Alzheimer’s disease is a neurodegenerative disease. In a person with Alzheimer's disease, cognitive decline and functional impairment are much more severe than can be explained by just the person’s age.
Alzheimer’s disease is a form of dementia, a general term for neurological conditions that impair cognitive function to the point of interfering with daily life. It is the most common type of dementia (representing around 60 to 80% of cases) and involves a progressive degeneration of brain cells. Alzheimer’s disease is currently the fifth-leading cause of death for people older than 65 in the United States.
One of the first symptoms of Alzheimer’s disease is memory loss, especially short-term memory loss of events and experiences. Other common symptoms of early disease include worsening verbal memory, impaired problem solving, lack of motivation, depression, and sleep disorders. In later stages of disease, memory and cognition continue to worsen, causing disability and deterioration of motor function, in addition to significant personality changes, behavioral changes, and psychosis.
A conclusive diagnosis of Alzheimer’s disease requires examining the brain during autopsy, meaning it can’t be definitively diagnosed in someone while they are alive. Still, doctors can make a possible or probable diagnosis based on signs and symptoms, performance on neurocognitive tests (which assess things like memory, concentration, and reasoning), and the exclusion of other causes. More recently developed diagnostic methods using positron-emission tomography (PET) scans can identify amyloid accumulation (an indicator of Alzheimer’s disease) with a high level of accuracy, but this testing remains limited and is used primarily for research purposes at this time.
No medical treatments have been clearly shown to stop or slow the underlying disease process in Alzheimer’s disease. However, some medication can improve symptoms. Acetylcholinesterase inhibitors can improve cognitive function in people with Alzheimer’s disease, although the effect is generally small.
In 2020, a medication called aducanumab was approved by the FDA for the treatment of Alzheimer’s disease based on its effects on amyloid plaques, but whether aducanumab improves clinical outcomes (e.g., cognitive function) remains to be established.
A few dietary patterns are associated with a lower risk of Alzheimer’s disease. This protective relationship is perhaps most commonly found with a Mediterranean diet. Among individual components of the diet, a higher intake of saturated fat and sugar has been linked to a higher risk of Alzheimer’s disease, while a higher intake of fish has been linked to a lower risk. Unfortunately, these findings derive from observational studies, meaning cause and effect can’t be determined with certainty, and there are almost no randomized clinical trials (RCTs) looking at the effect of diet on the incidence of Alzheimer’s disease.
RCTs have assessed a number of supplements’ effects on established Alzheimer’s disease. This includes omega-3s, B vitamins (usually folic acid, vitamin b6, and vitamin-b12), vitamin-d, vitamin-e, ginkgo-biloba, L-alpha glycerylphosphorylcholine (alpha-GPC), lionsmane mushroom, ginseng, saffron, and sodium oligomannate. For the most part, these supplements have only conflicting or limited evidence in favor of their use.
Exercise and physical activity have been shown to benefit physical function, functional independence, and neuropsychiatric symptoms in people with Alzheimer’s disease; aerobic exercise specifically improved cognitive function.
Several trials have investigated the effect of a keto diet and ketogenic supplements (e.g., medium-chain triglycerides) on Alzheimer’s disease and observed improvements — sometimes, but not always — in quality of life and cognitive function.
Music therapy centers around listening to music to stimulate the brain. Some research suggests the intervention can improve mood and cognitive function among people who have Alzheimer’s disease.
The underlying cause of Alzheimer’s is not known for certain, but several explanations have been proposed. The most common theory is that Alzheimer’s disease is the result of neurodegeneration and a buildup of misfolded proteins called amyloid plaques and tau tangles, which are almost always found in the brains of people with the disease. However, this “amyloid hypothesis” has been criticized. Regardless of the cause of Alzheimer’s disease, various modifiable and nonmodifiable factors, including aging, depression, diabetes, and genetics, have been linked to a higher risk of the disease.