibited systolic blood pressure of <140 mmHg and pulse pressure of <60 mmHg.

CONCLUSIONS

Among older adults, pulse pressure is associated with a decline in physical function, especially in terms of strength and locomotion.

Inverse association between arterial stiffness and perceived fatigue independent of disability status and BMI in multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is an immune-mediated, neurodegenerative disease of the central nervous system. Fatigue represents one of the most prevalent and limiting symptoms of MS, and is associated with vascular dysfunction, notably increased arterial stiffness.

OBJECTIVE

This study examined the relationship between arterial stiffness and perceived fatigue in persons with MS.

METHODS

The sample of 52 persons with MS (71.2% Female; Age: 46.7 ± 12.3 yrs.) completed arterial stiffness and fatigue assessments as baseline for an exercise training intervention. Applanation tonometry measured arterial stiffness, pulsatility and waveform characteristics, and yielded the following outcomes: carotid-femoral pulse wave velocity (cfPWV), carotid pulse-pressure (cPP), and aortic augmentation pressure (AP). Perceived fatigue was measured using the Fatigue Severity Scale (FSS).

RESULTS

The mean (SD) scores for cfPWV, cPP, and AP were 7.0 ± 1.8 m/s, 35.7 ± 8.8 mmHg, 8.2 ± 6.2 mmHg, respectively. The mean (SD) FSS score was 4.6 ± 1.4 and indicated elevated fatigue. There were statistically significant (p < .05) inverse correlations between cfPWV (r = -.32), cPP (r = -.37) and AP (r = -.32) with FSS scores, and the correlations remained significant even after controlling for disability, body mass index, age, and sex.

CONCLUSION

Our results indicate a consistent pattern of inverse relationships between arterial stiffness, pulsatility, and waveforms with fatigue independent of disability, body mass index, age, and sex in MS. This could be explained by lower sympathetic activation linking higher arterial stiffness, pulsatility and augmentation pressure with lower fatigue in persons with MS.

Comorbid Conditions and Physical Function in Adults With Multiple Sclerosis

OBJECTIVE

We examined the total number of comorbid conditions as a correlate of physical function in persons with multiple sclerosis (MS). We further identified the presence of common comorbid conditions and examined physical function outcomes based on presence or absence of the comorbid conditions in persons with MS.

DESIGN

Cross-sectional, comparative study.

SETTING

University-based laboratory.

PARTICIPANTS

Two hundred seven persons with MS (N=207) completed the study.

MAIN OUTCOME MEASURES

Participants provided demographic, clinical, and comorbidity information. Participants then completed the 6-minute walk (6MW), timed 25-foot walk (T25FW), timed Up and Go (TUG), and short physical performance battery (SPPB).

INTERVENTIONS

Not applicable.

RESULTS

The number of comorbid conditions was associated with 6MW, T25FW, TUG, and SPPB scores (all P≤.001). Persons with MS who had hypertension performed worse on the 6MW, T25FW, TUG, and SPPB than persons without hypertension. Persons who had osteoarthritis performed worse on the 6MW, T25FW, and SPPB than persons without osteoarthritis.

CONCLUSIONS

The results demonstrate that persons who report more comorbid conditions have worse physical function, and this may largely be associated with hypertension or osteoarthritis. There are opportunities for the design of behavioral interventions that target physical activity and/or diet for improving physical function via comorbid conditions in persons with MS.

Arterial stiffness in persons with multiple sclerosis and controls: Does aerobic fitness account for group differences?

Vascular function is worse in multiple sclerosis (MS) than healthy controls perhaps based on differences in aerobic fitness. We compared carotid-femoral pulse wave velocity (cfPWV) and augmentation index (AIx75) between MS and controls while accounting for aerobic fitness. Aerobic fitness was measured as peak oxygen consumption on a recumbent stepper. cfPWV and AIx75 were measured using applanation tonometry. Persons with MS demonstrated lower aerobic fitness and higher cfPWV, but no difference in AIx75 compared with controls. The difference in cfPWV remained statistically significant after controlling for aerobic fitness, suggesting that arterial stiffness might reflect underlying pathophysiology processes of MS.

Vascular dysfunction in multiple sclerosis: Scoping review of current evidence for informing future research directions

BACKGROUND

The research involving vascular comorbidity in people with multiple sclerosis (MS) could be advanced through investigations applying measurements of vascular function such as pulse wave velocity or flow mediated dilation as mechanistic endpoints in the study of physical comorbidity management in MS across the lifespan. We conducted a scoping review of research on vascular function parameters and outcomes in MS and developed a research agenda for future inquiry.

