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.

    科学调查又一次证实了老祖母们的说法：一夜好睡眠，感冒挡在门外面。

    一项新的研究发现，那些在接触感冒病毒前的一周内平均每晚睡眠时间不足7小时的人患病几率是睡眠不少于8小时的人的近3倍。

    研究人员通过经常性的电话访问跟踪了150多名21-55岁年龄段的人（有男有女）几周内的睡眠习惯。然后让这些研究对象接触感冒病毒，隔离5天之后，看看哪些人患上了感冒。

    除延长睡眠时间外，提高睡眠质量看起来也有助于人体抵抗疾病。那些在"睡眠效率"评测中表现较好的病人患病的几率也较低。"睡眠效率"是受访者睡下后实际"睡着"的时间所占的百分比。

    即便是在研究人员将身高体重指数（BMI）、年龄、性别、是否吸烟以及是否早有抗体等因素考虑进来进行调整之后，这个结论仍然成立。

    和老祖母们一样，研究人员也不能肯定为什么睡得好能降低患感冒的几率。不过他们猜测原因可能是：睡眠不良会影响人体对促炎细胞因子、组胺和其他为应对病毒感染而释放的症状调节因子的调节。说白了，就是染上感冒病毒后睡觉时的辗转反侧可能是造成感冒症状的原因之一。

    这项研究是由来自卡内基梅隆大学、匹兹堡大学和弗吉尼亚大学的人员完成的，研究经费由美国国家卫生研究院（National Institutes of Health）提供。