Chris Hemsworth Has the Genetic Risk Factor for Alzheimer’s

Source: Gage Skidmore via Wikimedia

Recently, Marvel actor and celebrity Chris Hemsworth found out that he shares something in common with about 2 percent of people around the world: having two Ɛ4 alleles of the APOE gene, the highest genetic risk factor for Alzheimer’s disease. People with two APOE Ɛ4 alleles are 12 times more likely to develop Alzheimer's.

While this is devastating news, thanks to ongoing studies such as the Wisconsin Registry for Alzheimer’s Prevention (WRAP), it turns out that people with the genetic risk factor or a family history of Alzheimer’s can decrease their likelihood of developing the disease with a healthy lifestyle.

The WRAP study is a large-scale longitudinal study of over 1500 adults aged 50 to 70 years at their initial assessment. Seventy percent of participants are at high risk for developing Alzheimer’s disease because they either have the APOE Ɛ4 gene variant or have at least one parent with a confirmed diagnosis of the disease.

The WRAP researchers have extensively investigated whether healthy lifestyle activities that have been shown to help slow down cognitive decline among the general older adult population would also be beneficial for their participant population. What makes the WRAP findings particularly important is that the scientists have examined whether a healthy lifestyle can delay the onset of the neuropathology that leads to Alzheimer’s disease.

The neuropathology of Alzheimer’s

While most people associate Alzheimer’s disease with memory loss and cognitive impairment, its underpinnings stem from several neuropathologies (abnormalities in the brain that can lead to disease). These abnormalities include the accumulation of proteins called amyloid beta and tau, glucose metabolism dysfunction, neuroinflammation, and white matter hyperintensities.

The hallmark signature of Alzheimer’s is the development of plaques and tangles that cause shrinkage of healthy brain tissue, including gray matter. Gray matter is crucial for the brain to process information. Scientists have determined that the plaques and tangles are formed by amyloid beta and tau.

Key WRAP finding: Exercise offers double-whammy brain protection

It turns out that regular cardiovascular exercise is one of the best things people at high risk of Alzheimer’s disease can do. Regular cardiovascular exercise provides two levels of protection for the brain. On the one hand, it strengthens neural connections and cerebral blood flow, which is great for the brain. On the other hand, it reduces the risk of cardiovascular disease, poor sleep, and chronic stress, all of which are risk factors for Alzheimer’s.

WRAP researchers have investigated the relationship between exercise and the presence of neuropathology including amyloid beta and white matter hyperintensities, as well as the amount of gray matter in the brain. The researchers consistently find that among participants with poor cardiovascular fitness, age was associated with increased levels of neuropathology and less gray matter. However, not only did aerobically fit participants perform better on cognitive tests and have larger amounts of gray matter than the more sedentary participants, but older aerobically fit participants had similarly low levels of neuropathology as younger aerobically fit participants. This is a remarkable finding: Among people who are at high risk for developing Alzheimer’s, regular cardiovascular exercise may help keep some of the neuropathology at bay.

You may be wondering how much cardiovascular exercise you need to do to get these brain benefits. The current recommendation by the CDC is 150 minutes a week of moderate to vigorous exercise. Hemsworth may easily exceed this amount by exercising at least one hour a day, as speculated in the press.

Exercise can compensate for the negative brain effects of poor sleep

Chronic poor sleep is a risk factor for Alzheimer’s disease; unfortunately, people with APOE Ɛ4 are susceptible to poor sleep. WRAP scientists sought to determine if exercise could ameliorate the impact of poor sleep on the amount of tau in the brain. Overall, poor sleep was associated with greater amounts of tau in the brain, but cardiovascular fitness level ameliorated this effect. Once again, the scientists found that only among sedentary WRAP participants was poor sleep linked with greater levels of tau in the brain.

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If you're unable to exercise

Not everyone is capable of sustained cardiovascular exercise. For people with arthritis, chronic pain, or other health conditions, cardiovascular exercise simply may not be feasible. If you fall into this category, you can still benefit from pursuing other aspects of a healthy lifestyle.

Longitudinal findings from WRAP demonstrate that participants with APOE Ɛ4 who report leading an overall healthy lifestyle have better cognitive functioning than APOE Ɛ4 carriers who report following a less healthy lifestyle. The scientists created a global measure of lifestyle factors in which a healthy lifestyle consisted of a healthy diet, physical activity, not smoking, moderate alcohol intake, cognitive stimulation, and the absence of certain diseases (obesity, diabetes, depression, high cholesterol, coronary artery disease, and renal disease).

If you or a loved one shows signs of Alzheimer’s disease

Check out the Alzheimer’s Association’s Know the 10 Signs. For each early sign of Alzheimer’s disease, it describes what is considered typical aging and when it is cause for concern.

If you are still concerned after reading the 10 signs, make a memory evaluation appointment at a center such as the Stanford VA Alzheimer’s Center, where they conduct comprehensive memory evaluations for free. These Alzheimer’s disease diagnostic centers are located around the country and typically are affiliated with a university.

Summary

Finding out that you have the genetic risk factor for Alzheimer’s disease is a life-altering event. The good news is that this knowledge enables you to take proactive measures to reduce the likelihood of developing it. Exercise isn’t a cure for Alzheimer’s disease, but it can help delay the onset by staving off the beginning of the neuropathology, even for people at heightened risk such as Hemsworth. In other words, you don’t have to have a movie star’s resources and access to specialists to lower your dementia risk; most of us may just need a pair of sneakers.