HRV and diabetes
What is the relationship between heart rate variability (HRV) and diabetes?
The disease diabetes mellitus is a chronic metabolic disorder that is associated with a chronically elevated blood sugar level.
More than 90 percent of all diabetes sufferers are affected by type 2 diabetes, which often starts in adulthood. Type 2 diabetes partly has genetic causes and is often associated with overweight and obesity.
The much rarer type 1 diabetes usually occurs in childhood or adolescence and develops as a result of an autoimmune reaction.
If you have diabetes, the body can no longer produce enough insulin (type 1) or use it accordingly (type 2). As a result, the sugar taken in with food cannot be sufficiently transported from the blood into the cells. There is always too much glucose in the blood (hyperglycemia), at the same time the sugar utilization of the cells is disturbed.
Thanks to modern therapies and comprehensive treatment programs, nowadays diabetes is easy to handle.
(For more information about diabetes mellitus, please read relevant literature).
Diabetes and the autonomic nervous system
sympathetic and parasympathetic nerve
In general, the sympathetic nerve triggers a “fight or flight” response to stress. The heart rate increases, the lungs expand or open, digestion is inhibited, pupils dilate, and the body is provided with the resources it needs to protect itself in times of danger. The parasympathetic nervous system reacts “in reverse” as a “rest and digest” system. It promotes digestion, lowers the heart rate, increases the salivation, increases the urine secretion from the kidneys and narrows the pupils. They are not opponents but work in parallel to maintain the homeostatic balance in the body.
The blood and tissue glucose levels are maintained through several different processes, most of them are stimulated by various hormones. The following section focuses on processes that affect the autonomic nervous system.
When the blood sugar level drops, the sympathetic nerve is activated in healthy persons. This stimulates glucose production in the liver and kidneys and reduces glucose consumption in the muscles through adrenaline release. Parasympathetic stimulation has the opposite effect: insulin release from the pancreas, which stimulates glucose uptake by the cells, & reduction of glucose release from the tissue, and increased liver glycogen formation.
Hypoglycemia or low blood sugar levels leads to sympathetic activation, which raises blood sugar levels, while hyperglycemia, a high blood sugar level, leads to parasympathetic activation to lower blood sugar levels.
These two systems work together to maintain a healthy blood sugar level. Therefore, impaired parasympathetic regulation (decreased HRV) increases the risk of chronic hyperglycemia and hyperinsulinemia (increased insulin levels, also known as insulin resistance), which is a precursor to diabetes mellitus.
HRV & Diabetes
Cardiac autonomic neuropathy – an impairment of the nerves – in patients with type 2 diabetes mellitus (T2DM) is common and associated with high cardiovascular mortality. Heart Rate Variability (HRV), as a measurement system for detecting changes in the autonomic nervous system, is therefore suitable for measurement.
Some interesting study results of the last years
Kudat & colleagues (2006) studied cardiovascular autonomic neuropathy in diabetics (31 subjects) and healthy control persons (30 subjects) using HRV. It was found that both time- (pNN50, SDNN, RMSSD) and frequency- (High Frequency, Low Frequency) parameters of HRV were reduced in diabetic subjects compared to healthy control subjects. This means that both sympathetic and parasympathetic activity were reduced, which can be explained by the deleterious effects of altered glucose metabolism on HRV, which can lead to cardiac autonomic neuropathy.
Javorka et al. (2008) analyzed HRV measurements of 17 young patients with type 1 diabetes and 17 healthy control persons. It turned out that diabetes patients had a below-average HRV.
Also, Benichou and colleagues (2018) came to a similar conclusion in the study of persons with type 2 diabetes. Type 2 diabetes generally causes a reduction in HRV. Both sympathetic and parasympathetic activity were reduced, which may be explained by the deleterious effects of altered glucose metabolism on HRV. This in turn can lead to cardiac autonomic neuropathy.
So far, not all effects of diabetes on the HRV have been clarified, but a big step has already been done. Several researchers from various studies have found that diabetes, whether Type 1 or Type 2, can lead to a reduction in HRV. Different parameters were examined, time- and frequency-dependent. Little research has been done on VLF, although it is considered to be the most effective independent predictor of mortality in patients with heart failure.
HRV & Diabetes in the HRV spectrogram
The HRV spectrogram of a 62-year-old man with diabetes and obesity shows a significant reduction in HRV. VLF and LF are below the average of men of the same age, the heart rate over 24h is well above average.
The two-digit GVI, the high biological age and the reduced pNN50 are just a few selected parameters that suggest that the overall system of the measured is heavily loaded.
Of course, and not only because of a reduced HRV can and should be concluded on diabetes. Diagnosis always happens in combination with anamnesis and other, possibly medical, clarifications. However, the HRV can be used to reduce the burden of the system, among others. to depict.
(A reduced HRV is not automatically an indicator for diabetes!)
Benichout, T., Pereira, B., Mermillod, M., Tauveron, I, Pfebigan, D., Magdasy, S. & Dutheil, F. (2018). Heart rate variability in type 2 diabetes mellitus: A systematic review and meta-analysis. PloS one 13(4), e0195166.
Kudat, H., Akkaya, V., Sozen, A., Salman, S., Demirel, S., Ozcan, M., … Guven, O. (2006). Heart Rate Variability in Diabetes Patients. Journal of International Medical Research, 34(3), 291–296. https://doi.org/10.1177/147323000603400308
Javorka, M., Trunkvalterova,Z., Tonhajzerova, I., Lazarova, Z., Javorkova, J & Javorka, K. (2008). Recurrences in heart rate dynamics are changed in patients with diabetes mellitus. Clinical Physiology and Functional Imaging, 28(5), 326-331. https://doi.org/10.1111/j.1475-097X.2008.00813.x