Alzheimer's disease - causes, symptoms, prevention

Alzheimer’s disease is the most common form of dementia. The frequency of Alzheimer's disease is increasing as the New Zealand population ages. It has been estimated that the number of New Zealanders living with Alzheimer's disease will reach 70,000 by 2031 (from 28,000 in 2006).

There is no cure for Alzheimer's disease, nor any proven ways to prevent its onset. Treatment focuses on support and managing symptoms to maximize a person's ability to function and maintain independence for as long as possible. The condition is ultimately fatal.

Causes

In Alzheimer’s disease, brain cells start to deteriorate. The body attempts to stop this process by producing a protein called amyloid. However, amyloid deposits build up in the brain, leading to further deterioration. These deposits of amyloid are referred to as "plaques" and cause the brain cells to shrivel up and form "tangles", which in turn lead to changes in the brain structure and cause the brain cells to die. The formation of plaques and tangles also prevents the production of some important brain chemicals, called neurotransmitters (eg: acetylcholine, which is important in memory function). Over time the loss of brain cells causes the brain to shrink.

While there is no known cause for Alzheimer's disease, some research studies have indicated that the following factors may play an important role in the development of the condition:

Genetic factors, such as the presence of, or changes to, certain genes
Environmental factors, such as long-term exposure to some environmental solvents (eg: pesticides, glues and paints) or infection with certain viruses or bacteria
Lifestyle factors, such as a lack of exercise, poor-quality sleep and a diet lacking fruit and vegetables.

Researchers now believe that a combination of these lifestyle, environmental and genetic risk factors trigger an abnormal biological process in the brain that, over decades, results in Alzheimer-type dementia. Identified risk factors for developing the condition include:

Increasing age
Down syndrome
History of a head injury
Risk factors for blood vessel disease such as smoking
Family history of Alzheimer's disease
Obesity
High blood pressure
High cholesterol
Insulin resistance.

There is some evidence of a slightly higher prevalence of Alzheimer's disease in females than males, but this may reflect their longer life expectancy.

Signs and symptoms

The degenerative changes that occur with Alzheimer's disease affect the areas of the brain that control thought, memory and language resulting in gradual signs and symptoms related to a person’s behaviour and mental function. Often, physical functions such as bowel and bladder control are also affected.

With Alzheimer’s disease there is great individual variability as to the nature of symptoms experienced and the speed at which deterioration occurs. The types of behaviour change and the length of time symptoms are present are different for each person. The symptoms of Alzheimer's disease typically develop quite slowly. The time between the onset of the disease and death can range from five to 20 years.

Symptoms commonly experienced during the early stages of Alzheimer's disease include:

Mild forgetfulness – especially short-term memory loss
Mood changes, including irritability and anxiety
Difficulty processing new information and learning new things
Loss of spontaneity and initiative
Confusion about time and place
Communication difficulties
Decline in ability to perform routine tasks.

As Alzheimer’s disease progresses the following symptoms may develop:

Increasing short-term memory loss and confusion
Difficulty recognising family and friends
Shorter attention span and feelings of restlessness
Difficulty with reading, writing and numbers
Possibly neglectful of hygiene
Loss of appetite
Personality changes (eg: aggression, significant mood swings)
Requires increasing assistance with daily tasks.

Towards the later stages of the disease the following symptoms may be experienced:

Inability to understand or use speech
Incontinence of urine / faeces
Inability to recognise self or family
Severe disorientation
Increasing immobility and sleep time.

The changes brought about by Alzheimer's disease can be increasingly difficult for family members and friends as the person’s condition deteriorates and they become unable to recognise loved ones.

Although a person loses many abilities as the disease progresses, it is often helpful to focus on the abilities that do remain, such as the senses of touch and hearing and the ability to respond to emotion.

Diagnosis

There is a no single test to diagnose Alzheimer’s disease. Diagnosis involves a full assessment of medical and psychiatric history to rule out other possible causes. Therefore, a variety of tests are required to obtain a conclusive diagnosis, which may include:

A neurological and physical examination
Blood and urine tests
Brain scans
Mental status assessment to determine the level of mental deterioration
Caregiver interview to determine the level of dependency.

