We know that the brain contains tens of billions of neurons. These neurons build connections and communicate, forming our thoughts, perceptions, and memories. But is this number of neurons set? Can we do anything to increase the number of neurons in the brain? Or at least, can we stop the brain from shrinking?
Yes, the brain shrinks. Depending on your age and lifestyle, it is likely shrinking right now! If you want to keep your brain healthy, keep reading. You will learn how, why, and where the brain shrinks most.
Which Parts of the Brain Shrink the Most in Later Life?
Aging is a very normal cause of brain shrinkage. This shrinkage typically happens in the frontal lobe and other areas responsible for high-level thinking. Grey matter in areas like the hippocampus may shrink as a result of depression, diabetes, or other medical disorders.
Why Does the Brain Shrink?
Some causes of brain shrinkage include:
- Aging
- Anxiety
- Autoimmune diseases
- Brain damage
- Depression
- Sleep disorders
- Lower levels of Vitamin B12
- Alcohol and drug abuse
- Prolonged liver dysfunction
- Alzheimer’s disease
- Stroke
- Chronic stress
- Diabetes
- Lack of exercise
- Long COVID
- Other medical infections (cerebral palsy, infections, etc.)
That is a lot of causes that might lead to brain shrinkage. I want to point out the first one in particular. Brain shrinkage may be due to an unhealthy lifestyle, but not always. In fact, aging causes the brain to shrink by about 5% each decade after you turn 40. That number bumps up even higher after you turn 70. This is completely normal.
Shrinkage may be the result of neurons dying, but it may also be the result of the neurons becoming more densely packed. Blood flow, for example, also decreases in the brain as you age. Not all signs of shrinkage indicate that you are going into cognitive decline, but at some point in life, you may go through that experience.
Where Does The Brain Shrinkage Begin?
The brain contains white matter and grey matter. White matter consists of myelinated, or protected, axons. Grey matter consists of cells, dendrites, and synapses. Brain shrinkage is more likely to affect grey matter before white matter, and this can have a variety of effects on a person’s abilities. Shrinkage of grey matter could have effects on muscle control, vision and hearing, memory, or emotions.
Hippocampus
The areas of the brain where shrinkage occurs may depend on why the brain is shrinking. If the brain is shrinking due to depression in young adulthood, the hippocampus may be the first area to shrink. The hippocampus is generally associated with learning and memory. The severity of the shrinkage depends on the severity of the depression and how prolonged the person experiences major depressive disorder. In some cases, a person may not be able to grow the cells from their hippocampus back and will have a harder time learning and storing memories due to their battle with mental health.
Frontal Cortex
Heavy alcohol consumption, age, and certain disorders may result in the frontal cortex shrinking. The frontal cortex, interestingly enough, is the last part of the brain to develop. It plays a role in rational thinking, logic, and decision-making. If you have ever noticed a loved one experiencing wild temper tantrums or acting like a child due to dementia, it is because they have sustained damage to the frontal cortex.
Frontotemporal disorders may affect the frontal and temporal areas of the brain. Symptoms may range from difficulty with motor control to difficulty communicating. In 2022, legendary actor Bruce Willis retired after being diagnosed with aphasia. Aphasia is an example of a frontotemporal disorder. This disorder specifically inhibits people from being able to communicate.
Although a small percentage of people in their 30s may experience shrinkage of the frontal lobes, that number continues to jump with every decade. A study showed that while only 8% of 30-year-olds had any sign of shrunken frontal lobes, 20% of 60-year-olds had signs of moderate to severe shrinkage. Almost double that number had any sign of shrinkage at all.
Forgetfulness or a frequent loss of temper may not just be a sign of aging. They could be signs that the frontal lobe is shrinking, and action may need to be taken to slow down that shrinkage!
Other Areas of the Brain
None of this means that other parts of the brain are immune from brain shrinkage. Multiple sclerosis is an autoimmune disease that causes damage and shrinkage to the myelin sheath surrounding the axons of the brain. Rather than damaging the grey matter, this disease directly affects white matter. Researchers are not sure why this happens, beyond the body’s immune system reading the myelin sheath as a “threat.”
Recent studies show that alcohol can also shrink white matter as well as grey matter in specific parts of the brain.
Another way that alcohol can harm the brain is by harming the liver. Yes, harm to the liver can cause additional harm to brain cells. A lot of these causes are interconnected, which is why scientists are not always able to pin down one single cause of brain shrinkage or damage. A person may drink alcohol because they are depressed. Does the shrinkage in their brain result from alcohol use, depression, or something else entirely? How does our age take into account all of these other factors? If we can replace or regrow neurons, how do we know the real rate of shrinkage?
Can Brain Shrinkage Be Reversed?
Don’t worry. If you have pulled a few all-nighters or binge drank with friends, your brain isn’t doomed to shrink. Brain shrinkage can be reversed, although maybe not at the rate at which your brain is rapidly growing. Your brain may stop shrinking or new connections and neurons may be made. This happens even as you age.
How can you keep your brain healthy? Here are just a few suggestions:
- Get your daily recommended amount of B vitamins each day (likely, you will have to take vitamins or buy supplements to reach that amount!)
- Get your daily recommended amount of Omega-3 fatty acids (supplements like cod liver oil or other types of fish oil likely include Omega-3s)
- Exercise your body regularly
- Reach out to a mental health professional to treat depression, anxiety, PTSD, etc.
- Use your brain! Do puzzles, take a dance class, learn a new instrument, or learn a new language! Gardening, reading, or any new hobbies can help to slow down shrinkage in your brain.
Even if our brains will not grow in size tremendously as we age, we can continue to change their structure. Neuroplasticity, or brain plasticity, occurs when we encounter new experiences and make new connections in the brain. Have you ever heard the phrase “use it or lose it?” This also applies to the brain. Use it, or it will shrink!
