Types of Alzheimer's Disease - Early Onset - Late Onset
There are basically three types of Alzheimer’s disease – late onset Alzheimer’s, early-onset Alzheimer’s and familial Alzheimer’s. Usually the last two are linked together as they both occur in people under 65.
1. Late onset Alzheimer’s
This is the most common type of the disease affecting about 90% of all those with Alzheimer’s. It affects people over the age of 65 with around 50% of all people over the age of 85 suffering from it. And the likelihood of developing late-onset Alzheimer’s doubles every five years after the age of 65.
It is also known as “sporadic Alzheimer’s” because it can affect any elderly person with no other common link other than the fact that they are all over 65.
So far researchers haven’t come across one single common factor to determine the eventual development of late-onset Alzheimer’s. What they have done, however, is identify a gene which may be a risk factor. Apolipoprotein E (ApoE) is interesting in that it has both a negative and positive side in the development of Alzheimer’s. The e4 type of the gene is found to carry a higher risk of Alzheimer’s while the e2 type is believed to offer protection against it. Having this gene doesn’t necessarily mean that a person will get Alzheimer’s – what it does mean is that it may increase their risk. Environmental factors, lifestyle and toxins can all play a part in weakening genes and making a person more susceptible to an illness.
2. Early onset Alzheimer’s
Early-onset Alzheimer’s is associated with the mutations of three genes – presenilin 1, presenilin 2 and amyloid precursor protein. In isolation these genes do not cause Alzheimer’s – in fact they probably have a very good positive reason for being in the body - but scientists have found that if they mutate they can spark the disease.
Memory loss, confusion, personality changes and difficulties performing simple tasks are all very common symptoms and as the disease progresses emotional and social withdrawal is the norm.
A condition called myoclonus which causes muscle twitching and spasms is much more common in people with early onset than those who develop the disease later in life. These will all combine to make it very difficult for someone in the younger age group to continue to work or even take part in normal family life.
This is a very rare type of Alzheimer’s Disease affecting less than 1% of sufferers and in nearly all cases it attacks younger people, mainly in their 40s and 50s. In some extremely rare cases people in their 30s have been known to develop it.
As the name suggests, this type of Alzheimer’s runs in families. These families usually inherit a genetic fault on specific chromosomes – in this case, chromosomes 21, 14 or 1. When this happens roughly 50% of the offspring of these sufferers will carry the genetic fault and all of them will go on to develop Alzheimer’s.