- Genes may play a significant role
in the development of dementia.
- Though the genes associated with
Alzheimer's have been identified, it is still tough to predict people who
are at risk of developing this disease.
- A new genetic test could predict
who are at higher risk of developing Alzheimer's disease even before
symptoms appear; possibly in healthy young adults too.
one of the common forms of dementia affects 47 million people in the world.
Most of the people affected with Alzheimer's disease consider that they have
inherited the condition from their parents.
Facts you should know about Alzheimer's Disease
Genetic link of Alzheimer's
- Every 66 seconds someone in the United States develops Alzheimer's
- One in three old-aged people dies with Alzheimer's or another form of dementia
- The cost of caring for patients with Alzheimer's is estimated to be $236 billion in 2016
- In India more than 4 million people have some form of dementia.
has been extensively studied and previous researchers have highlighted that genes do play a significant role in the development of dementia. There are two forms of Alzheimer's disease - rare Early Onset and common Late Onset
‘Genetic risk of Alzheimer's disease may exert an effect on the hippocampus region of the brain very early in life. This can make these individuals more susceptible to Alzheimer's disease later in life.’
Early onset is
when the symptoms of the Alzheimer's disease appear before the age of 65 and
late onset is when the symptoms typically develop after this age. But these two
types have different patterns of genetic inheritance.
Early Onset of Alzheimer's disease
(EOAD) is due to mutations in three genes, amyloid precursor protein (APP) gene and two presenilin genes (PSEN-1 and PSEN-2). Mutations in these genes can trigger the development of dementia in
the age of 30 or 40 years, but it is very rare.
Late Onset of
Alzheimer's Disease (LOAD) is very common and it is attributed to mutations in
one gene called the apolipoprotein E (APOE)
. Though the genes associated with Alzheimer's
have been identified, it is still tough to predict people who are
at risk of developing this disease.
A study recently published in the journal Neurology,
the medical journal
of the American Academy of Neurology reported that a genetic score could
predict who are at higher risk of developing Alzheimer's disease even before
; possibly in healthy young adults too.
The Research team from the Massachusetts General Hospital calculated polygenetic risk scores (PGRS)
using data from the International Genomics of Alzheimer's Project
166 older patients with dementia and 1026 patients without dementia for
identifying an association between PGRS and certain Alzheimer's markers such as
cognitive decline, clinical progression, hippocampus volume, and β-amyloid,
while 1,322 healthy young adults between 18-35 years were assessed for an
association between PGRS and hippocampus volume.
They found that
a higher PGRS was associated with poor memory and smaller hippocampus region in
older patients without dementia at the start of the study
. Over a period of
three years, the researchers found that higher PGRS was also associated with
cognitive decline and clinical progression of the disease.
deviation increase in polygenic risk was associated with a 1.6 times increase
in the risk of clinical progression of Alzheimer's.
healthy young adults, the study noted that a higher progenetic risk score was
associated with smaller hippocampus volume. Furthermore, researchers found that healthy adults who had more genetic
variants had developed mild cognitive impairment; later progressing into Alzheimer's disease.
region of the brain deals with learning and memory and this undergoes critical
damage in early stages of Alzheimer's disease. Therefore, shrinking hippocampus
signals the start of Alzheimer's.
"Our study was
small and larger numbers of participants will need to be studied to confirm our
findings. The goal of this type of research is to help physicians better
identify those at high risk of dementia so that future preventative treatments
may be used as early as possible," said Elizabeth C. Mormino, Massachusetts
General Hospital. References :
- Elizabeth C. Mormino, Reisa A. Sperling, Avram J. Holmes, Randy L. Buckner, Philip L. De Jager, Jordan W. Smoller, Mert R. Sabuncu; Polygenic risk of Alzheimer disease is associated with early- and late-life processes; Neurology 2016; 10.1212/WNL.0000000000002922.
- Genetics of Dementia - (https://www.alzheimers.org.uk/factsheet/405)
- Alzheimer's & Dementia: Global Resources - (https://alz.org/global/)
- Alzheimer's and Dementia in India - (http://www.alz.org/in/dementia-alzheimers-en.asp)