Sleep Is When Your Brain Cleans Itself
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I want to talk to you about sleep, and why it matters so much more than most people realize, both in the short term and over the course of your life.
Most of us think of sleep as simply rest, a time when the brain switches off. It’s the opposite. When you sleep, your brain goes into a rinsing and washing cycle. And once you understand how that cycle works, you start to treat your sleep very differently.
The Nightly Wash Cycle
Here is what actually happens inside your head at night.
With each beat of your heart, the arteries in your brain pulsate a little. That small pulsation pushes the fluid in your brain, the cerebrospinal fluid, or CSF, through the brain tissue. As it moves, it rinses away debris and waste. The now-dirty CSF is then collected and carried out of the brain.
This cleaning process is particularly active during deep sleep. It is, in a very real sense, your brain’s waste management system.
So what happens if you don’t get enough sleep? The rinsing doesn’t work properly. Debris and waste byproducts start to accumulate, and your neurons end up surrounded by dirt. Neurons sitting in their own waste are not happy neurons, and unhappy neurons do not function well.
Why I Think of New York City
Let me give you an analogy I come back to often.
Imagine New York City, and imagine that every night the garbage collection gets disrupted. For a day or two, you might not notice much. But after a couple of weeks, piles of garbage bags would start blocking the streets. Within a month or so, the whole city could grind to a halt.
The nightly collection and cleaning system is essential for a city to function. Your brain is no different. That nightly rinse is not a luxury. It is what keeps everything else working.
What Poor Sleep Does to You, Short Term and Long Term
In the short term, the effects of not sleeping enough are familiar to all of us. You feel tired and grumpy. You make mistakes at work. You become irritable. Your anxiety climbs, and your mood can sink toward depression.
The long-term consequences are far more serious, and they are the reason I take sleep so seriously with my patients.
Chronic poor sleep raises your risk of heart attacks and strokes. It can contribute to depression. And, most concerning of all, it raises your risk of Alzheimer’s disease.
I want to be precise about the timeline, because the details matter and I don’t want to frighten anyone unnecessarily. If you go through a difficult stretch and sleep fewer than six hours a night for a year or two, your brain can recover once you get your sleep back on track. Everything can be fine.
It is the long, uninterrupted years of poor sleep that cause real structural damage. A person who has lived with insomnia for twenty years may end up with a hippocampus, the memory center of the brain, that is roughly half the size it would otherwise have been.
Long-term insomnia is a major risk factor for Alzheimer’s disease. We know that for a fact.
How Do You Know If You’re Sleeping Well?
The simplest measure is how you feel when you wake up in the morning.
Beyond that, we now have plenty of tools. The rings and smartwatches many people wear can give you useful data about your nights. There are also questionnaires that can help you gauge how poor your sleep really is, such as the Pittsburgh Insomnia Rating Scale.
And if you have significant sleep problems, please see a specialist. In most cases, they will order a sleep study to understand what is actually going on.
The First Step Is Believing It Can Be Fixed
Let’s say you have insomnia. Some nights you get four hours, some nights five, and you’re frustrated. What should you do?
The first thing, and I mean this genuinely, is to adopt a positive attitude toward improving your sleep.
In my experience, too many patients tell me, “Well, everybody has sleep problems. I’m just like everybody else.” That is not true. Sleep problems are almost always treatable. But you have to make a real effort to treat your insomnia, and to make sure it is fully treated, not just partly managed. Sometimes that means addressing an underlying medical issue, like chronic pain, that is disrupting your sleep in the first place.
What Actually Works
There are some standard, well-established habits that genuinely help.
Don’t drink coffee or caffeinated products in the afternoon. Limit how much alcohol you drink at night. Wind down with a book or a warm shower. Avoid a large meal right before bed. You might try a small snack instead, like yogurt, a banana, or cherries. And some people find supplements like magnesium or melatonin helpful.
If those measures aren’t enough, the next step I recommend is cognitive behavioral therapy for insomnia. When you work with a therapist, they can go through your thought process and figure out what is keeping you up at night. Very often it is anxiety, and that anxiety has to be resolved before real sleep can return. I find this approach extremely helpful with my own patients. In fact, cognitive behavioral therapy is the most effective treatment for insomnia that I know of.
I leave sleeping medications as a last resort. Honestly, I don’t like them, and I very rarely prescribe them.
