Alzheimer’s Disease (AD) is a progressive form of (irreversible) dementia characterized by deteriorating language, speech skills, memory loss, a decline in intellectual ability over time, and behavioral/personality changes that affect a person’s usual way of life. The condition mainly affects older adults, with approximately 5.5 million Americans (aged above 65) and 200,000 younger persons having been diagnosed with the disease.
Although some symptoms of Alzheimer’s Disease mimic certain aging signs, AD isn’t part of the normal aging process. The condition may set in due to the injury and death of nerve cells. This happens as a result of abnormal protein structures (known as amyloid/senile plagues) building up in the brain and neurofibrillary tangles. The damaged or dead nerve cells disrupt the normal functioning of neurotransmitters (such as acetylcholine); this makes it hard for chemical signals to find their way to the brain. This cuts off/reduces the interaction of various parts/areas of the brain, hence reduced brain action.
Aging and Alzheimer’s Disease
As mentioned earlier, the risk of dementia increases as one approaches senior hood. According to research, at least 10% of the American population will be diagnosed with dementia by the time they are 65, with a 50% risk for individuals who live to see 100 years. Studies by the Alzheimer’s Association show that the number of dementia patients may increase to 16 million by the year 2050.
Early-onset Alzheimer’s disease starts before 65 years and accounts for approximately 7.5% of all recorded cases. Late-onset AD, on the other hand, is prevalent with individuals over this age, though not believed to be hereditary. Early-onset Alzheimer’s is more likely caused by disease-causing variants of mutation from inherited genes.
Genetics and Alzheimer’s
The cause of late-onset Alzheimer’s (the most common type) is yet to be known. Researchers have, however, identified three genes associated with various kinds of early-onset Alzheimer’s disease. These are APP, PSEN1, and PSEN2. Any slight alteration/change of these genes causes abnormal protein production, one of the contributing factors of senile plagues hence progressive dementia. A small mutation of one of these genes is enough to cause AD. The mutated genes can, therefore, be passed down several generations, hence early-onset AD.
Although scientists are yet to discover the causative genes of late-onset Alzheimer’s disease, some genes have been linked with this disorder. While individuals who have this variant of genes may not automatically develop Alzheimer’s in their adulthood, their risk is greatly increased when compared to those without the said genes. Commonly referred to as ‘susceptibility genes,’ these genes have helped shed light on the risk of developing late-onset AD, and especially in families with members suffering from AD.
The APOE gene is an excellent example of an established susceptibility gene. This gene helps induce apolipoprotein E production, the protein responsible for transporting fats and cholesterol (lipids) in the blood. The APOE gene occurs in 3 forms: e2, e3, and e4, also known as alleles. A combination of, or all these, alleles can be found in almost everyone, with e3 being the most common. About 60% of the entire population has the e3 allele gene. One allele the e3 allele, has been linked to Alzheimer’s disease.
Many individuals suffering from Down Syndrome (DS) are at a higher risk of developing Alzheimer’s Disease. An abnormal trisomy of chromosome 21 causes the condition. The additional copy of chromosome 21 is believed to trigger an increased production of proteins in the brain, which accumulates to form senile plaques. The plagues are quite identical to those seen in Alzheimer’s Disease. Although a DS patient may show mental changes linked to AD, their relatives do not have a high risk of developing Alzheimer’s. This is because they (the relatives) may/do not have the additional chromosome 21 copy.
Additional Risk Factors
Your ethnicity may or may not increase your risk of developing Alzheimer’s. A good example of this are persons of African American ancestry and Caucasians. African Americans are times more likely to develop Alzheimer’s when compared to their Caucasian counterparts. Other factors that may influence your risk of AD include obesity, insulin resistance (from diabetes type 2), high blood pressure, high levels of inflammatory markers (C-reactive proteins), and unhealthy lipid levels. Although these factors may influence your risk of developing the condition, this doesn’t mean an obese person, for example, will have the disease.
New guidelines and criteria for Alzheimer’s disease diagnosis were released in 2011 by the National Institute on Aging NIA, the Alzheimer’s Association, and the National Institutes of Health (NIH). These Expert workgroups have helped provide additional ways and methods of diagnosing the conditions. They have also published articles on Alzheimer’s Disease and the various stages. These are:
- 1. Preclinical Alzheimer’s Disease – This involves identifying biomarkers that indicate onset, such as the presence of specific proteins in the cerebrospinal fluids, and brain imaging. The idea is to define a preclinical state to guide research on the same, and especially where there are no outward symptoms.
