Just one extra hour of sleep a day appears to lower the risk of developing calcium deposits in the arteries, a precursor to heart disease, U.S. researchers said on Tuesday.

    The finding adds to a growing list of health consequences — including weight gain, diabetes, high blood pressure — linked to getting too little sleep.

    "We found that people who on average slept longer were at reduced risk of developing new coronary artery calcifications over five years," said Diane Lauderdale of the University of Chicago Medical Center, whose study appears in the Journal of the American Medical Association.

    "It was surprisingly strong," Lauderdale said in a telephone interview.

    Calcium deposits in the coronary arteries are considered a precursor of future heart disease. "It's a very early marker of future risk," she said.

    Unlike other studies looking at the risks of getting too little sleep, which use people's own estimates of their sleep patterns, Lauderdale's team set out to measure actual sleep patterns.

    They fitted 495 people aged 35 to 47 with sophisticated wrist bands that tracked subtle body movements. Information from these recorders was fed into a computer program that was able to detect actual sleep patterns.

    The team used special computed tomography, or CT, scans to assess the buildup of calcium inside heart arteries, performing one scan at the start of the study and one five years later.

    After accounting for other differences such as age, gender, race, education, smoking and risk for sleep apnea, the team found sleep duration appeared to play a significant role in the development of coronary artery calcification.

    About 12 percent of the people in the study developed artery calcification during the five-year study period. Among those who had slept less than five hours a night, 27 percent had developed artery calcification.

    That dropped to 11 percent among those who slept five to seven hours, and to 6 percent among those who slept more than seven hours a night.

    Lauderdale said it is not clear why this difference occurred in people who slept less, but they had some theories. Because blood pressure tends to fall off during sleep, it could be that people who slept longer had lower blood pressure over a 24-hour period.

    Or, it could be related to reduced exposure to the stress hormone cortisol, which is decreased during sleep.

    Or it may be some unidentified process.

    "It's something of a mystery," Lauderdale said.

    Kathy Parker, a sleep researcher from the University of Rochester's School of Nursing in New York, said the study underscores the role sleep plays in health.

    "People think that sleep doesn't matter but clearly it does. Sleep deprivation is a public health problem and studies such as this show how increasing sleep duration can have tremendously positive effects," Parker, who was not involved in the research, said in a statement.

    Lauderdale said her findings should be confirmed by others, but said many studies point to the need for at least six hours of sleep a night.

    美国研究学者周二指出，每天多睡一个小时，可以降低动脉钙化沉积的风险，而动脉钙化沉积正是心脏病的一种先兆。

    研究还发现，一组正在不断增长的健康问题与睡眠太少有关，包括体重增加、糖尿病和高血压等。

    “我们发现，那些平均睡眠时间比较长的人群，五年内发现新的冠状动脉硬化的风险减低了。”美国芝加哥医学中心的戴安娜·劳德代尔说，她的研究成果发表在美国医学会杂志上。

    “它的效果非常明显。”劳德代尔在一次电话采访中说。

    冠状动脉钙化沉积被视为将来心脏病发作的先兆之一。“这是一种预示未来心脏病发作风险的早期表现。”她说。

    在针对睡眠过少带来风险的研究当中，其他研究者利用的是受访者对自己睡眠模式的评估，而劳德代尔不同，她的研究团队使用了一种可以直接测量受访者实际睡眠形式的方法。

    他们为495名35岁至47岁的受访者配备了先进的手腕带，可以追踪记录其细微的身体动作，记录下来的信息被输入一项计算机程序，从而发现其实际的睡眠模式。

    该研究小组采用了一种特殊的计算机断层扫描或者CT技术来评估心脏动脉内的钙化沉积状况，扫描共进行两次，一次在研究开始时，另一次在五年之后。

    在将其他诸如年龄、性别、种族、教育程度、吸烟及睡眠呼吸暂停风险等差异因素计入之后，研究团队发现睡眠时间长短在冠状动脉硬化的形成过程中起到了非常重要的作用。

    在此项研究中，在五年内约有12%的受访者存在动脉硬化问题。每天睡眠不足五小时的受访者中，有27%患有动脉硬化。

    而每天睡眠在5-7小时的人动脉硬化比例降到了11%，每天睡眠超过7小时者，有动脉硬化问题的只有6%。

    劳德代尔指出，目前造成这种差异的原因上不明确，但有其理论基础。因为在睡眠期间，血压会下降，因此那些睡眠时间较长的人在24小时内的平均血压较低。

    或者，它可能与压力荷尔蒙皮质醇在睡眠期间降低有关。

    或者是与其他一些未知原因的反应有关。

    “这是一个谜。”劳德代尔说。

    美国纽约罗切斯特大学护理学院的睡眠研究员凯西·帕克表示，该项研究强调了睡眠在健康方面的作用。

    帕克，没有参与过该项研究，而她在一份声明中声称：“人们以为睡眠无关紧要，但实际上非常重要。睡眠剥夺已是一个公共健康问题，而像这样的研究表明了睡眠时间的延长对于健康具有非常巨大的积极影响。”

    劳德代尔表示她的研究发现应得到其他研究者的证实，不过许多其他研究指出，人们每天至少需要的睡眠时间为6个小时。