Correlations of First and Second Heart Sounds with Age, Sex, and Body Mass Index

Abstract

Although auscultation of heart sounds is a commonly used diagnostic tool in preliminary investigation of heart function, no description of normal amplitudes of the two major heart sounds, the first (S1) and second (S2) heart sounds, and their relation to age, sex, and body mass index (BMI), exist. Heart sound recordings from 739 healthy subjects, from the Dan-NICAD study, recorded with Acarix CADScor System at the left fourth inter-costal space (IC4), were investigated. The S1 and S2 sounds were isolated using an automated segmentation algorithm and their absolute amplitudes, |S1| and |S2|, were tested for correlation with age, sex, and BMI. Mean S11 was 95.4 (±6.2) dB for men and 93.7 (±6.8) dB for women, which showed a significant difference (p<0.05). Mean |S2| was 91.9 (±5.1) dB for men and 91.8 (±5.6) dB for women, showing no significant difference (p=0.82). |S1| and |S2| were only weakly correlated with age (r=−0.084 and r=−0.069 respectively). Both |S1| and |S2| were well correlated with BMI (r=−0.42 and r=−0.50 respectively). The correlation between BMI and the amplitude of heart sounds is an important baseline knowledge when developing algorithms for automated analysis of heart sounds.