Alzheimer’s Disease Symptoms and Causes


Alzheimer’s disease (AD) is an irreversible form of dementia characterized by memory loss, gradual decline in mental abilities, worsening language and speech skills, and personal and behavioral changes that ultimately affect daily life . 

Although AD in some ways mimics the changes detected in the brain as we age, AD is not a normal component of the normal aging process. Nerve cell damage and cell death occur due to the accumulation of abnormal protein formations called senile plaques (SPs) and tangles of nerve fibers  in the brain . The destruction of nerve cells also leads to a decrease in the levels of substances called neurotransmitters (most importantly acetylcholine), which help the transmission of brain signals. AD results in decreased interaction between different areas of the brain over time.

Association with aging The
risk of having AD and other dementias increases greatly with age. Approximately 10-12% of the population will develop dementia at the age of 65, and the risk will increase to 50% when approaching the age of 100.

Generally, “Late Onset” AD starts after age 65 and is not thought to be hereditary. AD onset before 65 years of age constitutes 5-10% of all AD cases and is probably related to heredity.

 Genetic Relationship
Alzheimer’s disease appears to be caused by a variety of, but poorly understood, factors. Three genes whose normal function has not yet been determined have been associated with Early Onset Familial Alzheimer’s Disease (called EOFAD Alzheimer’s disease type 3 or AH3). Certain mutations in each of these genes (known as PSEN1, PSEN2, and APP) will produce abnormal proteins  that cause AD. The probability of passing the gene mutation on to the children of affected people is 50%. Until now, mutations in these three genes have been identified in only a small number of certain families.

Currently, there are tests for the presenilin 1 gene (PSEN1 on 14th chromosome), presenilin II gene (PSEN2 on 1st chromosome) and amyloid precursor protein gene (APP on 21st chromosome) which are not commercially available but are used for research purposes.

Although other genes have been identified and associated with late-onset AD, they are not thought to directly cause AD. These “predisposition” genes may explain why people with affected family members have an increased risk of developing late-onset AD. It has been most clearly determined that the gene for “predisposition” to late-onset AD is the ApoE gene. This gene combines with body fat to direct the production of lipoproteins, the major component of very low-density lipoproteins (VLDL). These lipoproteins “pack” excess cholesterol and transport it through the blood to the liver, where it is processed. Everyone has two copies of the Apo E gene, which exists as a combination of three forms (e2, e3, and e4). of the ApoE4 alleleIts presence has been associated with most familial cases and an increased risk of AD.

Other risk factors associated with AD include metabolic disorders due to insulin resistance, obesity, high blood pressure, lipid metabolism disorders ( dyslipidemia ), inflammatory markers, and diabetes .

Most people with Down Syndrome (DS) (an inherited disease caused by an abnormal trisomy on chromosome 21) will have mental changes often associated with AD by the time they reach their 40s or 50s. The pathological changes found in the brains of these adult DS patients are very similar to those found in patients with AD. An extra copy of the 21st chromosome leads to increased protein deposits that cause senile plaques similar to those seen in AD. Relatives of individuals with DS do not carry an additional risk as they will not have an extra copy of this 21st chromosome.


There is no laboratory test that will definitely diagnose Alzheimer’s disease throughout a person’s life. Currently, the definitive diagnosis of AD is made only after death by examining a section of a person’s brain tissue under a microscope. Pathologists try to find the senile plaques and tangles of nerve fibers characteristic of AD . Since plaque and tangle formation is observed with normal aging, the sample taken should be compared with normal brain tissue of a person of the same age as the patient without AD (control).

Physicians can  make a reasonably accurate clinical diagnosis of AD using a variety of tests and procedures to rule out other causes of dementia . When a patient comes with symptoms of dementia, the doctor will evaluate the person’s personal and family history (preferably several generations), perform a physical examination, determine the age at which the disease occurs, and perform neuropsychological tests to measure the patient’s recollection, language skills, and other cognitive functions. The doctor may perform a series of classical laboratory tests to rule out deficiencies, other diseases and conditions that can impair a person’s memory. Doctors will investigate drug overdoses. Also, trauma, tumors and stroke can cause dementia.They can use computed tomography (CT), magnetic resonance imaging scans (MRI) to look for evidence of brain atrophy and shrinkage that can occur in advanced stages of Alzheimer’s disease. If the doctor suspects AD, he or she may perform less frequently performed laboratory tests (see Table ) to distinguish between AD and other forms of dementia and to check for genetic risk factors.

