Alzheimer’s disease is a progressive neurological disorder characterized by memory loss, cognitive decline, and behavioral changes.
It is the most common cause of dementia, affecting over 5 million people in the United States. As Alzheimer’s progresses, it can significantly impact a person’s sleep patterns and quality of sleep.
Conversely, existing sleep disorders may also increase one’s risk of developing Alzheimer’s. Understanding this complex bidirectional relationship is key to managing symptoms and improving the quality of life for Alzheimer’s patients.
The Bidirectional Relationship Between Sleep Disorders And Alzheimer’s
Research has demonstrated a clear two-way association between sleep disorders and Alzheimer’s disease. Sleep disturbances are very common in Alzheimer’s, affecting up to 60% of patients.
These include increased nighttime waking, reduced slow-wave and REM sleep, and disrupted circadian rhythms. At the same time, studies show that people with certain sleep disorders have an elevated risk of eventually developing Alzheimer’s.
For example, those with obstructive sleep apnea (OSA) have been found to score lower on cognitive tests and are diagnosed with mild cognitive impairment at higher rates. Restless leg syndrome, insomnia, and excessive daytime sleepiness have also been linked to an increased risk of Alzheimer’s onset.
The reasons for this bidirectional relationship are multifactorial. Poor quality sleep contributes to the accumulation of beta-amyloid plaques in the brain, a hallmark of Alzheimer’s pathology. Chronic sleep deprivation increases inflammation which damages neurons. Sleep is also critical for consolidating memories and clearing metabolic waste from the brain.
On the flip side, Alzheimer ‘s-related changes in the brain disrupt the normal sleep/wake cycle. Degeneration of neurotransmitter systems leads to imbalances in melatonin and serotonin. Loss of brain cells in key areas like the hypothalamus alters the body’s circadian rhythms. This complex interaction demonstrates why sleep disorders and Alzheimer’s exacerbate one another.
How Poor Sleep May Contribute To Alzheimer’s Progression?
With this understanding of the bidirectional relationship between sleep and Alzheimer’s, it is clear that poor sleep quality often compounds the course of the disease. While Alzheimer’s itself disrupts sleep, pre-existing sleep problems or unhealthy sleep habits may hasten cognitive decline.
There are a few key ways in which insufficient sleep is thought to contribute to Alzheimer’s progression:
Increased Beta-Amyloid Accumulation
One of the defining pathological changes in Alzheimer’s is the buildup of beta-amyloid protein fragments in the brain. These sticky plaques disrupt communication between neurons. Evidence shows that chronic sleep deprivation leads to higher levels of beta-amyloid in the brain and cerebrospinal fluid.
One hypothesis is that the brain’s glymphatic system, which clears metabolic waste, is more active during sleep. Lack of sleep prevents effective beta-amyloid clearance.
Cognitive Impairment
Healthy sleep is essential for consolidating memories, learning, focus, and cognitive performance. Chronic sleep deprivation has been shown to cause deficits in attention, working memory, and long-term recall.
For those already experiencing Alzheimer ‘s-related cognitive decline, poor sleep further compounds these effects and quickens impairment. Even for healthy adults, just one night of missed sleep can temporarily reduce cognitive speed and accuracy.
Increased Inflammation
Inflammatory markers are commonly elevated in Alzheimer’s patients. Lack of sleep is also known to increase inflammation through several biological pathways. This sustained inflammation damages neurons and other brain cells, contributing to cognitive decline.
One study found that sleep-deprived mice had higher brain inflammation and more beta-amyloid plaques than those getting normal sleep.
By improving sleep quality and adhering to good sleep hygiene practices, patients may be able to slow the progression of Alzheimer’s symptoms. Prioritizing sleep is an important component of Alzheimer’s management.
Do People With Alzheimer’s Sleep More During The Day?
Excessive daytime sleeping, also known as hypersomnia, is quite common in patients with Alzheimer’s. An estimated 25-35% of Alzheimer’s patients experience increased sleepiness and napping during the day.
