Polysomnographic features of low arousal threshold in overlap syndrome involving obstructive sleep apnea and chronic obstructive pulmonary disease

Abstract

Purpose

In patients with overlap syndrome (OVS), the pathophysiologies of obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease can interact with one another. Focusing on low arousal threshold, the authors evaluated polysomnographic features of OVS patients.

Methods

This retrospective, multicenter study was conducted at three hospitals in Japan. Patients aged ≥ 60 years who underwent polysomnography and pulmonary function testing were reviewed. Severity of airflow limitation (AFL) was classified according to the Global Initiative for Chronic Obstructive Lung Disease criteria. Low arousal threshold was predicted based on the following polysomnography features: lower apnea-hypopnea index (AHI); higher nadir oxygen saturation, and larger hypopnea fraction of total respiratory events. These features were compared among patients with only OSA (n = 126), OVS with mild AFL (n = 16), and OVS with moderate/severe AFL (n = 22).

Results

A low arousal threshold was more frequently exhibited by OVS patients with moderate/severe AFL than by those with OSA only (p = 0.016) and OVS with mild AFL (p = 0.026). As forced expiratory volume in 1 s/forced vital capacity (FEV₁/FVC) decreased in OVS patients, the mean length of apnea decreased (r = 0.388, p = 0.016), hypopnea fractions increased (r = − 0.337, p = 0.039), and AHI decreased (r = 0.424, p = 0.008). FEV₁/FVC contributed to low arousal threshold independent of age, sex, smoking history, hospital, or body mass index in all subjects (OR 0.946 [95% CI 0.909–0.984]) and in OVS patients (OR 0.799 [95% CI 0.679–0.940]).

Conclusions

This study first described peculiar polysomnographic features in OVS patients with moderate/severe AFL, suggesting a high prevalence of low arousal threshold.

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