Can we stop our brains from ageing? Yes, says leading neurologist Dr Dale Bredesen in a new book which sets out the key lifestyle changes you need to make to prevent cognitive decline. Today, in the final part of his definitive guide, he reveals the importance of deep sleep and the tweaks to your diet that will boost your memory and mental agility.
A good night’s sleep washes far more than our troubles away. As we snooze, our brains perform a complex clean-up operation, filtering out the waste products and toxic proteins associated with cognitive decline that build up throughout the day. It does this via the glymphatic system, which is the brain’s own waste disposal system. How efficiently this nocturnal wash cycle runs each night directly impacts the maintenance and protection of your cognitive abilities.
Even though all this takes place while we slumber, there’s plenty we can do to assist with this process, starting with ensuring we get enough shut-eye in the first place.
One of the fundamental goals anyone looking to have an ageless brain should be striving for is to get between seven and eight-and-a-half hours of sleep each night.
The good news is, around two-thirds of us achieve that.
A good night’s sleep washes far more than our troubles away. As we snooze, our brains perform a complex clean-up operation, filtering out the waste products and toxic proteins associated with cognitive decline that build up throughout the day
But even if you include yourself in that statistic, don’t assume that automatically means you are getting exactly the sleep you need.
Because emerging research suggests it’s during deep sleep when the gunk-cleaning magic truly happens. This stage of sleep is a particularly powerful glymphatic activator.
The human brain reaches this state of rejuvenating sleep multiple times in a night – and often early on in the night, which is why the old rhyme ‘early to bed, early to rise’ really is a good idea.
As we sleep, we move through variations in the electrical signals in our brains – with multiple descents into deep sleep and multiple ascents into REM sleep (the state most associated with dreaming, characterised by rapid eye movement). REM tends to occur later in the night and early in the morning.
Clearly total sleep time matters – and not simply because the glymphatic filter is on for longer, but also because it gets to run at its maximum power more times over the course of a night.
So, one of the best things we can do to help the glymphatic clearance pathway do its work is to optimise our slumber with the express intention of reaching a sufficient dose of deep sleep each night, which will automatically boost the amount of REM and deep sleep you’ll get.
The goals I encourage patients to aim for (which you can keep a check on via relatively inexpensive sleep monitoring devices such as smartwatches and bio-tracking rings) include between seven and eight-and-a-half hours sleep a night, REM sleep of at least one-and-a-half hours and deep sleep of at least an hour.
Remember what you do during the day can have a big impact on the quality of your sleep at the end of it. For example, the night before I wrote this, I slept quite poorly.
It was almost certainly because I didn’t get everything done during the day that I wanted to, so instead of winding down as my bedtime approached, I was still in my study working.
This meant I got a late start on my sleep and this resulted in a shorter window of opportunity to achieve the sort of sleep I need.
When I woke, I learned from my smartwatch that I missed both my deep sleep and REM targets, owing to less total sleep time and fewer complete cycles through these important stages.
To achieve more restorative sleep, I recommend making the following changes…
Switch off screens
TV sets, laptops, and smartphones attack sleep as they are designed to keep our brains passively engaged
We could all improve our chances of getting to sleep earlier by changing our relationships with screens. Yet this is something people seem most determined to resist.
TV sets, laptops, and smartphones attack sleep from three angles.
First, they are designed to keep our brains passively engaged – to give us just enough stimulation to keep us quietly enthralled without putting us to sleep.
Second, the content, especially that which is loud, emotionally arousing or thought-provoking, can stimulate feelings of stress, anxiety, or interest at the exact time your nervous system needs to be winding down.
Third, the light from these screens, especially if on the blue spectrum, has been shown to suppress production of melatonin, the hormone typically released as the sun goes down to make us feel sleepy. Eliminate all screens from your bedroom (or at the least use blue-blocking filters) and stop using screen-based devices at least an hour before you intend to sleep.
Leading neurologist Dr Dale Bredesen sets out the key lifestyle changes you need to make to prevent cognitive decline
Dim lights before bed
Human beings have evolved to respond physically and mentally to the rising and setting of the sun.
Today though, our brains must contend with fake suns – electric lights – that can be flicked on and off at will. Artificial lights wreak havoc on our circadian rhythms, chiefly by preventing sleep because of how they allow us to stay awake long after darkness falls.
Also, long-lasting LED lights now in general use are worse for sleep disruption than the old incandescent bulbs because they emit much more high-energy blue light.
Try dimming house lights in the evenings, or begin turning them off one by one over the course of a few hours as you get closer to bedtime, which will help you fall asleep more quickly.
Stick to the same bedtimes and don’t have lie-ins
Adhering to set bedtimes (no later than midnight, although a few hours before is better) and wake up times can be a sleep game-changer.
That’s because we are hard-wired to respond physiologically to a 24-hour circadian cycle – in which the sunrise and sunset might come at different times throughout a year, but change very little from one day to the next. People find this hard, me included. Of all the principles I recommend to prevent brain aging, this is the one I struggle with most.
