Nine RCTs were identified that met the inclusion criteria (n=161). Sample sizes ranged from 10 to 38 participants.
One study (n=22), a pilot RCT, investigated the effect of surgical nasal intervention (temperature controlled radio frequency reduction of turbinate hypertrophy). An assessment of nasal obstruction on a visual analogue scale by a blinded assessor showed no statistically significant difference between surgery and placebo, but participants reported a significant improvement in continuous positive airways pressure. This study was underpowered and randomisation may have been performed incorrectly.
Five RCTs (n=96), all cross over in design, investigated effects of nasal dilators. In three studies the nasal dilator was compared to a placebo. In two studies the intervention was compared to no treatment. With the exception of one study, which reported no difference in outcome measures between the intervention and placebo/non-treatment group, all studies reported an improvement in at least one outcome measure. Outcome measures varied between studies.
Three RCTs (n=43), all crossover in design, investigated the effects of topical drug treatments of steroids (fluticasone) or nasal decongestants (oxymetazoline). All studies compared the intervention to placebo. In the one study using steroids there was no difference in outcome between the intervention and placebo group. The two trials that used decongestants reported an improvement in sleep architecture, but only one reported a positive effect on apnoea/hypopnoea index (average change -12, 95% CI: -3 to -22).