Tests to help identify dementia categories





Vitamin B12

Able to

B12 deficiency


Able to

thyroid function


Able to

thyroid function

Complete Blood Count

Able to

anemia, infection


Able to

Na+, K+, Cl-, CO2 and pH balance


Able to


HIV Antibody

Able to



Able to


drug screening


Illegal drug use


Other tests that help identify dementia categories






Imaging tests

CT (computed tomography)

body scan

Exclude AD or advanced AD

Stroke and brain immaturity (shrinkage in the brain in advanced AD)

MRI (magnetic resonance imaging)

body scan

Exclude AD or advanced AD

Stroke and brain immaturity (shrinkage in the brain in advanced AD)

Less used lab tests

Amyloid Beta 42 peptide and Tau protein correlation ( Tau/Aß42 )

CSF (cerebrospinal fluid)

It helps to differentiate AD from other types of dementia.

Elevated Tau protein level together with decreased Aß42 level in patients with symptoms increases the probability of AD regardless of the cause.

ApoE genotypes

Able to

Identify ApoE genotype and perform additional tests to confirm/exclude possible AD

In those with symptoms, ApoE e4 is associated with an increased risk of late-onset AD, and e4 and e2 variations are associated with lipid disorders.


Able to

Genetic mutation testing

It is thought to cause half of the early-onset familial AD cases.


Blood can only be made in a small number of laboratories.

Genetic mutation testing; can only be done in a small number of laboratories.

Early-onset familial AD; The mutation is very rare and has been described in only a few family pedigrees.


Able to

Genetic mutation tests; It has not entered clinical practice and is still used in research.

Early-onset familial AD; The mutation is very rare and has been described in only a few family pedigrees.


Currently, there is no treatment method that prevents or completely cures Alzheimer’s disease (AD). AH patients can live between 1 and 25 years (average 8-10 years). Treatment consists of slowing the course of the disease, overcoming behavioral problems, and providing support and education to the patient and caregivers. In the early stages of the disease, patients with AD can lead a fairly normal life with some help, such as memory aids and providing a structured environment for the patient. Meanwhile, the person can make plans for their future care and participate in the relevant decision processes.

Early diagnosis of AD may allow some people to benefit moderately from cholinesterase inhibitors such as galantamine, donepezil and rivastigmine, which preserve the function of the acetylcholine neurotransmitter. Whenever possible, other medications the person is taking are evaluated, and medications such as central nervous system depressants, antihistamines , sleeping pills, and pain relievers that can worsen the person’s confusion can be discontinued.

During the course of AD, antidepressants and other drugs may be used in small amounts, along with environmental modifications aimed at making the home environment safer and more friendly, alleviating personal and behavioral problems such as depression, agitation, paranoia, and violence, and providing greater comfort to the patient.

Although current research on the protective and therapeutic effects of some substances is promising, certain drugs cannot be recommended yet. Each of these drugs carries its own risks and side effects. Further studies are needed to determine their actual effectiveness and long-term safety.

Frequently Asked Questions

         1. What are other causes of confusion, memory loss, and decreased cognitive function?

Occasional forgetfulness is normal and should not be a cause for anxiety unless it increases in frequency or interferes with daily life. However, some causes of decline in cognitive functions include nutritional deficiencies such as Vitamin B12 deficiency , metabolism disorders such as diabetes , electrolyte imbalances, high blood pressure ( hypertension ),  kidney, liver  and thyroid disorders ; Structural disorders such as brain tumors, head traumas, normal pressure hydrocephalus , vascular dementia, age-related decline in cognitive functions, Degenerative disease such as Diffuse Lewy Disease, Huntington’s Chorea Disease, Parkinson’s Disease and Pick’s Disease,It includes infectious diseases such as HIV/AIDS , Creutzfeldt-Jakob, meningitis, encephalitis and syphilis , anxiety, depression, heavy metal poisoning (eg lead poisoning ), drug interactions and side effects, overdose and seizures.

          2. Is there a way to participate in research efforts related to Alzheimer’s disease?

Has. Both affected and unaffected individuals can participate in clinical trials. Also, brain tissue of a family member may be donated after their death. Scientists need to continue to examine brain tissue samples from older people with and without AD.

3.Is there a link between Mad Cow disease and Alzheimer’s disease?

While some of the symptoms appear to be similar, there is currently no evidence of any link between Mad Cow Disease and Alzheimer’s Disease.

Sources of the article

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