Chris Hemsworth, the Hollywood action star who grew up exploring the Australian outback, is known for performing astonishing physical stunts on screen. He has scaled dam walls, trained with elite military units, and watched his children launch themselves off dirt-bike ramps without hesitation. Yet, true bravery is not always about physical danger. Sometimes it is found in vulnerability and in confronting fears that cannot be outrun.
For the 42-year-old Thor actor, that fear is not death. It is something quieter and far more devastating: the loss of memory. Today, Hemsworth is living with that fear while trying to face it with honesty and intention. His 71-year-old father, Craig, has been diagnosed with Alzheimer's disease.
Hemsworth is not only helping his father through a difficult diagnosis. He is also preparing for the possibility that one day he might have to face the same battle, a journey he is now sharing publicly through his new documentary, "A Road Trip to Remember."
Hemsworth's journey with Alzheimer's began unexpectedly during the filming of his National Geographic longevity series "Limitless." The project took more than two years to complete because of pandemic delays and breaks for his movie schedule. Inspired by the 2006 film "The Fountain," the series invited Hemsworth to explore human potential, aging, and resilience through extreme challenges.
In one episode, he played underwater hockey during a four-day fast, testing how fasting influences health and performance. The tone remained light and humorous until Peter Attia, a physician who specializes in preventative care, delivered life-changing news. Blood tests revealed that Hemsworth carries two copies of the APOE4 gene variant. This genetic profile gives him roughly ten times the average risk of developing Alzheimer's disease.
Attia explained that habits like daily exercise, quality sleep, and stress reduction may help lower the likelihood of developing the disease, but the underlying genetic reality stays the same.
According to NHS ,"Alzheimer's disease is a progressive condition, which means the symptoms develop gradually over many years and eventually become more severe. It affects multiple brain functions."
The apolipoprotein E gene appears in three common forms, but APOE4 is recognized as the strongest genetic risk factor for Alzheimer's disease.
About 20 percent of the population carries a single copy of APOE4. This raises their risk by two to three times. Only 2 to 3 percent of people worldwide carry two copies, as Hemsworth does, which increases their risk eight to ten times according to Stanford Medicine.
Dr. Mike Greicius, a Stanford Medicine neurologist, notes that about one quarter of people of European ancestry are APOE4 carriers.
However, the variant is present in more than half of European ancestry patients with Alzheimer's disease. He adds that people who carry APOE4 and eventually develop Alzheimer's tend to show symptoms five to ten years earlier than those with two copies of the common APOE3 variant. As he explains, "APOE4 starts the ball rolling well before it would normally start."
The first sign of Alzheimer's disease is usually minor memory problems. As the condition develops, memory problems become more severe and further symptoms can develop that can include confusion, disorientation and getting lost in familiar places and problems with speech and language.
The revelation prompted the entire Hemsworth family to undergo genetic testing. Results showed that Craig also carries the APOE4 gene, an inherited risk that has now manifested in his diagnosis. The family's vulnerability became even more significant when they learned that one of Chris's grandparents also suffered from Alzheimer.
At 71, Craig's symptoms are becoming increasingly visible. Occasional confusion and memory lapses reflect the early but active stage of the disease. Discussing the diagnosis proved surprisingly difficult for both father and son. Hemsworth shared with National Geographic that they had rarely spoken about it directly. It was not avoidance, but uncertainty about how to begin a conversation that felt heavy and unfamiliar.
"A Road Trip to Remember," an intimate one-hour documentary, will air on National Geographic on November 23, 2025. It will also stream on Disney Plus and Hulu the following day.
The documentary follows Chris and Craig on a motorcycle journey across Australia as they revisit places from Craig's childhood in the small outback town of Bulman. Although it appears to be a sentimental journey, it is also a carefully structured form of reminiscence therapy guided by neuroscientists.
The documentary also explores reminiscence therapy, guided by Dr. Suraj Samtani from the Centre for Healthy Brain Ageing at the University of Sydney.
Chris explains that the idea is to capture as many memories as possible while his father still can, and also to revisit earlier experiences. Throughout the film, viewers see the two sitting by campfires, flipping through old photographs, and navigating emotional and physical landscapes together. The documentary feels like a race against time, an effort to anchor memories before they fade.
Reminiscence therapy began in the late 1970s and has grown into an important intervention for patients with dementia. It involves structured conversations about past experiences supported by prompts like photographs, familiar objects, music, or recorded memories. Today, digital tools are widely used to store and present these prompts. 1
Hemsworth explains the neuroscience behind the therapy in simple terms. It stimulates the hippocampus, the same brain region that Alzheimer's attacks. Revisiting memories activates this region and may help build a degree of cognitive resilience.
Alzheimer's disease is a global challenge that continues to expand.
According to WHO in 2021, approximately 57 million people worldwide lived with dementia. More than 60 percent reside in low and middle income countries, and close to 10 million new cases occur every year.
Alzheimer's disease is the most common cause of dementia in the UK.
It is the most common cause of dementia and contributes to 60 to 70 percent of cases. Dementia is currently the seventh leading cause of death globally and is a major cause of disability and dependence among older adults.
In the United Kingdom, Alzheimer's affects about one in fourteen people over the age of 65 and one in six people over 80.
1. Woods B, O'Philbin L, Farrell EM, Spector AE, Orrell M. Reminiscence therapy for dementia. Cochrane Database Syst Rev. 2018;3(3):CD001120. Published 2018 Mar 1. doi:10.1002/14651858.CD001120.pub3
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