While researching the science and culture of breathing for his new book, Breath: The New Science of a Lost Art, journalist James Nestor participated in a study in which his nose was completely plugged for 10 days, forcing him to breathe solely through his mouth, reports NPR.

“I went from snoring a couple minutes a night to, within three days, I was snoring four hours a night,” he says of the forced mouth-breathing. “I developed sleep apnea. My stress levels were off the charts. My nervous system was a mess. … I felt awful.”

Listen to the segment at npr.org