Sian Claire Owen, Cardio Debate medical journalist

Sleep is important for our general health and wellbeing. According to data from the National Sleep Foundation, published in Sleep Health, the optimal amount of sleep needed to function properly is seven to nine hours per night for young adults, and for older adults seven to eight hours. [1]

However, there is a substantial body of evidence that associates sleep disorders with cardiovascular disease, obesity, type 2 diabetes and hypertension.

A recent scientific statement from the American Heart Association [2] provides a comprehensive overview of what we know, and what we don’t know about the link between sleep disorders and cardiometabolic risk. [2]

Dr Marie-Pierre St-Onge, associate professor of nutritional medicine at Columbia University in New York City and lead author of the statement tells Medical News Today that: “We know that short sleep, usually defined as under 7 hours per night, overly long sleep, usually defined as more than 9 hours per night, and sleep disorders may increase some cardiovascular risk factors, but we don’t know if improving sleep quality reduces those risk factors.” [3]

Between 50 and 70 million adults in the US have sleep disorders – insomnia being the most frequently reported, along with obstructive sleep apnea (OSA). And, as is reported in this scientific statement, population studies have shown both these conditions are linked with a ‘significantly greater risk for CVD and cerebrovascular disease.”

However, there is a fine line between having too much sleep and too little – with both producing different outcomes in terms of risk.

Sleep deprivation tends to disrupt mechanisms associated with inflammation, glucose metabolism and blood pressure, whereas too much sleep is linked with an increased risk of CHD. [2] Although, in studies investigating the relationship between sleep deprivation and obesity, very short sleep duration (< 4 hours per night) were most strongly associated with weight gain, a U-shaped relationship was observed with similar patterns observed in those who had too much sleep (> 9 hours per night). [4, 5]

Experimental sleep restriction studies have also shown that sleep deprivation is associated with a “3-fold increase in the odds of having impaired fasting glucose.” [2]

Furthermore, recent data published in Circ Heart Fail showed that effective treatment of sleep apnea can help prevent heart failure. [8] In this study, patients with moderate to severe OSA but were otherwise healthy were compared to patients with hypertension (no OSA) and healthy patients. They were evaluated using a range of imaging techniques. The study revealed that moderate to severe OSA resulted in structural and functional changes in left ventricular function. However, treatment with Continuous Positive Airways Pressure (CPAP) for six months significantly improved these changes. [8]

Therefore, after reviewing the available data the AHA statement concludes by recommending that the AHA “directly address sleep behavior in a public health campaign”, and conducts more research in order to release appropriate guidelines and introduce routine screening for sleep disorders in the clinical care setting.

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