Objective

Obstructive sleep apnea (OSA) is now widely seen as a major public health issue with widespread societal consequences. In addition to an increased stroke risk, OSA leads to cerebral consequences including cognitive deficits that impair quality of life and daily functioning. In a recent uncontrolled study, moderate-to-severe OSA have been associated with higher stride time variability (STV), reflecting poor gait control (Celle, Annweiler et al., 2014). STV is a clinical marker of cortical gait control linked with cognitive performance and cerebral integrity (Beauchet, Annweiler et al., 2014). Whether continuous positive airway pressure (CPAP), the most effective and widely used treatment in OSA, could improve gait impairments remains to be investigated. This study aims to evaluate the impact of an 8-week CPAP treatment on gait performance evaluated by STV in OSA patients.

Material/patients and methods

Twelve non-obese, severe OSA patients (age = 57.2 ± 8.9 years, BMI = 27.4 ± 3.1 kg·m ⁻² , AHI = 46.3 ± 11.7) and 10 healthy matched subjects were included for comparison. In this prospective controlled study, gait was assessed overground, at spontaneous speed, using a 10-meter Optogait walkway. Gait spatio-temporal parameters were recorded and STV was calculated. The role of cognition in gait control was investigated using a dual-task paradigm. Spatiotemporal gait parameters were recorded at preferred speed on a treadmill in single and in dual task condition, using a Stroop interference task. Cognitive performance at Stroop test was assessed at rest (single task) and while walking (dual task) by calculating the correct response rate. All the assessments were performed before and after 8 weeks of CPAP treatment.

Results

At baseline, OSA patients showed higher STV (3.1 ± 1.1% vs 2.1 ± 0.5%, P = 0.02) and step width (16.1 ± 2.9 cm vs 12.3 ± 1.3 cm, P = 0.001) as compared to controls. They also showed a lower rate of correct responses at the Stroop test when walking (66.5 ± 9.3 vs 90.5 ± 10.9, P < 0.001). After CPAP treatment, both spatiotemporal gait parameters (post-CPAP STV: 2.4 ± 0.5%, P = 0.005 vs baseline) and cognitive performances when walking (post-CPAP correct response rate 74.4 ± 13.04, P = 0.016 vs baseline) were improved in OSA patients and did not differ anymore from controls.

Discussion–conclusion

Severe non-obese OSA patients have an impaired gait control, which may be reversed after 8 weeks of CPAP treatment. Our data suggest its cognitive origin.