What Is Alzheimer’s Disease? Symptoms, Causes, Diagnosis, Treatment, and Prevention
Alzheimer’s disease is a progressive, irreversible brain disorder that slowly destroys memory and cognition — the ability to think and reason.
While there is currently no cure for Alzheimer’s, there are medications that improve symptoms and delay progression into the later stages of the disease.
Alzheimer’s disease is named for a German psychiatrist and neuropathologist named Alois Alzheimer. While conducting an autopsy in 1906, the doctor noticed abnormalities in the brain of a woman with a mysterious illness that caused memory loss, language problems, unpredictable behavior, and, ultimately, death.
The woman’s brain, Alzheimer reported, had many abnormal protein clumps (now called amyloid plaques) as well as tangled bundles of fibers (now called neurofibrillary tangles composed of tau, another type of protein). Those plaques and tangles are the hallmarks of Alzheimer’s disease.
Alzheimer’s disease causes nerve cells (neurons) to stop functioning, lose their connections with other neurons, and die.
Amyloid accumulates into toxic species, or variants — tiny little clusters called oligomers and protofibrils — eventually coalescing into plaques. Amyloid causes Alzheimer’s disease by making nerve cells dysfunction, permitting tau tangles to spread in the brain.
While a certain amount of forgetfulness — losing things from time to time, sometimes forgetting which word to use — is a normal part of aging, certain types of memory loss can indicate either the possibility or the presence of early-stage Alzheimer’s disease.
Scientists have identified a condition called mild cognitive impairment (MCI) that for some (not all) people is an early sign of Alzheimer’s disease. MCI involves problems with memory or mental function that are noticeable to the person affected but not serious enough to interfere with everyday life.
Symptoms of Alzheimer’s disease are generally mild at first, but become more noticeable as the disease progresses. The person may begin having difficulty with:
What causes Alzheimer’s? That is the billion-dollar question of dementia research. Scientists have made progress in understanding what happens in the brain as the disease progresses, but they still don’t know just what kicks off these changes.
As mentioned above, the genes you inherit from your parents can raise your risk of developing Alzheimer’s. The APOE gene raises risk quite a bit.
Alzheimer’s disease associated with Down syndrome is not passed down from parent to child.
Healthcare practitioners ask about current and past symptoms, illnesses, and medications and inquire about health issues affecting family members, such as Alzheimer’s and other forms of dementia.
Doctors listen to your heart and lungs and examine other relevant areas of the body. They may also collect blood and urine samples for lab testing and perform additional assessments to help identify ailments that may cause dementia-like symptoms (such as depression, untreated sleep apnea, delirium, certain vitamin deficiencies, side effects of medication, thyroid problems, or excess alcohol use).
A lumbar puncture can be done to measure the amyloid and tau levels in spinal fluid; this test can help to identify most people with Alzheimer’s disease.
A neurological exam that tests strength, sensation, reflexes, and eye movements can evaluate for medical conditions that may lead to impaired memory and cognition, like stroke or Parkinson’s disease.
This type of testing assesses memory, ability to solve simple problems, and other cognitive skills. During a test called the Mini-Cog, for instance, you’re asked to remember and, a few minutes later, repeat the names of three common objects. The doctor will also ask questions to determine whether you could have a mood disorder with symptoms that mimic Alzheimer’s disease.
A brain scan, such as a magnetic resonance imaging (MRI) or computerized tomography (CT) scan, may be used to rule out the presence of a tumor or another abnormality that could be responsible for Alzheimer’s-like symptoms. An amyloid positron emission tomography (PET) scan can reveal beta-amyloid plaques in the brain.
People of any age can be free of any signs of cognitive or functional decline or associated changes in behavior or mood. These mentally healthy people belong in this “normal” stage 1 category.
Many adults age 65 and older believe their memory is slipping a bit — that they have more trouble remembering names than they used to, for instance. But other people may not notice these changes, and they’re unlikely to cause concern even if others do notice.
Memory problems are subtle but significant enough for close friends and family to notice. The person might ask the same question repeatedly or have trouble acquiring new skills or performing tasks involving a series of steps.
Someone at this stage may become increasingly unable to handle the more complex demands of daily life, such as ordering from a menu at a restaurant.
The basic demands of everyday life, such as picking out clothing suitable for the weather, become difficult. The person may not be able to remember the name of the president or count backwards from 20 by twos.
The person may have trouble walking or putting on their clothing correctly and become reliant on caregivers for help with bathing and using the toilet. The end of this stage is marked by incontinence (inability to control urination or bowel movements) and inability to speak coherently.
Speech is essentially lost. The person loses their ability to walk or sit up independently, to smile, and to hold their head up without assistance. Physical rigidity sets in.
There’s no cure for Alzheimer’s disease, and current treatments can only slow its progression — meaning that the person’s cognitive decline continues until death. But especially in its earlier stages, Alzheimer’s related cognitive decline may be slowed by lifestyle measures like staying physically active and socially engaged and following a healthy diet.
