Heart rate variability, insulin resistance and insulin sensitivity in Japanese adults: the Toon Health Study

INTRODUCTION:  Varied genetic backgrounds due to ethnicity are implicated in the pathogenesis of diabetes.  Although abnormal cardiac autonomic function is associated with increased risk of diabetes in Caucasians, evidence is limited in Asian populations with lower body weight.

METHODS:  The Toon Health Study recruited 1,899 individuals without medication for diabetes, ages 30-79 years during 2009-2012.  A 75-g oral glucose tolerance test was used to diagnose diabetes, and fasting and 2h-postload glucose and insulin concentrations were measured.  We assessed 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) measures were assessed: standard deviation of all normal-to-normal RR intervals (SDNN), and square root of mean squared differences of NN intervals (RMSSD).  Power spectral analysis provided high frequency (HF) power, low frequency (LF) power and LF/HF, as frequency domain measures of HRV. 

RESULTS:  Decreased SDNN, RMSSD and HF, and increased LF/HF ratio were significantly associated with increased HOMA-IR or decreased ISI in multivariable-adjusted logistic regression models.  When stratified by overweight status, associations of RMSSD, HF and LF/HF ratio with decreased ISI were also apparent in non-overweight individuals.  An interaction of LF/HF ratio for decreased ISI with overweight conditions was significant, and the odds ratio for decreased ISI in highest quartile of LF/HF ratio in non-overweight was 2.09 (95% confidence interval, 1.41-3.10).

CONCLUSIONS:  HRV was associated positively with insulin resistance, and inversely with insulin sensitivity.  Reduced ISI was associated with decreased parasympathetic function, primarily in non-overweight individuals.