Oneirology in Cognitive Decline: How Dementia Impacts Dreams and REM Sleep

Explaining Oneirology

Have you ever been curious to learn more about dreams? Why do we dream? What do they represent? If so, oneirology may be of interest to you! Oneirology is the scientific field of dreams in relation to brain functioning. Oneirologists study how dreams are influenced by a person’s emotions, memories, and behavioral actions. It is a field that combines psychology and neuroscience principles, meaning it is often considered secular because it does not derive its findings from supernatural or spiritual explanations.

One of the main topics oneirologists study is memory consolidation during sleep. Scientists theorize that we start to dream when we’re in deep sleep. Dreams are important, as they help us rehearse different situations and challenges we are experiencing in our lives. We generally start to dream when we enter a certain stage of sleep called REM (rapid eye movement) sleep. REM sleep does not happen instantaneously; it is actually the final stage of the sleep cycle that accounts for 25% of sleep in adults. It lasts for 90 minutes and repeats as the person cycles through the sleep process four to five times per night. It is characterized by: our eyes moving rapidly; our bodies being in a state of atonia (i.e., temporary paralysis), except for the eyes and muscles controlling our breathing; and our brain activity, body temperature, pulse, and breathing increasing.

REM Sleep Significance

Without enough sleep, namely REM sleep, we will experience difficulty with thinking and taking care of our emotional and physical health. In fact, those who spend more time in REM sleep have lower fear-related brain activity, causing researchers to hypothesize that more sleep leads participants to have less emotionally charged responses to stressful stimuli. These findings were confirmed by MRI scans, which exposed the differences in brainwaves between participants who received a full night’s sleep compared to those who did not. All this data showcases the importance of sleeping the recommended amount, especially as REM sleep is not experienced until the later portions of sleep. Therefore, if someone does not get the recommended amount, they are at risk for developing further complications.

A common complication associated with reduced REM sleep is cognitive decline, particularly dementia. As a person ages, they experience lower rates of REM sleep and a heightened risk of developing neurodegenerative diseases.

Dementia and Dreams Sleep Studies

New studies suggest that delayed REM sleep may be an early sign of Alzheimer’s disease. This is because delayed sleep is associated with the release of the stress hormone, cortisol. As a result, the brain’s hippocampus, which is its spatial memory center, gets impaired.

One sleep study at the China-Japan Friendship Hospital in Beijing tracked 128 participants: half were diagnosed with Alzheimer’s disease, a third had mild cognitive impairment, and the remainder had no neurological conditions. The participants were divided into early or delayed REM sleep and were instructed to spend the night at the sleep clinic so researchers could measure their brainwave activity. At the end of the experiment, scientists found that participants with Alzheimer’s disease had higher rates of delayed REM sleep and the presence of two toxic proteins, tau and amyloid; these protein buildups are common hallmark toxins found in cognitive decline. Statistically speaking, participants with delayed REM sleep were found to have 16% more amyloid and 29% more tau than participants with early REM sleep. Furthermore, the delayed REM sleep participants had 39% less brain neurotrophic factor (BDNF). BDNF is important because it is a protein that promotes the growth, survival, and development of neurons, strengthening memory and cognitive function.

In another longitudinal sleep study, called The Framingham Heart, researchers recruited 321 participants from Massachusetts; again, their brainwave activity was measured and tracked for 12 years. During that time, 32 participants were diagnosed with some form of dementia, with 24 resulting in Alzheimer’s disease. Like the previous study, participants who reported the least amount of REM sleep or spent a longer time reaching the REM sleep stage had a greater risk for developing dementia. Here, those who developed dementia spent 17% of sleep in REM, in contrast to the 20% of time spent for those who did not develop dementia. From this, scientists concluded that every percent reduction in REM sleep equated to a 9% increased risk for dementia.

What could be impairing sleep for dementia patients is the quality of sleep they are getting per night. Scientists are finding that people with dementia often experience frequent nightmares per night, waking them up from their sleep and preventing them from entering REM sleep. Sleeping problems are associated with advanced aging, which researchers predict is the body priming the brain for its atrophy.

Lewy Body Dementia Sleeping Patterns

Lewy Body Dementia (LBD) is frequently connected with sleep disturbances. It is the second most common type of dementia, right under Alzheimer’s disease. LBD is characterized by the protein deposit of Lewy bodies in the brain’s nerve cells, causing individuals to experience confusion, hallucinations, delusions, neuropsychiatric comorbidities (e.g., depression), and memory difficulties. While asleep, patients with LBD tend to act out their dreams in real life, which can include punching, kicking, and yelling. This can be quite dangerous, as it can cause injury, especially since LBD is a progressive disease, meaning its signs and symptoms get worse over time.

When awake, the person may experience even more confusion, as they might not be able to distinguish they are awake. This phenomenon is called oneirophrenia. A common sentiment patients report is, ‘“When I wake up, and for a while, I’m not sure whether I’m still dreaming or awake.’” Therefore, this may mean that people with dementia often do not experience lucid dreaming, which means a person is aware they are in a dreamlike state.

Circadian Rhythm Disruptions

The circadian rhythm is our body’s internal clock that regulates our 24-hour sleep-wake cycle. It helps us know when we should go to sleep in response to light and darkness exposure, while also influencing hormones, body temperature, and digestion. People with a strong circadian rhythm are able to sleep at a routine time. In contrast, those with weak/fragmented circadian rhythms experience peak activity in the late afternoon. They additionally find it harder to maintain a consistent sleep schedule as their internal clock does not match the environmental cues (i.e., light versus dark) that it is time for sleep, which often occurs with aging. In turn, having issues with one’s circadian rhythm is another risk factor for dementia, as it is linked with increased amyloid plaque accumulation and inflammation.

Final Thoughts

As oneirologists uncover more information about the connection among our dreams, sleep, and dementia, it is still important that we consider the information presented in this article in our daily lives. Sleep is such a vital process that we need to prioritize and look after it, as this is a time where our bodies can relax and form new neuroconnections based on the events we experienced throughout the day by transferring short-term memories to long-term ones. Consequently, we can wake up the next day feeling energized and alert, especially as sleep helps rid us of the metabolic waste we built up throughout the day. That way, our qualities of life can be improved and our risks for developing dementia can be reduced.

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