Sex-and age-related variations in myocardial tissue composition of the healthy heart: a native T1 mapping cohort study

Cardiovascular diseases manifest differently in males and females, potentially influenced by inherent sex- and age-related differences in myocardial tissue composition. Such inherent differences are not well-established in the literature. With this study using cardiac magnetic resonance (CMR) native T1 mapping, we aim to determine the effect of sex and age on myocardial tissue composition in healthy individuals. CMR native T1 mapping was performed in 276 healthy individuals (55% male, age 8---84 years) on a 1.5 Tesla scanner using a MOLLI 5(3)3 acquisition scheme. Additionally, 30 healthy participants (47% male, age 24-68 years) underwent a 1-year follow-up CMR to assess the longitudinal changes of native T1. Mean native T1 values were 1000 ± 22 ms in males and 1022 ± 23 ms in females [mean difference (MD) = 22 ms, 95% confidence interval (CI) (17, 27)]. Female sex was associated with higher native T1 in multivariable linear regression adjusting for age, heart rate, left ventricular mass index, and blood T1 [β=10 ms, 95% CI (3.4, 15.8)]. There was no significant interaction between sex and age (P = 0.27). Further, age was not associated with native T1 [β=0.1 ms, 95% CI (-0.02, 0.2)], and native T1 did not change during a 1-year period [MD -4 ms, 95% CI (-11, 3)]. Female sex was associated with higher native T1; however, there was no association between age and native T1. Additionally, there was no evidence of an interaction between sex and age. Our findings indicate intrinsic sex-based disparities in myocardial tissue composition.