Trent Johnston of ‘7 Little Johnstons’ shares his current health situation. Fans are worried about him.

In an exclusive clip from the upcoming season premiere of “7 Little Johnstons,” Trent Johnston reveals some devastating news about his health — he has white matter disease, a condition that normally impacts older people.

“White matter disease is basically dead brain tissue from a lack of oxygen,” Johnston said in the episode.

Last season, Johnston underwent an MRI, and doctors suspected he might have had multiple sclerosis. He also learned that his brain resembles that of an 81-year-old, meaning the 49-year-old has experienced significant brain tissue loss.

Johnston shared some insight into what may be causing his health troubles. His white matter disease is likely from years of not treating his sleep apnea properly.

“I have had some form of sleep apnea my entire life, and I have not been using a CPAP machine,” he said in the clip. “I felt like I was sleeping fine and waking up and living life and going to work and being productive. … At 48 years old and not treating my sleep apnea with a CPAP machine, this is definitely the contributing factor to white matter disease.”

White matter disease impacts axons, a type of nerve fiber that enables communication between the various regions in the brain, the Cleveland Clinic says. A myelin sheath, which looks white, covers these axons, giving them the name white matter.

People with reduced blood flow to the white matter in their brain can develop white matter disease, where the tissue decreases and leads to neurological and cognitive problems, per Cleveland Clinic. It generally occurs in people 60 and older.

Symptoms of white matter disease include:

• Trouble with memory

• Difficultly balancing and falling frequently

• An inability to do two things at once, such as driving and listening to music

• A slower paced gait

• Moodiness and depression

• Incontinence

“White matter disease can cause a whole host of symptoms,” Johnston’s wife, Amber, said in the episode. “The top three being memory loss, dizziness and incontinence.”

Unfortunately, Trent Johnston learned that he can’t regenerate his lost white matter.

“Dad can’t get it back,” Amber Johnston said. “But Dad can prevent it from getting worse.”

The news has implications for the whole family. Two of the Johnston children, Alex and Jonah, also have sleep apnea.

“I was feeling a little bit nervous for Dad about this whole white matter disease, basically like parts of his brain are basically dying,” Alex Johnston said. “Since Jonah and I have that same apnea, that made me nervous for myself and Jonah.”

The three plan to sleep with CPAP machines to prevent damage to their white matter.

“I’m an example of what can happen later,” Trent Johnston said.

People with the most common form of dwarfism, achondroplasia, like the Johnstons, often experience sleep apnea, the National Library of Medicine says.

“Sleep apnea is very prevalent in individuals with achondroplasia,” Amber Johnston explained. “Our head and our face and just like where the sinuses are … everything is very dwarfed. It is smaller. It is tighter. There is less room for air to pass.”