Lack of Sleep Increases the Risk of Catching a Cold
As cold season approaches, many Americans stock up on their vitamin C and Echinacea (紫锥花精油). But fallowing the age -old advice about catching up on sleep might be more important. Studies have demonstrated that poor sleep and susceptibility (易受影响) to colds go hand in hand, and scientists think it could be a reflection of the role sleep plays in maintaining the body’s defenses. In a recent study for the Archives of Internal Medicine, scientists followed 153 men and women for two weeks, keeping mack of their quality and duration of sleep. Then, during a five - day period, they quarantined (进行检疫隔离) the subjects and exposed them to cold viruses. Those who slept an average of fewer than seven hours a night, it turned out, were three times as likely to get sick as those who averaged at least eight hours. Sleep and immunity, it seems, are tightly linked. Studies have found that mammals that require the most sleep also produce greater levels of disease - fighting white blood cells--but not red blood cells, even though both are produced in bone marrow (骨髓) and stem from the same precursor (前体物). And researchers at the Max Planck Institute for Evolutionary Anthropology have shown that species that sleep more have greater resistance against pathogens (病原体). "Species that have evolved longer sleep durations," the Planck scientists wrote, "appear to be able to increase investment in their immune systems and be better protected. \ What did the scientists do in the study for the Archives of Internal Medicine
A. They checked the subjects’ health problems and gave advice. B. They made record of the subjects’ quality and length of sleep. C. They exposed the subjects to different kinds of viruses. D. They gave medicine to the subjects who had caught cold.