Dec. 18, 2023 – People who followed a short daily guided meditation video that taught them to actively relax the body improved their memory, reaction time, and sleep in just 2 weeks, according to a small new study.
People in the study spent 20 minutes lying down with their eyes closed in a meditative state during a daily practice called yoga nidra. At the end of 2 weeks, researchers observed improvements on 10 cognitive measures, and those who took part in the study fell asleep faster, slept longer, and spent more time in deep “delta wave” sleep. (Delta waves are the slow brain rhythms during deep sleep that occur when the brain and body recover.)
The study, published last week in PLOS One, didn’t rely solely on subjective sleep diaries to gauge the people's changes in sleep and cognitive performance. The researchers also used objective measures that included 10 standard cognitive tests, electroencephalogram (EEG), and polysomnography, the latter of which is the sensor-based technology used in overnight sleep studies. The study was led by Karuna Datta, MD, PhD, a professor at the Armed Forces Medical College in Pune, India.
“Yoga nidra practice is a kind of pratyahara, [which is a] withdrawal-of-senses technique. It is an easy-to-do practice. It is not mindfulness,” Datta said in an email, noting that “it has a huge potential.”
For the practice to help with sleep and cognition, she said, it’s important to follow a method that is known to work. In her study, people practiced 20 minutes of yoga nidra, following a video recording that also included a total of 6 minutes of instruction split before and after the meditation.
The findings point toward a simple treatment for the long-understood problem of poor sleep’s impact on how the brain works.
Considered a pilot study due to its small size, the analysis included data from 38 young men in India, all of whom kept a sleep diary before and after starting 2 weeks of daily yoga nidra sessions. The men also took many cognitive tests pre- and post-practice, and some also had EEG testing to evaluate brain activity and overnight polysomnography. The men in the study did not have existing sleep disorders, depression, or other psychiatric disorders, or acute illnesses that could affect their sleep schedules. Women were excluded because of known effects of menstrual cycles on sleep.
By the end of the study, the men reported falling asleep more quickly, sleeping longer, and spending more time sleeping when they were in bed, which is a measure known as sleep efficiency. When they woke during the night, they said they fell back to sleep more quickly. But Datta said one of the most interesting findings was that the people in the study spent a greater portion of their sleep time in the deep phase known as delta sleep.
“Delta wave in sleep helps in sleep quality. This may be the reason for subjectively reporting improvement in sleep by the participants,” she said.
Throughout the study, the people were evaluated for 10 cognitive functions, and reaction times for all 10 measures improved by the end of the study, which is a sign that the brain is processing more quickly. After practicing yoga nidra, they scored higher on working memory tests, indicating they were better able to use short-term memory to store information while completing other tasks.
The study didn’t determine the cause of the men's improved cognitive performance, but the researchers suggested the possibility that the yoga nidra practice was helpful, especially since some test results were better after daytime yoga practice, compared to measurements taken in the early morning. It’s also possible that cognitive performance was impacted by improved sleep, the authors wrote, such as resulting in strengthened connections in the brain.
The yoga nidra video used in the study instructs practitioners to close their eyes and relax the body, but not sleep. People are guided to listen to nearby sounds and to visualize the room they are in, to silently state a resolve or intention, and to become aware of individual body parts, visualize them, and relax them. The body part relaxation instruction begins with each finger on the right hand, then the palm of the hand, working through the entire right side of the body, down to the ankle, sole of the foot, to each individual toe.
People in the study were trained in how to practice yoga nidra, then they practiced on their own for the majority of the study. None of them had prior experience with yoga nidra; they were considered beginners.
Limitations of the study, the authors noted, were the small sample size and that there was no control group. The authors wrote that larger studies may help determine whether practicing yoga nidra could help people with mild learning disabilities or cognitive decline.