METHODS

We searched PubMed from inception through February 2023 for articles involving relevant central and peripheral vascular function data or correlates of vascular function (arterial stiffness, endothelial function, blood pressure parameters, etc.) in conjunction with relevant outcomes (walking function, cognition, etc.) in MS. Studies were limited to English-language and primary research articles.

RESULTS

Our search and subsequent screening identified 10 relevant articles. Four papers focused on arterial stiffness and reported pulse wave velocity and arterial compliance in MS compared with controls. Two papers focused on endothelial function and reported flow-mediated dilation in MS compared with controls. There was evidence that arterial stiffness and endothelial function were associated with cognition and disease progression in MS, respectively. One paper reported that physical activity was associated with arterial stiffness in MS. There was one protocol paper examining the effect of a home-based exercise program on markers of subclinical atherosclerosis; however, the results are unpublished, and there was no literature beyond this surrounding the impact of lifestyle behavior (e.g., diet) or exercise interventions on vascular function.

CONCLUSION

There is emerging evidence for vascular dysfunction in MS, and this is associated with cognition and disease progression; we know very little about approaches for managing vascular dysfunction in MS. To that end, we offer an agenda for research on measurements and outcomes of vascular function in relation to MS and disease attributes, along with proposed mechanisms and lifestyle changes that could aid in managing vascular dysfunction.

Vascular function and cognition in persons with multiple sclerosis: Preliminary examination

BACKGROUND

Cognitive dysfunction is one of the most common consequences of multiple sclerosis (MS). Recent studies have noted a high incidence of vascular comorbidity that might be associated with cognitive decline among persons with MS. However, there is a lack of evidence on vascular biomarkers (e.g., arterial stiffness indices) that are associated with cognition in MS. The current study characterized differences in vascular function between persons with MS and healthy controls, and examined the association between vascular and cognitive function in persons with MS compared with healthy controls.

RESULTS

The MS group had significantly worse cognitive performance and higher cfPWV than healthy controls. There were significant bivariate correlations between the Symbol Digit Modalities Test (SDMT) score with AIx75 (r_s = -0.45) and cfPWV (r_s = 0.30) in the MS sample, but not in healthy controls. Regression analyses further indicated a nonlinear association between cfPWV and the SDMT in the MS sample (p-values for β coefficients < 0.05; adjusted R² = 0.10). No significant associations were observed among other cognitive and vascular outcomes.

CONCLUSION

Our findings suggest significant associations between arterial stiffness and cognitive processing speed in MS. This preliminary examination provides initial, cross-sectional support for future population-based research on cognitive and vascular function in persons with MS. Such results may be clinically important for developing interventions that focus on regulating vascular dysfunction as an early treatment for preventing cognitive impairment in the MS population.

Blood lactate concentrations during rest and exercise in people with Multiple Sclerosis: A systematic review and meta-analysis

BACKGROUND

Multiple Sclerosis (MS) is a chronic disorder which irreversibly damages axons within brain matter. Blood lactate concentration could be a biomarker of MS onset and progression, but no systematic review has yet sought to confirm or dispute the elevation and biomarker potential of blood lactate in people with MS (PwMS) or to consolidate understanding of lactate production during exercise in PwMS.

OBJECTIVE

To perform a systematic review and meta-analysis on blood lactate in PwMS during rest and exertion compared to Healthy Controls (HC) and following chronic exercise intervention.

METHODS

A systematic search of six electronic databases (PubMed, CINAHL, Science Direct, Cochrane Library, SPORTDiscus and PEDro) was performed on 10th April 2020. Mean, standard deviation and sample size for lactate measures at rest and during exercise were pooled to determine overall effect size using a random effects model.  The 20-point Appraisal tool for Cross-Sectional Studies was utilised to assess study quality and inherent risk of bias. To qualify for inclusion, studies had to include human adults (>18 years) with a confirmed clinical diagnosis of MS, be published in English, have undergone peer review, report absolute blood lactate values for data extraction, and if involving testing during/after exercise, to do so during bilateral exercise methods.

