The Sleep–Brain Connection: Are Sleep and Dementia Linked

By Catherine Gorman  |  Nutritional Therapist & Health Writer, Naturally Healthy News

Published: July 2025  |  Last reviewed: July 2026

We all know a bad night’s sleep can leave us feeling tired and groggy. But did you know that poor sleep may have long-term consequences for your brain health? Increasing evidence suggests a strong link between sleep and dementia, with people who experience sleep disorders facing a significantly higher risk of developing neurodegenerative conditions later in life. [1]

How Poor Sleep May Increase Dementia Risk

A major international study analysing health records from over a million people found people with sleep disorders face a significantly higher risk of developing diseases like Alzheimer’s, Parkinson’s and vascular dementia. But what is even more worrying is that this risk persists for up to 15 years after a sleep disorder diagnosis. [1] [2]

What the Research Says About Sleep and Dementia

In one of the largest studies to date, researchers at the UK Dementia Research Institute at Cardiff University and the NIH Center for Alzheimer’s and Related Dementias in the USA analysed data from biobanks in Finland, Wales and the UK. [1]

They looked at individuals diagnosed with sleep disorders such as circadian rhythm disruptions, narcolepsy, sleep apnoea, excessive daytime sleepiness, sleepwalking, night terrors and generalised insomnia.

Using statistical analysis, the researchers mapped the relationships between various neurodegenerative diseases and sleep disorders, and investigated whether disrupted sleep is an early sign of neurodegeneration or something that makes dementia more likely later in life. [1]

The findings, published in npj Dementia, suggested that people diagnosed with sleep disorders were up to twice as likely to develop a neurodegenerative condition within the following 15 years, with those experiencing multiple or recurring sleep disorders at even higher risk. [1] [2]

Genetics, Sleep Disorders and Dementia Risk: A Surprising Twist

One of the most surprising findings was that sleep disorders and genetics appear to act independently of one another. Even in people with a low genetic risk for Alzheimer’s or Parkinson’s, having a sleep disorder still raised their chances of developing the disease. [1]

Which Sleep Disorders Raise Dementia Risk Most?

The study looked across several types of sleep disorder, including circadian rhythm disruptions, generalised insomnia and non-organic sleep disorders such as nightmares. Across the conditions studied, elevated risk of Alzheimer’s disease, vascular dementia and Parkinson’s disease showed up anywhere from 5 to 15 years after a sleep disorder diagnosis, with the strength of the association varying by condition. [1] [2]

Are Sleep Disorders a Cause or Early Warning Sign of Dementia?

One major question remains: Do sleep disorders cause neurodegeneration, or are they just early signs of it? This study suggests the answer may be both. [1]

There’s growing evidence that disrupted sleep may impair the brain’s ability to clear out waste products from the brain, which is a hallmark of Alzheimer’s disease. It also affects brain cell repair and communication. However, once degeneration begins, it creates a vicious cycle that further disrupts sleep. Conditions like insomnia, sleep apnoea, narcolepsy, night terrors and circadian rhythm disruptions could be early red flags for diseases of the ageing brain.

How to Protect Your Brain Through Better Sleep

Chronic insomnia affects around one in ten adults in Europe, and many more experience occasional sleep difficulties. [4] If you are one of them, there are several steps you can take to regain control.

Nutrition That Supports Restorative Sleep

Certain foods contain nutrients that may help enhance sleep by supporting the production of key sleep neurotransmitters, such as GABA and melatonin.

• Tryptophan-Rich Foods: The amino acid tryptophan helps support the production of serotonin and melatonin. Foods rich in tryptophan include turkey, chicken, eggs, dairy products, nuts, seeds, and bananas.
• Melatonin-Boosting Foods: Naturally present in certain foods, melatonin is found in cherries, grapes, tomatoes and oats.
• Magnesium-Rich Foods: Well-known as a natural relaxant, magnesium can have a calming effect on the mind and also helps relax muscles. Foods high in magnesium include leafy greens, almonds, cashews, pumpkin seeds and whole grains.
• Complex Carbohydrates: Whole grains, sweet potatoes, and quinoa can help regulate blood sugar levels, which in turn supports serotonin production.

Aim to leave at least a three-hour gap between your evening meal and bedtime. If you do need a small snack before bed, try an oatcake with kiwi fruit.

Build a Sleep Routine That Supports Brain Health

A regular sleep schedule reinforces your circadian rhythm, making it easier to fall asleep and wake up at the same time every day.

• Set a consistent bedtime and wake-up time, even on weekends.
• Establish a relaxing pre-sleep routine, such as reading a book, taking a warm bath, or practising deep breathing exercises.
• Limit your exposure to blue light in the hours leading up to bedtime. Try using blue light-blocking glasses or enabling night mode on your devices when watching television or using screens before bed.

