Although the exact cause or causes of Alzheimer’s disease (AD) are currently unknown, the disease is believed to be the result of a number of different factors. While some, like aging and genetics, cannot be controlled, others, like lifestyle choices, can affect the risk they present.
Age and gender
Age is one of the most significant risk factors associated with Alzheimer’s. The likelihood of developing this disease increases with age, and the majority of Alzheimer’s patients are older than 65.
Women over the age of 65 also have a higher risk of developing AD than men. The reason for this is not established, but it is thought to possibly be related to the reduction in estrogen that follows menopause.
Different genetic factors can increase the risk of developing Alzheimer’s.
Most cases of early-onset AD — when disease is found in people younger than 65 — are thought to be due to inherited mutations in particular genes, passed on from parent to child. This is also known as Familial Alzheimer’s disease (FAD). Research has currently identified at least three genes that could contribute to FAD: APP, PSEN1, and PSEN2, which can lead to the build-up of the toxic beta-amyloid peptides and brain cell death. Inheriting a single mutated copy of these genes can result in the development of early-onset Alzheimer’s.
Late-onset AD is most commonly associated with the apolipoprotein E (APOE) gene. However, there are a number of other genes that may also contribute to late-onset disease. Unlike with the early-onset genes, inheriting a mutated copy of this gene does not mean that the disease will develop, but it does make such an outcome more likely.
People with Down syndrome may also be predisposed to developing AD. Down syndrome is caused by inheriting an extra copy of chromosome 21, which contains the APP gene associated with early-onset disease.
A previous severe head injury can increase the risk of developing AD, due to damage to the brain.
Lifestyle and heart health
Evidence suggests that the risk of developing AD is influenced by the health of your heart. Many of the factors associated with cardiovascular disease can increase the risk of developing AD. These include smoking, obesity, diabetes, high blood pressure, and high cholesterol. The exact mechanism that may link cardiovascular disease to Alzheimer’s is not clear.
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