Alzheimer’s Disease
Alzheimer’s disease is a progressive neurodegenerative condition and the most common cause of dementia in older adults. It is characterized by gradual loss of memory, thinking skills, and the ability to carry out everyday activities. The disease is driven by changes in the brain—including the accumulation of amyloid plaques and tau tangles, loss of nerve cells, and shrinkage (atrophy) of specific brain regions. Imaging plays an important supportive role in diagnosis by showing characteristic patterns of brain atrophy and helping to exclude other causes of cognitive decline.
What is it?
Alzheimer’s disease is a progressive disorder of the brain that gradually damages and destroys nerve cells (neurons), leading to a slow but steady decline in memory, thinking, and the ability to function independently. It is the most common cause of dementia—an umbrella term for significant cognitive decline that interferes with daily life. The disease is named after Dr. Alois Alzheimer, who first described its characteristic brain changes in the early 1900s.
The biological hallmarks of Alzheimer’s disease include the accumulation of two abnormal proteins in the brain: amyloid-beta, which forms plaques between nerve cells, and tau, which forms tangles inside neurons. These changes are thought to disrupt communication between nerve cells, trigger inflammation, and ultimately lead to nerve cell death. Specific brain regions—particularly the medial temporal lobes, including the hippocampus, which is essential for forming new memories—are typically affected early. As the disease progresses, atrophy spreads to involve broader areas of the cerebral cortex.
The cause of Alzheimer’s disease is not fully understood and likely involves a combination of genetic, vascular, lifestyle, and other factors. Increasing age is the strongest risk factor. A family history of Alzheimer’s, certain genetic variants (such as the APOE ε4 allele), and rare inherited mutations (in early-onset familial forms) can increase risk. Cardiovascular risk factors such as high blood pressure, diabetes, high cholesterol, obesity, smoking, and physical inactivity, as well as untreated hearing loss, depression, and social isolation, have also been associated with higher risk.
Symptoms typically develop gradually over years. Early on, patients and families may notice difficulty remembering recent conversations, appointments, or events, repeating questions, misplacing items, and trouble finding the right words. As the disease progresses, additional changes can include difficulty with planning, organization, and problem-solving; getting lost in familiar places; trouble managing finances; changes in mood, judgment, or personality; and difficulty with everyday tasks such as cooking or driving. In later stages, more profound memory loss, communication difficulty, behavioral changes, and dependence on others for daily care occur. Importantly, occasional forgetfulness alone is not Alzheimer’s; ongoing, progressive changes that interfere with daily life are the concern.
MRI of the brain is widely used in the evaluation of suspected Alzheimer’s disease and other dementias. While imaging is not used in isolation to diagnose Alzheimer’s, it can show patterns of atrophy—particularly in the hippocampi and other medial temporal lobe structures—that support the clinical diagnosis. MRI also helps exclude other treatable or relevant causes of cognitive symptoms, such as strokes, vascular disease, hydrocephalus, tumors, or chronic blood collections. In selected cases, PET imaging can detect amyloid plaques (amyloid PET) or tau tangles (tau PET) directly, while FDG-PET shows characteristic patterns of reduced metabolism in affected brain regions. Cerebrospinal fluid and, increasingly, blood-based biomarkers are also used in specialized settings.
Important to Know
Alzheimer’s disease is currently a chronic condition without a cure, but a great deal can be done to support patients and families. Several medications—including cholinesterase inhibitors, memantine, and newer anti-amyloid therapies—may help temporarily improve symptoms or, in some patients, modify the disease course. Treatment of associated medical conditions, particularly cardiovascular risk factors, is important and may help slow decline. Lifestyle measures such as regular physical activity, cognitive engagement, social interaction, healthy diet, good sleep, treatment of hearing loss, and management of mood disorders are increasingly recognized as important parts of care.
Care typically involves a multidisciplinary approach that may include primary care, neurology, geriatrics, neuropsychology, psychiatry, occupational and physical therapy, social work, and supportive community resources. Practical planning—around safety in the home, driving, finances, legal documents, and future care preferences—is an important part of ongoing care and is best addressed early, while the person living with Alzheimer’s can participate in decisions.
Caregivers play a central role in the care of people with Alzheimer’s disease and may experience significant emotional, physical, and financial strain. Support for caregivers through education, respite, support groups, and community resources is essential.
Red flag symptoms include sudden or rapid worsening of cognition or behavior, severe confusion, new hallucinations, falls, sudden severe headache, weakness, vision changes, difficulty speaking, or signs of stroke. These warrant prompt medical evaluation, as they may indicate a different or additional condition that needs urgent attention.