Evidence Trace, complete trial record
In plain terms
In plain terms: Positional therapy for position-dependent sleep apnea shows early signals in human research but the evidence is limited -- small trials, surrogate endpoints, or not yet independently replicated. It is an emerging area, not yet a proven one.
Positional therapy for position-dependent sleep apnea
C
Limited: small, mixed or unreplicated trials
The endpoint this grade is based on: Surrogate biomarker endpoint
The evidence as the record states it
Kelly et al. (Thorax, 2026; PMID 40992934): double-blind sham-controlled multicenter trial, 120 patients, 3 months. ALQarni et al. (Thorax, 2023; PMID 37344178): meta-analysis of 10 randomized and 8 cohort studies against baseline, shown as context.
PMID 40992934 PMID 37344178
Evidence by specific use
Apnea-hypopnea index and daytime sleepiness in position-dependent obstructive sleep apnea
Grade C
A double-blind sham-controlled trial in 120 adults lowered the apnea-hypopnea index by 4.4 events an hour, with no change in Epworth sleepiness (Kelly et al., Thorax, 2026; PMID 40992934). A meta-analysis reported larger falls, but it pooled cohort studies against baseline, which cannot carry a letter; it is shown on the record as context. One controlled trial: C.
PMID 40992934
Why Grade C and not Grade B
Grade C reflects early or limited human evidence -- small trials, surrogate endpoints, or preliminary findings not yet independently replicated. The evidence points in a promising direction but does not yet meet the standard for Grade B. A single well-powered, independently replicated trial with a meaningful endpoint would move this to Grade B or higher.
What this grade covers and what it does not
Grade C on the apnea-hypopnea index in position-dependent sleep apnea: one sham-controlled randomized trial lowered it by 4.4 events an hour without changing daytime sleepiness (Kelly et al., 2026; PMID 40992934). WHY NOT B: one trial nobody has repeated; the meta-analysis reporting larger falls pooled cohort studies against baseline (PMID 37344178). WHAT THIS GRADE DOES NOT COVER: pillows, backpacks and tennis-ball methods, which the cited trial did not test; sleep apnea that is not position-dependent; and daytime sleepiness, which did not change in the trial.
What would move this grade
A well-powered randomized trial with an objective, clinically meaningful primary endpoint and at least one independent replication would support Grade B or higher.
How to track whether this is working
Apnea-hypopnea index by body position on a home study, time spent on the back, and the Epworth Sleepiness Scale.