Updated on March 7, 2023.
More than 6 million Americans currently live with Alzheimer’s disease, the most common cause of dementia. And we rightly associate Alzheimer’s with an older population, since most of the people who develop this progressive brain disorder are age 65 and older.
Some people develop the condition before the age of 65, however. This is known as younger-onset or early-onset Alzheimer’s disease. Although experts don’t know exactly how many people have early-onset Alzheimer’s, it's believed to affect approximately 5 to 6 percent of those with Alzheimer’s, according to the Mayo Clinic.
“Alzheimer’s is just one type of dementia,” says H. Rai Kakkar, MD, a neurologist at Presbyterian/St. Luke's Medical Center in Denver, Colorado. “And given the frequency of early-onset, it’s somewhat uncommon.”
How is early-onset different?
Early-onset Alzheimer’s disease (EOAD) is the same as Alzheimer's disease in terms of progressive deterioration of cognitive function, but the causes of early-onset Alzheimer’s may differ.
Experts don’t fully understand the origins of most cases of early-onset Alzheimer’s or why certain people develop the disease at younger ages. But they’ve determined that some cases are the result of familial Alzheimer’s disease (FAD), a form of Alzheimer’s in which an inherited change in one of several specific genes directly causes the disease. These genes differ from the apolipoprotein E (APOE) gene that increases one’s risk of Alzheimer’s generally but doesn’t guarantee that a person will develop the disease.
The first signs of early-onset Alzheimer’s disease
At its earliest stages, signs of Alzheimer’s disease may include memory loss, struggling to find a word, and losing track of dates. This list of EOAD stages may not sound alarming to the average adult, given their roles, responsibilities, and challenges of keeping track of home, family, school, and work. Misplacing things can often seem like a given in middle age, as well—and who doesn’t laugh off the inability to recall a word as an occasional “senior moment?"
This is why an early-onset Alzheimer’s diagnosis can sometimes be so vexing. Healthcare providers, not expecting a middle-aged person to have Alzheimer’s, may mistakenly attribute forgetfulness and trouble focusing to stress or some other condition.
“In a very early phase they can just have memory problems,” says Dr. Kakkar. But to make a diagnosis, there has to be something beyond memory loss, he explains.
"We used to call it mild cognitive impairment," Kakkar says. “They have memory loss and some impairment of the activities of daily living, with symptoms that fluctuate initially.”
These patients have to be monitored very closely, Kakkar adds, because "a significant percentage will convert to Alzheimer's disease."
Short-term memory loss, confusion, and a decline in thinking skills are all signs that it’s time to see your healthcare provider (HCP). It can be helpful to keep notes about any symptoms you observe to share with your HCP.
How is early-onset Alzheimer’s diagnosed?
There is no one test that indicates Alzheimer’s. A thorough medical history and complete medical exam can help rule out other health issues that might produce dementia-like symptoms.
A neurological test of cognitive function—including counting, memory, and problem solving—may be given. Blood tests and brain imaging, such as an MRI, can indicate other possible conditions.
In some cases, genetic testing may be considered in making a diagnosis. This depends on a variety of factors, including the age of the patient and the availability of family members who may have already developed the disease. Cost and insurance coverage can be another factor, since the test is expensive.
Other causes of early-onset dementia
According to Kakkar, other types of dementia that may materialize before the age of 65 include:
Vascular dementia. This is caused by damage to blood vessels leading to reduced blood flow to the brain. It typically results from bleeding in the brain or small strokes that damage brain cells. Initial symptoms of brain damage include trouble making decisions and impaired judgment.
Frontotemporal dementia (FTD). The typical age of diagnosis for FTD is between the ages of 45 and 65, when many people are still at the height of their financial and family responsibilities. Symptoms tend to revolve around difficulty with language and behavioral changes. These dementias are inherited in about one-third of cases, according to the Alzheimer’s Association. The only known risk factors are family history or having a similar disorder.
Traumatic brain injury (TBI). TBI is typically the result of acute trauma caused by a violent impact to the head (for example, a car accident or a concussion).
Chronic traumatic encephalopathy (CTE). CTE is the result of repetitive brain trauma, such as that sustained by athletes, like boxers and football players, or by military personnel who experience recurring blast injuries.
Alcohol-related brain damage (ARBD). The most common type of ARBD is cognitive impairment, experienced by 50 to 70 percent of alcohol abusers. This may be partially or fully reversible if the person stops drinking.
Another type of ARBD is Wernicke-Korsakoff syndrome. It’s actually two different conditions that are the result of thiamine (vitamin B1) deficiency, which tends to be common in people who drink excessively. Wernicke’s encephalopathy is a sudden and acute reaction to a severe lack of thiamine and requires immediate medical attention. Symptoms include stumbling, confusion, and lack of coordination; it may be reversed if caught early enough.
Korsakoff syndrome is chronic and irreversible. It causes both short and long-term memory loss, although other thinking skills remain intact. For example, a person may carry on a coherent conversation but have no recollection of it moments later.
Immunologically mediated dementia. These are the most challenging to identify. Other types of dementia are caused by diseases that lead the nervous system to lose function. But immunologically mediated dementia stems from different underlying conditions, such as an autoimmune disease or cancer. The dementia is typically identified by the presence of antigens/antibodies or extreme inflammation.
The one bright spot with autoimmune-mediated dementia is that once the underlying cause is identified, treatment for this type of dementia tends to be successful and immediate.
