Electrocardiographic Parameters and Short-Term Heart Rate Variability in Obese and Non-Obese Young Adults: A Cross-Sectional Comparative Study

Abstract

Objective: To compare selected Lead II electrocardiographic parameters and short-term heart rate variability indices between obese and non-obese young adults and to examine their relationships with body mass index. Methods: This cross-sectional comparative study included 600 apparently healthy adults aged 18-25 years. Participants were classified using Asian Indian body mass index criteria as obese (n=238) or non-obese (n=362). Anthropometry and blood pressure were recorded using standard procedures. A five-minute Lead II electrocardiogram was acquired using a Contec TLC-5000 system. Heart rate, P-wave duration, PR interval, QRS duration and Bazett-corrected QT interval were assessed. Short-term heart rate variability analysis included SDNN, RMSSD, pNN50, low-frequency power, high-frequency power and the LF/HF ratio. Group comparisons and Pearson correlations were performed. Results: Obese participants had higher systolic and diastolic blood pressure than non-obese participants (134.5±9.2 versus 114.2±7.8 mmHg and 86.4±7.5 versus 74.5±6.1 mmHg; p<0.001). SDNN, RMSSD, pNN50 and high-frequency power were lower, whereas low-frequency power and the LF/HF ratio were higher in the obese group (p<0.001). Heart rate and all measured ECG intervals were significantly higher in obese participants. Body mass index correlated positively with systolic pressure (r=0.610), QTc interval (r=0.332) and LF/HF ratio (r=0.576), and negatively with SDNN, RMSSD and high-frequency power (p<0.001). Conclusion: Obesity in young adults was associated with higher resting blood pressure, reduced vagally mediated heart rate variability and longer mean cardiac conduction and repolarisation intervals. These non-invasive findings support early cardiovascular risk assessment in young adults with increased adiposity.