While there is currently no cure for Alzheimer’s disease, certain treatments can slow cognitive decline for a limited time, help manage behavioral symptoms, and provide relief for symptoms like anxiety and depression.
Two drugs, lecanemab (Leqembi) and donanemab (Kisunla), address the underlying biology of the disease by removing beta-amyloid clumps from the brain. The drugs have been shown to slow the progression of cognitive decline when they’re started in early-stage Alzheimer’s. Both can cause brain swelling and bleeding as a side effect.
Doctors may also prescribe drugs for people experiencing behavioral symptoms of Alzheimer’s, targeting conditions such as depression, aggression, restlessness, and anxiety.
The drug brexpiprazole (Rexulti) is approved to treat agitation in Alzheimer’s, and the drug suvorexant (Belsomra) is approved to treat insomnia in people with Alzheimer’s.
Despite the growing number of herbal remedies, dietary supplements, and “medical foods” aimed at people with Alzheimer’s, there is no scientific proof that any of these products work.
For instance, some people with Alzheimer’s disease consume coconut oil based on the theory that the caprylic acid in the oil can provide energy to brain cells that are no longer able to metabolize glucose. But there has been no research confirming that this helps cognition.
In advanced stages of Alzheimer’s disease, complications from severe loss of brain function can include dehydration, malnutrition, or infection.
Can a healthy lifestyle reduce Alzheimer’s risk? A growing body of research suggests it can.
The Alzheimer’s Association estimates that 6.9 million people in the United States are living with Alzheimer’s disease, including about 1 in 9 people age 65 or older.
The percentage of people with Alzheimer’s increases with age. For example, 5.0 percent of people ages 65 to 74 have the disease, which rises to 13.2 percent of people ages 75 to 84 and 33.4 percent of people age 85 and older.
Among U.S. residents, there are striking differences in the risk of developing Alzheimer’s disease depending on a person’s sex, race, and ethnicity, according to the Alzheimer’s Association.
Nearly two-thirds of people with Alzheimer’s in the United States are women, largely because women tend to live longer than men, and older age is a major risk factor for Alzheimer’s disease. It’s estimated that 11 percent of women ages 65 and older have Alzheimer’s, compared with 9 percent of men.
Some researchers have pointed out that the higher risk for Alzheimer’s among women may reflect “survival bias” — since men are more likely than women to die from cardiovascular causes before age 65, those who survive past that age reflect a healthier subset of men who are also less likely to develop Alzheimer’s and other forms of dementia.
A number of studies have shown, however, that Black and Hispanic older adults are more likely to develop Alzheimer’s than their white counterparts — one study showed that among Americans ages 65 and older, the prevalence of Alzheimer’s was 10 percent for white older adults, 14 percent for Hispanic older adults, and 19 percent for Black older adults. These differences are not believed to reflect any genetic differences in Alzheimer’s risk. Instead, researchers believe they reflect differences in factors like educational and social opportunities, nutrition, healthcare access, and exposure to pollution.
Although the terms “dementia” and “Alzheimer’s disease” are sometimes used interchangeably, they are not the same thing.
Dementia isn’t a specific disease, but rather a general term to describe any decline in brain function that affects memory, language, and other cognitive abilities and is serious enough to interfere with daily life.
It is very common for people with Alzheimer’s disease to also experience brain abnormalities related to other types of dementia, a condition called mixed dementia.
Other types of dementia include:
Preserving quality of life for as long as possible is a widespread goal for people living with Alzheimer’s disease. The key is having strategies in place to maximize independence, minimize frustration, and build feelings of confidence and emotional connection that help make every day the best it can be.
Routines can ease the burden of short-term memory loss for people in the earlier stages of dementia. If you have Alzheimer’s, you might feel calmer and more in control knowing that your house keys are always on a hook by the door, for example, or that your caregiver always records appointments on a wall calendar.
As Alzheimer’s disease progresses, people often have more difficulty expressing their wants and needs to others. If you are a caregiver, there are strategies that can help you and the person you care for meet this challenge.
Early-onset Alzheimer’s describes Alzheimer’s disease in people younger than 65.
It’s unclear how many people with Alzheimer’s have early-onset disease, according to the Alzheimer’s Association. But many of these people develop the disease in their forties and fifties, which can make getting an accurate diagnosis difficult and frustrating.
In a few hundred families around the world, early-onset Alzheimer’s is caused by a specific genetic variant (mutation). This rare condition is known as familial Alzheimer’s disease and tends to affect many family members across generations.
Alzheimer’s disease is a serious brain disorder that leads to memory loss and other forms of cognitive and (eventually) physical decline. While there’s currently no cure, managing risk factors like high blood pressure, a sedentary lifestyle, and smoking may help to prevent it, and medications can slow its progression. If you’re concerned about forgetfulness, increased difficulty performing familiar tasks, or any other problems related to thinking or memory, seek advice and cognitive screening from a healthcare provider early on.
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