Independent predictors of cardiac parasympathetic dysfunction in type 2 diabetes mellitus

Introduction: Although the clinical implications of diabetic autonomic neuropathy have been described, the clinical determinants of parasympathetic dysfunction in type 2 diabetes mellitus are not clear. We investigated the clinical determinants of heart rate response to deep breathing in type 2 diabetes mellitus. Methods: This study involved 207 randomly selected patients with type 2 diabetes mellitus and 141 healthy controls. Heart rate response to deep breathing was measured in all the subjects. Heart rate response to Valsalva manoeuvre and active standing was measured in lesser numbers. Data analysis was done using unpaired Student's t-test, Pearson's correlation test and multiple regression. Results: Heart rate response to deep breathing, Valsalva manoeuvre and active standing was lower in patients with diabetes mellitus than in controls (p-value is less than 0.0001, 0.01 and 0.01, respectively). Age, female gender and presence of somatic neuropathy were the independent predictors of reduced heart rate response to deep breathing (p-value is 0.001). Independent positive correlation was found between resting heart rate and heart response to deep breathing (p-value is 0.02). Factors associated with depressed heart rate response to deep breathing, but not independently predictive, were duration of diabetes mellitus, presence of hypertension, coronary artery disease, foot ulcer and retinopathy. Mean heart rate response to deep breathing of 47 patients with diabetes mellitus free of all complications was lower compared to controls (p-value is less than 0.01). Conclusion: Our data suggests that parasympathetic dysfunction mainly coexists with somatic neuropathy. It may be isolated, or precede detection of other complications. Age and female gender are the other predictors of reduced heart rate response to deep breathing in type 2 diabetes mellitus.