Your Brain Will Thank You
So here is what I want you to take away.
Sleep is essential for your brain health, both in the short term and across your whole life. If you have sleep problems, please take them seriously, because there are many things you can do to improve your sleep.
Do them. Your brain will thank you for it.
Dr. Majid Fotuhi is a Harvard- and Johns Hopkins-trained neurologist, bestselling author of The Invincible Brain (USA TODAY Bestseller), and one of the world’s leading experts on brain health and cognitive performance. He has spent more than three decades studying the brain’s capacity for growth and repair. To discover your brain health score and receive a personalized 10-page report, take the free Invincible Brain Assessment at invincible.drfotuhi.com.
Watch the full video on Dr. Fotuhi’s YouTube Channel.
What Lack of Sleep Does to Your Brain – Dr. Fotuhi
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Test Your Own Brain Health in Ten Questions
Over about 30 years of clinical research and teaching, mostly at Johns Hopkins and Harvard Medical School, I built a 12-week brain fitness program. I have used it with patients who have attention deficit disorder, with people recovering from persistent concussion symptoms, and with those dealing with age-related memory loss. Around 80% of our patients improved with it.
I am proud of the program, and I want to make it useful to people who will never set foot in my clinic. So I want to give you one of the first tools we use with every patient: the brain health score. It takes a few minutes; you can do it at home, and you can repeat it week after week to watch your progress.
How the score works
There are ten questions. You rate yourself from 1 to 5 on each, which gives you a total out of 50.
A score of 40 or higher means you are in good shape, and your brain is set up to stay healthy now and in the years ahead. A score down around 15 or 20 means there is real work to do. The good news is that this number moves quickly once you start paying attention to it. Most people can raise it within 12 weeks.
One thing before you begin. You are the judge of your own answers, and you will be the same judge next week and the week after. So it does not matter much whether a given answer is a 3 or a 4. What matters is that you use the same standard each time, so the trend you see is honest.
Here are the ten questions.
1. Exercise
The goal is about three hours a week. If you hit that, give yourself a 5. If you are a couch potato, that is a 1. Anywhere in between earns a middle score.
2. Diet
If you eat a Mediterranean-style diet every day, give yourself a 5. If you eat junk food daily and rarely touch fruits and vegetables, that is a 1. Score 2 to 4 for everything in between.
3. Portion size
If your portions are reasonable and you eat about three times a day instead of grazing five or six times, give yourself a 5. If you eat huge portions and keep going until you are stuffed, that is a 1. The aim is to eat enough that you feel satisfied, without feeling full.
4. Omega-3
Omega-3 fatty acids are one of the most important ingredients for building a stronger brain. This is the one supplement I recommend to everyone, and I take it myself and give it to my own family. I suggest an omega-3 that includes DHA and EPA, at around 1000 mg a day. Take it daily and give yourself a 5. Never take it, and that is a 1. A day or two a week is a 2, and so on up the scale.
5. Stress
Your state of mind shapes how healthy your brain is. Here is something I find fascinating: your brain determines your state of mind, and then your state of mind turns around and affects the health of your brain. You have more control over that loop than you might think. If you stay calm and relaxed through the normal stress of a day, give yourself a 5. If every small thing sets you off, that is a 1. If you are generally steady but still get thrown by a missed bus or a hard moment at work, give yourself a 3, and score around there based on how easily you get stressed.
6. Meditation
Meditation raises BDNF in the brain, increases blood flow, and lowers cortisol. It is one of the best things you can do for yourself. I recommend 10 to 15 minutes a day. If a seated meditation is hard for you, do a simple breathing exercise instead: breathe in for a count of seven, hold for seven, breathe out for seven. Do it daily and give yourself a 5. Never do it, and that is a 1.
7. Attitude
You decide how you look at the world. If you are optimistic and generally expect things to work out, give yourself a 5. If you assume nothing will work and worry over every detail, that is a 1. Your daily outlook has a real effect on how healthy your brain is today and how healthy it will be later.
8. Sleep
Seven to eight hours a night is one of the most important things for your brain. If you sleep well most nights, give yourself a 5. If you struggle to fall asleep or stay asleep, that is a 1. Sleep is a big topic on its own, so if it is a real concern for you, read my separate article on how to improve it.
