Can lack of sleep lead to Alzheimer’s? 

Introduction

Figures from 2019 published by the Alzheimer’s Society state that 1 in every 14 of the population aged 65 years and over is living with dementia. ¹ Alzheimer’s disease is the most common form of dementia, accounting for between 50–75% of all cases.

People living with Alzheimer’s often experience changes to their sleep patterns and develop sleep issues. These problems result in disturbed sleep for the person with Alzheimer’s and in many instances this also impacts on the sleep of their caregivers.

If current trends continue, it’s predicted that by 2025, there will be a million people in the UK living with dementia. Add to this figure the caregivers and it becomes a vast amount of people potentially experiencing poor sleep.

Disrupted sleep can occur years before developing the clinical signs more commonly associated with Alzheimer’s, such as memory problems and behavioural changes.

However, we don’t yet know if poor sleep causes Alzheimer’s or if the changes in the brain that are associated with Alzheimer’s cause poor sleep. It’s a chicken and egg conundrum.

In this article we’ve summarised the current scientific knowledge around Alzheimer’s disease and sleep and we discuss a host of ways to promote better sleep for people with Alzheimer’s and their caregivers.

What happens to sleep architecture in Alzheimer’s disease?

During healthy sleep, you pass through four sleep stages: N1, N2, N3, and rapid eye movement (REM) sleep in what are known as ‘sleep cycles’. Sleep progresses cyclically from N1 through to REM and in adults, each sleep cycle lasts around 90 to 110 minutes.

REM is the phase of sleep in which most dreaming occurs. Brain activity increases but most muscles are in a state of paralysis, so you don’t act out your dreams. The eyes can be seen moving under the eyelids, which is why it’s called rapid eye movement sleep.

N1, N2 and N3 are termed non-REM (NREM) sleep and, during these stages, the brain waves on the EEG recording are typically slow, the breathing and heart rate are slow and regular, blood pressure is low and the sleeper is relatively still.

The first couple of sleep cycles have long periods of uninterrupted stage N3, which is also known as slow wave sleep (SWS), with relatively short REM periods. Later in the night, the REM periods lengthen and SWS is mostly absent.

So the first third of the night is predominantly SWS sleep and the later part of the night is spent in the lighter stages: N2 and REM sleep.

As we get older, our sleep naturally becomes lighter and more easily disrupted. This is because the amount of deep, stage N3 sleep naturally decreases with age. When you’re in your 20s and 30s about 25%, or about 2-3 hours, of your night is spent in deep sleep.

By the time we get to our 60s and 70s we may only get, at most, half an hour of deep sleep each night. ² N3 sleep plays a crucial role in the process of laying down new memories as well as learning new tasks.

Differences in the rate of loss of N3 sleep between individuals could, to some degree, explain why people experience different levels of cognitive decline as they age. This loss might also play a role in the development of Alzheimer’s.

In people with Alzheimer’s, night-time sleep is known to be made up of more lighter sleep, with significant losses to SWS and REM sleep, compared to that seen in normal, healthy sleep. ³

It also appears that as the disease progresses, the time spent in REM sleep tends to decrease. Additionally, a decrease in SWS in Alzheimer’s has also been shown to correlate with cognitive decline. What this means is that as slow wave sleep becomes less, so mental function also decreases.

How Alzheimer’s affects the brain

To understand the interplay between sleep and Alzheimer’s, it’s useful to understand a little of what happens in the brain with Alzheimer’s. Our brains are made up of many different types of cells but the most well known are neurones.

These cells transmit and receive electrical and chemical signals which allow them to convey messages throughout the brain and body. It’s neurones that allow us to move, think, experience emotions and interact with the world around us.

In Alzheimer’s there’s a gradual destruction of these cells. Initially, the disease attacks neurones responsible for memory ³, which is why confusion and forgetfulness are usually the first symptoms observed in Alzheimer’s.

Later in the progression, neurones in other regions all over the brain are targeted and the person will lose their ability to live and function independently.

