New research suggests that a specific stage of sleep may play a key role in controlling anxiety, especially as people get older.
Sleep and anxiety are closely connected. Poor sleep can make people feel emotionally fragile, while stress often makes it harder to fall asleep. But the link may go deeper than just feeling tired.
As people age, both sleep and emotional regulation tend to change. Older adults often sleep less, wake up more during the night, and experience lighter sleep. At the same time, anxiety symptoms can become more common later in life. Researchers wanted to know if changes in sleep itself could explain why anxiety rises with age.
A new study from the University of California, Berkeley suggests the answer may be found in deep sleep, also known as slow-wave sleep. This is the stage of sleep that helps the brain reset overnight.
What the study found
Researchers studied 61 adults over the age of 65 who were cognitively healthy and reported different levels of anxiety. Participants spent a night in a sleep lab, where their brain activity was tracked using polysomnography, a test that monitors brain waves throughout the night.
The researchers focused on slow-wave activity, the brain pattern that marks deep non-REM sleep. Participants also completed questionnaires measuring their anxiety before and after sleeping.
The next morning, brain scans were used to examine structural changes in regions of the brain that control emotions. These areas, part of the limbic system, often shrink with age. A smaller group of participants was followed for about four years to see if the link between sleep and anxiety held up over time.
The results showed a clear pattern. Older adults who had stronger slow-wave sleep tended to have lower anxiety levels. Those whose deep sleep was more disrupted were more likely to report higher anxiety the next day.
Brain scans offered another clue. Age-related shrinking in emotion-processing areas, including the amygdala, insula, and cingulate cortex, was linked to less slow-wave sleep. This suggests that structural changes in the brain may weaken its ability to produce restorative deep sleep.
But even when some brain shrinkage was present, people who still had strong slow-wave sleep showed better emotional stability. The researchers found that impaired deep sleep essentially explained the connection between brain changes and next-day anxiety.
How deep sleep affects emotions
During slow-wave sleep, the nervous system shifts into a “rest-and-recover” state. Stress hormones quiet down, heart rate variability improves, and the brain recalibrates circuits that control emotions.
This stage of sleep also strengthens communication between the prefrontal cortex, which handles rational thinking, and the limbic system, which processes fear and stress. When deep sleep declines, that emotional regulation system becomes less stable. The result can be heightened reactivity, more persistent worry, and a greater tendency toward anxiety.
Ways to support deep sleep
While sleep naturally changes with age, research suggests that slow-wave sleep can still be supported through daily habits.
Going to bed and waking up at the same time each day helps stabilize the brain’s circadian rhythm, which supports deeper sleep cycles. Aerobic activity and resistance training have both been linked to increased slow-wave sleep, especially when done earlier in the day.
Exposure to natural light soon after waking helps anchor circadian rhythms and improve nighttime sleep quality. Alcohol, while it can make people feel sleepy at first, disrupts deeper sleep stages later in the night. Keeping the bedroom cool and dark also helps the brain transition into slow-wave sleep.
The research suggests that each night of restorative sleep gives the brain a chance to recalibrate stress and anxiety. When deep sleep fades, emotional resilience may fade with it. The encouraging part is that sleep is not fixed. Small habits, from movement to light exposure to consistent schedules, can shape how people feel the next day.
