Bidirectional relationships of comorbidity with obstructive sleep apnoea

Abstract

Obstructive sleep apnoea (OSA) is frequently associated with comorbidities that include metabolic, cardiovascular, renal, pulmonary and neuropsychiatric. There is considerable evidence that OSA is an independent risk factor for many of these comorbidities but, more recently, there is evidence that some of these comorbidities may predispose to the development of OSA. Thus, there is growing evidence of a bidirectional relationship between OSA and comorbidity, especially for heart failure, metabolic syndrome and stroke. Potential mechanisms of bidirectional relationships differ in individual comorbidities with fluid retention and redistribution being especially important in heart failure and end-stage renal disease, whereas neural mechanisms may be more important in diabetes mellitus and stroke. The evidence for other comorbidities, such as hypertension and atrial fibrillation, support these being more a consequence of OSA with limited evidence to support a bidirectional relationship. The present review explores the evidence for such bidirectional relationships with a particular perspective on comorbidities that may predispose to OSA. The impact of therapy in bidirectional relationships is also reviewed, which highlights the clinical importance of accurate diagnosis. This aspect is especially true of COPD, where the identification of co-existing OSA has important implications for optimum therapy.

FIGURE 1

Potential mechanisms of increased pharyngeal collapsibility resulting from fluid accumulation in the neck region.

FIGURE 2

Inter-relationships between COPD and OSA demonstrating COPD-related factors that increase or decrease the likelihood of OSA, and OSA-related factors that may promote COPD. BMI: body mass index; OSA: obstructive sleep apnoea; REM: rapid eye movement.

FIGURE 3

Clinical features in obstructive sleep apnoea (OSA) and depression demonstrating shared features in the overlap of both disorders.

FIGURE 4

Proposed bidirectional relationships between obstructive sleep apnoea and comorbidity. The levels of evidence favouring inter-relationships ranging from strong to weak are the authors’ opinions based on the available evidence.