This loss of neurones is caused by a build up of certain proteins that form in plaques and tangles within the brain. If we think of the neurones as a giant highway connecting all of our brain and body together, then these protein build-ups act like road blocks and potholes.

They disrupt and ultimately stop information being sent from A to B within the body. The two main proteins so far identified in these processes are called beta-amyloid and tau.

Beta-amyloid forms plaques between neurones and tau forms tangles inside the neurones. These abnormal accumulations of proteins ultimately lead to brain cells dying. Once the neurones are gone, that part of the information highway is lost.

We don’t fully understand everything behind their abnormal accumulation and Alzheimer’s but we do know that their presence is a defining feature of the disease. Other proteins are also involved in this process and more remain to be identified.

But how does all of this relate to sleep? It’s been shown that over the course of the day, many proteins and molecules accumulate in the brain. These proteins are then removed from the brain at night, during our deep sleep.

The deep cleaning functions of deep sleep

During our deepest sleep, the brain and body are hard at work carrying out some major cellular housekeeping, removing toxic products that have built up over the day. When we don’t get enough deep sleep, the amount of deep cleaning time is reduced as a consequence.

Evidence that deep sleep becomes significantly reduced in Alzheimer’s — and knowing that there’s protein accumulation in the brains of people with the disease — has led to some excellent studies looking at how deep sleep affects these protein levels.

One particularly interesting study recently shone some light onto this process by using imaging techniques to look at the brains of healthy volunteers as they slept. The researchers found that during deep sleep, our brains are flushed by waves of cerebrospinal fluid (CSF). You can see a short video clip of this here.

These waves appear every 20 seconds during deep sleep and they essentially wash over the brain, cleaning away toxic proteins such as tau and beta-amyloid. ⁴ So in people experiencing a reduced amount of deep sleep, levels of these cleansing waves would also be reduced.

Research has shown that sleep disturbance causes both levels of beta-amyloids and tau to rise acutely in the brain and CSF. ^5 6

In one study, beta-amyloid increased about 5% in the participants’ brains after losing a single night of sleep.⁵ The researchers additionally found that changes occured in regions that are known to be affected early in Alzheimer’s.

They also noted that study participants with larger increases in beta-amyloid reported worse mood after sleep deprivation too, which backs up research from other groups.

Another study looked at how disrupting deep sleep would affect levels of tau and beta-amyloid in the CSF of volunteers.

They found that reducing deep sleep specifically increased levels of beta-amyloid, whereas poor sleep quality over several days was responsible for increasing levels of tau.⁶

The more deep sleep the person got, the more beta-amyloid was cleared from the brain and, interestingly, the less beta-amyloid was subsequently made by the brain.

This could be an important detail: adequate deep sleep may be key to how much beta-amyloid is made, not just now much is cleaned away during sleep.

Another group looked at the longer-term effects of poor sleep: they measured at beta-amyloid levels in people over 70, with no memory problems, taking part in a study looking at their levels of deep sleep. ⁷

Levels of beta-amyloid were regularly measured over the course of six years and compared to the participant’s deep sleep levels.

They found that people who got less deep sleep had more beta-amyloid. The researchers hope this information will help to identify people’s future risk of developing Alzheimer’s.

The crux of these studies is that without adequate deep sleep, it appears that the brain is not able to efficiently clear itself of toxic proteins, specifically those key to Alzheimer’s.

What these studies can’t tell us is whether or not this lack of deep sleep is the true cause of Alzheimer’s. It may be one of many causes, it may contribute somewhat or it may occur in tandem with the development of Alzheimer’s.

We’ll have a look next at what’s known about how poor sleep, disturbed sleep and lack of sleep are related to the risk of Alzheimer’s.

Can poor sleep cause Alzheimer’s?

We know that cognitive impairment, such as that seen in Alzheimer’s, leads to poor sleep. It’s also clear that poor sleep can itself lead to cognitive impairment.

