- βHigher blood sugar variability (CV and SD on CGM) is significantly linked to increased risk of heart nerve damage (CAN)
- βCGM devices can detect glucose fluctuations that standard HbA1c tests miss, potentially enabling earlier CAN screening
- βThe review included 1,814 participants across 16 studies, making its findings relatively robust for this topic
| Journal | Reviews in endocrine & metabolic disorders |
| Year | 2025 |
| PMID | 40543000 |
What This Study Is About
Researchers reviewed 16 studies involving 1,814 people with diabetes to explore whether readings from continuous glucose monitors (CGMs) could predict a condition called cardiovascular autonomic neuropathy (CAN) β nerve damage that affects heart rate and blood pressure control.
What Is Cardiovascular Autonomic Neuropathy?
CAN is a complication of diabetes where the nerves controlling your heart and blood vessels become damaged. It can cause dizziness when standing, an abnormally fast resting heart rate, and in serious cases, is linked to higher rates of death. Many people have it without knowing.
What Did the Study Find?
The key finding was that greater swings in blood sugar levels β called glycemic variability β were associated with a higher risk of CAN. Specifically:
- Coefficient of Variation (CV): Each unit increase was linked to an 8% higher risk of CAN.
- Standard Deviation (SD): Higher SD was also significantly linked to greater CAN risk.
- MAGE (Mean Amplitude of Glycemic Excursions): This measure did not show a statistically significant link to CAN risk.
- Time in Range (TIR), Time Above/Below Range, and Low Blood Glucose Index: Results were mixed across studies and inconclusive.
Why Does Glycemic Variability Matter?
It's not just about your average blood sugar or HbA1c. How much your blood sugar fluctuates throughout the day may independently stress your nervous system. CGM devices are uniquely able to capture these ups and downs in real time, offering information that traditional blood tests miss.
What Does This Mean for You?
If you wear a CGM, pay attention not only to your time in range but also to how variable your readings are. Discussing your CV and SD numbers with your diabetes care team could help identify early signs of nerve damage to the heart β potentially before symptoms appear.
Important Limitations
Most of the studies reviewed were observational, meaning they show an association but cannot prove that blood sugar swings directly cause CAN. Longer-term, higher-quality studies are still needed to confirm these findings.