Although it wasn't marketed as such when it first came out, the movie drew inspiration on events that actually happened! Obviously the supernatural elements and Freddie Krueger are not real, but Wes Craven was inspired by the real life tale of some people that died in their sleep.
In the 1970s, a group of refugees that fled from Cambodia to America began reporting extremely disturbing nightmares. The nightmares got so bad that some men refused to go to sleep, and some even died in their sleep soon after the nightmares began.
The phenomenon only affected men between 19 and 57. It was called Asian Death Syndrome. Although they never pinpointed exactly what the cause was, it's believed that the men suffered from some sort of cardiac episode that caused them to die in their sleep.