Delayed REM Sleep Linked to Higher Alzheimer’s Risk

“Previous studies have mostly focused on slow wave sleep, or deep sleep, as a risk factor for Alzheimer’s disease,” says senior study author Yue Leng, PhD, an associate professor in the department of psychiatry and behavioral sciences at University of California in San Francisco. “This is really the first study to look at how long it takes you to enter REM sleep as a novel mark for Alzheimer’s disease.”

The Link Between Sleep and Brain Health

Dr. Leng and her collaborators found that a delay in REM sleep appears to disrupt the brain’s ability to consolidate memories by interfering with the process that contributes to learning and memory.

She notes that poor or reduced REM sleep may raise levels of the stress hormone cortisol, which can impair the hippocampus, a part of the brain critical to memory consolidation.

More Toxic Brain Proteins in People With Late REM

For this investigation, researchers followed 128 adults, who were 70 years old on average, from the neurology unit of the China-Japan Friendship Hospital in Beijing. Half had Alzheimer’s disease and about one-third had mild cognitive impairment, a common precursor to Alzheimer’s. The remainder had normal cognition.

The team monitored participants while they slept overnight in a clinic and measured their brainwave activity, eye movement, heart rate, and breathing.

Researchers divided the patients into those who reached REM sleep early (in less than 98 minutes after falling asleep) and those who reached REM sleep late (more than 193 minutes after falling asleep).

Those with the markers for Alzheimer’s were more likely to have delayed REM sleep. These participants tended to have higher levels of the two toxic proteins, amyloid and tau, common in people with the disease.

The results showed that subjects with delayed REM sleep had 16 percent more amyloid and 29 percent more tau than those with early REM sleep. The late REM group also had 39 percent less of a healthy protein called brain derived neurotrophic factor (BDNF), which decreases in patients with Alzheimer’s.

Good Sleep Is Essential for Alzheimer’s Prevention

For Stefania Forner, PhD, director of medical and scientific relations for the Alzheimer’s Association, these outcomes support a growing body of evidence demonstrating that sleep disruption may impact the risk for Alzheimer’s and other brain diseases.

“This study may contribute to a better understanding of modifiable risk factors for Alzheimer’s, such as poor sleep,” she says. “However, replication of these findings in larger and more diverse study populations is needed. The study was conducted in a very controlled environment — inside a clinic — and a real world data study would be important for a future study.”

Paying More Attention to Healthy Sleep

Most people will not be able to tell on their own if their REM sleep is delayed, according to Yuko Hara, PhD, director of aging and Alzheimer’s prevention at the Alzheimer’s Drug Discovery Foundation.

But wearable devices like smartwatches and EEG headsets (devices for measuring brain activity) can estimate the timing and length of different sleep stages, she says.

• Get seven to eight hours of sleep every night.
• Abstain from caffeinated beverages near bedtime.
• Avoid alcohol several hours before sleeping.
• Keep your room dark and comfortable at night.
• Use blue light–blocking filters on your phones and computers after sunset. “Electronics are a major source of blue light, which promotes wakefulness,” says Hara.
• If you suspect you have insomnia, sleep apnea, or other sleep disorders, talk to your healthcare provider.
• Consult with your doctor about any medications that may be disrupting your REM sleep.

“If you don’t get enough sleep or have poor quality sleep, addressing these issues may optimize your sleep cycles and help lower your risk for Alzheimer’s disease,” says Hara.