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Dementia usually develops in people ages 65 years and older. So-called young-onset dementia, occurring in those younger than age 65, is uncommon. Now, a new study published in December 2023 in JAMA Neurology has identified 15 factors linked to a higher risk of young-onset dementia.

Let’s see what they found, and — most importantly — what you can do to reduce your own risks.

Are early dementia and young-onset dementia the same?

No. Experts think of early dementia as the first stage in dementia. Mild cognitive impairment and mild dementia are forms of early dementia. So, someone age 50, 65, or 88 could have early dementia.

Young-onset dementia refers to the age at which dementia is diagnosed. A person has young-onset dementia if symptoms and diagnosis occur before age 65.

What has previous research shown?

A previous study of men in Sweden identified some risk factors for young-onset dementia, including high blood pressure, stroke, depression, alcohol use disorder, vitamin D deficiency, drug use disorder, and overall cognitive function.

What to know about the new study

In the new study, a research team in the Netherlands and the United Kingdom looked at data from the UK Biobank. The biobank follows about half a million individuals in the United Kingdom who were 37 to 73 years old when they first joined the project between 2006 and 2010. Most participants identified as white (89%), and the remaining 11% were described only as “other.” Slightly more than half of the participants (54%) were women.

The researchers excluded anyone age 65 or older and people who already had dementia at the start of the study, leaving 356,052 participants for the analyses. Over roughly a decade, 485 participants developed young-onset dementia. The researchers compared participants who did and did not develop young-onset dementia to identify possible risk factors.

What did the researchers learn about risks for young-onset dementia?

In reviewing the results, I think it is helpful to group the risk factors into several categories, and then to examine each of them. These risks may act on the brain directly or indirectly.

Eight factors that we know or strongly suspect cause dementia:

• Genes: Carrying two apolipoprotein E (APOE) ε4 alleles is a major genetic risk factor for Alzheimer’s disease. The risk is thought to be caused by the APOE ε4 protein not clearing amyloid efficiently from the brain. This allows amyloid to accumulate and cause plaques, which starts the cascade to cell death and Alzheimer’s disease.
• Being diagnosed with alcohol use disorder (AUD) has been associated with damage to several parts of the brain, including the frontal lobes, which leads to trouble with executive function and working memory. When combined with poor nutrition, AUD also harms small regions connected to the hippocampus that are critical for forming new memories.
• Being socially isolated is a major risk factor for dementia. Although the exact mechanism is unknown, it may be because our brains evolved, in large part, for social interactions. Individuals with fewer social contacts have fewer social interactions, and simply don’t use their brains enough to keep them healthy.
• Not getting enough vitamin D can lead to more viral infections. A number of studies suggest that certain viral infections increase your risk of dementia.
• Not hearing well increases your risk for dementia, as I discussed in a prior post. This is likely because of reduced brain stimulation and reduced social interactions. Using hearing aids lessens that risk.
• Previously having had a stroke is a risk factor because strokes damage the brain directly, which can lead to vascular dementia.
• Having heart disease is a major risk factor for strokes, which can then lead to vascular dementia.
• Having diabetes if you’re a man can lead to dementia in many different ways. Why only if you’re a man? The researchers suggest that it is because middle-aged men are more likely to have a diabetes-related ministrokes than middle-aged women, which can, again, lead to vascular dementia.

Two factors that reduce cognitive reserve

Cognitive reserve can be described as our capacity to think, improvise, and problem-solve even as our brains change with age. These two risk factors make it more likely that dementia symptoms will show up at a younger age.

• Having less formal education may affect your familiarity with the items on the pencil-and-paper cognitive tests that are used to diagnose dementia.
• Having lower socioeconomic status may be related to lower-quality education.

Is every factor identified in the study a clear risk?

No, and here’s why not: Sometimes research turns up apparent risk factors that might be due to reverse causation. It’s possible, for example, that symptoms of impending dementia appear to be risk factors because they become noticeable before obvious dementia is diagnosed.

• Lower handgrip strength is a sign of frailty, which is often associated with dementia.
• No alcohol use is a risk factor because people may stop drinking when they develop memory loss (also known as the “healthy drinker effect” in dementia).
• Depression is a risk factor because many people get sad when they have trouble remembering or when they are worried about having dementia.

Lastly, there are risk factors that could be either a contributing cause or a result of the impending dementia.

• High C-reactive protein is a sign of inflammation.
• Orthostatic hypotension is an abnormal drop in blood pressure when a person stands up after lying down or sitting. While this condition can lead to brain damage and dementia, it can also be a result of some types of dementia, such as Parkinson’s disease dementia and dementia with Lewy bodies.

What can you do to prevent young-onset dementia?

Taking these five steps can reduce your risk for developing dementia before age 65:

• Don’t drink alcohol in excess.
• Seek opportunities to socialize with others regularly.
• Make sure that you’re getting enough vitamin D. You can make your own vitamin D if your skin (without sunblock) is exposed to sunlight. But in northern climates you might need to take a supplement, especially in the winter. Because vitamin D can interact with other medications, ask your doctor about this option.
• Make sure you are hearing well and use hearing aids if you are not.
• Exercise regularly, eat a healthy diet, maintain a healthy body weight, and work with your doctor to reduce your risk of strokes, heart disease, and diabetes.

About the Author

Andrew E. Budson, MD, Contributor; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Andrew E. Budson is chief of cognitive & behavioral neurology at the Veterans Affairs Boston Healthcare System, lecturer in neurology at Harvard Medical School, and chair of the Science of Learning Innovation Group at the … See Full Bio View all posts by Andrew E. Budson, MD

Ever wonder if every medical test or treatment you've taken was truly necessary? Or are you inclined to get every bit of health care you can? Maybe you feel good about getting the most out of your health insurance. Perhaps a neighborhood imaging center is advertising discounted screening tests, your employer offers health screens as a perk, or you're intrigued by ads touting supplements for a seemingly endless number of conditions.

