CNN  — 

Chris Hemsworth embarked on a personal and physically demanding journey for his new series “Limitless” that ultimately led to a sobering discovery.

The “Thor” actor, 39, learns in one episode of the limited Disney+/National Geographic series – which shows him exploring ways to enhance his longevity and combat aging – that he has two copies of the APOE4 gene, one from each of his parents, meaning he has a heightened predisposition for developing Alzheimer’s disease.

“They took all my bloodwork and did a bunch of tests and the plan was to on-camera tell me all the results and then talk about how you can improve this and that,” Hemsworth shared with Vanity Fair in an article published on Thursday. “And Peter Attia, who is the longevity doctor in that episode, and overseeing a lot of the show, called [“Limitless” creator] Darren [Aronofsky] and said, ‘I don’t want to tell him this on camera. We need to have an off-side conversation and see if he even wants this to be in the show.’ It was pretty shocking because he called me up and he told me.”

Upon learning the news, Hemsworth said he “had a bunch of questions,” later adding that he “didn’t really know what to think. I was like, ‘Am I supposed to be worried? Is this concerning?’”

He also said that the show then “became even more relevant and important for me, even more poignant than I ever thought it would be,” adding that APOE4 is “not a pre-deterministic gene, but it is a strong indication. Ten years ago, I think it was more thought of as determinant.”

The new information, which Hemsworth said makes him “eight to 10 times more likely” to eventually develop Alzheimer’s disease, naturally caused him to reflect on death and his own mortality.

“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,” he told Vanity Fair. “We all have this belief that we’ll figure it out. 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.”