How can you reduce your risk of dementia? 0:45

(CNN) — Cognitive decline can begin years before the first signs of dementia appear, which for some can occur as quickly as age 30, a condition known as early-onset or early-onset dementia. Nearly 4 million people between the ages of 30 and 64 are estimated to be living with the condition worldwide, according to a 2021 study, and the number of cases is rising.

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The key risk factors for dementia and Alzheimer's disease in old age are well known: advanced age and biological sex at birth (women are more likely to suffer from Alzheimer's). Genetics also determine risk, as people who inherit one or more copies of the APOE4 gene have a higher chance of developing Alzheimer's, although many never develop the disease. While those risks can't be changed, there are other factors that can, such as smoking, prediabetes and diabetes, obesity, high blood pressure, depression, social isolation, and hearing loss.

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Early-onset dementia is thought to be dictated primarily by the APOE4 gene, with little research on other causative factors. However, a new study found that many of the same risk factors may contribute to early dementia, offering new hope for slowing or preventing the disease.

"This changes our understanding of early-onset dementia, challenging the notion that genetics is the sole cause of the disease and highlighting that a variety of risk factors may be important," said study lead author Stevie Hendriks, a postdoctoral researcher in psychiatry and neuropsychology at Maastricht University in the Netherlands.

"In addition to physical factors, mental health also plays an important role, including avoiding chronic stress, loneliness, and depression," Hendriks explained in an email. "The fact that this is also evident in early dementia surprised us and may offer opportunities to reduce risk in this group as well."


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The results reflect clinical work done with patients trying to combat the progression of dementia, said Dr. Richard Isaacson, director of research at the Florida Institute of Neurodegenerative Diseases, who was not involved in the study.

"Based on my observations from more than a decade of caring for at-risk patients, I strongly disagree with people being powerless in the fight against early-onset cognitive decline," Isaacson said in an email. "My clinical experience aligns much more closely with the results of this new study: that it may really be possible to grab the bull by the horns and be proactive about certain lifestyles and other health factors to reduce risk," he added.

Modifiable Risk Factors

In the study, published Tuesday in the journal JAMA Neurology, researchers followed 356,000 men and women enrolled at age 40 in a longitudinal health study called the UK Biobank. Blood, urine and saliva levels were collected, along with weight and other health measures, and the researchers compared the levels between groups that developed and did not develop early-onset dementia.

The analysis found many similarities between the risk of late- and early-onset dementia, such as alcohol abuse, diabetes, depression, heart disease and stroke, the latter two linked to hypertension.

Considering the young age of the participants, other risk factors were more surprising. According to the study, being socially isolated, living with hearing loss, and low vitamin D levels were key risk factors for developing early-onset dementia.

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"Social isolation is linked to depression, but depression did not mediate the association of social isolation with early-onset dementia in our analyses, suggesting that both directly contribute to dementia risk," the study explained.

Having higher levels of C-reactive protein, which indicates an infection or inflammation in the body, was also linked to an increased risk of early-onset dementia, but only in women, the study found.

Orthostatic hypotension, a condition in which dizziness occurs when blood pressure drops the moment a person stands up, was also a factor.

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"The risk ratios for orthostatic hypotension and depression were the highest, meaning that the risk of developing early-onset dementia is higher in people with orthostatic hypotension or depression compared to people who don't have these factors," Hendriks said. "However, the risks were still very small, and most people with orthostatic hypotension or depression will not develop early-onset dementia," he added.

Having two copies of APOE4, a key genetic marker for Alzheimer's disease, was also a factor, as was a person's socioeconomic status and ability to pursue higher education. Diabetes played a role that differed by sex at birth: Men with diabetes had a higher risk than men without diabetes, but there was no association with diabetes in women, according to the research.

Reduce risk

There are several actions people can take to reduce their risk of early-onset dementia, Hendriks said, including not smoking and maintaining a healthy diet.

"Be curious: learn new things, dedicate space to a hobby, stay engaged and socially active by visiting friends and family or attending social gatherings," she said. "Exercise regularly – keep moving, all levels of exercise work, from walking to vigorous exercise. Find something that works for you," he said.

Overall, people should feel empowered by the results of this study, Isaacson said.

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"While more research is needed to more definitively demonstrate which factors may be the most protective in various individuals, I urge people at risk not to wait," he said.

"See your primary care doctor regularly and know your numbers: ask about vitamin D levels, follow blood pressure goals, cholesterol results, and blood sugar values. Get your hearing tested and seek treatment with a hearing aid when needed."