We all forget things from time to time. Whether it’s a mistaken name or a misplaced wallet, forgetfulness is a normal part of life. But older adults are particularly prone to worrying about their memory. According to recent research, around 48 percent of adults in their 50s and early 60s anticipate developing dementia in the United States as they age, and around 44 percent worry about the possibility of memory-deteriorating disorders.

Of course, that tendency to worry makes sense, since Alzheimer’s disease and other forms of dementia are much more common among older adults than younger adults. But just because Alzheimer’s tends to affect seniors doesn’t mean that the disease only affects seniors.

In fact, as many as 5 to 10 percent of people with Alzheimer’s disease develop their initial symptoms prior to the age of 65, making the disorder one of the most common forms of dementia (if not the most common) among younger adults.

Read More: The Origins and Young History of Early-Onset Alzheimer’s Disease

What Is Early-Onset Alzheimer’s?

Alzheimer’s is an aggressive, deteriorative disorder that targets the brain, attacking a person’s memory, reasoning, and rationality. Worsening with time, the disease disrupts a person’s day-to-day activities, typically reducing their ability to take care of themselves.

During the course of the disease, accumulations of proteins (including beta-amyloids and tau) build up in and around a person’s neurons, causing the breakdown of brain cells and brain cell communications throughout the brain. And though this damage tends to start in the parts of the brain that maintain and store memories (including the hippocampus), it soon spreads to other parts of the brain, too, resulting in a sizable shrink in brain volume.

Though the aging of the brain could contribute to the development of the disease, specialists stress that Alzheimer’s isn’t intrinsic to the aging process and that aging cannot cause Alzheimer’s in and of itself. While some older adults don’t develop the disease, some younger adults do develop the disease, suggesting that there are other causes that contribute to the disorder in addition to age.

The progression of the disease differs from patient to patient, though Alzheimer’s cases are all classified as one of two variants. While the late-onset variant of the disease — which develops in individuals older than 65 — is common, the early-onset variant of the disease — which develops in individuals younger than 65 — is relatively rare.

Early-Onset Alzheimer’s Age

The most aggressive estimates suggest that around 1 in 10 people with Alzheimer’s experience the early-onset variant of the disease, with the majority of those individuals being in their 40s, 50s, and early 60s when symptoms start to appear. Yet the signs of early-onset Alzheimer’s occasionally emerge in even younger individuals, with Alzheimer’s diagnoses being possible for patients as young as 19.

Early-Onset Alzheimer’s Life Expectancy

With that in mind, specialists stress that the variety of ages associated with symptom onset means that patients live with early-onset Alzheimer’s for dramatically different amounts of time. Typically, the earlier the symptoms appear, the longer the individual lives, with 30-year-old patients living with the disease for a longer period than 60-year-old patients.

Some specialists also add that people with early-onset Alzheimer’s lose as many as 15 to 18 years of their total life expectancy on average, making the disease especially destructive.

Read More: How Does Alzheimer’s Disease Lead to Death?

Early-Onset Alzheimer’s Symptoms

All in all, the progression of early-onset Alzheimer’s parallels that of late-onset Alzheimer’s.

In the initial stages of the disorder, some patients struggle with memory, forgetting important information and losing track of people, places, and times. Some see shifts in their planning and problem-solving skills, and some see shifts in their attention, attitude, and personality. In these initial stages, some patients also self-isolate, withdrawing from family and friends and avoiding social situations that they would’ve sought out in the past.

In the later stages of the disorder, memories become more and more muddled and mood swings become more and more severe. Some patients forget their family and friends, and some struggle to take care of themselves. As the disease progresses, people with early-onset Alzheimer’s tend to develop difficulties with basic bodily functioning, as well, with falls and difficulties swallowing food and fluids being two common causes of death.

In the later stages of the disorder, memories become more and more muddled and mood swings become more and more severe. Some people forget their family and friends, and some people struggle to take care of themselves. As the disease progresses, patients also tend to develop difficulties with basic body functions, with falls and difficulties swallowing food and fluid being two common causes of death associated with early-onset Alzheimer’s.

Some specific symptoms of the disease include:

• Problems with memory that disrupt day-to-day activities

• Problems with attention, planning, and problem solving

• Increases in impulsivity and in inappropriate outbursts

• Inability to identify family, friends, and familiar places

• Inability to learn, adjust, and adapt

• Inability to communicate

• Loss of awareness

• Loss of initiative

• Severe mood swings, depression, and anxiety

• Issues with wandering and withdrawal from social situations

• Issues with vision, walking, speaking, swallowing, and breathing, as well as seizures

All that said, the symptoms of early-onset Alzheimer’s do differ from late-onset Alzheimer’s in several substantial ways. While patients with early-onset Alzheimer’s are less likely to struggle with memory and more likely to struggle with attention, planning, and problem-solving as their initial symptoms, they are also more likely to feel a sense of loss over their “out-of-step” decline.

Studies also suggest that the early-onset variant of the disease progresses faster than the late-onset variant, leaving younger patients with severe impairment for longer periods of time.

Early-Onset Alzheimer’s Tests

Diagnosing the disease is a complicated task, taking an average of around 5.5 years for younger adults. And though there is no single, set procedure for identifying Alzheimer’s, physicians typically start the process by assessing a person’s symptoms, asking the patient and the patient’s family and friends about the patient’s ability to perform their day-to-day activities.

If a person’s symptoms appear consistent with Alzheimer’s following an initial assessment, physicians may conduct cognitive impairment tests to measure their memory and mental acuity. And though these tests vary in terms of their complexity, one of the most common — the Montreal Cognitive Assessment (MoCA) — is fairly simple, requiring patients to remember five words after five minutes, along with several similar tasks.

Physical and psychiatric assessments are used to rule out other possible causes for a patient’s symptoms. And while brain scans such as computed tomography (CT) and magnetic resonance imaging (MRI) can indicate damage and deterioration in a person’s brain, cerebrospinal fluid collections can indicate build-up of proteins associated with Alzheimer’s.

Read More: How to Diagnose Dementia

Early-Onset Alzheimer’s Treatments

As of now, there are no treatments that stop the progression of early-onset Alzheimer’s, though there are treatments that slow the declines associated with the disease. Among these treatments are drugs like Aducanumab and Lecanemab, which work by targeting the beta-amyloid proteins that build up in the brains affected by Alzheimer’s.

Effective only in the early stages of the disease, Aducanumab and Lecanemab stresse the importance of the early detection and diagnosis of Alzheimer’s, not just for older adults, but for younger adults, too.

Read More: How to Treat Dementia No Matter What Age You Are