A new study suggests that the amount of time it takes to enter REM sleep—the phase of sleep when vivid dreaming occurs—may be linked to the risk of developing Alzheimer’s disease. Researchers found that people who took longer to fall into REM sleep had a higher likelihood of later being diagnosed with Alzheimer’s.

While the study found a strong connection between delayed REM sleep and the disease, it’s still unclear whether disrupted sleep contributes to Alzheimer’s, or whether the disease itself causes changes in sleep patterns. Nonetheless, the findings offer more insight into how sleep and brain health are connected.

How REM Sleep and Alzheimer’s May Be Related

REM (rapid eye movement) is one of the four major stages of sleep, characterized by eye movement and reduced muscle tone. It typically begins about 90 minutes after falling asleep and occurs in longer phases as the night progresses. REM sleep is known to play a critical role in memory consolidation and learning.

Because sleep issues have long been associated with cognitive decline, researchers in this latest study wanted to see whether delays in REM sleep specifically could be tied to Alzheimer’s development.

In the study, researchers monitored the overnight sleep of 128 adults at a hospital in Beijing. The participants had an average age of 71, and they included individuals with Alzheimer’s, some with mild cognitive impairment (a possible precursor to dementia), and others with no cognitive issues.

The participants were split into two groups based on how long it took them to reach their first REM cycle. The "early REM" group reached it in about 98 minutes, while the "late REM" group took about 193 minutes.

Those in the delayed REM group were more likely to have Alzheimer’s and also had higher levels of amyloid and tau proteins—both markers commonly associated with the disease. They also showed lower levels of a brain-supporting protein called BDNF, which is known to be reduced in individuals with Alzheimer’s.

The study suggests that delayed REM may interfere with the brain's ability to process and store memories. However, experts say the relationship between REM sleep and Alzheimer's is likely bidirectional—delayed REM may contribute to brain changes seen in Alzheimer’s, and Alzheimer’s itself may disrupt the sleep cycle.

More research is needed to determine the precise connection.

Improving REM Sleep Through Healthy Habits

Experts agree that while we still have much to learn about the relationship between sleep and Alzheimer’s, we do know that REM sleep plays a vital role in overall brain function.

Even though REM typically accounts for about 25% of a full night’s sleep—roughly two hours during an eight-hour sleep—this amount can decrease with age. Other factors like room temperature, stress, or even antidepressant use can also affect REM sleep.

If you suspect you’re not getting enough REM sleep, or if your sleep is suddenly unrefreshing, experts recommend talking with a healthcare provider—especially if there are other concerning symptoms like snoring, breathing pauses during sleep, or significant changes in memory or focus.

Sleep trackers may give you some insight into your sleep stages, but professionals warn against over-relying on them. Some people develop a condition known as orthosomnia—becoming overly focused on achieving “perfect” sleep, which can ironically worsen sleep quality.

The most effective way to encourage healthy REM sleep is to follow a consistent sleep routine. That includes:

  • Going to bed and waking up at the same time every day

  • Avoiding screens at least 30 minutes before bed

  • Limiting alcohol and heavy meals at night

  • Creating a quiet, dark, and cool sleep environment

Rather than focusing on just one sleep phase, experts recommend aiming for overall good sleep hygiene to ensure you get enough of each stage throughout the night.