You may have consumed anywhere between 1,000 spiders in the past year in your sleep, and zero. Actually, that number is closer to zero.
"It would be a strictly random event," Rod Crawford of the Burke Museum of Natural History and Culture in Seattle says.
From the Scientific American:
More than anything, spiders probably find sleeping humans terrifying. A slumbering person breathes, has a beating heart and perhaps snores—all of which create vibrations that warn spiders of danger. "Vibrations are a big slice of spiders' sensory universe," Crawford explains, "A sleeping person is not something a spider would willingly approach."
They don't like you. They don't want to be in your mouth. Sleep well.