Impact of obesity on ECG waveforms across racial/ethnic groups in the general population

Obesity is associated with distinct ECG manifestations due to altered body fat distribution, which may vary by race/ethnicity. However, few studies have evaluated these differences.

We analyzed 7315 participants (mean age 59.6 ± 13.5 years; 52.4% female; 51.5% non-Hispanic White, 24.5% non-Hispanic Black, 24.0% Mexican American) from NHANES III, excluding those with prior cardiovascular disease or missing ECGs. Obesity was defined as BMI ≥30 kg/m². Standard 12‑lead ECGs were recorded and processed centrally. ECG waveform amplitudes and durations, PR, QRS and QT intervals, and P-, QRS-, and T-wave axes were measured automatically with visual inspection. Multivariable linear regression assessed associations between obesity and ECG parameters overall and stratified by race/ethnicity.

Obesity was associated with prolonged QRS, QT, and PR durations (differences [msec] obese vs. non-obese [95% CI]: 2.17 [1.43-2.90], 1.90 [0.87-3.01], and 4.82 [3.40-6.24], respectively; all p < 0.001), and more leftward P-, QRS-, and T-wave axes (differences [degrees]: -7.36 [-8.54, -6.18], -9.53 [-11.52, -7.53], -7.02 [-8.60, -5.43]; all p < 0.001). Obesity was further associated with lower R and S amplitudes and prolonged wave durations in nearly all leads, with exceptions in III and aVF. Most associations were consistent across races, though effects on S amplitude in V3/V4, R duration in aVL, and S duration in II were weaker in Mexican Americans and non-Hispanic Whites (interaction p = 0.01-0.03).

Obesity influences ECG waveform amplitudes and durations, largely independent of race/ethnicity. These findings support non-race-specific ECG interpretation while highlighting potential limitations of amplitude- and duration-based criteria.