Understanding 

Alzheimer's Disease

Dementia

Dementia is the general term for a progressive brain disorder that gradually destroys a person's ability to carry out daily activities. Alzheimer's disease (AD) is the most common form of dementia. AD is a multifactorial neurodegenerative disorder characterized by:[34-37]

It is estimated 10% of people in their 60s, 20% in their 70s, and 30% in their 80s have AD in the U.S.[28] On average, Alzheimer's patients live from 7 to 10 years after a diagnosis, with some living up to 20 years. Death normally occurs usually within ten years, and usually from the failure of a body system or an infection.

When American artist William Utermohlen was diagnosed with Alzheimer’s in 1995, he decided to make the best use of his limited time and memory. He began to use his art to understand himself better – for five years, he drew portraits of himself before he completely forgot how to draw.

Symptoms

Memory loss is the most common sign of cognitive impairment, but other brain processes can be affected, including communication skills (speech and writing), judgment and decision making, auditory scene analysis[23], olfactory function[24], and attention span. 

However, Dr. Bruce L. Miller's work at UCSF[53] has shown that creativity is an area of strength spared by the disease, and that for some persons with dementia their creative ability is even enhanced.

“Younger people can have memory problems, but in many cases it’s difficulty with visual and spatial perception,” said Brian Appleby, MD, who specializes in young-onset Alzheimer’s. “They have problems judging things in space — tripping over curbs, knocking things over or trouble with left-right orientation.” 

Pathology

The major underlying mechanism of Alzheimer's is the buildup of protein deposits in the brain. The recent research has shown that the tangled web in Alzheimer's protein deposits is more complex than once thought. In [25], Scientists from the National Institutes of Health have discovered that the protein tangles involve at least three different proteins rather than just one. Medical researchers still don't know what sparks the disease process, but it is now accepted that this protein buildup goes on for many years before patients develop symptoms[44]. 

New UC Riverside research points to cells’ slowing ability to clean themselves as the likely cause of unhealthy brain buildup (i.e., amyloid plaques and neurofibrillary tangles).[72]  Those with brain buildup but no dementia had normal tau while a different-handed form of tau was found in those who developed plaques or tangles as well as dementia.

As more of these proteins form in certain parts of the brain, healthy neurons stop functioning and eventually die. And as more neurons die, affected brain regions shrink, leading to memory loss and other functional problems that are signs of Alzheimer's. To find out more information about plaques, tangles and amyloid protein, check out some good links provided by the Alzheimers Association Web Page.

In the brains of people with Alzheimer's disease, acetylcholine neurons that project into the hippocampus and cortex die very slowly. In Your Brain on Food, Gary L. Wenk explains that:

It is interesting to find the similarities between patients with Down and Alzheimer's. Both patients have the same pathological brain findings and clinical signs. Both show similar brain amyloid disposition. Down Syndrome is due to a trisomy, an extra copy of chromosome 21. The gene for beta amyloid protein is located on chromosome 21 near the locus for earlier onset Alzheimer's disease. This explains why more and more Down syndrome patients, who have survived into middle age, also develop dementia that appears similar to the Alzheimer's type.

Genetics also shows a link between Type 2 diabetes and dementia. People with a mutation known as ApoE4, who are known to have a higher risk for Alzheimer's disease, also have an increased risk of diabetes. The relationship between diabetes and dementia diseases drew headlines in September when a large study conducted in Japan reported that people with diabetes are twice as likely to develop Alzheimer's disease[22].

Type 2 diabetes and dementia share several key biological processes. Diabetes appears to play a role in the buildup of amyloid plaque as found in the AD patients. Some researchers believe that poor blood sugar control can make it harder for the body to clear away amyloid. Others suspect that high levels of glucose create a kind of toxicity in the body related to oxidative stress, in which harmful free radical molecules build up and damage tissue[20].

Diagnosis

Although absolute diagnosis of Alzheimer's disease (AD) can only be made after death, clinicians who do this all the time are quite accurate in making a clinical diagnosis. In general, the more advanced the dementia is, the easier it is to know with certainty that your loved one has AD. Unlike cancer or other diseases that can be diagnosed with great accuracy under a microscope, there is no one single, definitive test for AD.

Some conditions can even masquerade as an AD , which are actually treatable and even curable. These include:

There are also other types of dementia, including:

There is no one single, simple test for AD. But, four types of tests are commonly performed:

However, there are new methods developed for detecting Alzheimer's disease. For example, one method tests the spine fluid[26]. Another detects deposits of tau protein on mucous nasal membranes, even before dementia commences[27].

10 Best questions to identify the warning signs of AD [1]

Risk Factors

Read this companion article—Risk Factors of Alzheimer's Disease 

References