What is Alzheimer’s Disease?

Alzheimer’s disease (AD) is the most common type of dementia, especially in people over the age of 60, although it can occur at a younger age. A genetic factor has been associated with development of AD. It is a gradually progressive neurological disease for which there is no cure. The changes that occur in the brain are non-reversible. Problems with memory are usually the earliest symptoms, which are often mistaken as symptoms of normal aging. This may be associated with progressive deterioration in thinking, judgment, language, and decision-making ability, thus making it difficult to conduct day-to-day activities. As the disease progresses, it becomes difficult for the person to remember even basic things. Some patients may even have trouble remembering his own name or recognizing family members.

Meaning of Alzheimer’s Disease

Healthy nerve cells (neurons) contain microtubules which guide nutrients and molecules from the cell body to the axons. Tau is a special type of protein which makes the microtubules stable. In Alzheimer’s disease, chemical changes in tau allows for it to become tangled with other threads of tau, resulting in disintegration of the microtubules. With the destruction of the neuron’s transport system, communication between the neurons is lost and the cells eventually die. This causes shrinkage of brain tissue.

The changes that may be seen in the brain tissue of people with AD are :

  • Neurofibrillary tangles where the nerve cells are clogged up by twisted bits of protein within it.
  • Neuritic plaques where dead and dying nerve cells, brain cells, and protein form clusters.
  • Senile plaques where the products of dying nerve cells group together around protein to form senile plaques. These are also known as beta-amyloid plaques.
  • Chemical messengers in the brain, known as neurotransmitters, help to transmit signals within the brain cells. As a result of destruction of the nerve cells, there is a reduction of the neurotransmitters that are responsible for transmission of messages from the brain.
  • Death and destruction of the neurons which result in memory impairment, personality changes, and other symptoms of the disease.

Why is it called Alzheimer’s disease?

Alzheimer’s disease (AD) is named after Dr Alois Alzheimer, a German psychiatrist, who first identified and co-related the symptoms and pathology of this form of dementia, which was at that time called pre-senile dementia.

Causes and Risk Factors

The exact cause of AD is not known but various risk factors have been associated with its development, such as :

  • Age – AD is a disease of old age. People over 60 are more at risk than younger persons.
  • Family history – having a close relative with AD increases the risk.
  • Genetic factor – apolipoprotein E epsilon 4 genotype has been associated with increased risk of AD.
  • Sex – women are said to be more at risk of developing AD than men, although this has not been proved substantially.
  • Obesity.
  • Insulin resistance.
  • Inflammatory markers.

These are the main risk factors but other likely risk factors include :

  • Head injury.
  • Chronic hypertension (high blood pressure).
  • High blood cholesterol levels.
  • Down syndrome.

Types of Alzheimer’s Disease

There are two types of Alzheimer’s disease based on the age when it starts.

Early Onset Alzheimer’s Disease

This type of AD tends to run in families and a genetic factor is strongly implicated. The symptoms, which may be observed before the age of 60, usually progress very rapidly. It is less common than late-onset Alzheimer’s disease.

Late Onset Alzheimer’s Disease

This is the more common type of AD. It usually affects people over 60 and disease progression is slower than in early onset AD. A family history may be present but a genetic factor is usually not involved.

Signs and Symptoms

The symptoms of AD may be broadly classified into 3 stages. The symptoms often overlap and can vary from person to person.

Early Stage Symptoms

These are the early warning signs and symptoms of Alzheimer’s disease :

  • Short-term memory loss – this is the most common symptom of AD.
  • Difficulty in performing simple daily physical activities.
  • Difficulty with mental tasks.
  • Disorientation, such as getting lost even in familiar surroundings.
  • Problems with language, such as forgetting simple words.
  • Difficulty in learning new tasks.
  • Problems with planning and decision-making.
  • Sleep difficulties.
  • Personality changes.
  • Mood swings.
  • Lack of interest in things that were previously enjoyable.

Middle Stage Symptoms

  • Short-term and long-term memory loss.
  • Personality changes.
  • Increasing difficulty in communicating with others.
  • Decision-making becomes extremely difficult.
  • Mental deterioration.
  • Inappropriate behavior.
  • The person may be physically fit.
  • Urinary incontinence may occur.

Late Stage Symptoms

  • Difficulty in recognizing people.
  • Problems in interacting with people.
  • Physical deterioration.
  • Incontinence.
  • Problems with eating.
  • Loss of interest in the surroundings.
  • More susceptible to infections.

Diagnosis of Alzheimer’s Disease

An absolute diagnosis of Alzheimer’s disease can only be made after death by a post-mortem examination of the brain tissue. However, AD may be diagnosed with some certainty by the following methods :

  • History – the symptoms of AD may be recognized on taking a thorough history.
  • Physical and neurological examination.
  • Mental status examination – the mini mental state examination results may be effective in evaluating cognitive functioning of the brain, such as memory and communication.
  • CT scan, MRI, or PET scan – these can help to assess any changes in the size and structure of the brain.
  • Blood tests and urinalysis – to rule out infection and other conditions that may produce similar symptoms.
  • Tests to rule out other conditions that may mimic AD.

Treatment of Alzheimer’s Disease

There is no known cure for AD. However, treatment can help to slow the progression of the disease and treat the psychological and emotional symptoms. Treatment consists of drug therapy and non-drug therapy.

Alzheimer’s Disease Drugs

For cognitive symptoms, drugs known as cognitive enhancers are used to slow the progression of the disease. These include :

  • cholinesterase inhibitors which act by increasing acetylcholine levels in the brain.
  • N-methyl D-aspartate (NMDA) antagonists which act by regulating glutamate levels in the brain.

The commonly used cholinesterase inhibitors are donepezil, tacrine, rivastigmine, and galantamine. The NMDA antagonist used is memantine.

For behavioral and emotional symptoms,  psychotropic drugs such as antidepressants, antipsychotics, mood-stabilizers, hypnotics, and anti-anxiety medication may be effective in controlling symptoms such as anxiety, depression, and hallucination. These are commonly used when non-drug approaches fail to control the symptoms.

Non-Drug Therapy

The behavioral and emotional symptoms of AD may be treated by non-drug approaches such as behavioral and environmental modifications.

A few simple measures may delay the onset of AD and possibly even slow the progression of the disease. This includes  :

  • Keeping the mind active.
  • Eating a healthy diet.
  • Exercising regularly.

Article reviewed by Dr. Greg. Last updated on December 3, 2011