Obstructive Sleep Apnoea (OSA) and Heart Disease (Cardiovascular Disease): A Summary

Author: Professor Ram Dhillon

An Apnoea is essentially a nocturnal strangulation, due to blockage of the upper breathing passages, for a minimum of 10 seconds, but could be more: 15, 20, 30, or 40+ seconds. If an individual has 5 or more of these episodes per hour during sleep, the disorder OSA is present. Mild OSA is 5-15 apnoeas per hour; Moderate OSA is 15-30 apnoeas per hour and severe is 30+ apnoeas per hour. This is called the AHI score/index and is a grading system of severity.

OSA is associated with obesity, diabetes (type 2), heart disease, and dementia, amongst many other disorders. These associations are due to the metabolic and physiological consequences of the strangulation/apnoea, and, in many individuals, the low blood oxygen levels that can accompany each episode.

OSA affects ~ 4-8% of the population. In the UK between 2.4-4.8 million, India: is mainly confined to the upper and middle classes with an estimated 35 million affected, and in the USA about 30 million. In the Middle East, Emirates, the local population risk is about 22% of the population. In China, the prevalence is about 12%, so 140 million affected, and generally the Chinese exhibit a lower BMI score.

Individuals with established OSA should be managed with proper medical assessment (a sleep study) and management, which would be lifestyle changes (which are hard to implement and maintain) but also consider interventions such as Mandibular Advancement Devices (MADs) and CPAP (Continuous Positive Airway Pressure).

The correlation between OSA and cardiovascular disease (CVD) is well-documented in scientific literature, underscoring a significant public health concern given the widespread prevalence of both conditions.

Numerous studies have established that individuals with OSA have a higher risk of developing various cardiovascular diseases. The mechanisms linking OSA to CVD include intermittent hypoxia (low oxygen levels in the blood) and sympathetic nervous system activation (the apnoea produces a flight/fight response with an outpouring of the hormone adrenaline). These factors collectively contribute to the development and progression of hypertension (high blood pressure), atherosclerosis (furring of the
arteries), heart failure, atrial fibrillation (an abnormal type of heartbeat), and other heart conditions.

The key critical mechanism by which OSA influences heart health is through intermittent hypoxia. Recurrent episodes of low oxygen levels during sleep lead to sympathetic nervous system activation, resulting in increased blood pressure and heart rate variability. This chronic sympathetic overactivity, due to the high levels of adrenaline, can cause sustained hypertension, which is a major risk factor for CVD. Studies have shown that OSA is independently associated with hypertension, and effective treatment of OSA can lead to significant reductions in blood pressure.

Systemic inflammation is another key pathway linking OSA to cardiovascular disease. The repetitive oxygen desaturation and reoxygenation cycles seen in OSA patients promote inflammatory responses, rather similar to an infection, leading to raised levels of inflammatory markers such as C-reactive protein (CRP) and interleukin-6 (IL-6). This chronic nocturnal inflammation contributes to the development of atherosclerosis, as it promotes abnormalities in the lining of the arteries, dysfunction of lipid (fat) metabolism, and ultimately plaque formation (furring) in the arteries.

Furthermore, OSA can lead to changes in cardiac structure, including cardiac muscle dysfunction and impaired resting phase of the heart best, which are precursors to heart failure.

The impact of continuous positive airway pressure (CPAP) therapy, the primary treatment for OSA, on cardiovascular outcomes has been extensively studied. CPAP therapy effectively mitigates the intermittent hypoxia and sympathetic activation caused by OSA.

Trials have shown that CPAP can reduce blood pressure, improve endothelial (blood vessel) function, and decrease the levels of inflammatory markers. CPAP therapy has demonstrated significant benefits in terms of managing symptoms and preventing hypertension, and reducing the incidence of myocardial infarction (heart attack) or stroke.

In conclusion, the correlation between obstructive sleep apnoea and cardiovascular disease is well supported by a substantial body of scientific literature. OSA contributes to cardiovascular medical disorders through mechanisms involving intermittent hypoxia, sympathetic activation, systemic inflammation, and structural cardiac changes. Effective management of OSA, particularly through CPAP therapy, plays a vital role in mitigating these adverse cardiovascular effects and improving overall health
outcomes.

FINALLY: Do you have Sleep Apnoea? Use the attached “Modified STOP BANG” triage questionnaire.

LISTEN TO THIS PODCAST: The Hidden Dangers of Untreated Sleep Apnoea with Professor Ram Dhillon

For more information on Obstructive Sleep Apnoea and Snoring, visit ENT London.