Currently, it is impossible to determine when a patient in a coma will regain consciousness. The timeframe can vary greatly, with some patients waking up shortly after the injury, while others may take days or even decades to regain partial consciousness. Unfortunately, some patients remain unconscious for the rest of their lives. Recent research suggests that analyzing sleep patterns in comatose patients could be a valuable tool in predicting their chances of recovery.

Researchers from Columbia University and New York-Presbyterian Hospital conducted a study where they cross-referenced sleep patterns of comatose patients with their recovery rates, discovering a promising connection. The study, published in the journal Nature Medicine, reveals that this approach has the potential to revolutionize the care of patients with brain injuries and provide more accurate predictions for family members.

According to lead author Jan Claassen, a neurologist at Columbia University, “Families of my patients often ask me if their loved one will wake up and how they will recover in the coming months. Unfortunately, we are often unable to provide precise guidance, and it is crucial that we improve our predictions to support their decision-making process,” as stated in a university statement.

A previous study conducted by Claassen and his team found that up to one-fourth of comatose patients with brain injuries may have undetected consciousness, also known as cognitive motor dissociation. Claassen developed a technique to detect hidden consciousness by identifying when a comatose patient responds to commands, such as moving their hand, despite being unable to physically do so.

Claassen explained, “We are at an exciting stage in neurocritical care, where we are discovering that many patients who appear to be unconscious may actually be recovering without our knowledge. We are starting to uncover signs of recovery as it happens.” Claassen is also the chief of critical care and hospitalist neurology at NewYork-Presbyterian/Columbia University Irving Medical Center.

In the recent study, Claassen focused on sleep patterns because the brain processes involved in sleep are also essential for consciousness. He and his team analyzed the overnight brain activity of 226 comatose patients who had undergone his technique to detect hidden consciousness. For simplicity, let’s refer to this as the “complex method.”

“The electrical activity during sleep appears chaotic at first, but then, in some patients, we see organized, fast frequencies emerge,” Claassen said. These fast frequencies, known as sleep spindles, often appeared before the complex method detected hidden consciousness and before patients woke up or made a long-term recovery.

“Sleep spindles are a normal part of sleep and indicate a level of organization in the brain, suggesting that the circuits between the thalamus and cortex necessary for consciousness are intact,” he continued.

Overall, patients with both sleep spindles and hidden consciousness were more likely to wake up from their coma and make a significant recovery. Specifically, 76% of these patients demonstrated consciousness by the time they left the hospital, and 41% recovered enough neurological function to be independent during the day within a year of being discharged. In contrast, 29% of patients without sleep spindles or cognitive motor dissociation showed signs of consciousness by the time they left the hospital, and only 7% regained neurological function a year later.

While the researchers emphasized that this is correlational data, meaning it does not prove that sleep spindles directly contribute to coma recovery, their research suggests that better sleep quality, indicated by the presence of sleep spindles, could improve a patient’s chances of recovery. For example, 19 of the 139 patients without sleep spindles or hidden consciousness still regained consciousness.

“The ICU environment can be disruptive to a good night’s sleep, with constant noise, alarms, and clinicians attending to the patients 24/7,” Claassen said. “While this is necessary, it can make it challenging for patients to get a good night’s sleep.”

Although their approach is not yet ready for clinical practice, it paves the way for a future where doctors can provide more accurate predictions of a comatose patient’s chances of recovery, offering anxious family members more guidance and support.