Optimise Your Sleep Environment

Your sleep environment plays a crucial role in sleep quality.

• Keep the bedroom dark and cool, as darkness is a signal for the body to produce melatonin, while a cooler temperature promotes better sleep.
• Minimise noise, and if outside sounds are keeping you awake, consider a white noise machine or earplugs to help block out disruptive sounds.

Managing Stress for Better Sleep

High stress and anxiety levels can interfere with sleep. Relaxation techniques can make a huge difference.

• Mindfulness and meditation can help calm the mind and prepare you for sleep.
• Deep breathing exercises activate the parasympathetic nervous system, helping reduce stress.
• Journaling or writing down thoughts before bed can help clear the mind.
• Yoga and stretching can relieve muscle tension and promote relaxation.
• Adding magnesium flakes to your evening bath, or applying it topically as a lotion or oil, can be a great way to help switch off before bed.

Can Supplements Help Improve Sleep Quality?

If you consistently experience difficulties getting a good night’s sleep, supplements may be beneficial.

• Magnesium Glycinate: This highly absorbable and well-tolerated form of magnesium has been shown in a 2025 randomised, placebo-controlled trial to modestly improve insomnia symptoms and sleep quality. [5]
• L-Tryptophan: This amino acid plays a key role in the production of serotonin and melatonin, neurotransmitters that regulate the sleep-wake cycle. [3]
• L-Theanine: Found naturally in green tea, theanine helps increase GABA levels and alpha brain waves, both associated with a relaxed mental state. A 2025 systematic review and meta-analysis found L-theanine can improve several measures of sleep quality. [6]

Frequently Asked Questions

Can improving my sleep reduce my risk of dementia?

There is no proof yet that improving sleep prevents dementia, but researchers believe that treating sleep disorders early could help reduce the cumulative strain on the brain over time. Since the same study found sleep-related risk to be largely independent of genetic risk, addressing sleep is a meaningful, modifiable factor regardless of family history.

Which sleep disorders are most linked to dementia risk?

The Cardiff and NIH study looked at circadian rhythm disruptions, narcolepsy, sleep apnoea, excessive daytime sleepiness, sleepwalking, night terrors and generalised insomnia, and found each was associated with a higher risk of at least one neurodegenerative condition. People experiencing multiple or recurring sleep disorders showed the highest risk.

Does having a sleep disorder mean I will develop dementia?

No. A sleep disorder increases statistical risk across large populations, but it does not mean any individual will go on to develop dementia. Many factors influence dementia risk, and sleep is just one modifiable piece of a much larger picture.

When should I speak to a doctor about sleep problems?

If you regularly struggle to fall or stay asleep, feel excessively tired during the day, or notice signs like loud snoring or breathing pauses during sleep, it is worth speaking to your GP. Persistent sleep problems are treatable, and addressing them early may benefit both your daily wellbeing and your long-term brain health.

Final Thoughts: Sleep Well to Age Well

This research offers a compelling reminder that our nights may shape our future. Identifying and managing sleep disorders early and making meaningful improvements to our sleep patterns may help reduce the risk of sleep and dementia being so closely linked. Prioritising good sleep today could be one of the most powerful tools we have to protect long-term brain health. You can read our full guide to diet and lifestyle tips for better sleep for more ways to get started.

References

[1] npj Dementia — Sleep disturbances as risk factors for neurodegeneration later in life (2025): https://www.nature.com/articles/s44400-025-00008-0

[2] UK Dementia Research Institute — Sleep problems could double risk of dementia in later life (2025): https://www.ukdri.ac.uk/news-and-events/sleep-problems-could-double-risk-dementia-later-life

[3] PMC7230229 — Effects of Diet on Sleep: A Narrative Review (Nutrients, 2020): https://pmc.ncbi.nlm.nih.gov/articles/PMC7230229/

[4] PMC10001099 — Chronic Insomnia Disorder across Europe: Expert Opinion on Challenges and Opportunities (2023): https://pmc.ncbi.nlm.nih.gov/articles/PMC10001099/

[5] PubMed 40918053 — Magnesium Bisglycinate Supplementation in Healthy Adults Reporting Poor Sleep: A Randomized, Placebo-Controlled Trial (2025): https://pubmed.ncbi.nlm.nih.gov/40918053/

[6] PubMed 40056718 — The Effects of L-Theanine Consumption on Sleep Outcomes: A Systematic Review and Meta-Analysis (2025): https://pubmed.ncbi.nlm.nih.gov/40056718/

Disclaimer: The information in this article is intended for general informational purposes only and does not constitute medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your GP or a qualified healthcare provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read here.

 

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