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Alzheimer's disease | HearLore
Alzheimer's disease
In 1901, a German psychiatrist named Alois Alzheimer encountered a patient who would change the understanding of mental illness forever. Auguste Deter, a fifty-year-old woman, presented with symptoms that baffled the medical community of the early twentieth century. She suffered from memory loss, paranoia, and hallucinations, behaviors that were dismissed at the time as normal aging or senility. Alzheimer followed her case closely until her death in 1906, at which point he performed an autopsy and discovered the microscopic hallmarks of the disease. He found dense amyloid plaques and neurofibrillary tangles in her brain, structures that had never been described before. This discovery marked the first identification of what would eventually be named Alzheimer's disease, though for decades it was restricted to cases of early-onset dementia in people between the ages of 45 and 65. The term senile dementia was used for older patients, and the two conditions were thought to be distinct entities until 1977, when a conference concluded that the clinical and pathological manifestations were identical regardless of age. The disease was then formally adopted to describe individuals of all ages sharing a common symptom pattern and neuropathology. Auguste Deter's story remains the foundational case study for a condition that now affects millions globally, yet her specific experience of being the first documented victim of this progressive neurodegenerative disease is often lost in modern statistics.
The Silent Invasion
The disease begins its work long before any symptoms become apparent to the patient or their family. By the time the first signs of memory loss appear, the complex degenerative mechanisms in the brain have been active for many years. The earliest symptoms are often mistaken for normal brain aging or stress, leading to a delay in diagnosis that can span up to eight years. Detailed neuropsychological testing can reveal mild cognitive difficulties during this prodromal phase, but these subtle changes frequently go unnoticed. The most noticeable deficit is short-term memory loss, manifesting as difficulty in remembering recently learned facts and an inability to acquire new information. This early stage also brings subtle problems with executive functions such as attentiveness, planning, and abstract thinking. Apathy and depression can emerge at this stage, with apathy remaining the most persistent symptom throughout the entire course of the disease. People with objective signs of cognitive impairment but no more severe symptoms may be diagnosed with mild cognitive impairment, a condition that has a greater than 90% likelihood of being associated with Alzheimer's disease. The disease targets the hippocampus, the area associated with memory, which is responsible for these initial symptoms. As the disease progresses, the degree of memory impairment worsens, and the person may fail to recognize close relatives. Long-term memory, which was previously intact, eventually becomes impaired, and the individual loses insight into their own disease process.
Common questions
Who discovered Alzheimer's disease and when was the first case documented?
Alois Alzheimer discovered the disease in 1901 when he encountered his patient Auguste Deter. He performed an autopsy on Auguste Deter after her death in 1906 and found the microscopic hallmarks of the disease. This marked the first identification of what would eventually be named Alzheimer's disease.
What are the two abnormal proteins that define the pathology of Alzheimer's disease?
The two abnormal proteins that define the pathology are amyloid beta protein and tau protein. Amyloid beta protein accumulates extracellularly as amyloid plaques, while tau protein forms neurofibrillary tangles inside neurons. These proteins misfold and proliferate in the brain by a prion-like mechanism of seeded protein aggregation.
Which genetic allele is the strongest risk factor for sporadic Alzheimer's disease?
The strongest genetic risk factor for sporadic Alzheimer's disease is the APOEε4 allele. Between 40% and 80% of people with Alzheimer's disease possess at least one APOEε4 allele, which increases the risk of the disease by three times in heterozygotes and by 15 times in homozygotes.
How much does it cost to care for a person with dementia in the United States annually?
The yearly cost of caring for a person with dementia ranges from 28,078 to 56,022 dollars for formal medical care and 36,667 to 92,689 dollars for informal care provided by a relative. In the United States, informal family care is estimated to constitute nearly three-fourths of caregiving for people with Alzheimer's disease, costing approximately 18.5 billion hours of care annually.
What treatments are currently approved for Alzheimer's disease as of early August 2024?
