How much of treatment effect is needed to actually matter?
Two articles on PainSci cite Williams 2011: (1) The Chiropractic Controversies (2) Statistical Significance Abuse
PainSci notes on Williams 2011:
There are various ways of measuring improvement in scientific tests of treatments. As this paper points out, “when an outcome measure improves by, say, five points it is not immediately apparent what this means.” How much improvement matters? It is extremely common for experimenters to confirm real, statistically significant treatment effects that are nevertheless trivial. This paper discusses how much benefit is needed to be taken seriously, and cites the damning example of spinal manipulation. Chiropractors routinely claim that the benefits of spinal adjustment are “proven,” but the authors point out that trials have “shown an effect size for manipulation that is less than the threshold for what is clinically worthwhile.”
I think it’s particularly noteworthy that these authors have no particular axe to grind about chiropractic treatment — this is not a paper about that. They simply needed a good example to make their point, and it’s telling that they picked spinal manipulative therapy.
original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
Patient-based outcome measures have been developed to measure the health status of patients suffering from many conditions found in musculoskeletal medicine. Many types have been developed. Generic measures can be used across a broad spectrum of illness and can compare the health of an affected group with that in the general population.1 Condition-specific instruments on the other hand measure the effect of a single condition on health. Compared to generic measures they have a narrower focus and are more sensitive to small but clinically significant changes in health status over short periods. Examples include the Roland–Morris questionnaire2 for low back pain and Western Ontario McMaster universities arthritis index (WOMAC) for osteoarthritis.
This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:
- Relationships Between Sleep Quality and Pain-Related Factors for People with Chronic Low Back Pain: Tests of Reciprocal and Time of Day Effects. Gerhart 2017 Ann Behav Med.
- Modulation in the elastic properties of gastrocnemius muscle heads in individuals with plantar fasciitis and its relationship with pain. Zhou 2020 Sci Rep.
- Association Between Plantar Fasciitis and Isolated Gastrocnemius Tightness. Nakale 2018 Foot Ankle Int.
- No Added Benefit of Combining Dry Needling With Guideline-Based Physical Therapy When Managing Chronic Neck Pain: A Randomized Controlled Trial. Stieven 2020 J Orthop Sports Phys Ther.
- Effectiveness of customised foot orthoses for Achilles tendinopathy: a randomised controlled trial. Munteanu 2015 Br J Sports Med.