Alzheimer’s disease (AD) is a progressive brain disorder that causes memory loss and other cognitive problems. It affects millions of people over age 65 throughout the world and nearly half a million people even younger.
There’s ongoing research into causes and risk factors for Alzheimer’s disease, and as we learn more about the risk factors of the disease and how Alzheimer’s disease develops, we may be able to prevent or slow the progression.
In today’s blog post, we are going to share with you the causes and risk factors for Alzheimer’s disease.
Causes of Alzheimer’s disease
The exact causes of Alzheimer’s disease aren’t fully understood. However, essentially, brain proteins fail to function normally, which disrupts the work of brain cells (neurons) and triggers a series of toxic events. Neurons are damaged, losing connection to each other, and eventually die.
Scientists believe that, for most people, Alzheimer’s disease is caused by a combination of genetic, lifestyle, and environmental factors that affect the brain over time.
In fewer than 1% of cases, Alzheimer’s is caused by specific genetic changes that virtually guarantee a person will develop the disease. These rare occurrences usually result in disease onset in middle age.
The damage most often starts in the region of the brain that controls memory, but the process begins years before the first symptoms. The loss of neurons spreads in a distinct pattern to other regions of the brain. By the late stage of the disease, the brain has shrunk significantly.
Researchers trying to understand the cause of Alzheimer’s disease are focused on the role of two proteins:
Plaques. Beta-amyloid is a fragment of a larger protein. When these fragments cluster together, they appear to have a toxic effect on neurons and to disrupt cell-to-cell communication. These clusters form larger deposits called amyloid plaques, which also include other cellular debris.
Tangles. Tau proteins play a part in a neuron’s internal support and transport system to carry nutrients and other essential materials. In Alzheimer’s disease, tau proteins change shape and organise themselves into structures called neurofibrillary tangles. The tangles disrupt the transport system and are toxic to cells.
Risk factors for Alzheimer’s disease
Age
Increasing age is the greatest known risk factor for Alzheimer’s disease. Alzheimer’s is not a part of normal aging, but as you grow older the likelihood of developing Alzheimer’s disease increases.
One study, for example, found that, each year, there were four new diagnoses per 1,000 people ages 65 to 74, 32 new diagnoses per 1,000 people ages 75 to 84, and 76 new diagnoses per 1,000 people aged 85 and older.
Family history and genetics
Your risk of developing Alzheimer’s is somewhat higher if a first-degree relative, such as a parent or sibling, has the disease. Most genetic mechanisms of Alzheimer’s among families remain largely unexplained, and the genetic factors are likely complex.
One better understood genetic factor is a form of the apolipoprotein E gene (APOE). A variation of the gene, APOE e4, increases the risk of Alzheimer’s disease. Approximately 25% to 30% of the population carries an APOE e4 allele, but not everyone with this variation of the gene develops the disease.
Scientists have identified rare changes (mutations) in three genes that virtually guarantee a person who inherits one of them will develop Alzheimer’s, but these mutations account for less than 1% of people with Alzheimer’s disease.
Down syndrome
Many people with Down syndrome develop Alzheimer’s disease. This is likely related to having three copies of chromosome 21 and subsequently three copies of the gene for the protein that leads to the creation of beta-amyloid.
Signs and symptoms of Alzheimer’s tend to appear 10 to 20 years earlier in people with Down syndrome than they do for the general population.
Head trauma
People who’ve had severe head trauma have a greater risk of Alzheimer’s disease. Several large studies found that, in people aged 50 years or older who had a traumatic brain injury (TBI), the risk of dementia and Alzheimer’s disease notably increased.
The risk increases in people with more-severe and multiple TBIs. Some studies indicate that the risk may be greatest within the first six months to two years after the TBI.
Mild cognitive impairment
Mild cognitive impairment (MCI) is a decline in memory or other thinking skills that is greater than normal for a person’s age, but the decline doesn’t prevent a person from functioning in social or work environments.
People who have MCI have a significant risk of developing dementia. When the primary MCI deficit is memory, the condition is more likely to progress to dementia due to Alzheimer’s disease.
A diagnosis of MCI encourages a greater focus on healthy lifestyle changes, developing strategies to make up for memory loss and scheduling regular doctor appointments to monitor symptoms.
Air pollution
Studies in animals have indicated that air pollutants can speed degeneration of the nervous system. Human studies have found that air pollution exposure, particularly from traffic exhaust and burning wood, is associated with greater dementia risk.
Excessive alcohol consumption
Drinking large amounts of alcohol has long been known to cause brain changes. Several large studies and reviews found that alcohol use disorders were linked to an increased risk of dementia, particularly early-onset dementia.
Poor sleep patterns
Research has shown that poor sleep patterns, such as difficulty falling asleep or staying asleep, are associated with an increased risk of Alzheimer’s disease.
Final thoughts
On the whole, Alzheimer’s disease can affect all aspects of a person’s life, as well as their family’s. There is currently no cure, but drugs and other treatments can help slow or ease the cognitive, emotional, and behavioral symptoms and improve the person’s quality of life.
If you have been diagnosed with Alzheimer’s disease, or you’re caring for someone with the condition, remember that advice and support is available to help you live well.