When you open your sleep tracker tomorrow morning, skip the sleep score and turn your attention to another number. A recent study has found time spent in REM sleep is a vital metric for understanding your longevity and illness risk — and most sleep trackers measure it.

A 2026 survey published in PLOS Medicine analyzed data from over 95,000 people wearing a sleep trackers. The researchers linked increased amounts of Rapid Eye Movement (REM) sleep with a lower risk of 83 conditions, including heart failure and dementia.

You might overlook REM in favor of juicier metrics like deep sleep and 3 a.m. wake ups , but this sleep stage is essential for your wellbeing. We asked sleep experts Dr. Hana Patel and Dr. Hanul Bhandari , what we need to know about REM sleep, including how to get more of it.

Dr. Hana Patel is a registered GP with a specialist interest clinically in sleep and mental health.

Dr.…