Postural stability and fall risk in patients with obstructive sleep apnea: A cross-sectional study

Abstract

Purpose Nocturnal hypoxia and daytime sleepiness resulting from fragmented sleep may impair the ability of postural stability in subjects with OSA. This study investigates the effect of disease severity on postural stability and whether or not it poses a fall risk in individuals with obstructive sleep apnea (OSA). Methods Forty-nine patients with OSA diagnosed by all-night polysomnography (apnea-hypopnea index (AHI) >= 5) and aged 51.4 +/- 7.2 years were included in the study. The patients were divided into two groups as severe OSA (AHI >= 30, n = 24) and non-severe OSA (5 <= AHI <= 30, n = 25). All patients were subjected to testing for postural stability (PS), limits of stability (LOST), and the stability index for fall risk (fall risk SI) with the Biodex Balance System (R). Daytime sleepiness was assessed using the Epworth Sleepiness Scale (ESS). Biodex measurements and daytime sleepiness were compared between severe and non-severe OSA groups. Univariate analysis was conducted to explore if AHI, ESS score, lowest SaO(2) (%), sleep stages (%), or total arousal index predict postural stability scores. Results Overall and anterior-posterior PS indices were higher in the severe OSA group (p < 0.05). Dynamic PS and fall risk indices did not differ between groups. AHI and lowest SaO(2) (%) were found to be an independent predictor for both overall PS (r = 0.300 and r = 0.286, respectively) and fall risk SI (r = 0.296 and r = 0.374, respectively), whereas stage N1 (%) and stage N3 (%) were an independent predictor for overall LOST score (r = -0.328 and r = 0.298, respectively) (p < 0.05). Conclusion Static postural stability of individuals with severe OSA is worse than those with non-severe OSA. Static postural stability worsens, and fall risk increases as AHI increases and the lowest SaO(2) decreases in individuals with OSA. On the other hand, dynamic postural stability worsens as stage N1 (%) sleep increases and stage N3 (%) sleep decreases. While nocturnal hypoxia indicators such as AHI and lowest SaO(2) are associated with static postural stability, sleep structure-related variables are associated with dynamic stability. Including postural stability assessments in the clinical practice for OSA may help addressing workplace accidents or tendency to fall.