The Thor star was told he carries two copies of the APOE4 gene which makes him eight to 10 times more likely than other people to develop the illness, which has already struck his father Craig, but he is adamant he doesn't want his life to be overshadowed by worries about the future.
"This has become a very prominent conversation in my world, because I also have two copies of the gene that puts me in a higher-risk category for Alzheimer's," the Australian actor said his new documentary A Road Trip to Remember.
"But it's not a problem at this point, and it may never be. So I'm far more focused on my dad right now.
"I feel like it's too far off, hopefully. I'd rather just continue on with life."
In the new Disney Plus documentary, Hemsworth is seen spending time with his dad as he battles symptoms of memory loss and confusion.
The actor explains his dad has "early-stage Alzheimer's, and there's definitely good days and bad days".
The pair embark on a road trip across Australia on motorbikes, making stops at their former homes in Melbourne and the Northern Territory in a bid to help Craig with his memory issues.
The Hemsworth family's home in Melbourne was given a major overhaul to return it to its state in the 1990s when they lived there as part of an exercise designed to help Craig, who admitted: "(It felt) strange. (But) it's very satisfying recognising stuff that I hadn't thought about for a long while."
The documentary also features Craig's wife Leonie, who confessed she's struggling to deal with her husband's prognosis and finds thinking about the future to be quite "terrifying".
"As a partner, it's difficult because I want him to still be the person he was, and I want the relationship. I want that relationship," she said in the film.
"Sometimes I wake up in the middle of the night, and it can be quite terrifying to think where it's all going."
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