But keep in mind: just because you could get a particular test or treatment or take a supplement doesn't mean you should. One study suggests that as much as 20% of all health care in the US is unneeded. In short: when it comes to health care, more is not always better.

Isn't it better to be proactive about your health?

We're all taught that knowledge is power. So it might seem reasonable to want to know as much as possible about how your body is working. And isn't it better to take action before there's a problem rather than waiting for one to develop? What's the harm of erring on the side of more rather than less?

The truth is that knowledge is not always power: if the information is irrelevant to your specific situation, redundant, or inaccurate, the knowledge gained through unnecessary health care can be unhelpful or even harmful. Unnecessary tests, treatments, and supplements come with risks, even when they seem harmless. And, of course, unnecessary care is not free — even if you're not paying a cent out of pocket, it drives up costs across health systems.

Screening tests, wellness strategies, and treatments to reconsider

Recommended screening tests, treatments, and supplements can be essential to good health. But when risks of harm outweigh benefits — or if proof of any benefit is lacking — think twice. Save your time, money, and effort for health care that is focused on the most important health threats and backed by evidence.

Cancer screening: When to stop?

Screening tests for some cancers are routinely recommended and can be lifesaving. But there's a reason they come with a recommended stop age. For instance, guidelines recommend that a person at average risk of colorectal cancer with previously normal colonoscopies stop having them once they turn 75. Similar limits apply to Pap smears (age 65) and mammograms (age 75). Studies suggest that beyond those ages, there is little benefit to continuing these screens.

Watch out for wellness marketing

Dietary supplements are a multibillion-dollar industry. And a whopping 70% or more of US adults take at least one, such as vitamin D, fish oil, or a multivitamin. People often consider them as insurance in case vital elements are missing from their diet, or they believe supplements can prevent dementia, heart disease, or another condition.

Yet little evidence supports a benefit of routine supplement use for everyone. While recent studies suggest a daily multivitamin might slow cognitive decline in older adults, there's no medical consensus that everyone should be taking a multivitamin. Fish oil (omega-3) supplements haven't proven to be as healthful as simply eating servings of fatty fish and other seafood low in toxic chemicals like mercury and PCBs. And the benefits of routinely taking vitamin D supplements remain unproven as well.

It's worth emphasizing that dietary supplements clearly provide significant benefit for some people, and may be recommended by your doctor accordingly. For example, if you have a vitamin or mineral deficiency or a condition like age-related macular degeneration, good evidence supports taking specific supplements.

Reconsider daily aspirin

Who should be taking low-dose aspirin regularly? Recommendations have changed in recent years, so this is worth revisiting with your health care team.

• Older recommendations favored daily low-dose aspirin to help prevent cardiovascular disease, including first instances of heart attack and stroke.
• New recommendations favor low-dose aspirin for people who've already experienced a heart attack, stroke, or other cardiovascular disease. Adults ages 40 to 59 who are at a high risk for these conditions and low risk for bleeding also may consider it.

Yet according to a recent study, nearly one-third of adults 60 and older without past cardiovascular disease take aspirin, despite evidence that it provides little benefit for those at average or low risk. Aspirin can cause stomach bleeding and raise risk for a certain type of stroke.

Weigh in on prostate cancer screening

Men hear about prostate cancer often. It's common, and the second leading cause of cancer deaths among men. But PSA blood tests and rectal exams to identify evidence of cancer in the prostate are no longer routinely recommended for men ages 55 to 69 by the United States Preventative Services Task Force.

The reason? Studies suggest that performing these tests does not reliably reduce suffering or prolong life. Nor do possible benefits offset downsides like false positives (test results that are abnormal despite the absence of cancer). That can lead to additional testing, some of which is invasive.

Current guidelines suggest making a shared decision with your doctor about whether to have PSA testing after reviewing the pros and cons. For men over age 70, no screening is recommended. Despite this, millions of men have PSA tests and rectal examinations routinely.

Not everyone needs heart tests

There are now more ways than ever to evaluate the health of your heart. But none are routinely recommended if you're at low risk and have no signs or symptoms of cardiovascular disease. That's right: in the absence of symptoms or a high risk of cardiovascular disease, it's generally safe to skip EKGs, stress tests, and other cardiac tests.

Yet many people have these tests as part of their routine care. Why is this a problem? Having these tests without a compelling reason comes with risks, especially false positive results that can lead to invasive testing and unneeded treatment.

Four more reasons to avoid unnecessary care

Besides the concerns mentioned already, there are other reasons to avoid unnecessary care, including:

• The discomfort or complications of testing. If you're needle-phobic, getting a blood test is a big deal. And while complications of noninvasive testing are rare (such as a skin infection from a blood test), they can occur.
• The anxiety associated with waiting to find out test results
• False reassurance that comes with false negatives (results that are normal or nearly so, suggesting no disease when disease is actually present)
• All treatments have side effects. Even minor reactions — like occasional nausea or constipation — seem unacceptable if there's no reason to expect benefit from treatment.

The bottom line

You may believe your doctor wants you to continue with your current schedule of tests and treatments, while they might think this is your preference! It's worth discussing if you haven't already, especially if you suspect you may be taking pills or getting tests you don't truly need.

If your doctor says you can safely skip certain tests, treatments, and supplements, it doesn't mean that he or she is neglecting your health or that you don't deserve great health care! It's likely that the balance of risks and benefits simply doesn't support doing these things.

Less unnecessary care could free up resources for those who need it most. And it could save you time, money, and unnecessary risks or side effects, thus improving your health. It's a good example of how less can truly be more.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD