The Key Causes of Age-Related Cognitive Impairment

This article is an excerpt from the Shortform book guide to "Keep Sharp" by Sanjay Gupta. Shortform has the world's best summaries and analyses of books you should be reading.

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What are the main factors implicated in age-related cognitive impairment? What are some things you can start doing today to slow down the rate of your cognitive decline?

In the last few decades, medical scientists and researchers have discovered a lot about cognitive decline, dementia, and Alzheimer’s, and their research suggests it’s probably due to many factors that differ for every person. If we want to take care of our brains and take measures to prevent them from declining, it will be helpful to know the suspected factors that lead to cognitive decline.

Keep reading to learn about the main causes of cognitive impairment.

Amyloid Plaque Buildup

An abundance of amyloid plaque in a person’s brain is a hallmark of Alzheimer’s disease. Amyloid is a protein that helps supply food to brain cells. For unknown reasons, these proteins sometimes become damaged and fold up into a sticky plaque that accumulates outside neurons. When plaques form, they prevent synapses from effectively communicating. If enough synapses are inhibited by amyloid plaques, the brain may lose many of its functions. 

Though amyloid plaque has long been connected to cognitive decline, it is still unknown if it is a cause, an effect, or both. Some autopsied brains have been filled with amyloid plaques, yet the patient never showed major signs of cognitive impairment. Also, dementia patients rarely show damage exclusively from amyloid plaques. There are many other ways a brain can be damaged that can lead to dementia.

Blood Flow

Gupta claims that blood flow abnormalities in the brain may also be an important factor in the development of Alzheimer’s disease. For one, amyloid plaques are seen more frequently in people with vascular diseases (diseases that affect the blood vessels). The brain requires a lot of nutrients and oxygen from our blood. Because of this, problems with the vascular system often lead to a dysfunctional brain. 

Because the brain is so important, it is protected by a barrier between the brain and the blood supply. This blood-brain barrier lets oxygen, glucose, and other nutrients in while keeping toxic substances out. Due to aging, infections, or vascular damage, gaps sometimes form in this blood barrier. When this happens, toxic substances from the blood can damage neurons and impair memory and other brain functions.

(Shortform note: Recent research provides further evidence that disrupted blood flow to the brain may lead to cognitive decline. Immune cells known as microglia are known to help protect the blood-brain barrier, but a new study suggests they also help regulate blood flow and maintain the brain’s blood vessels. Because of this, the loss of microglia could potentially lead to reduced blood flow and smaller capillaries in the brain. Scientists hope this discovery leads to more effective therapies or treatments for cognitive decline.)

Metabolic Disorders

Metabolic disorders include diabetes, obesity, and high blood pressure. They are extremely common in the West, and Gupta argues that these disorders are heavily associated with risk for dementia. Alzheimer’s disease often involves a problem with insulin, the hormone responsible for delivering glucose from the bloodstream to the cells.

Without insulin, the cells don’t get the glucose they need to produce energy, explains Gupta. In Type 2 diabetes, there is so much sugar in the blood, and so much insulin is pumped out by the pancreas in response, that the cells become desensitized to insulin. Some believe this insulin resistance plays a key role in cognitive decline, with studies suggesting those with Type 2 diabetes may be twice as likely to develop Alzheimer’s disease. In fact, Alzheimer’s is sometimes referred to as Type 3 diabetes. Not only this but high blood sugar, even without meeting diabetic conditions, has also been linked to cognitive decline. The higher your blood sugar, the more likely you are to develop dementia.

Chronic Inflammation

One of the major causes of cognitive impairment in neurodegenerative diseases such as Alzheimer’s is chronic inflammation. Inflammation is the body’s defense against infections, injuries, and toxins. It is meant to protect our bodies, but when it becomes chronic, it can be damaging. 

Research indicates that chronic inflammation both adds to and kick-starts the process of cognitive decline. For instance, some studies have linked dementia to higher levels of cytokines, which are released by cells during bouts of inflammation. Also, chronic inflammation in middle-aged adults has been linked to dementia later in life. Both of these findings suggest that chronic inflammation likely plays an important role in cognitive decline. 

The Key Causes of Age-Related Cognitive Impairment

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Darya Sinusoid

Darya’s love for reading started with fantasy novels (The LOTR trilogy is still her all-time-favorite). Growing up, however, she found herself transitioning to non-fiction, psychological, and self-help books. She has a degree in Psychology and a deep passion for the subject. She likes reading research-informed books that distill the workings of the human brain/mind/consciousness and thinking of ways to apply the insights to her own life. Some of her favorites include Thinking, Fast and Slow, How We Decide, and The Wisdom of the Enneagram.

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