Comparing 6-minute walk versus treadmill walking distance as outcomes in randomized trials of peripheral artery disease

Mary M. McDermott*, Jack M. Guralnik, Lu Tian, Lihui Zhao, Tamar S. Polonsky, Melina R Kibbe, Michael H. Criqui, Dongxue Zhang, Michael S. Conte, Kathryn Domanchuk, Lingyu Li, Robert Sufit, Christiaan Leeuwenburgh, Luigi Ferrucci

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Background: Randomized trials of people with peripheral artery disease (PAD) and intermittent claudication have traditionally used maximal treadmill walking distance as the primary outcome, but the 6-minute walk test is increasingly used as a primary outcome in randomized trials of PAD. This study compared relative changes in maximal treadmill walking distance versus 6-minute walk distance in response to a therapeutic intervention or control in randomized trials of participants with PAD. Methods: Data from four randomized trials of therapeutic interventions in participants with PAD that measured both 6-minute walk and treadmill walking performance at baseline and the 6-month follow-up were combined. Two trials studied supervised treadmill exercise, one studied home-based walking exercise, and one studied resveratrol. Results: Of 467 participants (mean age, 69.8; standard deviation, 9.7), the mean ankle-brachial index was 0.66 (standard deviation, 0.17). At the 6-month follow-up, participants with PAD randomized to control or placebo significantly declined in 6-minute walk distance (−10.2 m; 95% confidence interval, −18.2 to −2.2; P =.013), but improved maximal treadmill walking distance (+25.7 m; 95% CI, +6.0 to +45.3 m; P =.010; difference between change in 6-minute walk versus maximal treadmill walking distance: −37.3 m; 95% CI, −56.4 to −18.2; P <.001). Home-based exercise improved the 6-minute walk distance by 43.2 m (95% CI, +28.4 to +57.9), and supervised treadmill exercise improved the 6-minute walk distance by 25.0 m (95% CI, +14.7 to +35.2; mean difference, +18.2 m favoring home-based exercise [95% CI, +0.2 to +36.2 m; P =.048]). Among all participants, the presence (vs absence) of treadmill exercise training was associated with a 141.3-m greater improvement in maximal treadmill walking distance compared to 6-minute walk distance (95% CI, 88.2-194.4; P <.001), suggesting a benefit from treadmill training on the treadmill outcome. Conclusions: Maximal treadmill walking distance and the 6-minute walk distance are not interchangeable outcomes in participants with PAD. Participants with PAD randomized to control groups improved treadmill walking distance but simultaneously meaningfully declined in 6-minute walk distance. Supervised treadmill exercise training amplified improvement in treadmill walking distance because of a training to the outcome measure phenomenon.

Original languageEnglish (US)
Pages (from-to)988-1001
Number of pages14
JournalJournal of Vascular Surgery
Volume71
Issue number3
DOIs
StatePublished - Mar 2020

Keywords

  • 6-Minute walk
  • Clinical trials
  • Disability
  • Functional status
  • Peripheral artery disease

ASJC Scopus subject areas

  • Surgery
  • Cardiology and Cardiovascular Medicine

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    McDermott, M. M., Guralnik, J. M., Tian, L., Zhao, L., Polonsky, T. S., Kibbe, M. R., Criqui, M. H., Zhang, D., Conte, M. S., Domanchuk, K., Li, L., Sufit, R., Leeuwenburgh, C., & Ferrucci, L. (2020). Comparing 6-minute walk versus treadmill walking distance as outcomes in randomized trials of peripheral artery disease. Journal of Vascular Surgery, 71(3), 988-1001. https://doi.org/10.1016/j.jvs.2019.05.058