Abstract P019: Insulin resistance indexes and lower heart rate variability in older adults: the Atherosclerosis Risk in Communities Study (ARIC)

Abstract

Introduction: Lower heart rate variability (HRV) is an indicator of cardiac autonomic dysfunction which is associated with cardiovascular disease in diabetes. Whether pre-diabetes insulin resistance contributes to lower HRV is not clear; insulin resistance (IR) indexes reflect different aspects of IR, including dysregulation of glucose, insulin, and lipids. We hypothesized that IR indexes are inversely associated with HRV. Methods: We analyzed 48-hour ambulatory electrocardiograms on 759 adults in a sample of the ARIC Study, excluding diabetes, antiarrhythmic medications, and missing/poor quality recordings. Insulin resistance indexes were defined as quartiles for the homeostatic model assessment of insulin resistance (HOMA-IR), triglyceride to HDL-C ratio (TG/HDL-C), and triglyceride-glucose index (TyG). Low HRV was defined as <25 th percentile for time domain measures -- including the standard deviation of all NN intervals (SDNN) and square root of the mean squared differences of successive NN intervals (RMSSD), and frequency domain measures -- including the high-frequency (HF) and low-frequency (LF) spectral components. Logistic regression with weights for sampling and nonresponse was used to estimate odds ratios and 95% confidence intervals (OR, 95% CI). Results: Mean age was 75 years [993 (63%) women, 688 (43%) African American]. The following results are reported for TyG. For time domain measures, high IR indexes were significantly associated with low SDNN (OR 1.83, 95% CI 1.09, 3.07), but not with low RMSSD (OR 1.48, 95% CI 0.89, 2.46). For frequency domain measures, high IR indexes were not associated with low HF (OR 1.62, 95% CI 0.96, 2.74), but significantly associated with low LF (OR 1.95, 95% CI 1.15, 3.30). Although results for other indexes were in the same direction, most were not statistically significant. Conclusions: Insulin resistance indexes may be inversely associated with HRV. An understanding of this relationship informs public health strategies for prevention of cardiovascular risk.