Types of Alzheimer’s (characteristics, causes and symptoms)

There are many diseases and disorders in the world with the capacity to cause us suffering, disability or even death.

But today, at least in Western society, probably one of the most fearful and considered cruelest by a large majority of the population is Alzheimer’s . This disease, for the time being without curative treatment and with a relatively high prevalence in the population, supposes a progressive deterioration of those who suffer from it and the gradual loss of mental abilities.

In general, when we talk about Alzheimer’s we usually think of a single diagnostic entity, a single problem that occurs the same in all those who suffer from it. However, the truth is that some research seems to reflect the existence of different types of Alzheimer’s , which, although they seem to work in a similar way, have different characteristics from each other.

Let’s look at some of the main examples throughout this article.

• Related article: “The 10 most common psychological disorders”

Alzheimer’s disease

Before discussing the different types or subtypes of Alzheimer’s that have been identified or proposed, it is appropriate first to briefly review what Alzheimer’s disease in general is and what it involves.

When we talk about Alzheimer’s we are talking about a neurodegenerative disease , which implies the progressive deterioration and death of brain neurons . Likewise, this neurodegeneration translates at a functional level into the progressive loss of the different faculties and mental capacities.

Forecast

We are facing a disease with a chronic and non-curable course, with an insidious onset (that is, the change in capacities is gradual and not abrupt), in which the degeneration generally begins at the cortical level in the temporal lobes and subsequently progresses towards the frontal to finally expand towards the entire brain . Although initially it affects the cortical level, as the disease progresses it also affects the subcortical level.

At the neuronal level, beta-amyloid plaques or neurofibrillary tangles are observed, residues that hinder the transmission of nerve impulses and gradually cause synaptic connections to weaken.

phases

The deterioration occurs over three phases (until the death of the subject, and at its beginning the appearance of anterograde memory loss stands out fundamentally (difficulties occur when recording new information) and later retrograde memory loss with a temporal gradient (it is say forget the most recent first), anomie and attention problems.It is common that there are more and more carelessness (for example, leaving the fire on) and even that the affected person gets lost.

With the passage of time, a second phase is entered in which the problems become increasingly serious and the so-called aphaso-apraxo-agnosic syndrome appears, in which speech alterations and communication difficulties occur (there are problems understanding or emit language), problems appear in carrying out sequenced and instrumental movements and problems begin to exist in recognizing stimuli. Little by little autonomy is reduced, the person becoming dependent on the environment.

Finally, in the advanced phase, a point is reached in which the subject is unable to recognize those around him and even himself , he has less and less ability to remember his past (in some cases they suffer regressions to childhood ), goes into silence and even ends up bedridden and immobile.

The two main types of Alzheimer’s according to the age of onset

Traditionally, Alzheimer’s disease has been considered a single entity, although the existence of two fundamental patterns has been recognized depending on the age of onset of the disease. In this sense, the existence of two types of dementia caused by Alzheimer’s disease could be considered .

1. Senile or late-onset Alzheimer’s disease

The most frequent and well-known type of Alzheimer’s is the one that begins after 65 years of age, something understandable considering that age is one of the risk factors for the appearance of Alzheimer’s. We are talking about late-onset or senile Alzheimer’s disease .

The characteristics of this disorder are the basic ones that we have indicated before, with the disorder having an average of eight or ten years of evolution.

2. Early-onset or presenile Alzheimer’s disease

We can consider early-onset or presenile Alzheimer’s disease all those cases in which Alzheimer’s disease occurs before the age of 65 . It is a rare form of Alzheimer’s, but nevertheless represents 10% of all cases.

In these cases, the damage is more visible and generates more difficulties, since in many cases it involves people who could still be of working age or even have minor children. Also. As a general rule, this subtype of Alzheimer’s is much more aggressive than the previous one, generating a faster degeneration and evolving in less time than in senile onset.

This type of Alzheimer’s sometimes includes atypical symptoms or ways of presenting compared to the senile variant, which in fact give name to three main types of presentations or variants within early-onset Alzheimer’s:

• Frontal variant : This variant stands out for the presence of a high number of symptoms and alterations linked to behavioral control and executive functions.
• Language variant : Also called logopenic aphasia, this alteration is characterized by the decrease in the rhythm at which we can elaborate the language, pauses and repetitions of phases being common.
• Variant with corticobasal syndrome : This variant is characterized by manifesting an alteration in the subject’s motor skills as one of its most notorious and initial manifestations.
• Variant with posterior cortical atrophy : In this case, the most quickly detectable and relevant problem is the existence of problems when it comes to recognizing objects and even vision problems appear when the posterior part of the temporal and parietal lobes degenerate.

