Prevalence and Characteristics of Patients with Obstructive Sleep Apnea and Chronic Obstructive Pulmonary Disease: Overlap Syndrome

Abstract

Overlap syndrome (OVS) is a distinct clinical entity that seems to result in potential cardiovascular consequences. We aimed to estimate the prevalence and risk factors for OVS in OSA patients and analyze clinical and PSG characteristics associated with OVS. In this cross-sectional study, 2616 patients evaluated for OSA underwent type-1 polysomnography (PSG). They were grouped as pure OSA (AHI > 15/h) and OVS patients. Demographics, PSG data, pulmonary function tests and arterial blood gases (ABGs) were compared between groups after adjustments for confounders. OSA was diagnosed in 2108 out of 2616 patients. Of those, 398 (19%) had OVS. Independent predictors of OVS were older age [OR: 5.386 (4.153-6.987)], current/former smoking [OR: 11.577 (7.232-18.532)], BMI [OR: 2.901 (2.082-4.044)] and ABG measurements [PaCO₂ ≥ 45 OR: 4.648 (3.078-7.019), PO₂ [OR: 0.934 (0.920-0.949)], HCO₃^- [OR: 1.196 (1.133-1.263), all p < 0.001]. OVS was also associated with prevalent hypertension [OR: 1.345 (1.030-1.758), p = 0.03] and cardiovascular disease [OR: 1.617 (1.229-2.126), p < 0.001], depressive symptoms [OR: 1.741 (1.230-2.465), p = 0.002] and nocturia [OR: 1.944 (1.378-2.742), p < 0.001], as well as with indices of OSA severity. Disturbances in sleep architecture were more prominent in OVS expressed by lower %N3 and REM% and higher arousal index. Our data suggest that OVS is prevalent among OSA patients, with distinct clinical and PSG characteristics. These characteristics could be utilized as predictive factors for early identification and further evaluation of these patients towards desirable patient-reported outcomes.

Keywords: cardiovascular disease; chronic obstructive pulmonary disease; obstructive sleep apnea; overlap syndrome; polysomnography; sleep architecture.

Figure 1

The flowchart of patients that were finally included.

Figure 2

Prevalence of OVS across different age groups.

Figure 3

Differences in PSG characteristics between groups. NREM: Non-rapid eye movement; PSG: polysomnography; REM: rapid eye movement; SWS: Slow-wave sleep; TST: total sleep time; SE (%): sleep efficiency; WASO: wake after sleep onset; AI: arousal index; AHI: apnea–hypopnea index; ODI: oxygen desaturation index; SpO₂: resting room air pulse oximetry; TST90: sleep time with oxygen saturation < 90%.