Sleep apnea is associated with subclinical myocardial injury
Obstructive sleep apnea is known to be associated with an increased incidence of cardiovascular disease. Now a new study indicates that OSA is associated with subclinical myocardial injury, as indicated by increased high sensitivity troponin T (hs-TnT) levels. Elevated hs-TnT levels are predictive of both coronary heart disease (CHD) and heart failure (HF) in the general population. This is the first study to demonstrate an independent association between sleep apnea severity and this marker of early myocardial injury.
“Although OSA is associated with increased cardiovascular risk, a causal association has been hard to establish because of the association of OSA with other risk factors,” said researcher Amil M. Shah, MD, MPH, of the Brigham and Women’s Hospital in Boston. “In our study, we were able to demonstrate that greater OSA severity is independently associated with higher hs-TnT levels, suggesting a role for subclinical myocardial injury in the relationship between OSA and heart failure.”
The findings were published online ahead of print publication in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine.
The study included 1,645 middle-aged and older participants in both the Atherosclerosis Risk in Communities and the Sleep Health Study who were free of CHD and HF at baseline. All subjects underwent overnight home polysomnography. Median follow-up was 12.4 years. OSA severity was categorized as none, mild, moderate, or severe using the respiratory disturbance index.
Hs-TnT levels, but not N terminal pro B-type natriuretic peptide levels (a marker for increased ventricular wall stress), were significantly associated with OSA after adjustment for 17 potential confounders (p=0.02), including age, gender, body mass index, smoking status, hypertension, diabetes, alcohol intake, pulmonary function variables (FEV1 and FVC), COPD status, systolic blood pressure, total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, insulin level and estimated glomerular filtration rate (eGFR). In all OSA severity categories, hs-TnT was significantly related to the risk of death or incident heart failure, and this relationship was strongest in the severe OSA group.
Obstructive sleep apnoea (OSA) is a condition that causes interrupted breathing during sleep.
There are two types of breathing interruption characteristic of OSA:
apnoea - the muscles and soft tissues in the throat relax and collapse sufficiently to cause a total blockage of the airway; it is called an apnoea when the airflow is blocked for 10 seconds or more
hypopnoea - a partial blockage of the airway that results in an airflow reduction of greater than 50% for 10 seconds or more
Sleep apnoea is associated with being overweight, and other risk factors. Read more about the causes of sleep apnoea.
Because of the episodes of hypopnoea that occur during OSA, doctors sometimes refer to the condition as ‘obstructive sleep apnoea-hypopnoea syndrome’.
The term ‘obstructive’ distinguishes OSA from rarer forms of sleep apnoea, such as central sleep apnoea, which is caused by the brain ‘forgetting’ to breathe during sleep.
Limitations of the study include its cross-sectional design, which precludes conclusions on causality, and a limited number of participants with severe OSA.
“Our results suggest a relationship between subclinical myocardial injury and the increased cardiovascular risk seen in patients with OSA,” said Dr. Shah. “Monitoring of hs-TnT levels in these patients may have prognostic value, particularly in patients with severe OSA.”
How Do I Know I Have Sleep Apnoea?
People with sleep apnoea may complain of excessive daytime sleepiness often with irritability or restlessness. But it is normally the bed partner, family or friends who notice the symptoms first. Sufferers may experience some of the following:
Extremely loud heavy snoring, often interrupted by pauses and gasps
Excessive daytime sleepiness, e.g., falling asleep at work, whilst driving, during conversation or when watching TV. (This should not be confused with excessive tiredness with which we all suffer from time to time)
Irritability, short temper
Morning headaches
Forgetfulness
Changes in mood or behaviour
Anxiety or depression
Decreased interest in sex
Remember, not everyone who has these symptoms will necessarily have sleep apnoea. We possibly all suffer from these symptoms from time to time but people with sleep apnoea demonstrate some or all of these symptoms all the time.
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About the American Journal of Respiratory and Critical Care Medicine:
With an impact factor of 11.080, the AJRRCM is a peer-reviewed journal published by the American Thoracic Society.It aims to publish the most innovative science and the highest quality reviews, practice guidelines and statements in the pulmonary, critical care and sleep-related fields. Founded in 1905, the American Thoracic Society is the world’s leading medical association dedicated to advancing pulmonary, critical care and sleep medicine. The Society’s 15,000 members prevent and fight respiratory disease around the globe through research, education, patient care and advocacy.
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Nathaniel Dunford
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American Thoracic Society