It can be especially tempting to sleep in at weekends or during holidays but this only makes consistent sleep more difficult on adjoining days.
A 10pm bedtime and 6am wake-up each day (give or take one hour on either side), best creates the seven-to-nine-hour window that most people need to achieve enough cycles of deep sleep to let the glymphatic system do its brain-cleaning work.
Investigate loud snoring
Sleep apnea, which is the repeated stopping and starting of breathing throughout the night, impacts about one in five of us but is often undiagnosed.
It’s a common underlying condition we see in patients with cognitive decline. Its effects are generally attributed to the intermittent hypoxia – oxygen deprivation – that people with this condition experience.
Obvious symptoms include loud snoring, waking during the night gasping for breath, waking in the morning with a dry mouth, headaches, daytime sleepiness and trouble focusing during the day.
The most common treatment is the continuous positive airway pressure machine which helps maintain open airways during sleep, thus reducing or eliminating the episodes of hypoxia and sleep disruption.
Oral devices that hold a user’s tongue in place or slide their jaws forward to keep their airways open can also be highly effective in earlier stages, as can losing weight, which also reduces systemic inflammation. Far better to intervene early, when a mouth device might well be enough, than to wait until a major intervention like surgery to widen the upper airway is needed.
Exercise in the morning
Exercise is a powerful tool in your sleep-boosting arsenal – it makes you tired while reducing stress and anxiety, which leads to more restful sleep. But timingis key.
That’s because exercise also raises adrenaline, the hormone that signals our bodies to increase blood circulation, bring in more oxygen and more quickly metabolise carbohydrates to prepare our muscles for exertion. None of which you want to be happening in the lead up to bedtime.
I tell my patients that morning or afternoon exercise is best. A noontime run (especially in lieu of a large lunch) is brilliant.
But within three or four hours of bedtime, the advantages of physical activity are likely outweighed by the detriments of spiked adrenaline and the resultant trouble getting to sleep or staying asleep.
Fast before bed
No matter how healthy your diet, eating right before bedtime will impact the quality of your sleep.
Not only can a full stomach at bedtime lead to discomfort and heartburn, it can also shift the brain’s focus away from producing hormones that aid sleep, and towards providing those that aid digestion.
As a result insulin is high, which leads to restlessness and an inability to reach the multiple cycles of REM and deep sleep – those all-important sleep cycles our brains need to wash away the insults of the day.
You can counter that by strictly following a three-hour window of fasting before bed.
It’s not easy.
Eating earlier in the day, even if you’re not hungry, can help. As can ensuring your evening meal is especially satisfying and includes plenty of fibre, which digests slowly in the gut.
If the hunger pangs continue, an ultra low-calorie snack – some edamame beans, a few florets of broccoli or cauliflower, a carrot or celery stick, a few nuts or a ‘fat bomb’ like a shot of extra virgin olive oil – can help without negatively impacting your sleep.
The power of meditation
In dozens of trials with thousands of participants, meditation has been demonstrated to alleviate stress and anxiety, reduce depression, improve blood pressure, increase neuroplasticity and even mitigate physical pain
If the glymphatic system is our brain’s washing machine, then stress is the cause of much of the dirt it needs to wash away.
Since we all have trouble sleeping at times, which is when that wash cycle takes place, anything we do to address and reduce stress throughout the day will help to ensure everything comes out clean.
The data on meditation’s potential benefits for cognition are compelling. In dozens of trials with thousands of participants, it has been demonstrated to alleviate stress and anxiety, reduce depression, improve blood pressure, increase neuroplasticity and even mitigate physical pain.
It might also help control our appetites, and, unlike exercise, can be done in the hours before sleep without adversely affecting sleep quality.
Many patients have found meditative success through transcendental meditation, a practice of detachment often guided by the repetition of a mantra or a sound.
Others swear by tai chi, the Chinese martial art known for its slow, intentional movements, often called ‘moving meditation’. Forest bathing, a Japanese practice which simply involves spending time being calm and quiet in nature, is also gaining popularity.
Incorporating whatever form of meditation works for you will help to support good brain health.
Eat for brain health
When it comes to optimising cognition and protecting your brain, I firmly believe a plant-rich (not plant-only), mildly ketogenic diet (which is low sugar, so the body targets stored body fat for energy) is the most powerful place to start.
The benefits of a diet composed primarily of vegetables, fruits, nuts, seeds and legumes for general health have been robustly proven. But it is particularly valuable for brain health. To that end, I would suggest you aim to get at least 80 per cent of your calories from plants.
The mind boosters to add to your shopping basket
These foods are rich in nutrients that promote long-term brain function.
B Vitamins
B vitamins appear to be cognitively protective and support energy production.
B1 (thiamine) can be found in beans, fish, lentils, peas and sunflower seeds; B2 (riboflavin) is prevalent in almonds, eggs, milk, organ meats, spinach and yogurt; B9 (folate) comes from eggs, dark leafy vegetables, peanuts and liver; B12 (cobalamin) can be found in clams, liver, trout, salmon and yogurt.