9. Organization
If you start the day by writing down the three things that must get done, finish them, and handle more as time allows, you are in charge of your day, and that is a 5. If you are always running late and always behind, that is a 1. Staying organized keeps you from feeling overwhelmed, and that protects your brain.
10. Mental challenge
Your brain is a use-it-or-lose-it organ. If you do brain exercises or take on things that genuinely challenge your mind every day, give yourself a 5. If you avoid anything that requires hard thinking, that is a 1.
What your number means
Add up your ten answers.
If you are at 40 or higher, you are in good shape. You do not need to overhaul anything. Keep nudging individual scores up when you can.
If you are below 40, this is your starting line, and it is a useful one. Repeat the same ten questions every week for the next 12 weeks, and set a goal to reach 40 or higher. Watch which numbers are dragging the total down, and put your attention there first. Most people find the climb easier than they expected, because small, steady changes in sleep, diet, movement, and mindset add up fast.
The reason I like this score is that it turns a vague worry about your brain into something you can see and act on. You stop guessing about whether you are doing enough, and you start working from a number that tells you where you stand.
Frequently asked questions
What is a good brain health score?
How often should I score myself?
How long does it take to improve my score?
Does it matter if I score an answer a 3 instead of a 4?
What omega-3 dose do you recommend?
I do not enjoy sitting meditation, Is there an alternative?
My lowest score is sleep, Where do I start?
Can I really change my brain at my age?
What is the lowest possible score, and what does it mean?
Do I need any special equipment or tests to score myself?
Which of the ten should I fix first?
Can I improve more than one area at once?
Is a score of 40 a reason to stop trying?
How is this different from the free assessment on your website?
Is this a diagnosis?
Dr. Majid Fotuhi is a Harvard- and Johns Hopkins-trained neurologist, bestselling author of The Invincible Brain (USA TODAY Bestseller), and one of the world’s leading experts on brain health and cognitive performance. He has spent more than three decades studying the brain’s capacity for growth and repair. To discover your brain health score and receive a personalized 10-page report, take the free Invincible Brain Assessment at invincible.drfotuhi.com.
📺 Watch the full video on Dr. Fotuhi’s YouTube Channel.
Test your Brain Power in 7 Minutes
How HIV Affects the Brain, Even When the Virus Is Controlled
Most people know that HIV attacks the immune system. Fewer know that HIV can also affect the brain. And here is the part that surprises people most. Even when HIV is very well controlled with medication, some people still have trouble with memory, attention, or thinking speed.
I saw this for myself many years ago, during my neurology residency at Johns Hopkins.
The Patient I Never Forgot
A man in his 40s had been admitted to the hospital because of dizziness. When I sat down to talk with him, I noticed something beyond why he was there. He was awake and alert, but his answers came unusually slowly. He had trouble staying focused on our conversation, and he could not remember the names of his own medications. He was not confused or sleepy. His thinking had simply slowed down.
Then I learned that he had HIV, and that it was very well controlled. His viral load was almost zero, and his immune system was quite strong. So I kept asking myself the same question. Why was his thinking so slow? That question stayed with me for years.
ART Changed Everything, but Not for the Brain Alone
Antiretroviral therapy (ART) has been a lifesaving treatment for people with HIV. It turned a disease that was once fatal into one that many people live with for decades, and controlling the virus is essential.
When it comes to the brain, though, ART is not always the whole story. Even when the virus is under excellent control, some people living with HIV still experience problems with memory, attention, concentration, or slow thinking. Doctors sometimes call this HAND, which stands for HIV-associated neurocognitive disorder.
There is an important point to make here, and it changes how we should respond. Not every memory problem in a person living with HIV is caused by the virus.
The Brain Has Many Things Working on It
Think of your brain as a complicated system, with many things capable of putting stress on it. HIV can be one of them. So can aging, high blood pressure, diabetes, and poor sleep. So can depression, stress, alcohol, head injury, and other medical conditions.
When someone with HIV has trouble with memory or thinking, there are often several of these causes working together. That points to a useful idea. Instead of focusing on one cause, it often makes more sense to care for the brain from several directions at the same time.
Where This Idea Came From
This way of thinking grew out of my own clinical work. For years I treated people who came to me with memory loss and other cognitive difficulties, and I kept noticing the same thing. Rarely did anyone have only one problem. A single person might have poor sleep, high stress, low physical fitness, and a poor diet, along with difficulties in attention and memory, all at the same time.
In 2016, I published a study of a 12-week Brain Fitness Program in 127 older adults with mild cognitive impairment. The program combined cognitive training, biofeedback, and brain coaching built around physical fitness, diet, and stress reduction. After 12 weeks, 84% of the participants showed a statistically significant improvement on cognitive testing. We also looked at brain MRIs in a smaller group who had quantitative scans before and after. Half of them showed either no further shrinkage of the hippocampus or an actual increase in its volume. Those were encouraging findings, and I went on to develop the program for patients with concussion and ADHD as well, with similar results.
That experience led me to the idea at the center of my work. Brain health does not come from doing one thing. It comes from caring for the brain from several directions at once. Over the years, I organized this into what I call the five pillars of brain health: exercise, sleep, nutrition, managing stress with a positive mindset, and brain training through continued learning and challenge. Picture the five as members of a team. You do not have to be perfect at any single one. The goal is to work on all of them together.
A Landmark Study, and Its Limit
This idea was not unique to me. Researchers around the world were asking similar questions. One of the most important studies was a European clinical trial called FINGER, conducted in Finland with more than 1,200 older adults who had an increased risk of cognitive decline. Rather than asking people to do just one thing, the researchers combined several approaches at once: exercise, healthy eating, brain training, and more. After two years, the people in the multi-domain program had better overall cognitive performance than those who received general health advice.
FINGER mattered because it showed that protecting the brain may require more than one strategy at a time. But there is an important limit for our purposes. FINGER did not study people living with HIV, so we cannot assume the same approach will work the same way in this group. It has to be tested.
The Gap I Found in the Research
While preparing a lecture I recently gave at Johns Hopkins on this topic, I looked at the research with a simple question in mind. What happens when we use lifestyle changes to protect thinking in people living with HIV?
The answer surprised me. A 2026 systematic review, commissioned by the World Health Organization and published in The Lancet Healthy Longevity, screened almost 6,000 scientific papers. Only five met the strict criteria for the review, and all five tested medications. Not one tested a lifestyle program built on exercise, healthy eating, better sleep, stress management, and brain training.
That is a real gap in the science. We know a great deal about how to control HIV. We know a great deal about the value of lifestyle for brain health in the general population. We know much less about whether a comprehensive brain-health program can help people living with HIV who have cognitive problems. That is the question worth answering now.
Back to the Man at Johns Hopkins
So let me return to the patient I met all those years ago.
I cannot tell you exactly why his thinking was so slow. HIV may have played a part. Other things may have too. Most likely several factors were involved at once. But if I saw him again today, here is what I would say to him. Controlling the virus is essential. Let us also take care of your brain. Let us work on your exercise, look more carefully at your sleep, talk about your nutrition, manage your stress, and keep your brain active.
The brain is not a passive victim of disease. It is an organ that responds to how we live. We have made remarkable progress in treating HIV. I think it is time to ask a new question. How can we help people living with HIV keep their brains healthy for the rest of their lives?
We do not have all the answers yet. But we know enough to start asking, and to start looking. For now, my recommendation is simple. Control the virus. Take care of your body, your sleep, your mind, and your brain, because your brain is your biggest asset, and it is worth protecting, with or without HIV.
Dr. Majid Fotuhi is a Harvard- and Johns Hopkins-trained neurologist, bestselling author of The Invincible Brain (USA TODAY Bestseller), and one of the world’s leading experts on brain health and cognitive performance. He has spent more than three decades studying the brain’s capacity for growth and repair. To discover your brain health score and receive a personalized 10-page report, take the free Invincible Brain Assessment at invincible.drfotuhi.com.
📺 Watch the full video on Dr. Fotuhi’s YouTube Channel.
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Why I Stopped Accepting "It's Just Alzheimer's"
I want to tell you about myself, and about how I came to practice medicine the way I do.
I graduated from Harvard Medical School in 1997, and by then I was already deeply interested in Alzheimer’s disease. When I began my neurology residency at Johns Hopkins, I chose to focus on age-related cognitive decline. The more patients I saw, the more one thing troubled me. People who arrived carrying a diagnosis of Alzheimer’s usually had a whole mix of different problems feeding their decline, and many of those problems could be treated.
