Chandigarh, June 22 — New research has found that fluctuations in heart rhythm during sleep may signal future health risks, including stroke, depression, and metabolic diseases—even in individuals with no apparent sleep issues.
The 13-year study, conducted by the Department of Neurology at Inselspital, the University Hospital of Bern, monitored 4,170 people and revealed that patterns in heart rate variability (HRV) during sleep could serve as an early physiological marker for serious conditions long before clinical symptoms emerge.
“HRV matters for brain and overall health because it reflects how well the body regulates itself—primarily through the activity of the autonomic nervous system,” said Dr. Irina Filchenko, MD, PhD, the study’s lead author.
HRV, the variation in time between heartbeats, responds to emotional and physical states. It is typically higher during the day, when the body is active, and reduces at night, particularly in deep sleep, when the body shifts into repair mode. But the study found that atypical HRV patterns during sleep had strong predictive value. High and erratic HRV was common in individuals who later suffered strokes; low HRV patterns often preceded cases of depression. Meanwhile, altered high-frequency HRV was associated with future metabolic, cardiovascular, and endocrine disorders.
“Some participants had ‘normal’ sleep according to standard indicators, with balanced sleep stages and minimal interruptions. But HRV told a different story, revealing hidden risks missed by traditional metrics,” said Dr. Filchenko.
Researchers emphasized that the autonomic nervous system, which regulates involuntary functions such as breathing, digestion, and muscle tone, plays a critical role in interpreting HRV data. This underscores the complexity of sleep, which is often misunderstood as a passive state.
“Sleep is not merely downtime. It’s an active process where crucial physiological work takes place—cell repair, memory consolidation, and the brain’s clearance of metabolic waste,” Dr. Filchenko added. “Tracking HRV during this time gives us a unique and valuable lens into how the body is functioning beneath the surface.”
The findings also point to a future in which wearable technologies could help individuals monitor HRV trends at home. While current consumer devices have limitations in precision, researchers are hopeful that advancing technology could one day provide reliable early warnings for health deterioration.
Ultimately, the study deepens the understanding of sleep as a pillar of preventive health. “Our results reinforce the need to rethink how we define healthy sleep,” said Dr. Filchenko. “The signs of chronic disease often begin long before symptoms show. By paying attention to hidden patterns like HRV, we may have a better shot at early intervention and long-term wellness.”
