The idea of Freddy Krueger, the villain who kills you in your dreams, freaked me out when I was younger. Which is to say it also enthralled me.
The adult me, however, finds the science of sleep and paranormal experiences quite fascinating, so I was far more intrigued than terrified when I read that "A Nightmare on Elm Street" creator Wes Craven was inspired by actual news stories about nightmare-related deaths.*
The key bit of inspiration seems to be the mysterious deaths of 18 healthy Laotian refugees in 1981, just three years prior to the first Elm Street film. As related in the New York Times on May 9, 1981, Atlanta's Centers for Disease Control looked into several possible causes for the deaths, including the possibilities that they were frightened to death by nightmares. **
The theory holds more water when you consider the refugees were members of Laos' Hmong ethnic minority, suffering post-traumatic stress as they escaped alleged genocide in their home country.
Nightmare Death Syndrome
So what was actually going on? "Nightmare death syndrome" became the key candidate -- or as we know it today, Sudden Unexplained Death Syndrome (SUDS). More investigation gleaned that the underlying cause was something we call Brugada syndrome, which is disproportionately linked to individuals of Southeast Asian descent.
Not everyone with the condition dies in his or her sleep, and nightmares actually don't really have anything to do with it. Brugada syndrome is actually an inherited heart rhythm disorder, but its propensity to cause sleep deaths seems to have influenced the emphasis on sleep demons in South Asian mythology.***
According to this excellent overview in the Fortean Times, Brugada syndrome's genetic basis is a mutation in the gene SCN5a, which controls the flow of sodium ions into heart cells. This flow of ions generates the electrical field that controls heartbeat regularity. When the flow fails, the heart fibrillates.
Today, doctors can identify the condition by looking at ECG patterns and they can treat particularly bad cases with electrical implants. And it won't be too terribly long before gene therapies will allow us to tackle the mutation head on.
So take that, Freddy.
Oh and for what it's worth, yeah, I enjoyed the 2010 remake.
* Wikipedia claims that Craven was inspired by a news story involving multiple dream deaths and a "Mr. K," but the cited source on that factoid doesn't mention it at all. Wikifail.
** I also ran across a 1951 Time Magazine article on a similar death.
*** Fan death, anyone?