People who have Alzheimer's disease are known to have fewer of these slow waves, which means there are less chances for the brain to clear out the toxins associated with the disease.
These waves are associated with memory and other diseases.
Lewis said it’s important not only to get enough sleep, but the right kind of sleep. In order for the brain to produce the slow waves, you must first be in a deep sleep, also known as non-rapid eye movement sleep.
"Some disruption to the way sleep is working could potentially be contributing to the decline in brain health," Lewis said.
Researcher William Jagust told NPR people may be able to reduce their risk of Alzheimer's disease by making sure they are getting enough high-quality, deep sleep.
"There are a bunch of things that are probably contributing to people's likelihood (of) getting Alzheimer's, and I think sleep is going to turn out to be one of them," Jagust said.