As of early August 2024, two monoclonal antibodies, donanemab and lecanemab, are approved to target amyloid beta. Lecanemab was approved for sale in Japan, South Korea, China, Hong Kong, and Israel, although not by an advisory body of the European Union on July 26, citing side effects.
What is the average life expectancy following an Alzheimer's disease diagnosis?
The average life expectancy following diagnosis is three to twelve years, with the normal life expectancy for 60 to 70 years old being 23 to 15 years, but for 90 years old it is 4.5 years. Following AD diagnosis, life expectancy ranges from 7 to 10 years for those in their 60s and early 70s, to only about 3 years or less for those in their 90s.
The biological engine driving Alzheimer's disease is a misfolding of proteins that creates a toxic environment within the brain. Two abnormal proteins define the pathology: amyloid beta protein, which accumulates extracellularly as amyloid plaques, and tau protein, which forms neurofibrillary tangles inside neurons. These proteins share the feature of becoming abnormal by misfolding, assuming a shape rich in beta sheets, and they proliferate in the brain by a prion-like mechanism of seeded protein aggregation. The amyloid hypothesis posits that the accumulation of misfolded Aβ is the fundamental cause, triggering a cascade that leads to tauopathy and eventually the complex degenerative changes of advanced Alzheimer's disease. Abnormal Aβ is thought to damage the brain by directly interacting with cells or indirectly causing oxidative stress and neuroinflammation. The tau hypothesis suggests that abnormalities of the tau protein initiate the disease cascade, with evidence showing that tauopathy can be detected in certain neurons before Aβ plaques are evident. The disease starts with the hyperphosphorylation of tau in specific vulnerable neuronal populations such as the locus coeruleus and projection neurons of the association cortex. While the amyloid hypothesis is supported by genetics and biomarkers, the tau hypothesis is supported by histopathological findings. Current evidence suggests that abnormal Aβ acts as the prime mover, but tauopathy is required for the complete expression of the disease. The presence of these abnormal proteins leads to the disruption of neuronal metabolism, inflammation, and the loss of neurons and synapses, which is a particularly prominent correlate of dementia.
The Genetic Lottery
While environmental factors play a role, the genetic architecture of Alzheimer's disease reveals a complex interplay of risk factors that vary significantly across populations. The strongest genetic risk factor for sporadic Alzheimer's disease is the APOEε4 allele, one of four alleles of apolipoprotein E. Between 40% and 80% of people with Alzheimer's disease possess at least one APOEε4 allele, which increases the risk of the disease by three times in heterozygotes and by 15 times in homozygotes. However, the relationship is not absolute; for example, Nigerian Yoruba people do not show the relationship between the dose of APOEε4 and the incidence or age of onset for Alzheimer's disease seen in other human populations. Only 1 to 2% of Alzheimer's cases are inherited due to autosomal dominant mutations, known as early-onset familial Alzheimer's disease. These cases are attributed to mutations in one of three genes: those encoding amyloid-beta precursor protein and presenilins PSEN1 and PSEN2. A Japanese pedigree of familial Alzheimer's disease was found to be associated with a deletion mutation of codon 693 of APP, known as the Osaka mutation. This mutation accelerates Aβ oligomerization but the proteins do not form the amyloid fibrils that aggregate into plaques, suggesting that the oligomerization rather than the fibrils may be the cause. Alleles in the TREM2 gene have been associated with a three to five times higher risk of developing Alzheimer's disease. The genetic landscape is further complicated by the fact that environmental effects and genetic modifiers result in incomplete penetrance, meaning that carrying a risk gene does not guarantee the development of the disease.
