The Three Types of Alzheimer’s Diseaseadmin
Almost everyone has heard about Alzheimer’s disease, and some have experienced it up close and personal for the devastating disease that it is. Vast amounts of literature reveal the signs and symptoms of Alzheimer’s and even the genetic and lifestyle causes that experts believe can bring on the debilitating progression of the disease. Not everyone is aware, however, that there are actually three forms of Alzheimer’s disease. These include:
- Late onset
- Early onset
This article will describe the variants of Alzheimer’s disease, as well as some of the latest genetic discoveries that surround each type.
The most common form of Alzheimer’s disease and that for which most are aware is late-onset Alzheimer’s, which affects 50 percent of older adults age 85 and over. The chance of its development increases twofold every five years past the age of 65. About 90 percent of those afflicted with Alzheimer’s suffer from the late onset form, which is typically diagnosed at the age of 65 or older. It is sometimes referred to as sporadic Alzheimer’s.
Genetic variations and environmental factors are most often attributed to the cause of late-onset Alzheimer’s by researchers. A gene found on chromosome 19 known as APOE has been proven to affect the likelihood of developing Alzheimer’s. Until recently, the probability of another gene within chromosome 10 could not be conclusively linked to the dreaded disease. According to Philippe Marambaud of the Feinstein Institute for Medical Research and Albert Einstein College of Medicine and a group of his colleagues, their research is pointing to the likelihood of a gene that is active in the hippocampus region, which functions as a calcium channel.
Since Alzheimer’s results in a calcium or plaque build-up in the brain, this made complete sense to the researchers. The gene, prior to which had no known purpose, is called CALHM1. The brain’s regulation of calcium had been proposed for a causative factor of Alzheimer’s disease before, and the new study finds that it indeed may be the case. “The present work provides strong support for the calcium hypothesis of Alzheimer’s disease and is also an important step toward understanding the potential pathological cross talk between calcium signaling disturbances,” Marambaud reported.
A much less common variation of Alzheimer’s disease is the early onset form. Approximately 5 to 10 percent of those diagnosed with Alzheimer’s are under the age of 65. Most of these individuals experience symptoms in the 50s, with those in the age ranges of 30- to 40-year-olds less common. Persons with Down syndrome are more susceptible to early-onset Alzheimer’s disease.
Unlike late-onset Alzheimer’s, the genes that cause an early onset of the disease are very specific and not as general as the APOE gene. According to the Mayo Clinic, these genes have been identified within chromosome 14 as APP, PSEN 1, or the PSEN2 genes. Individuals who possess a genetic mutation of one of these three genes are very likely to develop early-onset Alzheimer’s.
Those who suffer from it may have difficulty obtaining a diagnosis due to busier lifestyles, initial misdiagnoses, or a general, understandable feeling of denial. The Mayo Clinic reports that research does not indicate a faster progression of early-onset Alzheimer’s as it relates to the other forms. Perhaps the misconception of a faster acceleration of early-onset Alzheimer’s is due to later diagnoses.
The rarest form of Alzheimer’s disease is the familial type. Also an early-onset form, Familial Alzheimer’s Disease (FAD) afflicts less than 1 percent of all persons suffering from Alzheimer’s. Inheriting a genetic fault on chromosomes 1, 14, or 21 occurs in 50 percent of next-generation offspring. So it is with very high probability that anyone who is diagnosed with early-onset Alzheimer’s has a parent or grandparent also diagnosed with this form of Alzheimer’s. Most individuals diagnosed with FAD are in the age group of 40 to 50, but it isn’t entirely uncommon to see those diagnosed with it to be in their 30s.
It is a very personal decision as to whether one should get tested for this genetic mutation, but it could be advantageous from the standpoint of coping with FAD. While it’s extremely challenging for the patient, it can also be difficult for family members or those persons who interact with the patient. By obtaining an early diagnosis, plans can be made ahead of time, and de-stressing of one’s environment as much as possible can take place. Moreover, pharmaceuticals or clinical trials can be considered for any form of early-onset Alzheimer’s or for Alzheimer’s disease in general.