February 9th, 2011
01:45 PM ET
We all know that getting enough shut-eye is good for us, but now a new study suggests that getting too little sleep can increase the risk of heart attack, stroke and other cardiovascular disease that can result in early death.
Researchers found if you sleep less than six hours, or have disturbed sleep you have a 48% chance of developing or dying from heart disease, and a 15% chance of having or dying of a stroke. The study, published in the European Heart Journal, is a meta-analysis of 15 other sleep studies. A meta-anaylsis integrates a number of studies into one study. Researchers followed nearly 475,000 adults from eight countries including the United States, United Kingdom, Japan, and Israel for seven to 25 years.
"There is an expectation in today's society to fit more into our lives. The whole work/life balance struggle is causing too many of us to trade in precious sleeping time to ensure we complete all the jobs we believe are expected of us," said Professor Francesco Cappuccio of the University of Warwick Medical School in the United Kingdom and a lead author of the study. "The trend for late nights and early mornings is actually a ticking time bomb for our health so you need to act now to reduce your risk of developing these life-threatening conditions."
Cappuccio says getting between six and eight hours of sleep regularly is optimum. "By ensuring you have about seven hours of sleep a night, you are protecting your future health and reducing the risk of developing chronic diseases. If you reduce your sleep below a certain level–five hours or less–you run into trouble," he said. "Not just tomorrow because you are tired, but you build up a steady risk of developing a chronic condition late in life. Sleep is not a commodity that can be traded off."
Dr. Michelle Miller, also from the University of Warwick and co-author of the study, says sleep deprivation actually causes a number of changes in the body. "Chronic short sleep produces hormones and chemicals in the body which increase the risk of developing heart disease and strokes, and other conditions like high blood pressure, cholesterol, diabetes and obesity." All of those conditions are also risk factors for heart attack and stroke. Hormone changes can lead to glucose intolerance and insulin resistance–both markers that lead to type 2 diabetes and increases in blood pressure. Chronic lack of sleep can activate a chemical in the body called cytokines, inflammation markers that are the basis for atherosclerosis–or hardening of the arteries–also common in people who have heart attacks and stroke.
But getting too much sleep can also have negative implications. Cappuccio says sleeping more than nine hours could be an indication of illness–including cardiovascular disease. "Long sleep rather than being the cause of disease is more likely to represent an early marker, the early stages of chronic conditions like depression."
He says sleep deprivation has to be considered a lifestyle risk factor similar to smoking, alcohol and lack of exercise.
According to American Heart Association spokesman Dr. Ralph Sacco, sleep is under recognized as a potential cardiovascular risk factor, and while this study provides intriguing evidence of the relationship, there is still a lot that is unknown about sleep disorders and their connection to heart disease and stroke.
"This is an association study that adds to evidence about an association but cannot determine mechanism or causation," said Sacco. "We can't make any causal claims yet based on this study that demonstrates an association but it raises suspicion about sleep disorder and cardiovascular and stroke risk."
Sacco says right now, there is a lot more evidence that the AHA's key health factors called "life's simple 7" improve heart health and reduce the risk of heart attack and stroke. They are:
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