O-42: Delayed heart rate recovery during submaximal exercise in Youth-Onset type 2 diabetes: the young at heart longitudinal study
S Chung, I Kacker, M Gaydos, N Sala, E Flacke, N Macheret, S Cantor, O Charles, N Rangos, L Mabundo, N Malandrino, A Ishihara, A Courville, A Hengist, S LaMunion, A Wentzel, R Brychta, K ChenAbstract
Introduction
Reduced heart rate variability (HRV) in youth-onset type 2 diabetes (Y-T2D) is a marker of altered autonomic nervous system (ANS) modulation, which is associated with high hemoglobin A1c. However, the progression of impaired ANS modulation in Y-T2D with good glycemic control compared to healthy peers with obesity (CON) is unclear.
Objectives
In Y-T2D and CON, we compared dynamic heart rate (HR) and HRV at rest and during exercise.
Methods
This baseline preliminary analysis (n=28, 22 Y-T2D, 6 CON) assessed HR and SDNN (a gold-standard HRV parameter) using 24h ECG monitors. We assessed a 5 min interval at rest and four 2 min intervals before, during, and after an Astrand-Rhyming submaximal exercise test (−10, peak (0), +2, and +4 min). Group differences were assessed using Wilcoxon rank-sum and chi-square tests. Mixed-effects models evaluated HRV metrics adjusted for age, sex, and body mass index (BMI).
Results
Y-T2D and CON (54% female, 79% Black) were similar in age, 21 [20, 21] y, resting HR, 78 [68, 87] bpm, systolic blood pressure, 122 [114, 129] mmHg, BMI, 37 [30.8, 39.3] kg/m2, A1c, 6 [5.3, 8.3] %, and estimated VO2 max: female 18.6 [14.7, 22.3], male 24 [17.2, 29.7] mL/kg/min (median [IQR])). Resting HR and SDNN were similar by group (HR: 72 ± 9 bpm, SDNN: 56.4 ± 23.5 ms, mean ± SD). During exercise, peak HR was similar, but in recovery, HR remained elevated in YT2D vs. CON (Figure 1A, P=0.04). Peak SDNN was similar but tended to be lower in Y-T2D across recovery intervals (Figure 1B, P>0.35).
Conclusions
In youth with Y-T2D and good glycemic control, delayed dynamic HR responses to exercise, despite similar resting HRV and estimated fitness compared to CON, may indicate early ANS impairments not evident at rest.