Two types depending on their origin

In addition to the previous two, we can consider the existence of two classes or types of Alzheimer’s depending on whether its appearance occurs in someone without any family history or if there is a family history in which several members have suffered from it .

1. Sporadic Alzheimer’s

We consider sporadic Alzheimer to be that case in which Alzheimer’s disease appears in a subject with no family history of this disease . Most of the population with Alzheimer’s belongs to this group, with Alzheimer’s arising without previous cases in the same family.

2. Familial Alzheimer’s

This type of Alzheimer’s is characterized by the fact that Alzheimer’s appears in a subject in whose family history there is one or more more or less close antecedents with the same pathology. Although the fact that it is family does not necessarily imply a genetic determination, the truth is that in the case of Alzheimer’s it has been observed that those who suffer from it usually have genetic alterations.

One of the most studied genes is APOE, which in its APOE4 allele is the only well-established genetic risk factor for late-onset Alzheimer’s. Other genes such as APP, PSN1 and PSEN2 have also been observed to be altered in other cases, being related to the production of beta-amyloid plaques and neurofibrillary tangles of TAU protein.

Although familial Alzheimer’s is not the most common, it accounts for between 1 and 6% of cases. However, in 62% of cases of presenile or early-onset Alzheimer’s, a family history has been observed.

A new proposal: 3 subtypes

The above two subtypes of Alzheimer’s are the two most widely recognized and accepted clinically. However, multiple investigations are being carried out regarding this disease, and some studies have allowed the establishment of different subtypes of this problem.

An investigation carried out in 2015 by the University of California and led by Dale E. Bredesen focused on the analysis of the metabolic profile of the brains of fifty patients, from which he established a classification into three large subtypes.

1. Alzheimer’s inflammatory subtype

The inflammatory subtype of Alzheimer’s is characterized by the presence of a large number of proinflammatory cytokines and a high concentration of C-reactive protein , in addition to an altered globulin/albumin ratio and multiple other indicators of inflammation.

This subtype is characterized by the fact that brain inflammation occurs in which microglia and astroglia are activated to produce it, with the patient’s immune system being involved in said activation. The presence of amnesic problems and atrophy in the hippocampus is common despite not presenting in the rest of the brain.

2. Alzheimer non-inflammatory subtype

This subtype of Alzheimer’s is characterized by the absence of altered indicators at the level of brain inflammation, the values ​​of these being normal . However, other types of biomarkers can be found altered in this subtype, such as the level of insulin resistance, hormonal problems and deficits, lack of vitamin D or high levels of homocysteine, as well as DNA methylation, stress oxidative stress, vascular damage, induced neuronal death or alterations at the mitochondrial level or in the endoplasmic reticulum.

Subjects with this type of Alzheimer’s are usually somewhat older than the rest, usually having been observed in septuagenarians or octogenarians. There is usually no visible inflammation, although this is possible to a lesser degree.

3. Alzheimer cortical subtype

The third and most discussed subtype of Alzheimer’s found in the study is cortical, as well as the one that presents the most differences in relation to the other subtypes at the level of symptomatology. A massive atrophy is observed at the cortical level and sometimes also in the cerebellum, as well as severe zinc deficiencies in the organism.

Although it is generally considered that one of the first symptoms of Alzheimer’s is anterograde amnesia, loss of the ability to record new information (after which, after a while, the losses of information from the past begin to appear), in the case of Alzheimer’s cortical presentation, there is usually a good capacity to record it in short-term memory, but problems appear when it comes to preserving it in the medium and long term.

The ability to describe recent events stands out, which is preserved , but nevertheless it is common for them to end up losing the thread by not being able to keep the information. The authors insinuate that it is sometimes linked to depressive episodes or depressive symptomatology, with great passivity and even infantilization.

Bibliographic references

• Balasa, M. (2013). Sporadic presenile onset Alzheimer’s disease: clinical-biological characterization and early diagnosis. doctoral thesis University of Barcelona. [On-line]. Available at: http://diposit.ub.edu/dspace/bitstream/2445/46023/1/MIRCEA_BALASA_TESIS.pdf
• Bredesen, DE (2015). Metabolic profiling distinguishes three subtypes of Alzheimer’s disease. AGING, 7(8), 595-600.
• Ling H, O’Sullivan SS, Holton JL et al. (2010). Does corticobasal degeneration exist? A clinicopathological re-evaluation. Brain, 133: 2045-2057.
• Taylor KI, Probst A, Miserez AR et al. (2008). Clinical course of neuropathologically confirmed frontal-variant Alzheimer disease. Nat. Clin. practice Neurol, 4: 226-232
• Rabinovici, GD, Jagust, WJ, Furst, AJ et al. (2008). A beta amyloid and glucose metabolism in three variants of primary progressive apraxia. Ann. Neuro., 64: 388-401.