Chris Hemsworth found out he was genetically inclined to develop Alzheimer's disease when he took a series of tests as part of a new documentary.

The 39-year-old actor is part of new documentary series on aging, titled "Limitless." The National Geographic series, released last Wednesday, explores topics on regenerating damage, maximizing strength, building resilience, shocking the body, supercharging memory and confronting mortality to "live better for longer."

While filming the show, Hemsworth underwent genetic tests and came across, as he says in the show, "my biggest fear." The "Thor" star carries two copies of the gene AP0E4 – from his father and mother, which are linked to an increased risk of Alzheimer's disease.

"There was an intensity to navigating it. Most of us, we like to avoid speaking about death in the hope that we'll somehow avoid it. We all have this belief that we'll figure it out," Hemsworth told Vanity Fair. "Then to all of a sudden be told some big indicators are actually pointing to this as the route which is going to happen, the reality of it sinks in. Your own mortality."

Alzheimer's disease is a chronic condition characterized by memory loss, mood and personality changes and difficulty completing tasks at home or at work.

The actor said this experience led him to pursue a healthier lifestyle.

"When you have a predisposition to cardiovascular heart disease, cancer, anything — it's all about sleep management, stress management, nutrition, movement, fitness. It's all kind of the same tools that need to be applied in a consistent way," he said.

The "Extraction" star already knew that the disease runs in his family as his grandfather has been suffering from it for many years now. Still, Hemsworth said the results made him a bit anxious about his own memory.

"I feel like my memory's getting worse. It's a placebo effect — or it's taking place! It's my excuse now," Hemsworth said.

While the producers of the show offered him an option to not speak about the test results, Hemsworth decided to reveal it on the show as "a motivator for people to take better care of themselves."

"My concern was I just didn't want to manipulate it and overdramatize it, and make it into some sort of hokey grab at empathy or whatever for entertainment," he said.