We rightly associate Alzheimer’s disease with an older population. Most people who develop this progressive brain disorder are age 65 and older. Currently some 5.5 million Americans — two-thirds of them women — live with the disease.
But hidden within that estimate, a smaller number — approximately 200,000 adults — develop the condition under the age of 65. When this happens, it’s called younger-onset or early-onset Alzheimer’s.
“Alzheimer’s is just one type of dementia, and given the frequency of early-onset it’s somewhat uncommon,” says H. Rai Kakkar, MD, a neurologist at Presbyterian/St. Luke's Medical Center in Denver, Colorado.
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 there are differences in causes. Some cases are the result of familial Alzheimer’s disease (FAD), caused by an inherited change in one of several specific genes.
A form of the apolipoprotein E (APOE) genemay also be involved, but its presence doesn’t guarantee that a person will develop the disease. Scientists also believe there may be a genetic component in early-onset.
The first signs of early-onset Alzheimer’s disease
At its earliest stages, signs of Alzheimer’s disease include memory loss, struggling to find a word and losing track of dates.
This list of symptoms may not sound alarming to many of us given the demands of daily life. Who doesn’t struggle to keep track of a parent’s doctor’s appointments, kids’ sports schedules and deadlines at work? Misplacing things seems like a given in middle age. And who doesn’t laugh off the inability to recall a word as a “senior moment”?
This is why 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 there has to be something beyond memory loss. We used to call it mild cognitive impairment. They have memory loss and some impairment of activities of daily living. Initially symptoms fluctuate. They have to be monitored very closely since 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 primary care physician. It can be helpful to keep notes about symptoms to share with your doctor.
How is it diagnosed?
There is no one test indicating Alzheimer’s. A thorough medical history and complete medical exam can help rule out other health issues that might produce dementia-type symptoms. A neurological test of cognitive function, including counting, memory and problem solving, may be given. Blood tests and brain imaging — typically an MRI — can indicate other possible conditions.
In some highly individual cases genetic testing may be considered in making a diagnosis. This depends on a variety of factors, including the age of the patient and 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 can start under the age of 65 include:
“This is caused by damage in the different vascular territories of the brain,” he says.
It typically results from small strokes, where oxygen to the brain is blocked, causing brain cells to die, or bleeding in the brain. Initial symptoms of brain damage include trouble making decisions and impaired judgment.
Frontotemporal dementias (FTD)
FTD is considered the third-most common dementia in people under age 65. The typical age of diagnosis is between the ages of 45 and 65, when people are still at the height of their financial and family responsibilities.
Symptoms tend to revolve around difficulty with language and behavioral changes. According to the Alzheimer’s Association, these dementias are inherited in about one-third of cases. The only known risk factors are family history or a similar disorder.
Traumatic brain injury (TBI)
This is typically the result of acute trauma caused by a violent impact to the head (car accidents and concussions).
Chronic traumatic encephalopathy (CTE)
CTE is the result of repetitive brain trauma, such as that sustained by athletes (boxers and football players) and military members (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.
Wernicke-Korsakoff syndrome is actually two different conditions that are the result of thiamine (vitamin B1) deficiency — 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 dementias
These are the most challenging to identify. While other types of dementia are caused by neurodegenerative disease, the cognitive and behavioral changes from this type is the result of another underlying condition, such as an autoimmune disease or cancer.
The dementia is typically identified by the presence of antigens/antibodies or extreme inflammation — and may overlap. The one bright spot with autoimmune-mediated dementia is that once the underlying cause is identified and treated, treatment for this type of dementia tends to be successful and immediate.