New research has found that sleeping less than six hours a night could increase the risk of cardiovascular disease. (Shutterstock/Syda Productions)
New research has found that sleeping less than six hours a night could increase the risk of cardiovascular disease, although sleeping too long may also have a negative effect on heart health.
Carried out by Spanish and US researchers, the new study looked at 3,974 Spanish adults with no known heart disease and asked participants to wear an actigraph -- a small device that continuously measures activity or movement -- for seven days to measure their sleep.
They were then divided into four groups: those who slept less than six hours, those who slept six to seven hours, those who slept seven to eight hours and those who slept more than eight hours.
The participants also completed a 3-D heart ultrasound and cardiac CT scans look for any signs of heart disease.
The findings, published in the Journal of the American College of Cardiology, showed that after taking into account other possible risk factors, participants who slept less than six hours were 27 percent more likely to have atherosclerosis, a plaque buildup in the arteries throughout the body, compared with those who slept seven to eight hours.
Participants with poor quality of sleep, defined by how many times they woke during the night and the frequency of their movements, were 34 percent more likely to have atherosclerosis compared with those who had a good quality of sleep.
"It is important to realize that shorter sleep duration that is of good quality can overcome the detrimental effects of the shorter length," said co-author Valentin Fuster.
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However, sleeping too long also appeared to have a detrimental effect on health, with the team finding an association between sleeping more than eight hours a night and an increase in atherosclerosis.
"Cardiovascular disease is a major global problem, and we are preventing and treating it using several approaches, including pharmaceuticals, physical activity and diet. But this study emphasizes we have to include sleep as one of the weapons we use to fight heart disease -- a factor we are compromising every day," said senior study author José M. Ordovás, PhD, "This is the first study to show that objectively measured sleep is independently associated with atherosclerosis throughout the body, not just in the heart."
Ordovás also added that previous studies have shown that lack of sleep raises the risk of cardiovascular disease by increasing heart disease risk factors such as glucose levels, blood pressure, inflammation and obesity.
For those who want to improve their sleep, avoiding or limiting alcohol and caffeine may help, with the researchers also finding that consumption of both were higher in participants with short and disrupted sleep.
"Many people think alcohol is a good inducer of sleep, but there's a rebound effect," Ordovás said. "If you drink alcohol, you may wake up after a short period of sleep and have a hard time getting back to sleep. And if you do get back to sleep, it's often a poor-quality sleep."
As for caffeine, he adds that, "Depending on your genetics, if you metabolize coffee faster, it won't affect your sleep, but if you metabolize it slowly, caffeine can affect your sleep and increase the odds of cardiovascular disease."