Epidemiological evidence of altered cardiac autonomic function in subjects with impaired glucose tolerance but not isolated impaired fasting glucose

Context: Autonomic dysfunction is present in diabetes mellitus (DM), but no study is available on alteration in cardiac autonomic function (CAF) across different glycemic statuses including normal glucose tolerance (NGT), isolated impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and DM. Objective: Our objective was to examine whether CAF is altered in subjects with IGT and isolated IFG. Design and Setting: The study was a stratified systematic cluster sampling design within the general community. Participants: A total of 1440 subjects were classified as NGT (n = 983), isolated IFG (n = 163), IGT (n = 188), and DM (n = 106). Main Outcome Measure: CAF was determined by 1) standard deviation of normal-to-normal (SDNN) or RR interval, power spectrum in low and high frequency (LF, 0.04-0.15 Hz; HF, 0.15-0.40 Hz), and LF/HF ratio in supine position for 5 min; 2) ratio between 30th and 15th RR interval after standing from supine position (30/15 ratio); and 3) average heart rate change during breathing of six deep breaths for 1 min (HR_DB). Results: Univariate analysis showed significant differences in SDNN, 30/15 ratio, HR_DB, HF power, and LF/HF ratio among subjects with NGT, isolated IFG, IGT, and DM. In multivariate analysis, none of the indices of CAF was related to isolated IFG in the reference group of NGT. IGT and DM were negatively associated with 30/15 ratio and HF power but positively associated with LF/HF ratio. In addition, DM was also related to a lower SDNN. Conclusions: DM and IGT subjects had an impaired CAF independent of other cardiovascular risk factors. The risk of altered CAF is not apparent in subjects with isolated IFG.