Do physical therapy and yoga improve pain and disability through psychological mechanisms? A causal mediation analysis of adults with chronic low back pain

Author: Christopher T Joyce1, Ariel Chernofsky2, Sara Lodi2, Karen J Sherman3, Robert B Saper4,5, Eric J Roseen5,6
1 School of Physical Therapy, Massachusetts College of Pharmacy and Health Sciences University, Worcester, MA, USA.
2 Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts, USA.
3 Kaiser Permanente Washington Health Research Institute and Department of Epidemiology, University of Washington, Seattle, WA, USA.
4 Department of Wellness and Preventative Medicine, Cleveland Clinic, Cleveland, OH, USA.
5 Department of Family Medicine, Boston University School of Medicine and Boston Medical Center, Boston, MA, USA.
6 Department of Rehabilitation Science, MGH Institute of Health Professions, Boston, MA, USA.
Conference/Journal: J Orthop Sports Phys Ther
Date published: 2022 May 18
Other: Special Notes: doi: 10.2519/jospt.2022.10813. , Word Count: 219

To investigate whether indirect effects via psychological mechanisms explain the effects of physical therapy (PT) or yoga, versus education, on back-related outcomes.

Mediation analyses using data from a randomized controlled trial of PT, yoga, and education interventions for chronic low back pain.

Primary outcomes were changes in back-related pain on the 11-point numerical rating scale and disability on the modified 23-point Roland Morris Disability Questionnaire, measured at 52-weeks post-randomization. Hypothesized mediators were 12-week changes in pain self-efficacy, fear avoidance beliefs, depression, anxiety, perceived stress, and sleep quality. We used causal mediation analysis to estimate the total effect, direct effect, indirect effect, and proportion mediated.

We analyzed data from 230 adults (mean age = 46.2 years, 69.6% female, 79.6% non-white). In the PT versus education model, when the mediator was perceived stress, the total effect on disability was 2.6 points (95% CI: 0.3, 4.9) and decomposed into a direct effect of 1.7 points (95% CI: -0.4, 3.8) and an indirect effect 0.9 points (95% CI: 0.1, 2.0; proportion mediated 34%). No other psychological construct was a significant mediator.

Improvements in perceived stress mediated improvements in disability after PT treatment compared to education. Other psychological outcomes did not mediate the effect of yoga or PT on pain or disability outcomes compared to education. J Orthop Sports Phys Ther, Epub 18 May 2022. doi:10.2519/jospt.2022.10813.

Keywords: Mediation; chronic pain; mechanisms; physical therapy; yoga.

PMID: 35584010 DOI: 10.2519/jospt.2022.10813