New research has uncovered a powerful link between nighttime heart rhythm and future health conditions, even in people with no obvious sleep problems.

The study, conducted at the Department of Neurology, Inselspital, the University Hospital of Bern, examined 4,170 people over a 13-year period and discovered that heart rate variability (HRV) during sleep can be a powerful early warning sign of future health conditions such as stroke, depression, and cognitive dysfunction.

HRV reflects the fluctuation of time intervals between heartbeats. 2 HRV adjusts constantly in response to the physical and emotional demands of the body. During the day, HRV is physiologically high, corresponding to high levels of activity. At night, and especially during deep sleep, HRV typically reduces, reflecting a shift into a rest and repair mode, where the body focuses on recovery and recharging for the next day.