So it seems like there could be a vicious circle where poor sleep → cognitive impairment → poor sleep. Herein lies the classic chicken and egg scenario, in that we don’t know which comes first:

• poor sleep → cognitive impairment, or
• cognitive impairment → poor sleep.

As we mentioned earlier, our sleep naturally becomes lighter and more easily disrupted as we age due to decreases in our deep sleep.

Strikingly, nearly half of older people report sleep problems and for people with cognitive decline this figure rises to as high as 70%. ⁸

Studies have suggested that getting inadequate sleep as we age can increase the risk of developing dementia in our old age. ^{3 9101112131415}

One such study followed the sleep of nearly 8,000 people aged over 50 in the UK over the course of 25 years. ⁹ They found that people who reported an average of six or less hours of sleep per night had a 30% higher likelihood of developing dementia, when compared to those sleeping for seven or more hours.

An even longer study looked at the sleep of around 1,500 men aged over 50 and found that those with sleep disturbance had a 51% increased risk of developing Alzheimer’s. ¹⁰

It’s not just sleep length that seems to be important here either. Disrupted sleep has also been found to increase the risk of dementia and Alzheimer’s disease. ¹¹¹²

In this study of people with no reported dementia, the participants wore actigraphs (research grade sleep trackers) on their wrists which tracked their sleep over the course of 10 days.

Their cognitive function was assessed at the end of the 10 days by specific memory, language and understanding tests.The results showed that people with higher sleep fragmentation had a significantly higher risk of developing Alzheimer’s disease.

Additionally, research has shown that insomnia can increase the likelihood of developing Alzheimer’s ¹³ and even levels of daytime napping in elderly patients can predict risk. ¹¹

So it’s clear that poor sleep can have a marked effects on how well the brain functions and can increase risks of developing dementia.

While all of these studies highlight links between Alzheimer’s and sleep disturbances, they can’t tell us which came first or if they even arise at the same time. A good summary by Lim and colleagues ¹⁴ sums up what we know about the development of Alzheimer’s disease:

A confluence of genetic, behavioral and environmental factors contributes to the risk of Alzheimer disease (AD) in old age.

So it’s probable that poor sleep is just one piece in a very complex puzzle and although we can’t say for certain that it causes Alzheimer’s, we do know that there’s a wealth of evidence linking poor sleep and Alzheimer’s.

One thing remains very clear: good sleep is key to good health so prioritising sleep should be something we all do.

We know that sleep disorders too often go untreated and many people try to just live with their poor sleep or worry that a sleep problem is not something easy to treat. In fact, the majority of sleep problems respond well to intervention.

Sleepstation’s sleep improvement programme consistently helps people fall asleep faster, stay asleep longer and get better quality sleep so if you’re experiencing sleep problems or feel like poor sleep is affecting your health or memory, take our short sleep quiz and see how we can help.

Sleep disorders commonly associated with Alzheimer’s

Estimates suggest that up to half of all people with Alzheimer’s experience sleep problems. Sleep in Alzheimer’s tends to be fragmented and often distributed across a 24-hour period rather than following the regular rhythms of sleeping during the night and waking with the light.

Many people with Alzheimer’s sleep excessively during the day and struggle to sleep during the night-time hours. It’s thought that this dysregulated sleep may result from damage to areas of the brain that control the body clock.

Our body clock refers to an internal system within our body that controls numerous physical processes related to wake and sleep. It’s well established that the body clock is dysregulated in Alzheimer’s disease.

Studies have shown that for people with Alzheimer’s, neuronal loss and tangles of tau protein can be observed within the part of the brain responsible for controlling the body clock. ¹⁶

This part of the brain also regulates release of melatonin, the hormone that signals to our brains that it’s time to sleep.