So I began writing review articles making a case for a different approach. Rather than labeling everyone with memory trouble as having Alzheimer’s and sending them off to a nursing home, we should treat the medical conditions pulling them down, and work directly on improving their brain function through diet, sleep, and mental challenge. I kept writing about this after I became an assistant professor of neurology at Johns Hopkins. Then one day I realized I needed to stop writing about it and start doing it. In 2012, I opened my own neurology practice and built a program I called the Brain Fitness Program.
Carol
One of my very first patients was Carol, a woman in her 70s with serious cognitive decline.
Her sister was the one who brought her in, and she had a clear purpose. She wanted me to confirm Carol’s Alzheimer’s diagnosis so she could obtain power of attorney, sell Carol’s house, and pay for a nursing home. She told me Carol just sat in front of the television all day and did nothing at all.
I asked her to wait a moment. Because when I looked at Carol, I saw a long list of conditions that could be treated. She had high blood pressure, diabetes, obesity, sleep apnea, and depression, and she was taking multiple medications for pain.
So we went to work. We reduced her pain medications, treated her depression, addressed her back problems, and worked on her diet. She began coming to our brain center twice a week to work with our brain coaches, who are trained to encourage patients to do more, to eat better, and to challenge their brains.
Little by little, Carol came to life. She started walking five minutes a day, then ten. She stayed with the program, and by the time she finished she was a different woman, full of energy, as though she had woken up. I finally got to meet the real Carol, and she turned out to be warm and funny and a pleasure to talk to.
Carol was not a lucky exception. I ran this program for many older patients with mild cognitive impairment or early-stage Alzheimer’s, and 84% of them showed significant, measurable improvement on their cognitive tests. I published those results in the Journal of Prevention of Alzheimer’s Disease.
Lisa
After that, I began offering the same program to younger people dealing with memory and thinking problems. One of them was Lisa.
Lisa was a schoolteacher in her 50s, worn down by both her work and her personal life. She was going through a divorce. She could not keep up at school. Her knees hurt, she had gained 20 pounds, she could not sleep, and she had headaches. She looked at me and said, “I’m a mess.” She was sure she was developing Alzheimer’s disease.
Her evaluation told a very different story. At her first visit, I had her fill out what I call spider-grams, diagrams built from 35 questions that map out exactly where a person is struggling, whether that is memory, attention, concentration, or processing speed, each rated from 0 to 10. Lisa scored as significantly affected across most of those areas.
Then I did formal cognitive testing to see which domains were truly weak. Her memory performance came back at the 5th percentile for her age. Her executive function was also struggling, though her processing speed was still fairly good. Her blood tests showed that her vitamin D was low and her B12 was low. None of that is Alzheimer’s disease, and all of it can be addressed.
When Lisa started the program, she worked with our brain coaches twice a week, 90 minutes at a time. They helped her exercise more, sleep better, take better care of herself, and receive brain training. After six weeks, her results were remarkable. Her memory had improved from the 5th percentile to the 35th, and her processing speed had climbed to about the 99th.
She was thrilled. I remember her telling me that in a way it was a good thing she had gotten so bad, because now she finally had a reason to take care of herself. She became more engaged with her students. By the time she finished the program she was a new person, full of energy and optimism. Her cognitive testing and her spider-grams, which had been mostly in the red when she started, were mostly in the green by the end.
The Pattern Behind the Book
Carol and Lisa were not isolated successes. I went on to see 223 other patients with memory loss or persistent cognitive symptoms, and they improved too. 80% of them showed objective improvement on their cognitive tests.
I want to be clear about what that means, because it is the heart of everything I do. These patients did not simply feel better, sleep better, and report being happier, although they did. Their objective cognitive testing showed real gains in attention, concentration, executive function, and mental speed.
This is the foundation of my book, The Invincible Brain. The lesson I learned from Carol, from Lisa, and from hundreds of others is one I want you to carry with you. A frightening label is not the end of the story. Underneath it there are almost always treatable causes, and the brain has a real capacity to recover when you give it the chance.
Dr. Majid Fotuhi is a Harvard- and Johns Hopkins-trained neurologist, bestselling author of The Invincible Brain (USA TODAY Bestseller), and one of the world’s leading experts on brain health and cognitive performance. He has spent more than three decades studying the brain’s capacity for growth and repair. To discover your brain health score and receive a personalized 10-page report, take the free Invincible Brain Assessment at invincible.drfotuhi.com.
📺 Watch the full video on Dr. Fotuhi’s YouTube Channel.
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