Alzheimer’s Disease


Alzheimer’s Disease (AD)

is a disorder of brain functioning that impacts behavior, memory and thinking.  Alzheimer’s Disease is progressive and gets worse over time.

Common Findings in Alzheimer’s Disease

AD is characterized by dementia with the following findings:

  • Memory loss
  • Confusion especially about the location of familiar places
  • Poor judgement often leading to bad decisions
  • Language disturbance
  • Taking longer to do daily normal tasks
  • Loss of spontaneity and initiative
  • Agitation sometimes with increased anxiety
  • Withdrawal
  • Hallucinations

There are other ifindings typical in Moderate or Severe Alzheimer’s Disease.  To see a full list CLICK HERE

Duration of Alzheimer’s Disease

AD often affects people between 8-10 years but the range can be between 1-25 years.

Are you at Risk of Developing Alzheimer’s Disease?

There are genetic factors in AD especially in Early-Onset Alzheimer’s Disease which is reviewed HERE.  For most individuals, the overall lifetime risk of developing dementia is 10-12%.  If you have a first-degree family member (Father, Mother, Brother, Sister)  with Alzheimer’s disease the risk increases to between 15%-30% or is about 2.5X the background risk.

Risks with Early-Onset Alzheimer’s are significantly different as this disorder is inherited in an autosomal dominant fashion and the risk may be as high as 50%.

Genetic Causes of Alzheimer’s Disease

  1. Chromosomal like Down’s Syndrome                             <1% of cases
  2. Late-Onset Familial Alzheimer’s Disease                       15-25%
  3. Early-Onset Familial Alzheimer’s Disease                      2%
  4. Unknown                                                                              75%

 

Late Onset Familial Alzheimer’s Disease and the APOE Gene

Familial Alzheimer’s disease is considered when two or more family members have AD.  Alzheimer’s Disease likely has multiple susceptibility genes and many different Single Nucleotide Polymorphisms (SNPs) have been identified in different ethnic backgrounds.  Variants in the genes, HLA0DRB5, SORL1, CELF1, FERMT2 and MEF2C have been identified with higher risk AD.  However, the gene with the best known association with Late-Onset Familial AD is the APOE gene.

The APOE allele appears to confer a risk of developing Alzheimer’s Disease at an earlier age.

Should I get APOE Tested?

Here is the data on the Association of APOE and Alzheimer’s Disease

From Jarvik et al (1996)

APOEGenotype Normal Controls (n=304) All Individuals with AD (n=233) Individuals with AD and Positive Family History of Dementia 1(n=85)
e2/e2 1.3% 0% 0%
e2/e3 12.5% 3.4% 3.5%
e2/e4 4.9% 4.3% 8.2%
e3/e3 59.9% 38.2% 23.5%
e3/e4 20.7% 41.2% 45.9%
e4/e4 0.7% 12.9% 18.8%
  • The medical community has not established a consensus for testing.  However, we consider APOE testing in all individuals where there are MULTIPLE family members who are affected with dementia and who were diagnosed after the age of 60.
  • Confirmation of AD – In individuals with only mild symptoms of AD (See the difference between mild, moderate and severe AD HERE).  AD is the correct diagnosis in 97% of individuals with mild symptoms and the APOE e4//e4 genotype. There is also a greater likelihood that this is the correct diagnosis with one allele in African-American and Hispanic populations

 

When Should I be Tested for Early-Onset Familial Alzheimer’s Disease?

EOFAD – can be diagnosed when there are multiple family members with Alzheimer’s Disease and when these individuals developed symptoms before the age of 65.  Typically, persons with EOFAD will develop symptoms in their 40s or 50s.  Most importantly, there is usually a family history in more than 3 generations

More information about EOFAD can be found HERE

For More Information on Diagnosis and Testing, Please

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