How do you die of insomnia?

I'm doing an essay on Fatal Familial Insomnia, i cant find where it in reality tells you what the exact of death is after the disease have taken its course. or is anyone has any other information of how insomnia if truth be told kills the human beingHow do you die of insomnia?
People can only stay awake for so long until that time it does severe damage to the body
it does depend on the individual and their health problems
a soul can only stay awake for 8 to 12 days until that time they will die
most of the time from a heart attack
it messes up their bodies chemistry and with the increases and decrease of certain hormones they can no longer regulate their body function
There is also a condition that some one think they are not sleeping but they do fall asleep for few secs or Min's and they do not know it and they do not hold any memory of it so if they are doing this while they are mostly staying awake it can add several days to the 8 - 12 days
Dain Bramage