In people with Alzheimer’s, melatonin levels are known to be reduced and, in more advanced Alzheimer’s, the timing of melatonin levels rising and falling has been shown to be disturbed.¹⁷

People with Alzheimer’s also commonly experience sleep disorders including:

• insomnia
• sleep apnoea
• restless legs syndrome
• REM sleep behaviour disorder
• sleep problems arising from mood disorders.

Insomnia in Alzheimer’s disease seems to result from damage to the area of the brain involved in regulating the body clock, discussed above, which causes the person to struggle to sleep at night.

Obstructive sleep apnoea (OSA) is a disorder in which the person repeatedly stops breathing for a short time during their sleep. It’s commonly seen in Alzheimer’s, with up to 50% of people with this disease experiencing OSA at some point. ¹⁸

OSA results from the collapse of the airway and it’s possible to rectify this by wearing a device that provides positive pressure to keep the airway open during sleep.

Various studies have shown that in people with both Alzheimer’s and OSA, treating the OSA can have positive effects on memory, sleep quality, amount of deep sleep and slowing cognitive decline.

Restless legs syndrome (RLS), is another sleep disorder that is associated with Alzheimer’s. This disorder presents as tingling or crawling feelings that are only resolved by moving the legs.

A diagnosis of RLS can be difficult to make in someone who’s experiencing cognitive impairment as a result of Alzheimer’s, so often it’s the person’s caregiver who brings this to the attention of the doctor.

Researchers are looking at ways to better diagnose RLS in people with dementia and Alzheimer’s. Medical treatments for RLS have been shown to improve sleep quality in people with Alzheimer’s but more research is needed to establish how effective these treatments are.

REM sleep behaviour disorder (RBD) is common in patients with dementia. In RBD, the normal loss of muscle tone that accompanies a dream doesn’t happen.

This means that the dreamer can physically act out their dreams, often with violent or injurious results, either to themselves or others. More than 85% of cases of RBD are reported in men. ¹⁹

Mood disorders can also affect the sleep of people with Alzheimer’s. Depression, stress and anxiety are common in people with this disease and we know that all of these can cause sleep disturbance.

Depending on the severity of the mood disorder, treatment can involve lifestyle changes, such as exercising more and spending time outdoors, cognitive behavioural therapy (CBT) or the use of medication.

So it’s clear that people with Alzheimer’s are at greater risk of experiencing sleep disorders but there’s a wealth of treatment options available to try to reduce the impact that these can have on day to day life.

Sundowning — how behaviour can change as the night draws in

Sundowning is a term used to describe behavioural changes that usually happen in the late afternoon/early evening. People with Alzheimer’s may experience symptoms such disorientation, confusion, hallucinations, agitation and aggression at these times. ²⁰

To some degree, sundowning is linked to the changes in the light/dark cycle, as it has been observed that incidence increases among dementia patients during winter when there is less natural light.

Another contributing factor can be increasing levels of mental and physical exhaustion that have built up over the day. This tiredness can intensify feelings of stress and anxiety.

Sundowning affects every person differently but for some it can mean that they find it difficult to sleep at night, often wandering and remaining highly agitated throughout the night-time hours.

There’s no one clear causative explanation for sundowning but there’s a host of methods that can be used to try to reduce its effects.

How to help somebody who is experiencing sundowning

Several methods can be used that may help to regulate the body clock of somebody experiencing sundowning.

• Bright light during the day coupled with darkness at night can improve the sleep-wake rhythm and reduce agitation.
• Physical activity during the day is a good way of strengthening the day/night cycle.
• Ensuring that the bedroom is cool during the night can lessen the likelihood of sleep fragmentation.
• Regular mealtimes can be an important time cue, signifying daytime.
• Limiting naps to one hour in the early afternoon can help impose a stronger day/night rhythm.

In long-term residential facilities, additional environmental factors that could negatively affect sleep include:

• frequent noise and light interruptions
• room lighting that’s bright enough to suppress melatonin, in turn leading to disrupted sleep and further disruption of the circadian rhythm
• high room temperatures when sleeping that can lead to further fragmentation of sleep.

