In the study, volunteers were subjected to a variety of noises from traffic to ringing phones while their brain activity was monitored with electrodes during sleep.
Results showed that light sleepers were the ones with the fewest sleep spindles.
Experts say the spindles block noise disruptions from the brain. So, the more spindles the brain produces, the more likely a person will stay asleep when exposed to sounds.
About 40 million Americans suffer from sleep disorders.
