A randomized sham-controlled trial on the effect of continuous positive airway pressure treatment on gait control in severe obstructive sleep apnea patients

Abstract

To determine the effect of continuous positive airway pressure (CPAP), the gold standard treatment for obstructive sleep apnea syndrome (OSAS), on gait control in severe OSAS patients. We conducted a randomized, double-blind, parallel-group, sham-controlled monocentric study in Grenoble Alpes University Hospital, France. Gait parameters were recorded under single and dual-task conditions using a visuo-verbal cognitive task (Stroop test), before and after the 8-week intervention period. Stride-time variability, a marker of gait control, was the primary study endpoint. Changes in the determinants of gait control were the main secondary outcomes. ClinicalTrials.gov Identifier: (NCT02345694). 24 patients [median (Q1; Q3)]: age: 59.5 (46.3; 66.8) years, 87.5% male, body mass index: 28.2 (24.7; 29.8) kg. m-2, apnea-hypopnea index: 51.6 (35.0; 61.4) events/h were randomized to be treated by effective CPAP (n = 12) or by sham-CPAP (n = 12). A complete case analysis was performed, using a mixed linear regression model. CPAP elicited no significant improvement in stride-time variability compared to sham-CPAP. No difference was found regarding the determinants of gait control. This study is the first RCT to investigate the effects of CPAP on gait control. Eight weeks of CPAP treatment did not improve gait control in severe non-obese OSAS patients. These results substantiate the complex OSAS-neurocognitive function relationship.

Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1

Study flow chart. CPAP continuous positive airway pressure treatment, OSAS obstructive sleep apnea syndrome.

Figure 2

Effect of continuous positive airway pressure (CPAP) on gait control (a) and Stroop test performance (b) assessed in single (gait or Stroop test only) and dual task (gait and Stroop test performed simultaneously) (linear mixed effect model analysis). CPAP continuous positive airway pressure, CRR correct response rate, DT dual task, ST single task, STV stride time variability.

Figure 3

Evolution of prefrontal cortices Oxy[HbO2]- and Total[HbTot]-hemoglobin concentration assessed by functional Near Infrared Spectroscopy during the treadmill test. (a) Evolution of [HbO2] and [HbTot] (in mmoles−1) pre (continuous line) and post (dotted line) intervention for sham-CPAP (n = 11, represented in black) and CPAP (n = 6, represented in red) groups. Data are the measured mean values of [HbO2] and [HbTot] over the first 30-s of each task, averaged for left and right prefrontal cortices. To assess the evoked hemodynamic response, five activation indices were calculated as the difference in [HbO2] and [HbTot] between task and rest (in ST) or task and walk (in DT): ① S-7 ST; ② Stroop test ST; ③ Walk ST; ④ S-7 DT; ⑤ Stroop test DT. (b) Comparisons of delta pre-post intervention of [HbO2] and [HbTot] between sham-CPAP (n = 11) and CPAP (n = 6) groups. Data are mean ± 1 standard deviation. Analysis of data by Wilcoxon-Mann–Whitney test for continuous data, provided with Cohen’s D for effect size estimation. CPAP continuous positive airway pressure, DT dual task, HbO2 Oxy-hemoglobin concentration, HbTot total hemoglobin concentration, S-7 Serial S-7 tasks, ST single task.

Figure 4

Overground gait and stride time variability assessment experimental setting. (a) Picture of the experimental setting. (b) Schematic representation of the oval gait circuit (outward in the 10-m long corridor delineated by the Optogait system, return outside of the corridor). Stroop test was displayed on a black background screen installed at the end of the corridor. (c) Schematic representation of the visuo-verbal Stroop test. Patients were instructed to name the words font color and to inhibit reading the word (Correct answers here: “red” then “yellow” then “blue”). Words were presented one by one, and the evaluator skipped manually to the next one after the subject gave an oral response.