Association of electrocardiographic PR interval and obesity with atrial fibrillation in older Chinese : the Guangzhou biobank cohort study

Abstract

Background: Obesity is related to altered atrioventricular conduction and an independent risk factor for AF. There has been no study on the longitudinal association of obesity with PR prolongation in community population. Few studies documented associations of longer and shorter PR interval with AF risk, and no study on Asian populations. Objectives 1. To examine the associations of body mass index (BMI) with PR interval/first-degree atrioventricular block (AVB1); examine the associations of BMI/obesity (BMI ≥25 mg/m2) with atrial fibrillation (AF) risk cross-sectionally and longitudinally;

2. To examine the association of PR interval with AF risk; and analyze whether longer PR interval acts as a mediator of the association between obesity and AF risk.

Methods: 30518 Chinese aged 50+ years (27% men) from the Guangzhou Biobank Cohort Study. 17129 participants (27% men) were repeated 12-lead electrocardiograms after a 4-year median follow-up. Electrocardiographic delta waves were excluded from the thesis.

Results: BMI was positively associated with PR interval in both sexes (P <0.001), and the association was stronger in men than in women from baseline data (P for interaction <0.001). A 12% increase in the risk of AVB1 at follow-up per kg/m2 increase in baseline BMI was observed; baseline obesity increased risk of AVB1 at follow-up adjusting for potential confounders in men (RR=2.34, 95% confidence interval (CI):1.55-3.53). No significant longitudinal association was found in women, which could be due to an insufficient follow-up period.

Current smoking was associated with shorter PR interval in baseline data (β-coefficients=-1.56, P <0.001). However, current smoking strengthened the positive association between BMI and PR interval in both normal and obese individuals (P for interaction=0.01).

Higher BMI was associated increased AF risk in baseline data (OR=1.07 per kg/m2, P <0.05). Baseline obesity increased risk of AF at follow-up adjusting for potential confounders (RR=2.43, P<0.05). Baseline underweight increased the risk for AF at follow-up (RR=3.04, 95% CI: 1.04-8.87), although this needs to be confirmed and checked whether this association was population-specific.

A J-shaped relation between PR interval and AF risk at follow-up after controlling for potential confounders was found. Both longer PR interval [≥160 ms] (RR=2.00, 95% CI: 1.07-3.75) and short PR interval [<140 ms] (RR=1.66, 95% CI: 0.83-3.32) had an adverse effect on the development of AF compared with healthy controls [PR interval within 140-159 ms], but shorter PR did not reach statistical significance.

Longer PR interval [≥160 ms] was a significant partial mediator (P=0.04); a minor effect of baseline higher BMI (8%) on the development of AF via longer PR interval was observed, and the majority of obesity effect acted on AF directly.

Conclusions: Data from southern Chinese showed obesity was associated with longer PR interval; and longer PR interval was an independent risk factor for new onset AF after controlling for obesity. PR interval ≥160 ms could be a partial mediator of the association between obesity and the development of AF. Moreover, current smoking was associated with shorter PR, and significantly strengthened the positive association between BMI and PR interval in both normal and obese individuals.