RESULTS

18 studies were qualitatively analysed and 15 studies quantitatively analysed. Outcome data was available for 1986 participants (n_MS = 1129). A total of 7 papers tested blood lactate during rest (Lactate_REST), 7 papers tested during sub-maximal intensity exercise (Lactate_SUB-MAX), and 8 papers tested during maximal intensity exercise (Lactate_MAX). Meta analyses showed elevated Lactate_REST and reduced Lactate_MAX in PwMS compared to HC, higher Lactate_MAX in lower EDSS-scoring PwMS compared to higher EDSS-scoring PwMS, and that Lactate_SUB-MAX decreases and Lactate_MAX increases in PwMS following a chronic exercise intervention. Qualitative analysis reported Lactate_REST to be reduced in PwMS following a chronic exercise intervention.

CONCLUSIONS

Lactate_REST is elevated in PwMS compared to HC. Lactate_MAX is lower in PwMS compared to HC and lower still in higher compared to lower EDSS-scoring groups of PwMS. Chronic exercise interventions have the potential to reduce Lacatate_SUB-MAX for a given power output and increase Lactate_MAX in PwMS compared to baseline values. Lactate_REST may be reduced in PwMS following a chronic exercise intervention but more research is required for confirmation. The results of this review were limited by small sample sizes and number of studies available for each testing condition, limited data available for potentially confounding/correlating factors (eg. VO₂ and power output) as well as heterogeneity of methodology adopted across studies, often due to lactate testing being a secondary outcome measure. PLS: Lactate levels in the blood are different during rest and at intense exercise levels in people with Multiple Sclerosis (MS) compared to healthy counterparts, with people with MS showing a smaller jump in lactate during intense exercise from a higher resting level. After exercising for at least 3 months, blood lactate levels during exercise may become more similar to the levels seen in people without Multiple Sclerosis, but more research is required to give a clearer picture of this. We can hopefully use blood lactate in future to measure the progression of MS in an individual as well as the effectiveness of their exercise programme.

Blood pressure and body fat percent in women with NMOSD

BACKGROUND

Hypertension is a prevalent and impactful comorbid condition among patients with multiple sclerosis (MS). High level of body mass index (BMI) is associated with the risk and poor outcomes of neuromyelitis optica spectrum disorder (NMOSD) in women. However, the clinical implication of blood pressure (BP) and body fat percent (BF%) based on the Clínica Universidad de Navarra-Body Adiposity Estimator (CUN-BAE) in NMOSD has not been investigated thus far.

METHODS

Case data were collected from 47 NMOSD and 28 MS patients at acute phase, 21 NMOSD and 25 MS patients at stable phase, and 68 age- and sex-matched HCs. Four BP measures including systolic BP (SBP), diastolic BP (DBP), pulse pressure (PP), and mean arterial pressure (MAP); BMI; and BF% between NMOSD, MS, and healthy controls were determined.

RESULTS

Comparing NMOSD patients with MS patients, the former have significantly higher SBP (p < 0.001), DBP (p < 0.001), PP (p < 0.001), MAP (p < 0.001), BF% (p = 0.001), and BMI (p < 0.001) levels at acute phase after adjusting for age. Acute myelitis (OR 3.719, 95% CI 1.110-12.453) is more likely to occur in NMOSD patients with high BF% (≥30%) at acute phase. BF% was negatively correlated with 1/AQP4 titer in NMOSD at acute phase (r = -0.522, p = 0.004).

CONCLUSIONS

Women with NMOSD are probably more prone to have an increased BP and fat mass compared to MS.

Sedentary Behavior and Blood Pressure in Patients with Multiple Sclerosis

Background

Sedentary behavior is a pervasive public health concern in the general population. To date, little is known regarding the possible health risks associated with sedentary behavior in patients with multiple sclerosis (MS), although this population has increased risks of comorbidities such as hypertension.

Methods

This cross-sectional study examined the association between sedentary behavior and blood pressure (BP) in 31 patients with MS and 31 matched controls. Self-reported sitting time, one form of sedentary behavior, was measured using the International Physical Activity Questionnaire. Using an automated oscillometric monitor, systolic BP, diastolic BP, and mean arterial pressure were measured in the supine position after 10 minutes of rest lying down in a quiet room.

Results

There were significant correlations between International Physical Activity Questionnaire-measured sitting time and systolic BP (r = 0.365, P = .044, 95% CI, 0.013-0.636), diastolic BP (r = 0.382, P = .034, 95% CI, 0.032-0.648), and mean arterial pressure (r = 0.425, P = .017, 95% CI, 0.084-0.677) in patients with MS but not in controls (P > .05). The associations in patients with MS were unchanged even after adjusting for body mass index in linear regression analyses.

