Silvano, an Italian man who suffered from such a condition, lost the ability to sleep at age 53. Four months after checking into a sleep clinic in Bologna, Italy, in 1984, Silvano went into a coma and died. Through Silvano's case, Italian scientists discovered an extremely rare genetic disease called fatal familial insomnia, or FFI.
FFI sufferers fall into a state in which they are neither fully asleep nor awake. The inability to sleep wreaks havoc on their lives. Sleeplessness deteriorates into exhaustion, dementia and, ultimately, death. There is no cure.
For scientists, why a lack of sleep could kill you is still an unsolved mystery.
"Sleep is the most extraordinary mystery, the most elusive biological function that we have," said Daniel Max, author of "The Family That Couldn't Sleep," who has chronicled Silvano's story and family lineage. "We know very little about how we sleep. But we know even less about why we sleep."
Max is featured in a National Geographic documentary called "Explorer: Fatal Insomnia," which airs Tuesday at 10 p.m., and explores the mysteries of sleep, and FFI.
The genetic mutation for FFI runs in families. Only 40 families are known to have this disease in the world, but most people have had at least one night where it seems impossible to fall asleep.
"If we look at surveys of the American population, a third of Americans continue to complain of insomnia," said Dr. Michel Cramer Bornemann of the Minnesota Regional Sleep Disorders Center in Minneapolis. "Many of these issues are difficulties within ourselves for which then insomnia becomes a symptom."
Americans spend nearly $24 billion a year on sleep-related goods and services. By 2012, the market for insomnia drugs is expected to grow 78 percent, to nearly $3.9 billion.
"I think that in general, Americans probably are getting sleepier," Bornemann said. "I think our culture is based on a 24-hour culture ... so I would imagine until we start to see these trends change that this will only continue to get worse."
To find out how important sleep is to the ability to function, "Nightline" conducted a sleep experiment.
ABC News' Eric Horng stayed awake for nearly 40 hours and traveled to the Minnesota Regional Sleep Disorders Center to explore the biological effects of not sleeping for one night.
Bornemann gave a sleep-deprived Horng a neuro-cognition test in verbal memory, sequencing numbers in order lowest to highest, and language fluency, where he was asked to name items in several categories, including supermarket items.
Then, Horng headed to the sleep lab, where a technician attached electrodes to the head, chest, arms and legs to test for sleep disorders such as apnea, sleep walking and insomnia.
After a full night of sleep, Horng took the cognition test again and showed significant improvement.
"With the supermarket items, this is access to language," Bornemann said. "You had 26 appropriate responses after sleep deprivation and you had 39, a significant improvement, after a full night of restorative sleep."