Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder that causes cognitive impairment and behavioral disorders. It is characterized, in its typical form, by a loss of memory and other mental abilities that worsen as different areas of the brain atrophy. It is the most common form of dementia, affecting more than 32 million people worldwide.

The exact causes of Alzheimer's disease are unknown, although research has shown the presence of neuronal damage, with loss of connections and cell death.

The development of AD appears to be triggered by a combination of genetic and environmental factors that affect the brain over time. There are also cases of familial Alzheimer's disease, caused by point mutations, but they account for less than 1% of the total. Among the most important risk factors, the following stand out:

  • Age: this is the most important risk factor, with a significant increase in cases after the age of 65.
  • Family history: the risk of developing Alzheimer's disease increases if there is a first-degree relative affected. The APOE4 gene is the most studied.
  • Down syndrome. Many people affected by Down syndrome develop Alzheimer's disease in adulthood, probably due to the presence of three copies of chromosome 21.
  • The incidence is slightly higher in women than in men.
  • Presence of mild cognitive impairment.
  • Head trauma.
  • Cardiovascular disease.

Symptoms

The damage begins years before the onset of symptoms. However, early diagnosis is important for a good therapeutic approach. The most common signs and symptoms of dementia of Alzheimer's type are:

  • Memory impairment, especially short-term.
  • Difficulty concentrating, planning or solving problems.
  • Inability to draw or copy figures.
  • Problems completing routine tasks.
  • Visual or spatial difficulties that may lead those affected to put things in the wrong places or even get lost.
  • Language problems.
  • Changes in mood, behavior and personality.
  • In more advanced stages, motor function and regulation of our internal organs may be affected.

Prevention

Mechanisms that allow total prevention of Alzheimer's disease are not known at this time. However, there is strong evidence that several factors related to a healthy lifestyle can reduce the risk of Alzheimer's disease and other types of dementia.

Studies conducted so far suggest that regular exercise, healthy eating and maintenance of brain activity through lifelong learning have a protective effect against Alzheimer's disease.

In addition, controlling blood pressure and blood glucose levels and avoiding alcohol and tobacco consumption also seem to have the effect of reducing the risk of dementia.

Number of observed variants

13.5 million variants

Number of risk loci

38 loci

Genes analyzed

ABCA7 ACE ADAM10 ADAMTS1 APH1B APOC1 APOC4 APOE B4GALT3 BIN1 CASS4 CCDC6 CD2AP CD33 CLNK CLU CR1 ECHDC3 EPHA1 EXOC3L2 FERMT2 INPP5D KAT8 MS4A6E NECTIN2 OARD1 PICALM PILRA PTK2B SCIMP SLC24A4 SORL1 SPI1 SPRED2 TRPM7 TSPAN14 USP6NL

Bibliography

Schwartzentruber J, Cooper S, Liu JZ, et al. Genome-wide meta-analysis, fine-mapping and integrative prioritization implicate new Alzheimer's disease risk genes. Nature Genetics. 2021 Mar;53(3):392-402.

National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Health Sciences Policy; Committee on Preventing Dementia and Cognitive Impairment.Downey A et al. National Academies Press (US); 2017.

Alzheimer´s Association [April 2022]

World Health Organization (WHO) [April 2022]

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