By Professor Alun Jackson, Director, Australian Centre for Heart Health
Obstructive sleep apnoea (OSA) is highly prevalent in patients with hypertension and cardiovascular disorders, yet it is estimated that over 85% of people with OSA have never been treated.
Large population-based epidemiology studies have indicated that rates of hypertension, type II diabetes, stroke and cardiovascular disease are higher in people with OSA. However, the cause and effect relationship between OSA and cardiovascular disease remains unclear. Both are chronic conditions with common risk factors, including: male sex, older age, overweight, central body fat deposition, alcohol intake, smoking and lack of physical activity.
In the American Heart Association/American College of Cardiology Foundation Expert Consensus Document, several mechanisms by which OSA contributes to cardiovascular risk are described. Individuals with OSA have diminished heart rate variability, which can be a precursor to the development of hypertension. Hypoxeamia caused by OSA appears to trigger systemic inflammation and oxidative stress mechanisms, which may contribute to the development of endothelial dysfunction. In addition, OSA is associated with insulin resistance, and intrathoracic pressure changes which may lead to increased wall stress, impaired diastolic function and susceptibility for dissection.
In general, research indicates that individuals with OSA have lower levels of wellbeing compared to people without OSA experiencing reduced quality of life1. Furthermore, up to half the people with OSA were depressed, with depressive symptoms significantly impairing quality of life. In research undertaken by the Heart Research Centre, long-standing depression was associated with mortality after a heart event 2 . While the bidirectional relationships between depression, OSA and cardiac disease needs further exploration, the above findings highlight the importance of screening for both OSA and depression in cardiac patients.