Getting less sleep associated with lower resistance to colds

Individuals who get less than seven hours of sleep per night appear about three times as likely to develop respiratory illness following exposure to a cold virus as those who sleep eight hours or more, according to a report in the January 12 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

Studies have demonstrated that sleep deprivation impairs some immune function, according to background information in the article. Research indicates that those who sleep approximately seven to eight hours per night have the lowest rates of heart disease illness and death. However, there has previously been little direct evidence that poor sleep increases susceptibility to the common cold.

Sheldon Cohen, Ph.D., of Carnegie Mellon University, Pittsburgh, and colleagues studied 153 healthy men and women (average age 37) between 2000 and 2004. Participants were interviewed daily over a two-week period, reporting how many hours they slept per night, what percentage of their time in bed was spent asleep (sleep efficiency) and whether they felt rested. They were then quarantined and administered nasal drops containing the common-cold-causing rhinovirus. For five days afterward, the study participants reported any signs and symptoms of illness and had mucus samples collected from their nasal passages for virus cultures; about 28 days later, they submitted a blood sample that was tested for antibody responses to the virus.

The less an individual slept, the more likely he or she was to develop a cold. Lower sleep efficiency was also associated with developing a cold-participants who spent less than 92 percent of their time in bed asleep were five and a half times more likely to become ill than those whose efficiency was 98 percent or more. Feeling rested was not associated with colds.

"What mechanisms might link sleep to cold susceptibility? When the components of clinical illness (infection and signs or symptoms) were examined separately, sleep efficiency but not sleep duration was associated with signs and symptoms of illness. However, neither was associated with infection," the authors write. "A possible explanation for this finding is that sleep disturbance influences the regulation of pro-inflammatory cytokines, histamines and other symptom mediators that are released in response to infection."

The results suggest that seven to eight hours of sleep per night is a reasonable target, they conclude.

睡眠不足易患感冒

据1月12日《内科医学档案》刊登的一篇文章说，每晚睡眠不足7小时的人和每晚睡眠在八小时及以上的人相比，在遭遇感冒病毒后患上呼吸道疾病的可能性要大三倍。该杂志是

JAMA档案杂志集团旗下的一份刊物。

根据这篇文章里的一些背景资料显示，研究表明缺乏睡眠会破坏某些免疫系统的功能。研究结果还显示，那些每晚睡眠在7到8小时的人患心脏病和死亡的几率最低。然而，没有直接证据表明睡眠质量不高会增加患普通感冒的几率。

Sheldon Cohen是位于匹兹堡市的卡内基·麦伦大学的博士，他和他的同事们在2000年到20004年之间研究了平均年龄为37岁的153名身体健康的人群。参加试验者接受了为期两周的观察，他们向研究人员报告每晚的睡眠时间，他们在床上有多长时间是用来睡觉的（也就是睡眠效率）以及他们睡眠质量怎么样。他们随后被隔离，在指导下服用含有感冒病毒的鼻病毒。随后的5天里，参加试验者随时报告他们出现病症的迹象，从他们的鼻腔内提取的粘液被用来进行病毒培养。28天后，他们提交一份血样，来检验他们的身体对病毒的抵抗力。

睡眠越少，越容易患感冒。睡眠效率低，也易患感冒。那些睡眠效率低于92%的人和那些效率在98%以上的人相比，生病的几率要高1.5倍。睡眠质量跟感冒没有关系。

"什么机理导致了睡眠和患感冒的几率？对临床疾病的组成（传染性和症状）分别进行研究的时候，睡眠质量而不是睡眠时间和感冒的症状有关。然而二者都和传染性没关联。"作者写到，"对这项发现的一个可能解释就是睡眠会影响导致发炎的细胞因子，组胺及其他症状催化剂，正是这些物质会在传染时得到释放。

他们最后得出的结论是，研究结果表明每晚保证7到8小时的睡眠是一个合理的目标。
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