Lean body mass is the independent and predominant anthropometric variable associated with atrioventricular block

Information regarding the association between lean body mass (LBM) and atrioventricular (AV) block risk is lacking.

The purpose of this study was to determine the associations of LBM with the risk of AV block.

We analyzed 370,415 UK Biobank participants who underwent bioimpedance analysis and had no history of AV block or cardiac implantable electronic devices. The primary outcome was a composite of second- or third-degree AV block. Secondary outcomes included each component of the primary outcome and AV block-related pacemaker implantation. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) per 1-SD increase in LBM were estimated using multivariable Cox regression.

The mean age was 56.8 years, and 52.4% were women. During a median follow-up of 11.8 years, 1519 (0.9%) and 677 (0.4%) primary outcome events occurred in men and women, respectively. LBM per 1-SD increase (7.7 kg in men and 5.0 kg in women) was associated with a 15% (HR 1.15; 95% CI 1.09-1.21; P < .001) and 13% (HR 1.13; 95% CI 1.05-1.22; P = .001) higher risk of the primary outcome in men and women, respectively. Associations remained significant even after adjustment for various anthropometric variables. Similar patterns were observed for all secondary outcomes. Higher LBM was associated with a prolonged PQ interval. The sex difference in incident primary outcome was attenuated after LBM adjustment.

Higher LBM was associated with an increased AV block risk in both sexes and with a higher prevalence of a prolonged PQ interval. Sex differences in AV block risk may be partly mediated by differences in LBM.