Conclusions

This study identified a significant association between sitting time and BP outcomes in patients with MS, supporting the need for additional examinations of sitting time and its possible health consequences in patients with MS.

Identification and validation of clinically meaningful benchmarks in the 12-item Multiple Sclerosis Walking Scale

BACKGROUND

The 12-item Multiple Sclerosis Walking Scale (12-MSWS) is a validated questionnaire which assessed walking function; it has been widely adopted in multiple sclerosis (MS) clinical research.

OBJECTIVE

Identify and validate clinically meaningful 12-MSWS benchmarks in MS.

METHODS

Cross-sectional study of 159 MS patients permitted identification of clinically meaningful 12-MSWS benchmarks based on their relationship to real-life anchors. Identified 12-MSWS benchmarks were then validated in a second population of 96 subjects using measures of ambulation, cognition, and patient-reported outcomes.

RESULTS

12-MSWS score of 0-24.99 was associated with working outside the home and assistance-free mobility; 25-49.99 was associated with gait disability and difficulty doing housework; 50-74.99 was associated with unemployment, government healthcare, cane use, and difficulty performing instrumental activities of daily living (IADLs); and 75-100 was associated with change in occupation due to walking, mobility impairment requiring bilateral assistance, and inability to perform IADLs. During the validation step, strong linear associations were identified between 12-MSWS benchmarks and other MS-related disability outcome measures, including ambulatory and non-ambulatory measures.

CONCLUSION

We have identified clinically meaningful 12-MSWS benchmarks which define four groups differentiated by increasing levels of mobility impairment and associated loss of functional independence. These data provide insight into how 12-MSWS translate to meaningful functional limitations in MS.

A comparison between the pathophysiology of multiple sclerosis and normal pressure hydrocephalus: is pulse wave encephalopathy a component of MS?

BACKGROUND

It has been suggested there is a chronic neurodegenerative disorder, underlying the pathophysiology of multiple sclerosis (MS), which is distinct from the more obvious immune-mediated attack on the white matter. Limited data exists indicating there is an alteration in pulse wave propagation within the craniospinal cavity in MS, similar to the findings in normal pressure hydrocephalus (NPH). It is hypothesized MS may harbor pulse wave encephalopathy. The purpose of this study is to compare blood flow and pulse wave measurements in MS patients with a cohort of NPH patients and control subjects, to test this hypothesis.

METHODS

Twenty patients with MS underwent magnetic resonance (MR) flow quantification techniques. Mean blood flow and stroke volume were measured in the arterial inflow and venous out flow from the sagittal (SSS) and straight sinus (ST). The arteriovenous delay (AVD) was defined. The results were compared with both age-matched controls and NPH patients.

RESULTS

In MS there was a 35 % reduction in arteriovenous delay and a 5 % reduction in the percentage of the arterial inflow returning via the sagittal sinus compared to age matched controls. There was an alteration in pulse wave propagation, with a 26 % increase in arterial stroke volume but 30 % reduction in SSS and ST stroke volume. The AVD and blood flow changes were in the same direction to those of NPH patients.

CONCLUSIONS

There are blood flow and pulsation propagation changes in MS patients which are similar to those of NPH patients. The findings would be consistent with an underlying pulse wave encephalopathy component in MS.

Neurological disability and its association with walking impairment in multiple sclerosis: brief review

SUMMARY 

Neurological disability and walking impairment are two common, co-varying consequences of multiple sclerosis (MS) that can result in substantial patient burden for daily activities and quality of life. Indeed, neurological disability and walking impairment are driven by pathological changes in the central nervous system, and measurement of walking function is a common method of monitoring the progression of disease and neurological disability. The existing data indicate that the presence of walking impairments range from performance through real-world outcomes based on comparison of MS versus healthy controls, and walking impairments become worse with increasing severity of neurological disability (i.e., progression). Accordingly, researchers and clinicians have considered both pharmaceutical and rehabilitation approaches for managing walking impairment in MS. Both approaches yield beneficial effects on walking outcomes, although the majority of research has focused on exercise training rather than pharmaceutical interventions. Overall, this underscores the importance of continued efforts toward identifying approaches for preventing, forestalling and restoring walking function in persons with MS across the spectrum of neurological disability and its progression.

Clinically meaningful performance benchmarks in MS: timed 25-foot walk and the real world

OBJECTIVE

Identify and validate clinically meaningful Timed 25-Foot Walk (T25FW) performance benchmarks in individuals living with multiple sclerosis (MS).

