Alzheimer’s Disease (AD)

Alzheimer’s Disease (AD) is the most common cause of dementia and it affects millions of people around the world. But what exactly is it?

 

Neuron

Neuron

1. What is Alzheimer’s Disease?

Alzheimer’s Disease is an irreversible, chronic neurodegenerative disease of the central nervous system , characterized by progressive loss of memory and reduction of other cognitive functions of the brain. It is considered as the most common cause of dementia among people older than 65 and it affects even the simplest daily tasks. The disease is named after the German psychiatrist and pathologist Dr. Alois Alzheimer who first described the symptoms in 1901.

2. Cause & Pathophysiology

Scientists don’t yet fully understand what causes the Alzheimer’s Disease. The most probable factors are genetic, environmental, and lifestyle but the importance of those may vary from person to person. In most cases, people have the late-onset form of the disease which is symptom-free until their mid-60s. The early-onset of the disease occurs prior to the age of 60 but it represents a low 5% of all people with Alzheimer’s.

There are many hypotheses trying to explain the cause of the disease. Two abnormal structures caused by misfolded proteins (amyloid plaques and neurofibrillary tangles) and the loss of communication between cells are the major features of Alzheimer’s Disease.

Genetics

Genetics seem to be a major factor. The apolipoprotein E (APOE) gene is associated with late-onset Alzheimer’s and there are 3 common versions (alleles) of it, APOEe2, APOEe3 and APOEe4 with the last one being the one that seems to increase the risk of Alzheimer’s Disease. Other significant genes that seem to affect the risk are trem2, picalm, abca7, clu, and cr1.

Amyloid Theory

Scientists also inquire the significance of amyloid precursor protein (APP) that along with APOEe4 is involved in the amyloid plaque buildup. Beta-amyloid is a protein fragment of the amyloid precursor protein (APP) that is normally eliminated but in Alzheimer’s disease, it accumulates and forms the amyloid plaques. These hard, insoluble plaques block the connection between cells leading to diminished cell function and cell death.

Tau Theory

The tau protein normally has a certain number of phosphate molecules attached to it in order to form structures called microtubules. According to the tau hypothesis. when the model becomes hyperphosphorylated, the protein begins to come together with other tau proteins, forming neurofibrillary tangles that cause the destabilization and the disintegration of the microtubules structures.

Other

There is also the cholinergic hypothesis, on which most drug therapies are based, and many more.

3. Signs & Symptoms

Signs & Symptoms of Alzheimer's Disease AD

Signs & Symptoms of Alzheimer’s Disease AD

4. Diagnosis & Prevention

The early diagnosis is of great importance in order to manage the disease in better ways. Although there is no cure yet, there are certain drugs that can slow down the progression of the disease and others that can control the psychological symptoms. People who are experiencing memory problems should visit a doctor. Depending on the severity of the signs, family medical history, memory and language test, standard medical tests (blood,urine tests) or even brain scans (CT, MRI, PET) may be required.

Not much can be done to prevent the disease. It seems, though, that a healthy diet, such as the Mediterranean diet, and a lifestyle that includes various intellectual activities, lead to a lower risk of Alzheimer’s Disease. The association of the disease with diabetes, obesity, high blood pressure and long-term usage of NSAIDs and other drugs, is under investigation.

5. Management & Treatment

  • Cholinesterase Inhibitors : rivastigmine (Exelon), donepezil (Aricept), and galantamine (Razadyne)
  • Moderate-Affinity NMDA-Receptor Antagonist : memantine (Ebixa, Namenda)
  • Anti-depressants, anti-psychotics, anxiolytics and other medications that treat behavioral symptoms
  • Caregiving and patience

Sources
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