Autonomic Function Tests in Diabetic Hypertensive and Non-Diabetic Hypertensive Patients: A Case-Control Study

Abstract

Background and Objective: Autonomic neuropathy, particularly cardiovascular autonomic dysfunction, is a common complication in individuals with long-standing hypertension and diabetes mellitus. Both conditions are associated with increased risks of adverse cardiovascular outcomes. Although autonomic dysfunction has been extensively studied in diabetes and in hypertension separately, the comparative assessment of autonomic dysfunction between diabetic hypertensive and non-diabetic hypertensive patients remains understudied. This study aimed to evaluate and compare cardiovascular autonomic functions in diabetic hypertensive (DH) and non-diabetic hypertensive (NDH) individuals using standard clinical autonomic function tests, thus providing insights into the extent and patterns of autonomic impairment in each group.
Methods: This study included 260 participants split into two groups: 130 DH patients (cases) and 130 NDH patients (controls), matched for age, sex, and duration of hypertension. Data on baseline clinical characteristics, including body mass index (BMI), duration of hypertension, glycemic control, and comorbidities, were recorded. Standard cardiovascular autonomic function tests were performed, including the heart rate response to deep breathing (HRDB), Valsalva maneuver (Valsalva ratio), orthostatic blood pressure changes, handgrip test, and heart rate variability (HRV) analysis. Statistical comparisons were made using univariate and multivariate analyses to account for covariates such as age, sex, and body mass index.
Results: The DH group showed significantly lower HRDB and HRV indices than the NDH group (p < 0.05). Furthermore, the drop in systolic blood pressure upon standing was more pronounced in the DH group, while the Valsalva ratio was decreased to a similar extent in both groups, suggesting a significant parasympathetic impairment in DH participants. Duration of diabetes, poor glycemic control (higher HbA1c), and longer duration of hypertension were significantly correlated with impaired autonomic function.
Conclusion: Diabetic hypertensive patients exhibit more pronounced abnormalities in cardiovascular autonomic control when compared to non-diabetic hypertensive patients. Comprehensive autonomic function testing should be considered in routine clinical assessments for hypertensive patients, especially those with concomitant diabetes, to detect and manage autonomic dysfunction at an early stage.