Is Comorbid Insomnia in Obstructive Sleep Apnea Linked to Heart Disease?

Abstract

Introduction: Obstructive Sleep Apnea (OSA) and chronic insomnia are two the most common sleep disorders. There is still controversy that insomnia and OSA are associated with cardiovascular disease. The aim of this study was to investigate the prevalence of OSA patients with insomnia and to compare the clinical characteristics between patients who suffer from only OSA versus OSA with insomnia.

Materials and methods: We have retrospectively screened the patients who visited two tertiary university hospital sleep centers. A total of 476 adult patients diagnosed with OSA by polysomnography (PSG), were divided into two groups based on their insomnia severity index (ISI) score: OSA with insomnia (ISI ≥15) and OSA without insomnia (ISI < 15). For all of the subjects, subjective symptoms were evaluated using various questionnaires, including the Korean versions of the Pittsburg Sleep Quality Index (PSQI-K), the Epworth Sleepiness Scale (ESS-K), the Insomnia Severity Index (ISI-K), and the Beck Depression Inventory (BDI-2-K). Demographic and clinical factors were compared between the two groups.

Results: As a result of the total 476 patients diagnosed with OSA, 139 (29.2%) patients had significant insomnia symptoms. The OSA with insomnia group were more likely to be women (35.3% vs 19.6%, p< 0.001) and showed more prevalence of heart disease (19.4% vs 8.6%, p< 0.001) compared to the OSA without insomnia group. In questionnaires, subjects in the OSA with insomnia group had lower quality of life (SF-36) and quality of sleep (PSQI-K) with more excessive daytime sleepiness (ESS-K) and depression (BDI-K). There was no significant difference in the current CPAP users and compliance of CPAP use between the two groups.

Conclusions: The prevalence of OSA patients with insomnia symptoms was 29.2% which is comparable to the results of Western studies. The OSA with insomnia group showed more heart disease which was an interesting result, although we could not determine causality. This study supports the link between co-occurring insomnia with OSA and heart disease, however further investigation is needed regarding the detailed pathophysiology.