METHODS

Cross-sectional study of 159 MS patients first identified candidate T25FW benchmarks. To characterize the clinical meaningfulness of T25FW benchmarks, we ascertained their relationships to real-life anchors, functional independence, and physiologic measurements of gait and disease progression. Candidate T25FW benchmarks were then prospectively validated in 95 subjects using 13 measures of ambulation and cognition, patient-reported outcomes, and optical coherence tomography.

RESULTS

T25FW of 6 to 7.99 seconds was associated with a change in occupation due to MS, occupational disability, walking with a cane, and needing "some help" with instrumental activities of daily living; T25FW ≥8 seconds was associated with collecting Supplemental Security Income and government health care, walking with a walker, and inability to do instrumental activities of daily living. During prospective benchmark validation, we trichotomized data by T25FW benchmarks (<6 seconds, 6-7.99 seconds, and ≥8 seconds) and found group main effects on 12 of 13 objective and subjective measures (p < 0.05).

CONCLUSIONS

Using a cross-sectional design, we identified 2 clinically meaningful T25FW benchmarks of ≥6 seconds (6-7.99) and ≥8 seconds. Longitudinal and larger studies are needed to confirm the clinical utility and relevance of these proposed T25FW benchmarks and to parse out whether there are additional benchmarks in the lower (<6 seconds) and higher (>10 seconds) ranges of performance.

The reliability, precision and clinically meaningful change of walking assessments in multiple sclerosis

BACKGROUND

Assessing walking impairment in those with multiple sclerosis (MS) is common, however little is known about the reliability, precision and clinically important change of walking outcomes.

OBJECTIVE

The purpose of this study was to determine the reliability, precision and clinically important change of the Timed 25-Foot Walk (T25FW), Six-Minute Walk (6MW), Multiple Sclerosis Walking Scale-12 (MSWS-12) and accelerometry.

METHODS

Data were collected from 82 persons with MS at two time points, six months apart. Analyses were undertaken for the whole sample and stratified based on disability level and usage of walking aids. Intraclass correlation coefficient (ICC) analyses established reliability: standard error of measurement (SEM) and coefficient of variation (CV) determined precision; and minimal detectable change (MDC) defined clinically important change.

RESULTS

All outcome measures were reliable with precision and MDC varying between measures in the whole sample: T25FW: ICC=0.991; SEM=1 s; CV=6.2%; MDC=2.7 s (36%), 6MW: ICC=0.959; SEM=32 m; CV=6.2%; MDC=88 m (20%), MSWS-12: ICC=0.927; SEM=8; CV=27%; MDC=22 (53%), accelerometry counts/day: ICC=0.883; SEM=28450; CV=17%; MDC=78860 (52%), accelerometry steps/day: ICC=0.907; SEM=726; CV=16%; MDC=2011 (45%). Variation in these estimates was seen based on disability level and walking aid.

CONCLUSION

The reliability of these outcomes is good and falls within acceptable ranges. Precision and clinically important change estimates provide guidelines for interpreting these outcomes in clinical and research settings.

Gait performance in relation to aortic pulse wave velocity, carotid artery elasticity and peripheral perfusion in healthy older adults

Arterial stiffening is a widely known physiological change that occurs with ageing, but the functional consequences of vascular ageing are unclear. The purpose of this study was to determine whether carotid-femoral pulse wave velocity (PWV), mechanical properties of the carotid and femoral arteries and/or peripheral perfusion was associated with gait performance measured using a 400-m walk test. Twenty-one healthy older (68 ± 5 years) adults without cardiovascular disease participated in this study. Applanation tonometry was used to measure PWV, and Doppler ultrasound was used to measure arterial wall properties of the left common carotid and common femoral artery along with femoral blood flow. The median walk distance in the first 2 min of the test was 585 ft, and the overall gait speed was 1·5 m s(-1). Gait performance was inversely correlated with PWV (distance: r = -0·51; speed: r = -0·48; P<0·05) and carotid artery stiffness index β (distance: r = -0·56; speed: r = -0·51; P<0·05) after adjustment for age, body mass index, waist circumference and systolic blood pressure. No significant correlations were found between gait performance and femoral artery stiffness index β or femoral artery blood flow. These results found higher central arterial stiffness, as assessed by segmental arterial stiffness or local arterial wall properties, is associated with lower gait performance in older adults independent of other confounders.

