Understanding the Multifaceted Aspects of Dementia, Its Stages, Subtypes

July 11, 2022 - Dementia is an overarching term for multiple diseases and disorders that impair cognition and memory. According to the WHO, 55 million people in the world have dementia, and Alzheimer’s Disease International anticipates that this number will double every 20 years.  

In 2050, the number of dementia patients is expected to grow to 139 million. Of the people affected by dementia, a vast majority of them live in low- or middle-income areas.  

Stages of Dementia  

The Alzheimer’s Society in England divides dementia into three stages, early, middle, and late. The early stage of the disease — sometimes called the preclinical stage — is often challenging to detect as only a small portion of the brain is damaged, meaning functions are minimally impaired. Most patients at this stage are self-sufficient and do not require extensive assistance. 

On average, the early stage of dementia lasts about 2 years. Once a diagnosis is made, many patients choose to put together advanced directives and legal documents for use in the later stages of the disease.  

Symptoms in the early stage include memory issues, impaired decision-making, language and communication difficulties, limited depth perception, and mood changes.  

The next stage of disease progression is the middle stage. At this point, dementia patients require more regular assistance. Early-stage symptoms are exacerbated in the middle stage, and new changes such as visual hallucinations develop. These effects can also contribute to a decline in mental health as they can be frustrating for patients.  

In the final and most severe stage of dementia (the late stage), most patients require full-time constant care because symptoms are at their worst.  

Prognosis and Risk Factors 

People with dementia typically have a shorter-than-average lifespan. According to the Alzheimer's Society, dementia prognosis is impacted by multiple factors, including the stage of diagnosis, comorbidities, and age of onset.  

According to the Cleveland Clinic, risk factors of dementia are divided into two categories: those that can be changed and those that cannot. Factors that cannot be changed are age, genetic or family history, and the presence or absence of own syndrome.  

Manageable factors include diet, exercise, drinking and smoking, vitamin deficiencies, medication regimens, and more. 

Alzheimer’s Disease 

Of the 55 million people with dementia, 60–80% have Alzheimer’s, making Alzheimer’s disease the most common form of dementia. The risk of developing Alzheimer’s increases in patients with Down syndrome.  

The National Institute on Aging cites the first Alzheimer’s diagnosis as having occurred in 1906 by Dr. Alzheimer. He examined the brain of a patient and found two unusual features that now characterize Alzheimer’s disease: abnormal clumping called amyloid plaques and tau tangles. 

Alzheimer’s begins by damaging cells in the entorhinal cortex and hippocampus — the part of the temporal lobe primarily associated with memory. The hippocampus communicates directly with the entorhinal cortex, which is anterior to the hippocampus.  

While Alzheimer’s begins with damage in the hippocampus, neurons in other brain areas are also damaged as the disease progresses. In the late stages of the disease, damage to the cerebral cortex diminishes language and cognitive abilities.  

Damage to the neurons in Alzheimer’s disease can occur from amyloid plaques, tau tangles, and chronic inflammation. Amyloid plaque is the build-up of beta-amyloid proteins, which disrupt cell-to-cell communication. Tau tangles, sometimes called neurofibrillary tangles, occur when tau molecules attach to each other rather than microtubules. Finally, chronic inflammation is caused by an accumulation of microglia that does not properly clear out debris in the brain.  

Furthermore, posterior cortical atrophy (PCA) is another kind of dementia that causes neuronal degeneration in the cortex at the back of the brain. Because PCA exhibits amyloid plaques and tau tangles, PCA is viewed as a subset of Alzheimer’s disease. 

Lewy Body Dementia  

Lewy body dementia (LBD) includes symptoms such as cognitive impairment, hallucinations, impaired motor functions, and memory loss. LBD is the second most common type of dementia, characterized by alpha-synuclein protein deposits, referred to as Lewy bodies.  

There are two kinds of Lewy body dementia — dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD), and both types of LBD begin with motor impairments.  

The diagnostic difference between the two conditions is the time of cognitive symptom onset. In DLB, cognitive symptoms begin within one year of motor symptoms, while in PDD, cognitive decline does not begin until after a year of motor impairment.  

Vascular Dementia 

According to the Alzheimer’s Association, vascular dementia — as reflected in its name — is associated with blood flow. In vascular dementia patients, blood flow to the brain is limited, killing neurons. Insufficient blood flow is often seen in other forms of dementia as well. However, between 5% and 10% of all dementia patients exclusively have vascular dementia.  

Since vascular dementia is caused by limited blood flow in any brain area, its symptoms are more variable than other forms of dementia, depending on the affected area. This disorder is also associated with a stroke, so that symptoms can include stroke-like symptoms such as headache and numbness or paralysis on one side of the body, among other symptoms.  

Creutzfeldt–Jakob Disease Dementia 

Creutzfeldt–Jakob disease dementia (CJDD) is a form of dementia that — like most forms — is not yet well understood. CJDD is caused by CJD (Creutzfeldt–Jakob disease). The CDC classifies CJD as a human prion disease. The CDC states that CJD is “believed to be caused by an abnormal isoform of a cellular glycoprotein known as the prion protein.” 

The Alzheimer Association identifies CJDD as one of the rarest and most progressive forms of dementia. It occurs in approximately 1 of every 1,000,000 people. However, within one year of disease onset, most patients die. Symptoms of CJDD are like general symptoms of dementia but worsen rapidly.  

Frontotemporal Dementia  

Frontotemporal dementia (FTD) is another subset of dementia with its own subsets. The Alzheimer’s Association categorizes FTD as a type of dementia caused by the degeneration of frontal or temporal lobe nerve cells. “The two most prominent are (1) a group of brain disorders involving the protein tau and (2) a group of brain disorders involving the protein called TDP43,” states the Alzheimer’s Association site. 

Types of FTD include behavior variant frontotemporal dementia (bvFTD), primary progressive aphasia (PPA), and disturbances of motor function. ALS, Corticobasal syndrome, and Progressive supranuclear palsy (PSP) are all types of motor function disturbances that do not also exhibit symptoms of bvFTD or PPA. In the United States, PPA and bvFTD impact upwards of 50,000 people.  

Other Types of Dementia  

The Alzheimer’s Association lists multiple other kinds of dementia.  

Huntington’s disease (HD) is caused by a genetic mutation on chromosome 4 that causes defects in the brain’s center, impacting motor skills and cognition. Huntington’s disease causes chorea, which are involuntary movements, a decline in critical thinking skills, depression, irritability, and obseswhsive–compulsive behaviors. 

Dementia caused by normal pressure hydrocephalus (NPH) is due to the accumulation of cerebrospinal fluid. Enlarged brain ventricles due to increased pressure can damage areas of the brain, causing dementia. In addition to dementia symptoms, patients with NPH also have difficulty walking and controlling their bladder. 

Korsakoff syndrome is another kind of dementia associated with alcohol misuse and is caused by thiamine deficiency.  

Finally, mixed dementia is dementia caused by a multitude of different reasons. Most mixed dementia cases are not diagnosed until an autopsy can be performed on the patient’s brain. Patients with mixed dementia are typically diagnosed and treated for one kind of dementia.   

Overall, dementia is an umbrella term for cognitive impairment. Causes of dementia vary dramatically, and symptoms can manifest differently at different extremities. Understanding a patient’s risk of developing dementia can help physicians test and lead to increased early-stage diagnoses. Early diagnosis of dementia can impact patient prognosis by informing treatment plans, thus allowing for more robust medication regimens and counseling to improve quality of life.