What is early-onset Alzheimer’s disease, and who is at risk? Here’s what you should know about the condition that affects about 200,000 people in the United States.

It’s not just for old people.

Alzheimer’s disease is usually thought of as something senior citizens get. While that is often true, it’s not always the case: Up to 5% of people diagnosed with Alzheimer’s are under age 65—usually in their 40s or 50s—and are considered to have an “early onset” or “younger onset” of the disease.

The symptoms are the same, but may be hard to recognize.

Symptoms of early-onset Alzheimer’s are no different than symptoms of more traditional cases, says Mary Sano, Ph.D., professor of psychiatry and director of Alzheimer’s disease research at Mount Sinai School of Medicine in the Bronx. But because the condition is so rare in adults under 65, the signs may not be recognized as quickly by patients themselves, or by those around them.

“By the time people ask for help, something strange has probably been going on for at least six months,” says Sano. “And often, it’s family members and close friends who can provide a point of view that a change has occurred, which can allow that person to realize something is wrong.”

Younger people may need extra testing.

Because early-onset Alzheimer’s disease is so uncommon, diagnosis may also require testing above and beyond what a senior citizen might undergo. “We want to demonstrate that what’s really present is a cognitive problem and not a psychological or physical problem,” says Sano. “For a younger person, we’ll do a more rigorous workup, including imaging and other tests, because we want to make sure we get this right.”

Early-onset disease has a strong genetic component, so family history—if the patient knows enough about it—can be a big part of a person’s diagnosis, as well. A blood test can determine whether someone has a gene mutation that puts them at higher risk for familial Alzheimer’s, but cannot prove whether they have (or will get) the disease.

Keep in mind, it’s not common.

First things first: Early-onset Alzheimer’s disease is uncommon, and it’s not responsible for most cases of middle-aged forgetfulness—like not being able to remember where you put your keys, or the name of someone you met at a cocktail party last night, for example.

Episodes like these, says Sano, are most likely due to preoccupation or periods of temporary stress, and usually aren’t anything to worry about.

But you should know the warning signs.

When you should be concerned, she says, is when problems with your memory begin to interfere with your ability to do the things that are most important to you, or when you start to have difficulty completing common, everyday tasks. “It’s the persistence and the erratic nature of the symptoms that’s the real warning sign.”

In fact, Sano says, people with early-stage Alzheimer’s disease often subconsciously modify or adapt their routines to the point where they don’t even notice specific red-flag incidents. According to the Alzheimer’s Association, warning signs may include the regular use of memory devices, relying on friends and family to do things you used to handle yourself, or withdrawal from work or social activities.

Symptoms are different for everyone, but one thing to watch for is difficulty remembering and retaining new information, says Sano. “Not being able to learn your new computer password, or to learn a new activity or take on a new project—those are usually the challenges at the earliest stages of the disease,” she says.

As the disease progresses, however, all forms of memory are affected. Early-onset Alzheimer’s can be especially devastating because people in their 40s and 50s are often still working and caring for children. “They’re at risk for having more functional loss, and having their life and their family’s lives affected much more than someone who’s several decades older,” says Sano. “And so the management of the disease really requires a lot of thoughtfulness and a lot of extra service.”

This is how it’s treated.

There is no cure for Alzheimer’s disease, no matter what age onset occurs. But there are drugs that can slow its progression, and there are ways in which Alzheimer’s patients and their families can better manage living with the disease.

Staying physically, socially and mentally active can also provide protection against the disease and may help people with early-stage Alzheimer’s disease maintain their cognition longer, says Sano. Specifically, research has shown that doing crossword puzzles and speaking a second language may help slow declines in thinking and memory.

In addition, there are many opportunities for Alzheimer’s patients to take part in ongoing research, says Sano, which may lead the way to better treatment options. She recommends talking to your doctor or visiting the National Institutes of Health’s Alzheimer’s Disease Education and Referral Center online for information about clinical trials happening near you.