Endocrine Abstracts

Background: Diabetes mellitus is associated with abnormal autonomic function. Diabetes and impaired fasting glucose are associated with increased mortality, particularly from cardiovascular causes. Several factors, including fast heart rate, have been identified to be associated with an increased likelihood of having diabetes. Heart rate is a crude index of the autonomic nervous system tone, reflecting a balance of sympathetic and parasympathetic inputs, and correlates with muscle sympathetic nerve activity and noradrenaline serum levels. Examining its potential role in diabetes risk could improve our understanding of the pathogenesis of diabetes.

Aim: Aim of our study was to establish correlation between fasting heart rate and fasting and post prandial blood glucose levels.

Materials and Methods: 509 patients between age group 25 years to 75 years were studied at different centers in India. Resting heart rate was recorded on finger pulse oximeter before taking fasting blood sample. Fasting and post prandial blood samples were obtained by venepuncture and estimation was done by the hexokinase method. Diabetes mellitus was defined as use of insulin or a hypoglycemic agent, a fasting plasma glucose level of 126 mg/dl or more (≥7.0 mmol/l), or a 2-hour postprandial plasma glucose level of 200 mg/dl or more (≥11.1 mmol/l). Pearsons correlation test was used for statistical analysis.

Results: We found that resting heart rate was significantly higher in patients with higher fasting blood glucose levels compared with patients with normal glucose levels. This difference was statistically significant with P = 0.002 (r:0.137). It was also noted that fasting heart rate was also significantly higher in patients with higher post prandial blood glucose levels with P value of 0.002.

Conclusions: Our study strongly supports faster resting heart rate as an independent risk factor for incident diabetes and impaired fasting glucose. Meta-analysis of seven published studies confirmed the positive association between resting heart rate and diabetes risks. A resting heart rate is generally considered as a surrogate marker for autonomic activity, and increased sympathetic nerve system activity is associated with both acute and chronic insulin resistance. One of the most important mechanisms for increased diabetic risk might be that sympathetic activation causes vasoconstriction and decreases skeletal muscle blood flow, resulting in the impairment of glucose uptake into the skeletal muscle. Ultimately, the exact mechanism by which increased heart rate is induced remains to be elucidated; however, our findings suggest that this area of investigation may be relevant for future studies.