Once again, science supports what your grandmother told you: A good night's sleep helps your body fight a cold.

    People who averaged fewer than seven hours of sleep per night in the weeks before being exposed to the cold virus were nearly three times as likely to get sick as those who averaged eight hours or more, a new study found.

    Researchers used frequent telephone interviews to track the sleep habits of more than 150 men and women aged 21 to 55 over the course of a few weeks. Then they exposed the subjects to the virus, quarantined them for five days and kept track of who got sick.

    Besides sleeping more, sleeping better also seemed to help the body fight illness: Patients who fared better on a measure known as 'sleep efficiency' - the percentage of time in bed that you're actually sleeping - were also less likely to get sick.

    The results held true even after researchers adjusted for variables such as body-mass index, age, sex, smoking and pre-existing antibodies to the virus.

    Like your grandmother, the researchers aren't exactly sure why sleeping better makes you less likely to develop a cold. But they do take a stab at the answer: 'Sleep disturbance influences the regulation of proinflammatory cytokines, histamines, and other symptom mediators that are released in response to infection.' In plain English, maybe tossing and turning when you're infected with the cold virus contributes to the symptoms that define a cold.

    The researchers were based at Carnegie Mellon, the University of Pittsburgh and the University of Virginia, and the study was funded by the National Institutes of Health.

    科學調查又一次證實了老祖母們的說法：一夜好睡眠，感冒擋在門外面。

    一項新的研究發現，那些在接觸感冒病毒前的一周內平均每晚睡眠時間不足7小時的人患病幾率是睡眠不少于8小時的人的近3倍。

    研究人員通過經常性的電話訪問跟蹤了150多名21-55歲年齡段的人（有男有女）幾周內的睡眠習慣。然后讓這些研究對象接觸感冒病毒，隔離5天之后，看看哪些人患上了感冒。

    除延長睡眠時間外，提高睡眠質量看起來也有助于人體抵抗疾病。那些在"睡眠效率"評測中表現較好的病人患病的幾率也較低。"睡眠效率"是受訪者睡下后實際"睡著"的時間所占的百分比。

    即便是在研究人員將身高體重指數（BMI）、年齡、性別、是否吸煙以及是否早有抗體等因素考慮進來進行調整之后，這個結論仍然成立。

    和老祖母們一樣，研究人員也不能肯定為什么睡得好能降低患感冒的幾率。不過他們猜測原因可能是：睡眠不良會影響人體對促炎細胞因子、組胺和其他為應對病毒感染而釋放的癥狀調節因子的調節。說白了，就是染上感冒病毒后睡覺時的輾轉反側可能是造成感冒癥狀的原因之一。

    這項研究是由來自卡內基梅隆大學、匹茲堡大學和弗吉尼亞大學的人員完成的，研究經費由美國國家衛生研究院（National Institutes of Health）提供。