每天要睡多久才足夠？美國有研究指出是七個小時。據報道，美國西弗吉尼亞大學醫學系的一項研究發現，連小睡在內，每日睡眠七小時最為理想，而睡眠時間多于或少于七小時者，患上心血管疾病的風險將會增加。這份報告已刊登在“睡眠”(Sleep)期刊內。
Seven hours sleep is the recipe for health
Sleeping for seven hours each night can help you stay healthy, according to new research.
For years, we have been told that eight hours of sleep provides the best start to the day.
But now experts have found that it is seven hours that brings optimal heath – and that more or less sleep than that may do us harm.
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A study of more than 30,000 adults has found cardiovascular disease is twice as high among those sleeping less than five hours a day, compared with those getting seven hours. (Agencies)
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A study of more than 30,000 adults has found cardiovascular disease – which includes heart attacks, strokes and angina attacks – is twice as high among those sleeping less than five hours a day, compared with those getting seven hours.
Those who slept nine hours or more also had a markedly increased risk.
However, even one hour more or less than seven hours increased the likelihood of heart disease, the study found.
Authors of the US research, published today in the scientific journal Sleep, said sleep patterns could affect metabolic function, and hormones, while sleep deprivation was known to elevate blood pressure, and reduce glucose tolerance, both of which increased the risk of artery damage.
The mass study did not establish the causes of the subject's heart disease, but said those who slept for long periods might be suffering from breathing disorders which could have increased their risks.
Anoop Shankar, the study's principal investigator, from the West Virginia University School of Medicine, said: "Our study findings suggest that abnormal sleep duration adversely affects cardiovascular health.
"Sleep disturbances may be a risk factor for cardiovascular disease even among apparently healthy subjects".
Earlier this year, a study found that people who sleep fewer than six hours a night are more likely to die prematurely – before the age of 65 – than those who slept between six to eight hours a night.
The team from the University of Warwick and Federico II University Medical School in Naples analysed 16 studies involving a total of 1.3 million people before reaching their conclusions.
In March, a British study of 3,000 people found the average Briton sleeps for just six hours a night.
Sleep deprivation has been shown to make people hungrier and fatter, because of its impact on hormones, and has been linked with the development of diabetes and proteins which can cause Alzheimers.
Poor sleep has also been identified as both a cause and symptom of depression.
A study earlier this year by the European Sleep Research Society found that people who were short of sleep were also more likely to be rated as less attractive and with poorer skin tone.
That may be because during deep sleep, new skin cells are produced.
Those who sleep badly in the week cannot make up for it at the weekend, according to more research.
A separate study published on Sunday found that even a night of 10 hours in bed may not be enough to cure the negative effects of several nights of poor sleep.
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（來源：telegraph.co.uk 編輯：Julie）
