Originally Published: 26 DEC 23 11:00 ET

By Sandee LaMotte, CNN

(CNN) — Cognitive decline can begin years before signs of dementia set in, which for some can be as early as age 30, a condition known as young-onset dementia. Globally, it’s estimated nearly 4 million people ages 30 to 64 are living with the condition, according to a 2021 study, and case numbers have been rising.

Key risk factors for later-life dementia and Alzheimer’s disease are well-known: older age and biological sex at birth (women are more likely to get Alzheimer’s). Genetics also determine risk — people who inherit one or more copies of the APOE4 gene are at greater risk of Alzheimer’s, although many never develop the disease. While those risks may not be modifiable, other risk factors are, including smoking, prediabetes and diabetes, obesity, high blood pressure, depression, social isolation and hearing loss.

Young-onset dementia has been thought to be primarily dictated by the APOE4 gene, with little research on other causative factors. A new study, however, has found many of the same risk factors can contribute to early-onset dementia, offering new hope of slowing or preventing the disease.

“This changes our understanding of young-onset dementia, challenging the notion that genetics are the sole cause of the condition and highlighting that a range of risk factors may be important,” said lead study 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 said in an email. “The fact that this is also evident in young-onset dementia came as a surprise to us, and it may offer opportunities to reduce risk in this group too.”

The results echo clinical work done with patients who are attempting to fight the advance of dementia, said Dr. Richard Isaacson, director of research at the Institute for Neurodegenerative Diseases in Florida, who was not involved in the study.

“Based on my observations from over a decade of seeing patients at risk, I wholeheartedly disagree that people are powerless in the fight against early onset cognitive decline,” Isaacson said in an email. “Rather, my clinical experience much more closely aligns with results of this new study — that it truly may be possible to grab the bull by the horns, and be proactive about certain lifestyle and other health factors, to reduce risk.”

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. Levels of blood, urine and saliva, along with weight and other health measurements were gathered, and researchers compared levels between groups who did and did not develop early dementia.

The analysis found many similarities between the risk of late-onset and early-onset dementia, such as alcohol abuse, diabetes, depression, and heart disease and stroke, both of which are linked to high blood pressure.

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

“Social isolation is linked to depression, but depression did not mediate the association of social isolation with YOD (young-onset dementia) in our analyses, suggesting that both directly contribute to dementia risk,” the study noted.

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

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

“Hazard ratios for orthostatic hypotension and depression were highest, meaning that the risk of getting young-onset dementia is higher in persons with orthostatic hypotension or depression compared to persons who do not have these factors,” Hendriks said. “However, risks were still very small, and the majority of persons with orthostatic hypotension or depression will not develop young-onset dementia.”

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 obtain 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, the study found.

Reducing risk

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

“Be curious: learn new things, spend time on a hobby, stay engaged and socially active by visiting friends and families or going to social gatherings,” she said. “Exercise regularly: keep moving, all levels of exercise work, from walking to vigorous exercise, find something that works for you.”

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

“While more research is needed to more definitively prove 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 on a regular basis and know your numbers — ask about vitamin D levels, follow blood pressure targets, cholesterol results, and blood sugar values. Get your hearing checked and seek treatment with a hearing aid when necessary.”

The-CNN-Wire