It’s also important to establish whether there’s an underlying reason behind the sleep problem (independent of the Alzheimer’s symptom). There can be numerous other causes of sleep problems, unrelated to those associated with dementia, including:

• depression
• nocturia
• pain
• obstructive sleep apnoea.

Addressing the points above may help to resolve some of the behaviours associated with sundowning but it’s also important to consider any medication that the person is taking.

It’s worth speaking to your healthcare provider if you’ve considered all of the above and are still struggling to support someone who is sundowning.

Caring for the caregivers

When we talk about the effects of Alzheimer’s on sleep, it’s important not to overlook the fact that there’s a whole army of caregivers who are also at high risk of experiencing sleep problems.

Caring for someone with Alzheimer’s is a full-time task and it can be both mentally and physically exhausting. As a caregiver, if your sleep is being compromised or you’re struggling to sleep, then you shouldn’t feel as if you’re fighting a lone battle.

Surveys show that around 70% of caregivers for people with dementia report problems sleeping. The majority sleep for fewer than seven hours per night and up to a fifth use alcohol or medication to get to sleep. ^{21 22 23 24}

These figures are worrisome and show that there’s a definite need for greater support for caregivers of people with Alzheimer’s.

Encouragingly, there’s plenty of research looking into the best ways to improve the sleep and overall quality of life of people in caregiving roles.

Research has shown that non-medical interventions are successful in improving sleep in caregivers and may additionally help to reduce stress levels. ²¹

Sleepstation’s drug-free and clinically validated sleep improvement programme can help you to identify your sleep problems and will give you the tools you need to get your sleep back on track.

Our programme uses a form of cognitive behavioural therapy for insomnia (CBTi) and this is one method that’s being examined in many clinical trials as a way to help caregivers improve their sleep.

If you’re a caregiver and you feel you need help with your sleep, see if Sleepstation is suitable for you by answering a few simple questions, here. Within a few minutes you could be on your journey to better sleep.

How to support good overall sleep

There’s a host of simple lifestyle changes we can all incorporate into our daily routines to ensure we’re setting ourselves up for a good night’s sleep and these are no different for people with Alzheimer’s.

Maintaining a daytime routine in which wake time, meals and bed time are fairly consistent is a good first step. This may not always be simple to implement for someone who has Alzheimer’s, but keeping mealtimes as regular as possible can provide some level of routine.

Getting adequate exposure to sunlight is also important in helping to keep your body clock regulated, so spending some time outside every day when possible is a good idea.

Take time to exercise each day. This can be as simple as going for a nice walk, which also ticks the box of getting exposure to sunlight! Regular exercise helps to create a sleep debt and can help you sleep better at night.

Avoid caffeine, alcohol and nicotine in the evening as these all stimulate the body and mind when it needs to be winding down.

Limit screentime in the hour before bed. This includes TVs, computer, tablets and smart phones, which all emit blue light and can interfere with sleep.

Create a consistent and relaxing night-time routine to help relax and unwind before bed. Whether it’s taking a bath or reading a nice book before bed, a regular bedtime wind-down routine can set you up for a good night’s rest.

Numerous medications are used to help alleviate some of the symptoms that come with Alzheimer’s disease and these may also interfere with sleep. It’s worth discussing these with a GP to ensure that the dosage and timing of any such drugs is optimal and not potentially interfering with sleep.

All of these measure can help to provide consistency to someone with Alzheimer’s and are just as beneficial to their caregivers. If these steps aren’t working though it’s essential to seek the advice of a medical provider who can provide further support.

Summary

• People with Alzheimer’s disease have an increased risk of experiencing sleep disorders.
• Poor sleep can affect cognitive function, but we can’t conclude that it causes Alzheimer’s disease.
• We do know that getting good quality sleep has a protective effect on your overall health.
• Caregivers for people with Alzheimer’s also report higher levels of sleep disruption and should keep in mind that taking care of their own sleep needs to be prioritised.