JACC: Increased activity, walking speed improves PAD outcomes
Peripheral artery disease (PAD) affects between eight and 12 million U.S. patients, who lose functionality quicker than those without the disease. New research has shown that a more sedentary lifestyle and slower walking speed can decrease a patient’s abilities and reduce calf muscle density; however, lifestyle interventions that promote exercise could possibly help prevent a quicker loss of functionality, according to research published in the June 7 issue of the Journal of the American College of Cardiology.

To evaluate the association of the number of sedentary hours per day with rates of functional decline and change in calf muscle characteristics in PAD patients, Mary M. McDermott, MD, of the Feinberg School of Medicine at Northwestern University in Chicago, and colleagues enrolled 384 patients with an ankle brachial index that was less than 0.90 to better understand functional decline.

Previously, McDermott and colleagues found that women with PAD lose mobility and function quicker than men with the same disease. The researchers attributed this difference to women’s smaller baseline calf muscle.

Within the current study, the mean study follow-up was 47 months and the researchers used Spearman correlation coefficients to measure physician activity with sitting hours per day.

The average ages across the categories of total hours spent sitting per day were: less than four hours: 73 years; four to seven hours: 75.5 years; eight to 11 hours: 74 years and more than 12 hours: 74.5 years. The number of patients within each of these groups in terms of hours spent sitting per day was: 60, 163, 111 and 50, respectively.

Patients who spent a greater amount of time per day sitting or lying down were more likely to have pulmonary disease and angina, a higher body mass index and poorer six-minute walk performance.

The researchers reported the average age of patients across four categories: no walking, casual strolling, average or normal and brisk or striding. The average age of these patients in each of these categories was 76, 75.6, 73.5 and 70.4 years, respectively.

“Slower walking speed outside the home was associated with more adverse baseline calf muscle characteristics and poorer performance on each measure of baseline walking performance,” the authors wrote.

The researchers linked more hours spent sitting/laying down with a greater decline in six-minute walk performance, four-minute walking velocity and fast-paced four-minute walking velocity. However, walking speed outside the home did not have any significant association with the aforementioned measurements, according to the authors.

McDermott et al reported that slower walking speeds were associated with a greater decline in calf muscle density. Compared with patients who had a brisk stride, patients who casually strolled had a greater decline in calf muscle density.

Despite evidence that PAD patients lose functionality faster than those without PAD, very few treatments have been identified to improve functional performance in patients with the disease. The researchers said that home-based exercise interventions have not demonstrated efficacy in PAD patients.

In fact, in an accompanying JACC editorial, Mehdi H. Shishehbor, DO, MPH, of the Cleveland Clinic, noted that home-based exercise programs fail because of the fact that a large number of PAD patients are from a lower socioeconomic status and live in neighborhoods were resources, like recreational facilities, sidewalks and parks are less safe and/ or hard to find.

Additionally, the study authors noted that while supervised treadmill exercise has been shown to improve walking endurance in PAD patients, it goes underutilized because payors do not typically cover this therapy. However, they also wrote that there may be more of an opportunity to decrease the number of hours seated than actually install interventions to increase exercise behaviors. This is due to the fact that increasing walking speed in PAD patients can cause ischemic pain.

“Further study is needed to identify interventions that increase walking speed outside the home and to determine whether these interventions prevent declines in calf muscle density and other outcomes in patients with PAD,” the authors wrote. “[T]he association of greater sedentary hours per day with faster functional decline may be mediated by worsening cardiovascular fitness, greater inflammation, worsening calf muscle mitochondrial function, or greater progression of lower extremity atherosclerosis among participants with PAD who were more sedentary.”

Shishehbor noted that the lack of physical activity may the culprit as to why PAD patients experience worse outcomes. Additionally, he said that the six-minute walking test may be an important tool that is underused in clinical practice. “Using it to identify individuals with PAD who are at risk of declining function may provide an opportunity to intervene early and potentially abrogate this process,” Shishehbor noted.

The link between walking speed and calf muscle density could welcome the increased use of endovascular therapy, which could alleviate symptoms and help improve walking distances and speeds, Shishehbor said.

“Clearly, endovascular therapy for claudication can only be viewed as a vehicle to enable a more rigorous supervised and home-based physical activity program and should never replace risk factor modification and exercise.” However, Shishehbor concluded that only implementing lifestyle modifications may be inadequate in preventing functional decline. Therefore, behavioral and environmental changes could improve “exercise programs, risk factor modification and revascularization.”