The Caregiver's Burden
The human cost of Alzheimer's disease extends far beyond the patient, creating a profound burden on families and society that is often invisible to the public eye. As the disease progresses, affected people become increasingly reliant on others for assistance, often placing a heavy burden on caregivers. The pressures include social, psychological, physical, and economic elements. In the United States, informal family care is estimated to constitute nearly three-fourths of caregiving for people with Alzheimer's disease, costing approximately 18.5 billion hours of care annually. The financial strain is immense, with the yearly cost of caring for a person with dementia ranging from 28,078 to 56,022 dollars for formal medical care and 36,667 to 92,689 dollars for informal care provided by a relative. Dementia caregivers are subject to high rates of physical and mental disorders, with factors such as having an affected person at home and the caregiver being a spouse significantly increasing psychosocial problems. The disease is known for placing a great burden on caregivers, which includes social, psychological, physical, or economic aspects. Home care is usually preferred by both those people with Alzheimer's disease and their families, yet two-thirds of nursing home residents have dementias. The emotional toll is compounded by behavioral changes such as wandering, irritability, and resistance to caregiving, which create stress for relatives. The economic impact is projected to increase nearly ten-fold, reaching about 9.1 trillion dollars by 2050, making it one of the most costly diseases for societies worldwide.
The Race for a Cure
Despite the devastating impact of Alzheimer's disease, no treatments can stop or reverse its progression, though some may temporarily improve symptoms. The pharmaceutical landscape has seen significant developments, with two monoclonal antibodies, donanemab and lecanemab, approved to target amyloid beta, yet their role in treatment remains uncertain due to side effects, questions about efficacy, and cost. As of early August 2024, lecanemab was approved for sale in Japan, South Korea, China, Hong Kong, and Israel, although not by an advisory body of the European Union on July 26, citing side effects. The most common medications used to treat cognitive symptoms include four acetylcholinesterase inhibitors and memantine, but the benefit from their use is small. A 2016 review concluded that the quality of evidence from clinical trials on Ginkgo biloba has been insufficient to warrant its use. Atypical antipsychotics are modestly useful in reducing aggression and psychosis, but their advantages are offset by serious adverse effects, such as stroke, movement difficulties, or cognitive decline. The disease has spurred massive research efforts, with the US National Institutes of Health program for Alzheimer's research, the National Plan to Address Alzheimer's Disease, having a budget of 3.98 billion dollars for fiscal year 2026. In the European Union, the 2020 Horizon Europe research programme awarded over 570 million euros for dementia-related projects. As of 2025, 182 clinical trials were testing 138 drugs against multiple targets, reflecting the global commitment to finding a solution. Machine learning algorithms with electronic health records are also being studied as a way to predict Alzheimer's disease earlier, offering hope for future interventions.
The Final Silence
The progression of Alzheimer's disease inevitably leads to a state of complete dependence and the loss of all bodily functions. In the late stage, known as the severe stage, language is reduced to simple phrases or even single words, eventually leading to complete loss of speech. Despite the loss of verbal language abilities, people can often understand and return emotional signals. Extreme apathy and exhaustion are much more common symptoms than aggressiveness, and people with Alzheimer's disease will ultimately not be able to perform even the simplest tasks independently. Muscle mass and mobility deteriorate to the point where they are bedridden and unable to feed themselves. The cause of death is usually an external factor, such as infection of pressure ulcers or pneumonia, not the disease itself. In some cases, there is a paradoxical lucidity immediately before death, where there is an unexpected recovery of mental clarity. The average life expectancy following diagnosis is three to twelve years, with the normal life expectancy for 60 to 70 years old being 23 to 15 years, but for 90 years old it is 4.5 years. Following AD diagnosis, life expectancy ranges from 7 to 10 years for those in their 60s and early 70s, to only about 3 years or less for those in their 90s. As of 1995, fewer than 3% of people lived more than fourteen years after diagnosis. The disease features significantly associated with reduced survival include increased severity of cognitive impairment, decreased functional level, disturbances in the neurological examination, history of falls, malnutrition, dehydration, and weight loss. The final stage is characterized by a complete loss of independence, requiring full-time care and often hospice support until death.