Beyond steps per day: other measures of real-world walking after stroke related to cardiovascular risk

It is YOUR DOCTOR'S ABSOLUTE RESPONSIBILITY to get you recovered enough to do this and reduce your CVD risk. If they don't take responsibility you don't have a functioning stroke doctor or hospital.  I.E. they spout the craptastic 'get out of Jail Free card'; 'All strokes are different, all stroke recoveries are different.'

Beyond steps per day: other measures of real-world walking after stroke related to cardiovascular risk

• Allison Miller,
• Zachary Collier &
• Darcy S. Reisman 

Journal of NeuroEngineering and Rehabilitation volume 19, Article number: 111 (2022) Cite this article

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Abstract

Background

Significant variability exists in how real-world walking has been measured in prior studies in individuals with stroke and it is unknown which measures are most important for cardiovascular risk. It is also unknown whether real-world monitoring is more informative than laboratory-based measures of walking capacity in the context of cardiovascular risk. The purpose of this study was to determine a subset of real-world walking activity measures most strongly associated with systolic blood pressure (SBP), a measure of cardiovascular risk, in people with stroke and if these measures are associated with SBP after accounting for laboratory-based measures of walking capacity.

Methods

This was a cross-sectional analysis of 276 individuals with chronic (≥ 6 months) stroke. Participants wore an activity monitor for ≥ 3 days. Measures of activity volume, activity frequency, activity intensity, and sedentary behavior were calculated. Best subset selection and lasso regression were used to determine which activity measures were most strongly associated with systolic blood pressure. Sequential linear regression was used to determine if these activity measures were associated with systolic blood pressure after accounting for walking capacity (6-Minute Walk Test).

Results

Average bout cadence (i.e., the average steps/minute across all bouts of walking) and the number of long (≥ 30 min) sedentary bouts were most strongly associated with systolic blood pressure. After accounting for covariates (ΔR² = 0.089, p < 0.001) and walking capacity (ΔR² = 0.002, p = 0.48), these activity measures were significantly associated with systolic blood pressure (ΔR² = 0.027, p = 0.02). Higher systolic blood pressure was associated with older age (β = 0.219, p < 0.001), male gender (β = − 0.121, p = 0.046), black race (β = 0.165, p = 0.008), and a slower average bout cadence (β = − 0.159, p = 0.022).

Conclusions

Measures of activity intensity and sedentary behavior may be superior to commonly used measures, such as steps/day, when the outcome of interest is cardiovascular risk. The relationship between walking activity and cardiovascular risk cannot be inferred through laboratory-based assessments of walking capacity.

Introduction

Low physical activity is an important modifiable risk factor for stroke and future cardiovascular events [1,2,3,4,5]. In fact, low physical activity may be the second most important modifiable risk factor for stroke, aside from blood pressure [6]. Thus, controlling a person’s risk factors for stroke often involves modifications to their activity behavior to reduce these risks [2]. This is a particularly salient concept in people who have already sustained a stroke who typically demonstrate lower activity levels and greater sedentary behavior compared to persons without stroke [7,8,9,10,11].

The application of sensor technology has enabled rehabilitation professionals to measure real-world activity (i.e., activity that occurs outside the clinic or laboratory setting) to better understand the activity levels of individuals with stroke and its effects on cardiovascular risk [1, 12,13,14]. In general, two lines of work have garnered significant attention in the sensor field, one related to the measurement of activity and the other focused on understanding predictors of activity. In terms of measurement, the most common way that real-world walking activity has been quantified in stroke rehabilitation studies is by calculating average steps/day (ASPD) [15,16,17,18,19]. Using this measure, a person’s daily stepping activity is monitored over a period of time (preferably at least 7 days) [20, 21], summed and averaged across the number of valid recording days [22, 23]. Thus, ASPD is easy to calculate and interpret, likely contributing to its ubiquitous use in studies in individuals with stroke. There is, however, significant variability in how real-world activity is measured in studies in people with stroke [7, 10, 11, 14, 24,25,26,27,28,29], with some studies emphasizing the importance of measuring sedentary behavior [11, 25, 28, 30, 31] and others examining measures of activity intensity using metabolic equivalents of task (METS) or cadence [14, 26, 27, 32], among other measures. Thus, it remains unknown which measures of real-world walking activity are most important for cardiovascular risk in people with stroke.

A second line of work has focused on examining predictors of real-world walking activity in people with stroke [15, 28, 33,34,35]. This line of work has revealed that measures of walking capacity are strongly related to real-world walking activity after stroke. A recent meta-analysis by Thilarajah and colleagues found that the 6-Minute Walk Test, a measure of walking capacity, explains 37% of the variance in physical activity in people with stroke [15]. This suggests that measures of walking capacity are critically important and could potentially serve as a proxy for real-world walking activity in people with stroke. Real-world activity monitoring can be costly and cumbersome [36]; thus, if rehabilitation professionals were able to utilize laboratory-based measures of walking capacity as a proxy for real-world walking activity, this could potentially save time and resources. However, other work suggests that performance on laboratory-based measures of walking capacity does not necessarily translate to real-world walking behavior [18, 37,38,39]. Thus, whether real-world monitoring is more informative than laboratory-based measures of walking capacity in understanding the relationship with cardiovascular risk is not known at this time.

These lines of work have exposed two critical knowledge gaps. The first is that it remains unknown which measures of real-world walking activity are most important for cardiovascular risk in people with stroke. While previous studies have selected measures of potential importance, the first objective of this work was to determine which measures of real-world activity are most important to identify cardiovascular risk in people with stroke. Elevated systolic blood pressure (SBP) is an important cardiovascular risk factor and likely the strongest risk factor for stroke [3, 6, 40]. We therefore examined the relationship between measures of real-world walking activity and SBP. The second knowledge gap is that it is not known whether real-world monitoring is more informative than laboratory-based measures of capacity in the context of cardiovascular risk. Therefore, our second objective was to determine if measures of real-world walking activity would be associated with SBP after accounting for measures of walking capacity (6-Minute Walk Test, 6MWT). We hypothesized that average steps/day, average number of walking bouts/day, the percent time spent in sedentary behaviors, and the fragmentation index would be significantly associated with SBP and that these activity measures would be significantly associated with SBP after accounting for the 6MWT.