Heart Rate Variability, Insulin Resistance, and Insulin Sensitivity in Japanese Adults: The Toon Health Study.

ABSTRACT

BACKGROUND: Although impaired cardiac autonomic function is associated with an increased risk of type 2 diabetes in Caucasians, evidence in Asian populations with a lower body mass index is limited. METHODS: Between 2009-2012, the Toon Health Study recruited 1899 individuals aged 30-79 years who were not taking medication for diabetes. A 75-g oral glucose tolerance test was used to diagnose type 2 diabetes, and fasting and 2-h-postload glucose and insulin concentrations were measured. We assessed the homeostasis model assessment index for insulin resistance (HOMA-IR) and Gutt's insulin sensitivity index (ISI). Pulse was recorded for 5 min, and time-domain heart rate variability (HRV) indices were calculated the standard deviation of normal-to-normal intervals (SDNN) and the root mean square of successive difference (RMSSD). Power spectral analysis provided frequency domain measures of HRV high frequency (HF) power, low frequency (LF) power, and the LFHF ratio. RESULTS: Multivariate-adjusted logistic regression models showed decreased SDNN, RMSSD, and HF, and increased LFHF ratio were associated significantly with increased HOMA-IR and decreased ISI. When stratified by overweight status, the association of RMSSD, HF, and LFHF ratio with decreased ISI was also apparent in non-overweight individuals. The interaction between LFHF ratio and decreased ISI in overweight individuals was significant, with the odds ratio for decreased ISI in the highest quartile of LFHF ratio in non-overweight individuals being 2.09 (95% confidence interval, 1.41-3.10). CONCLUSIONS: Reduced HRV was associated with insulin resistance and lower insulin sensitivity. Decreased ISI was linked with parasympathetic dysfunction, primarily in non-overweight individuals.