Alzheimer’s and the Brain

Posted: June 14, 2021 Author: Patti Dipanfilo

The terms “Alzheimer’s disease” and “dementia” are often used interchangeably, but they’re not the same thing. Dementia is a broad term for a group of conditions that negatively affect memory, thinking and behavior. Alzheimer’s disease, or AD, is a progressive type of dementia. According to the Alzheimer’s Association, AD accounts for 60 to 80 percent of dementia cases.

Most of the time, people are diagnosed with AD after age 65, but it can appear in younger people as well. In those cases, it’s called early-onset Alzheimer’s disease. Research has linked early-onset AD to poorer executive and visual/spacial functioning. Early-onset AD is generally diagnosed in people in their 40s and 50s.

In the US, an estimated 5.5 million people have AD. Of those, approximately 5.3 million are 65 years old or older and 200,000 are younger than 65 and have early-onset AD. About two-thirds of Americans with AD, or 3.6 million people, are women ages 65 and older. Two million are men.

The National Institute on Aging reports that the number of Americans with AD doubles
every five years beyond the age of 65. By 2050, the number of people with AD is expected to top 16 million and cost the US as much as $1.4 trillion! AD is the sixth leading cause of death in the US and the fifth leading cause of death for those ages 65 and older.

Generally, the first symptom in people with AD is a loss of memory that can affect daily functioning. You might forget recently learned information, as well as important dates or events. You may begin asking the same questions over and over and relying more heavily on notes or family members to remember how to perform everyday tasks, such as using the microwave.

Other symptoms of Alzheimer’s disease include: difficulty with problem-solving, trouble with speech or writing, disorientation about times or places, decreased or poor judgement, decreased personal hygiene, changes in mood and personality, inability to recognize loved ones, and withdrawal from family, friends and community.

The exact cause of AD is unknown, but age, family history and genetics are believed to play a role in its development. One specific gene, apolipoprotein E, or APOE, has been linked to the onset of AD symptoms in older adults. But keep in mind that you can have this gene and not develop AD, and you can develop AD even if you don’t have this gene.

AD is a degenerative disease that interferes with memory and thinking. It also impairs and eventually destroys brain cells, causing certain changes to your brain. AD can only be definitively diagnosed after you die and doctors can look for these changes in your brain during an autopsy.

With AD, fragments of a protein called beta amyloid form irregular clumps called plaques that interrupt communication between nerve cells in the brain. It’s uncertain whether these plaques cause AD or result from the disease process. It is known that mutations to the precursor protein that forms beta amyloid plaque cause early-onset AD.

Another change with AD involves a protein in brain tissue called tau. Tau stabilizes the microtubules, which are a key part of a brain cell’s structure. In a brain with AD, strands of tau become tangled and interfere with the transportation of nutrients into the brain’s cells. Without nutrients, the cells die.

Memory and thinking depend on the transmission of signals across 100 billion nerve cells in the brain. AD interferes with this transmission of information by affecting the activity of the neurotransmitters, chemicals that assist in carrying the messages from one nerve cell to the next. With AD, these messages become distorted or lost, which impairs your ability to learn, remember and communicate.

AD also affects the microglia, the cells responsible for immune activity in your central nervous system: your brain and spinal cord. With AD, the microglia see the beta amyloid plaques as an injury to the brain and initiate an immune response. This response leads to inflammation that further damages the brain.

Beyond those changes, advanced AD shrinks the surface layer of the cerebrum, the largest part of your brain. This change wreaks havoc on your ability to plan ahead, recall information and concentrate. AD also affects the hippocampus, which plays a role in learning and memory. AD causes this part of your brain to shrivel, impairing your ability to create new memories.

All of these brain changes can be visualized on autopsy.

Doctors make a diagnosis of AD in living people based on multiple factors, including an extensive medical history; a thorough physical exam; tests of memory, problem-solving, attention, counting and language skills; and standard medical tests such as blood and urine tests to identify other possible causes for your symptoms.

Your doctor may also use imaging tests such as MRI, CT and PET scans. These tests can help rule out disorders such as tumors, stroke, Parkinson’s disease and a non-Alzheimer’s dementia, such as vascular dementia. These conditions are treatable, and some of their effects may be reversible.

Treatment cannot strop AD from progressing, but it can temporarily slow down the worsening of symptoms and improve quality of life. AD is typically treated with medication. For mild to moderate AD, medications called cholinesterase inhibitors are most often prescribed.

Cholinesterase inhibitors prevent the breakdown of acetylcholine, a brain chemical believed to play a key role in memory and thinking. These medications include Razadyne®, Exelon® and Aricept®. Unfortunately, as AD progresses, the brain produces less and less acetylcholine, so cholinesterase inhibitors may eventually lose their effectiveness.

Namenda®, an N-methyl D-aspartate (NMDA) agonist, is generally used to treat moderate to severe AD. Namenda is believed to work by regulating glutamate, an important brain chemical. When produced in excessive amounts, glutamate may lead to brain cell death. The FDA has also approved Namzaric®, a combination of Namenda and Aricept, for the treatment of moderate to severe AD.

Living a healthy lifestyle can help you preserve your brain health. Exercise regularly, eat a balanced diet rich in fruits and vegetables, maintain a healthy body weight, stop smoking and manage your blood pressure and cholesterol at healthy levels. Keep your mind active. Spend quality time with your family and friends, get involved with your community and get help for depression. And if you notice symptoms of AD, see your doctor right away.

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