Relation of pulse pressure to long-distance gait speed in community-dwelling older adults: findings from the LIFE-P study

Background

Reduced gait speed is associated with falls, late-life disability, hospitalization/institutionalization and cardiovascular morbidity and mortality. Aging is also accompanied by a widening of pulse pressure (PP) that contributes to ventricular-vascular uncoupling. The purpose of this study was to test the hypothesis that PP is associated with long-distance gait speed in community-dwelling older adults in the Lifestyle Interventions and Independence for Elders Pilot (LIFE-P) study.

Methods

Brachial blood pressure and 400-meter gait speed (average speed maintained over a 400-meter walk at “usual” pace) were assessed in 424 older adults between the ages of 70–89 yrs at risk for mobility disability (mean age = 77 yrs; 31% male). PP was calculated as systolic blood pressure (BP) – diastolic BP.

Results

Patients with a history of heart failure and stroke (n = 42) were excluded leaving 382 participants for final analysis. When categorized into tertiles of PP, participants within the highest PP tertile had significantly slower gait speed than those within the lowest PP tertile (p<0.05). Following stepwise multiple regression, PP was significantly and inversely associated with 400-meter gait speed (p<0.05). Other significant predictors of gait speed included: handgrip strength, body weight, age and history of diabetes mellitus (p<0.05). Mean arterial pressure, systolic BP and diastolic BP were not predictors of gait speed.

Conclusions

Pulse pressure is associated long-distance gait speed in community-dwelling older adults. Vascular senescence and altered ventricular-vascular coupling may be associated with the deterioration of mobility and physical function in older adults.

Prevalence of low ankle brachial index and its association with pulse pressure in an elderly Chinese population: a cross-sectional study

Background

We investigated the prevalence of low ankle brachial index (ABI) and the association of low ABI with pulse pressure among elderly community residents in China.

Methods

This population-based cross-sectional study was conducted in Beijing and recruited 2982 participants who were aged 60 years or older in 2007. Low ABI was defined as an ABI value less than 0.9 in either leg. Participants with or without stroke or coronary heart disease (CHD) were analyzed separately. The association between pulse pressure and low ABI was examined by using multiple logistic regression models.

Results

The prevalence of low ABI was 5.65% (4.24% among men and 6.52% among women; P = 0.0221) among participants without stroke or CHD and 10.91% (13.07% among men and 9.49% among women; P = 0.1328) among those with stroke or CHD. After adjusting for confounders, the odds ratio (95% CI) for each 5-mm Hg increase in pulse pressure was 1.19 (1.07, 1.33) and 1.10 (1.02, 1.20) for men and women, respectively, among participants without stroke or CHD and 1.17 (1.03, 1.34) and 1.15 (1.02, 1.30) for men and women with stroke or CHD. When pulse pressure was classified into quartiles and the lowest quartile was used as reference, the association between pulse pressure and low ABI remained positive in men and women.

Conclusions

Low ABI was prevalent among elderly Chinese, and pulse pressure was positively associated with low ABI.

Evidence for the different physiological significance of the 6- and 2-minute walk tests in multiple sclerosis

BACKGROUND

Researchers have recently advocated for the 2-minute walk (2MW) as an alternative for the 6-minute walk (6MW) to assess long distance ambulation in persons with multiple sclerosis (MS). This recommendation has not been based on physiological considerations such as the rate of oxygen consumption (V·O2) over the 6MW range.

OBJECTIVE

This study examined the pattern of change in V·O2 over the range of the 6MW in a large sample of persons with MS who varied as a function of disability status.

METHOD

Ninety-five persons with clinically-definite MS underwent a neurological examination for generating an Expanded Disability Status Scale (EDSS) score, and then completion of the 6MW protocol while wearing a portable metabolic unit and an accelerometer.

RESULTS

There was a time main effect on V·O2 during the 6MW (p=.0001) such that V·O2 increased significantly every 30 seconds over the first 3 minutes of the 6MW, and then remained stable over the second 3 minutes of the 6MW. This occurred despite no change in cadence across the 6MW (p=.84).

CONCLUSIONS

The pattern of change in V·O2 indicates that there are different metabolic systems providing energy for ambulation during the 6MW in MS subjects and steady state aerobic metabolism is reached during the last 3 minutes of the 6MW. By extension, the first 3 minutes would represent a test of mixed aerobic and anaerobic work, whereas the second 3 minutes would represent a test of aerobic work during walking.