Alzheimer's and Dementia. What's The Difference?

Updated: Jan 11, 2019


Alzheimer’s and dementia are terms which are often used interchangeably but are in fact different. From many standpoints they may appear similar but they do vary from each other if looked at from a medical point of view. Dementia is an umbrella term for a set of symptoms caused by irreversible and incurable disease (neurodegenerative disorders).  Alzheimer’s is the most common neurodegenerative disorder to have dementia as its symptoms, and affects 1% of people between the ages of 60 and 65 and over 50% of people over the age of 85. Other neurodegenerative disorders which cause dementia include Parkinson's disease, Lewy Body disease, and vascular problems. Alzheimer’s disorder is a gradual progression that can begin in middle age while dementia is usually found in later years in the advanced stage of neurodegenerative disorders such as Alzheimer’s. In other words, all people  with Alzheimer’s have dementia but all people with dementia do not have Alzheimer’s.


Dementia:

Dementia is usually caused by damage to neurons in the brain. Two of the symptoms must be met before diagnosing someone with dementia. Dementia symptoms include:

  • Poor judgement and reasoning

  • Decline in memory

  • Change of thinking skills

  • Decreased focus and attention

  • Change in language and communication

  • Change in personality and mood

  • Loss of ability to control emotions

  • Difficulty learning

Unfortunately, dementia due to neurodegenerative disorders is incurable and irreversible. However, according to Mayo Clinic, dementia that is caused by a vitamin deficiency or drug interaction is treatable and reversible. To find the right cure for this certain type of dementia it is best to consult a doctor about treatment methods. In relation to Alzheimer’s, dementia symptoms progressively gets worse as neurons continue to undergo apoptosis (cell death).


Alzheimer’s:

Alzheimer’s is the most common form of dementia and is the degeneration of neurons in the cortex(the section of the brain which controls thoughts and actions). According to Osmosis, there are two main factors that contribute to Alzheimer’s, beta amyloid plaques and neurofibrillary tangles.


The first component of Alzheimer’s is the development of  beta amyloid plaque. In the cell membrane of a neuron, a protein called amyloid precursor protein (APP) resides half in the cell and half out of the cell. The purpose of this protein is to help neurons grow and repair themselves from any injuries. Normally, APP gets released from the cell membrane by two enzymes known as alpha-secretase and gamma-secretase. This chopped up form of APP is soluble in the brain and eventually disappears. However, if gamma-secretase chops up APP with beta-secretase instead of alpha secretase it creates amyloid beta which is not soluble. Amyloid beta is very chemically sticky, so it clumps together outside of neurons forming beta amyloid plaque. Beta amyloid plaque gets in between neurons and disrupts neuron signalling which impairs functioning. This can also start up a response from the immune system which will damage surrounding neurons as well.


The second component to Alzheimer’s is neurofibrillary tangles. These tangles are located inside neurons as opposed to the outside of neurons where beta amyloid plaque is found. Neurons are held together by a cytoskeleton which is made up of microtubules used to transport nutrients throughout the neuron. Tau proteins make sure that microtubules stick together. If there is beta amyloid plaque outside of neurons, it causes pathways inside neurons to activate the enzyme known as kinase. Kinase transports phosphate groups to tau proteins in microtubules which degenerates them causing them to stop supporting the microtubule. Tau proteins then bundle together to form neurofibrillary tangles inside the neuron. Since the microtubule gets broken apart, the neuron isn’t  able to transport nutrients which leads to apoptosis. On a large scale, the brain atrophies and the gyries(ridges of the brain) get narrower which can be seen in an magnetic resonance imaging (MRI) scan of a person’s brain who has Alzheimer’s.


The progression of Alzheimer's’ worsens over time. The symptoms at first are not detectable as beta amyloid plaque just starts to build up. As time goes on, short term memory loss occurs, as well as a loss of motor skills and language functioning. This eventually leads to long term memory loss as apoptosis of neurons occurs. Dementia is seen as the symptoms of this neurodegenerative disorder.

Overall, dementia is a term for a set of symptoms where as Alzheimer’s is a neurodegenerative disorder that has dementia as its symptoms.

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