A group of scientists from Israel and Germany has discovered a new way to monitor sleep and potentially diagnose sleep disorders by recording heart rate. By utilizing a mathematical technique, the researchers analyzed the heart rate recordings to tease out information related to the synchronization between heartbeat and breathing.

According to the researchers, monitoring the heartbeat provides information about breathing because the two physiological processes are weakly coupled; during inhalation, the heart beats faster, and during exhalation, the heart slows down—effects that are seen during sleep as well.

During their study, which appears in the journal Chaos, the researchers used heartbeats to reconstruct the breathing patterns of 150 people who had no known sleep disorders. Comparison showed the reconstructions accurately reflected the actual recorded breathing data collected in sleep labs.

The study found that the relationship between sleep stages and heartbeat and breathing mostly synchronizes during non-REM sleep, and cardio-respiratory synchronization is almost absent during REM sleep. This means that by mathematically analyzing someone’s heart rate throughout the night, information can be gained on the person’s breathing and sleep stage.