Is obstructive sleep apnea syndrome a risk factor for pulmonary thromboembolism?

Background  In many studies, obstructive sleep apnea (OSA) has been shown to be an independent risk factor for cardiovascular disease. Conversely, there are few reports establishing possible relation between OSA and venous thromboembolism (VTE). In this study, the aim is to evaluate OSA via polysomnography in patients with pulmonary embolism and drawing the attention of clinicians to the presence of obstructive sleep apnea syndrome (OSAS) may be a risk factor for pulmonary embolism.

Methods  Fifty consecutive patients who were diagnosed with pulmonary embolism (PE) were evaluated prospectively for OSAS. Polysomnographic examination was conducted on 30 volunteer patients. The frequency of OSAS in PE was determined and PE cases were compared to each other after being divided into two groups based on the presence of a major risk factor.

Results  The study consisted of a total of 30 patients (14 females and 16 males). In 56.7% of the patients (17/30), OSAS was determined. The percent of cases with moderate and severe OSAS (apnea hipoapnea index >15) was 26.7% (8/30). Patients who had pulmonary thromboembolism (PTE) without any known major VTE risk (n=20), were compared to patients with VTE risk factors (n=10), and significantly higher rates of OSAS were seen (70% and 30% respectively; P=0.045). The mean age of the group with major PE risk factors was lower than the group without major PE risk factors (52 years old and 66 years old, respectively; P=0.015), however, weight was greater in the group with major PE risk factors (88 kg and 81 kg, respectively; P=0.025). By multivariate Logistic regression analysis, in the group without any visible major risk factors, the only independent risk factor for PE was OSAS (P=0.049).

Conclusions  In patients with PTE, OSA rates were much higher than in the general population. Moreover, the rate for patients with clinically significant moderate and severe OSA was quite high. PTE patients with OSA symptoms (not syndromes) and without known major risk factor should be examined for OSA. There seems to be a relationship between OSA and PTE. However, whether this relationship is a causal relationship or a relationship due to common risk factors or long-term complications of OSA is not clear. Further comprehensive studies on those special topics are needed to clarify these points.