Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder that presents with cognitive decline and behavioral disturbances. It is characterized, in its typical form, by memory loss 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 seems 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, caused by point mutations, but they account for less than 1% of the total. Among the most important risk factors are:

  • Age: it is the most important risk factor, with a significant increase in cases after 65 years.
  • Family history: the risk of developing Alzheimer's increases if you have a first-degree relative affected. The APOE4 gene is the most studied.
  • Down syndrome: Many people affected by Down syndrome develop Alzheimer's 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 injuries.
  • Cardiovascular diseases.

Symptoms

The damage begins years before symptoms start to appear. However, early diagnosis is important for good therapeutic management. The most common signs and symptoms of Alzheimer's-type dementia are:

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

Prevention

At present, mechanisms for the total prevention of Alzheimer's disease are unknown. However, there is solid evidence that several factors related to a healthy lifestyle can reduce the risk of developing this disease and other types of dementia.

Studies carried out so far suggest that regular exercise, a healthy diet, and maintaining brain activity through lifelong learning have a protective effect against this pathology.

Additionally, controlling blood pressure, blood glucose levels, and avoiding alcohol and tobacco consumption also appear to have a risk-reducing effect for developing 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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