Sex-specific cardiac ageing and sympathetic compensation: a translational study

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BACKGROUND AND AIMS: Recent evidence suggests that individuals with smaller left ventricular (LV) volumes and high LV ejection fraction face an increased risk of cardiovascular morbidity and mortality. Age-related cardiac changes may particularly predispose women to these risk conditions. METHODS: LV morphometry was analysed by cardiac magnetic resonance imaging in 39 616 individuals (aged 45-85 years, 52.2% women) from the UK Biobank using an observational cross-sectional study design. Additional analyses were conducted in a mouse model of hormone withdrawal and ageing (118 mice aged 4-6 [young cohort] or 18-20 [aged cohort] months, 50% females) as well as in a 3D human microtissue (hMT) model assessing the cellular effects of sex hormones. RESULTS: Both women and men exhibited age-related reduction of LV volumes, with women showing a significantly stronger decline than men (indexed LV end-diastolic volume [LVEDVI]: r = -0.272, P = .037 vs men). A compensatory increase in baseline heart rate (HR) was more pronounced in women (r = 0.121, P < .001 vs men) resulting in a lesser age-related decline in cardiac indices in women than in men (r = -0.169 in women vs r = -0.211 in men, P = .045 vs men). In mice, sex differences in cardiac ageing were more pronounced than in humans, with age-related reductions in LV volumes alongside an increase in collagen I production (0.743 ± 0.364 vs 1.611 ± 0.372 arbitrary units [AU], P = .002 and 1.925 ± 0.27 vs 1.838 ± 0.329 AU, P = .0972 for young vs old in males), being significant only in females (LVEDVI: P < .001 for young vs old females). Withdrawal of sex hormones in mice eliminated age-related changes in LV volumes. Compensatory mechanisms accounting for smaller LV volumes, including an age-related increase in HR (377 ± 45 vs 438 ± 40 bpm, P = .012 for young vs old females) and cardiac sympathetic activity (0.206 ± 0.02 vs 0.148 ± 0.03% injected dose per mL, P = .008 for young vs old females), were significant only in female mice. In a 3D hMT model, both female and male sex hormones exerted anti-fibrotic and anti-apoptotic effects on cardiomyocytes and fibroblasts. A decline in female sex hormone production with age was observed in both species, while testosterone levels remained essentially unchanged over the lifespan. CONCLUSIONS: Age-related cardiac changes affect both women and men in similar ways, but are more pronounced in women-likely reflecting a greater decline in sex hormones. This is associated with more prominent compensatory mechanisms to offset their disadvantage of having a smaller heart. Animal and tissue models support these findings by revealing hormone- and sex-specific effects on cardiac structure and sympathetic regulation.

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