Vitamin C
This vitamin is among the best-studied nutrients in association with cognitive function and the research is very clear – it plays a major role in the process of brain cell development and the protection of nerves.
It also has a major role in many other processes that impact brain health and thus cognitive performance.
High-C foods include broccoli, brussels sprouts, currants, bell peppers and strawberries.
Vitamin D
It’s long been known that vitamin D deficiency is associated with a greater risk of dementia and Alzheimer’s disease.
Even if you’re getting plenty of sun, you may nonetheless suffer from vitamin D deficiency if you are a carrier of any of the dozens of gene variants that have been shown to make it harder to absorb and retain this nutrient.
It’s easy to ‘supplement the sun’ with eggs, salmon, tuna and shiitake mushrooms, or D-fortified dairy and plant-milk products.
Omega-3
Omega-3 fatty acids have long been associated with early brain development, which is why pregnant women and women who are breastfeeding are often advised by their doctors to eat extra omega-3-rich foods or take omega-3 supplements.
These polyunsaturated fats have also long been known to exert anti-inflammatory and antioxidative effects.
These are some of the reasons why they have been shown to improve cognition in older people.
(It is important to note here that plant-rich is not synonymous with ‘vegan’ or ‘vegetarian’. Vegan diets can be brain-healthy when they are primarily composed of fresh fruits, vegetables, nuts, seeds and legumes. But so can vegetarian diets, pescatarian diets and other kinds of omnivorous diets. What matters is that your brain-sustaining nutrient needs are being met.)
Plants have direct and profound effects on our brains, in part because of the antioxidants that are particularly prevalent in fruits and vegetables.
Antioxidants are compounds in foods that seek and destroy free radicals, the unstable molecules that are a natural outcome of cell metabolism but can damage other molecules, such as the lipids – important fatty compounds supporting brain function. While only 15 per cent of a body is composed of lipids, about 50 per cent of the brain is made up of these fatty compounds.
That’s a big part of the reason why the brain is especially vulnerable to cell and tissue damage, and has much to do with why antioxidants appear to play a substantial role in protecting, maintaining and improving brain function.
An antioxidant-rich diet is baked into just about any plant-rich way of eating. Artichokes, beans, berries, broccoli, carrots, greens and nuts are particularly antioxidant-rich foods.
Plants are also a major source of polyphenols, which are naturally occurring chemical compounds that have consistently been shown to lead to enhancement of cognitive health, including alertness, attention, focus, learning, and memory.
Boost your intake by making a conscious effort to eat a rainbow of plants. This might include white radishes, yellow peaches, red raspberries, purple onions and green avocados one day.
The next it might be white cauliflower, yellow bell peppers, red strawberries, purple cabbage and green brussels sprouts.
This sort of strategy will, over time, make it hard to miss out on the myriad polyphenols available.
A plant-rich diet also ensures you get enough fibre, both soluble and insoluble, which reduces diabetes risk, improves insulin sensitivity, improves cholesterol levels, supports gut health and helps to reduce toxic burden. Aim for 30 grams of fibre each day.
Choose the right protein
Low-protein diets have been associated with greater longevity but they have also been connected to increased dementia risk – the central nervous system can’t operate without the amino acids that protein provides.
The vast majority of us eat meat – it remains the easiest and least expensive source for the complete set of essential amino acids humans need to survive.
Grass-fed beef contains less saturated fat, more healthy omega-3 fats, is leaner and thus has more protein than grain-fed. Free range chicken contains more protein, iron and zinc than factory-farmed. When it comes to fish, we need to be careful to avoid eating those that will increase our exposure to mercury, which is toxic to the brain.
Tuna is a high-mercury fish. But smaller fish such as salmon, mackerel, anchovies, sardines and herring (collectively known as SMASH fish) are easy to digest, contain brain-healthy fats that are quickly absorbed into our bodies, are high in many essential vitamins and minerals, and are low in mercury.
I also strongly recommend wild-caught fish over those that are farmed and are thus stuck swimming in their own pollutants.
For most people, a daily protein intake of about one gram per kilogram of bodyweight will support brain health and prevent sarcopenia, the age-related progressive loss of muscle mass and strength.
Feed your gut
Increasing your intake of fibre to at least 30 grams a day (through wholefoods, vegetables and eating whole fruits) is essential to achieving a long brainspan, not least because of how it will help feed your gut microbiome.
Fibre is prebiotic, meaning it acts as food for the bacteria that live in our guts which play an important role in brain health. The gut produces many of the same neurotransmitters as the brain – it’s sometimes called the second brain.
Probiotics are also important to brain health. These are foods like kimchi, sauerkraut, sour pickles, miso soup, kombucha and yogurt that contain live microorganisms, thus helping to maintain the so-called good bacteria in our guts.
- Adapted from The Ageless Brain, by Dr Dale Bredesen (Vermilion, £22), to be published March 27.
- © Dale Bredesen 2025. To order a copy for £18.70 (offer valid to 05/04/25; UK P&P free on orders over £25) go to www.mailshop.co.uk/books or call 020 3176 2937.
