After a week of sur­viv­ing on min­i­mal sleep you may assume that a lazy week­end will allow you to recover in time for the com­ing days. Not so: research has shown that not even a full week of qual­ity sleep can reverse the cog­ni­tive and phys­i­o­log­i­cal ‘dam­age’ just five days of poor sleep can inflict on us.

Jonah Lehrer notes that it’s not just our cog­ni­tive func­tions that become impaired by a lack of sleep–it’s our immune sys­tem, too:

In a recent study for The Archives of Inter­nal Med­i­cine, sci­en­tists fol­lowed 153 men and women for two weeks, keep­ing track of their qual­ity and dura­tion of sleep. Then, dur­ing a five-day period, they quar­an­tined 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.