Thousands of years ago, Hippocrates suggested that sleep appeared to improve recovery from illness. Yet despite this ancient observation, it is only quite recently that the link between sleep and our immune system has been elucidated. Much of our knowledge of the importance of sleep for health emanates from studies examining the effects of sleep loss, and they are compelling. We see that lack of sleep is linked to a whole array of issues: mood disturbances , overeating and weight gain , reduced insulin sensitivity , cardiovascular disease , and many other maladies. Interestingly, it is also linked to increased susceptibility to respiratory infection – a health concern that is at the forefront of our minds more now than perhaps ever before. Sleep and Risk for the Common Cold One study put this link to the test in a very direct way. They recruited 153 healthy volunteers, and had them report their sleep duration and sleep efficiency (percent of time spent in bed when they ar