A lack of sleep can make people unhappy, irritable, and more susceptible to colds, but there is no proof that sleep deprivation ever directly killed someone, reports Business Insider.

Prolonged exhaustion, though, has been cited as a factor in the deaths of many otherwise-healthy people.

In 2012, for example, a Chinese man stayed up for 11 consecutive nights to watch all of the soccer games in the European Championship. The 26-year-old died in his sleep shortly after, and doctors said a combination of sleep deprivation, alcohol, and tobacco were the cause.

Randy Gardner beat the record for staying awake in 1964, making it into the Guinness Book of Records. Gardner, then 17, was up for 11 days and 25 minutes. Though he did not experience physical symptoms right after his endeavor, he reportedly suffered from insomnia for years.