- 2. Mild Cognitive Impairment (MCI) – These are the insignificant changes in thinking abilities and memory, which do not affect daily activities. Individuals with MCI may or may not develop Alzheimer’s Disease.
- 3. Dementia due to Alzheimer’s Disease – thinking, memory, and behavioral symptoms are evident and impact the person’s ability to lead a normal life.
The criteria and guidelines outlined above should help provide more information on Alzheimer’s disease, as well as provide a way forward for research in the future. These are also intended to propose the importance of biomarkers in diagnosing the condition in the future too.
Signs and Symptoms of Alzheimer’s Disease
There are ten signs and symptoms to watch out for Alzheimer’s Disease. Although some people may have memory problems as they get older, memory loss issues with persons with AD are more pronounced and severe. These include:
- 1. Forgetfulness. The person will become more and more forgetful, making it hard to learn anything new, and even forget important events and dates. The individual may have to depend on memory aids and notebooks to remember most of the hard-to-forget events. He/she will ask for the same information repeatedly without noticing it.
- 2. Difficulties solving simple problems, and planning- The individual might find it hard to keep track of bills and payments.
- 3. Problems solving simple tasks, such as finding his/her way back home, computing taxes, etc.
- 4. Losing track of time and place
- 5. Difficulties judging distances and reading.
- 6. Difficulties in reading, writing, and speaking. The person may struggle with simple vocabularies, forget words, and repeating phrases.
- 7. Losing personal items and the inability to retrace steps back to the house.
- 8. Impaired judgment. The individual will often make mistakes paying for something by either giving too much or fail to pay at all.
- 9. Withdrawal from social activities, family events, and work
- 10. Mood and personality change. He/she may experience increased fear, depression, suspicion, and anxiety.
There is no tangible way of determining if someone has Alzheimer’s or not, at least not when he/she is alive. The only feasible way to determine this is by examining a section of the patient’s brain tissue microscopically after their death. The pathologist will look for neurofibrillary tangles and senile tangles characteristic of Alzheimer’s. The tangle formation and plague may also be seen from normal aging, which is why the pathologist must compare a normal non-Ad tissue with a normal healthy one.
The healthcare practitioner can, however, use reasonable clinical diagnosis (by running a series of tests and procedures) to eliminate other causes of dementia. The doctor will first evaluate the patient’s family and personal history, do a physical examination, give neuropsychological tests to measure language skills, memory, and other cognitive functions, and determine the age of onset. All these tests must be done and especially where the patient has symptoms of dementia.
Several general lab tests may also need to be done to rule out other conditions, diseases, and nutritional deficiencies that might be affecting the individual’s brain performance. Overmedication may have similar signs and symptoms too. The health practitioner may also choose to use imaging tools such as MRI (magnetic resonance imaging) scans, and Computed Tomography (CT)scans to look for evidence of tumors, trauma, and stroke, which may cause dementia as well. These imaging tests help identify shrinkage and atrophy that show in advanced stages of Alzheimer’s disease.
All these tests may be used to help rule out potentially reversible dementia – Alzheimer’s is, however, irreversible.
Less common lab tests may be done if the health practitioner suspects Alzheimer’s disease. These tests are meant to help distinguish between other forms of dementia and AD, and to check genetics. See the table below for more info.
More than 65% of all patients have one type of APOE e4 allele. Individuals with e4 alleles are at the highest risk of developing AD. This genotype isn’t, however, very common.
Less Common Lab Tests
- PSEN1 blood Test: Test for gene mutation: Associated with 50% of all cases of early-onset AD
- PSEN2 blood test: Test for genetic mutation; it is only available on select labs: It tests for early-onset AD due to variation, though very rare.
- APP test: Blood: Test for gene mutation: which is only available in a few laboratories:.This test is used for diagnosing early-onset AD. Although mutation may be rare, several families may have this marker.
Research and studies on possible new biomarkers that may help diagnose Alzheimer’s disease easily are ongoing. Only the studies and tests outlined above can be used to learn more about Alzheimer’s for the moment.