Scans to check brain structure and function may be recommended. The different types of scans used may include CT scanning (computerised tomography), MRI (magnetic resonance imaging) and PET (positron emission tomography).

Treatment

As there is no known cure for Alzheimer’s disease, treatment focuses on managing symptoms and supporting the person and their family. This may include:

Treating medical conditions that may contribute to confusion or physical decline eg: lung disease or anaemia
Encouraging stimulating activities in order to encourage the person to continue their normal activities as much as possible
Providing memory aids and memory triggers such as calendars and written reminders
Encouraging social interaction to help prevent feelings of loneliness and depression
Contacting support groups that may be able to offer family/caregivers assistance
Encouraging regular routine to reduce confusion
Not smoking.

Medications

Medications such as sleeping tablets and tranquillisers may help to control symptoms such as sleeplessness and agitation. However, they often cause increased confusion, so their use should be limited.

A group of medications called cholinesterase inhibitors have shown some effectiveness in slowing the progression of the condition in some people. These medications help prevent the breakdown of acetylcholine, a neurotransmitter responsible for memory. Cholinesterase inhibitor medications that are available in New Zealand include donepezil, rivastigmine and galantamine.

More recently, another drug - memantine - has become available in New Zealand. Memantine works in a different way to the cholinesterase inhibitors, aiming to prevent the entry of an excess amount of calcium into brain cells. Higher than normal levels of calcium in the brain cells causes damage to them and also prevents them from receiving signals from other brain cells.

Research continues into the development of other medications for the treatment of Alzheimer's disease. Medications being investigated include those that prevent the build-up of amyloid deposits in the brain, as well as looking at the use of some anti-inflammatory and hormone medications. Research also continues into the use of alternative therapies such as anti-oxidants like Vitamin E, curcumin, selenium and some herbal extracts (ginko balboas in particular).

Prevention / risk reduction

There are no proven ways to prevent the development of Alzheimer's disease. However, there is epidemiological evidence to suggest that leading a healthy lifestyle can reduce the risk of Alzheimer's disease. Regular physical activity and exercise may have a general protective effect on brain health and may slow progression of Alzheimer's disease. Although there are no specific dietary specifications for Alzheimer's, a Mediterranean-style diet (ie: plant foods such as vegetables, fruits, beans, whole grains, nuts, olives and olive oil, along with some cheeses, yoghurt, fish, poultry and eggs) may reduce the risk of Alzheimer's disease, and has the added benefit of lowering cardiovascular disease and type 2 diabetes risk. For more diet information, refer to our Healthy heart diet

Further support

Alzheimer's New Zealand (National Office)
Freephone: 0800 004 001
Email: admin@alzheimers.org.nz
Website: www.alzheimers.org.nz

References

Alzheimer Society of Canada (2016). Stages of Alzheimer's Disease (Web Page). Toronto: Alzheimer Society Canada. www.alzheimer.ca/en/About-dementia/Alzheimer-s-disease/Stages-of-Alzheimer-s-disease [Accessed: 11/07/17]
Alzheimer Society of Canada (2016). Alzheimer's disease (Web Page). Toronto: Alzheimer Society Canada. http://www.alzheimer.ca/en/About-dementia/Alzheimer-s-disease [Accessed: 11/07/17]
Mayo Clinic (2015). Alzheimer’s disease (Web Page). Rochester, NY: Mayo Foundation for Medical Education and Research. http://www.mayoclinic.org/diseases-conditions/alzheimers-disease/home/ovc-20167098 [Accessed: 11/07/17]
Lakhan, S.E. (2017). Alzheimer disease (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. http://emedicine.medscape.com/article/1134817-overview [Accessed: 11/07/17]
Tobias, M, Yeh, L.C., Johnson, E. (2008). Burden of Alzheimer's disease: population-based estimates and projections for New Zealand, 2006-2031. Aust NZ J Psychiatry; 42(9):828-36.

Last Reviewed – July 2017

Southern Cross Medical Library