However, this daytime sleep provides little restorative benefit. People with Alzheimer’s tend to have very fragmented sleep at night, with frequent awakenings and difficulty falling back asleep.
They develop deficits in certain stages of sleep architecture. The quality of their nighttime sleep suffers, so they are not restored and still tired during the day.
While daytime sleeping becomes more frequent as Alzheimer’s progresses, increased napping may also be an early warning sign of cognitive impairment. Those experiencing cognitive decline often feel sleepier during the day and take more naps. However, hypersomnia can also stem from other factors like medication side effects.
Overall, increased daytime sleep is a hallmark of Alzheimer’s, but is an involuntary result of poor nighttime sleep rather than a deliberate choice to sleep more. Treating underlying sleep disorders can help minimize excessive daytime sleepiness. Maintaining a regular sleep-wake cycle with sunlight exposure helps regulate circadian rhythms.
Other Effects Of Alzheimer’s Disease On Sleep Patterns
Beyond daytime hypersomnia, Alzheimer’s affects sleep in other ways as well. Here are some additional sleep disruptions experienced by many Alzheimer’s patients:
👉Increased nocturnal awakenings and wandering at night. Patients are confused when they wake up and can experience anxiety and agitation.
👉Decreased time spent in deep, restorative stages of non-REM sleep. Patients spend more time in lighter stages.
👉Disruption of normal sleep architecture and REM sleep. Loss of neurons affects the regulation of sleep stages.
👉Irregular sleep-wake cycles and disturbed circadian rhythms. The perception of day/night becomes blurred.
👉”Sundowning” – increased agitation, confusion, and pacing in the late afternoon or evening. Internal body clocks get misaligned.
👉Sleep-disordered breathing – sleep apnea is more common in Alzheimer’s patients compared to older adults without dementia.
👉Restless leg syndrome – uncomfortable sensations in the legs that disturb sleep. Prevalence is 4x higher in those with Alzheimer’s compared to the general public.
👉REM sleep behavior disorder involves acting out vivid dreams. Clonazepam may help reduce symptoms.
Conclusion
There is clearly a very close relationship between sleep disorders and Alzheimer’s disease. Alzheimer’s both contributes to and is exacerbated by poor sleep. Insufficient sleep, sleep apnea, and other disturbances appear to increase one’s risk of developing Alzheimer’s.
Within Alzheimer’s patients, lack of restful sleep accelerates cognitive decline and worsens behavioral symptoms. While more research is needed, improving sleep quality through both non-pharmacological and medical approaches provides real benefits for those living with Alzheimer’s.
Treating sleep disorders can help delay the progression of the disease and allow patients to maintain quality of life for a longer period.
Frequently Asked Questions
Alzheimer’s disease leads to the degeneration of brain regions and neurotransmitters involved in regulating sleep. Loss of neurons in the hypothalamus and deficiency of melatonin lead to disturbed circadian rhythms. Failing memory centers also impair the ability to sustain uninterrupted sleep.
Yes, research indicates that treating sleep apnea with CPAP therapy can help modestly improve cognition, memory, and executive functioning in those with Alzheimer’s. However, it does not alter the underlying disease progression.
Maintaining a regular sleep-wake schedule, limiting daytime naps, reducing evening caffeine, keeping the bedroom comfortable and dark, using nightlights, reducing fluids before bedtime, and avoiding stimulating activities at night are some examples of good sleep hygiene for Alzheimer’s patients.
Melatonin supplementation, sedatives like trazodone or benzodiazepines, sleep apnea devices, and REM-suppressing antidepressants are some medications that may improve sleep. However, non-drug approaches should be tried first
While studies are still ongoing, it does appear that increasing slow-wave deep sleep may help clear beta-amyloid from the brain and offset cognitive impairment. More research is needed, but methods to enhance deep sleep hold promise for Alzheimer’s prevention.
