INCREASED BLOOD PRESSURE VARIABILITY AND DECREASED HEART RATE VARIABILITY IN OLDER VS. YOUNGER INDIVIDUALS: MARKERS OF DISTURBED CARDIOVASCULAR AUTONOMIC MODULATION WITH AGEING?

Objective: Cardiovascular regulation is affected by ageing through different mechanisms, including arterial baroreflex dysfunction and increased arterial stiffness, with an impact on blood pressure (BP) and heart rate (HR) variability (V), established risk factors for cardiovascular morbidity and mortality. The aim of this study was to compare BPV and HRV in older vs. younger individuals. Design and method: 1080 hypertensive patients (704 younger, 40-55yrs, YH and 376 older, >=75yrs, OH) underwent 24h BP monitoring (ABPM) from 2018 to 2023. Patients with known dysautonomy, Parkinson or other neurodegenerative diseases were excluded. Short-term BPV indexes including standard deviation (SD), weighted standard deviation (wSD), average real variability (ARV), coefficient of variation (CV), and variability independent of mean (VIM) were estimated over 24h. HRV was assessed by SD and CV of heart rate measured during ABPM. The same analysis was replicated in a sample of 343 untreated individuals from the general population (309 YH; 34 OH). Results: As compared to YH, (mean age: 49.5±4.5yrs), OH (mean age: 80.2±4.5yrs) had significantly higher 24h systolic BPV (SD: 15.7±4.6 vs.13.6±4.0; wSD: 15.5±4.6 vs.13.5±4.0; ARV: 12.3±2.9 vs.10.0±2.7; VIM: 15.8±4.5 vs.13.9±4.0 mm Hg; CV: 12.2±3.5 vs.10.8±3.1%; p<0.001). In contrast, 24h HRV was significantly lower in OH than in YH group (SD: 7.2±3.0 vs. 9.1±3.4 beats/min; CV: 11.5±4.5 vs. 12.8.1±4.5%; p<0.001). Higher tertiles of BPV were associated with higher mean pulse pressure and higher pulsatility (pulse pressure normalized for mean arterial pressure), in both YH and OH. Similar results were obtained when comparing OH vs. YH individuals in the general population sample, both for 24h systolic BPV (SD: 14.7±3.1 vs.12.2±2.8; wSD: 14.9±3.1 vs.12.7 ±3.0; ARV: 11.5±2.1 vs.9.2±2.0; VIM: 13.6±2.5 vs.12.3±2.4 mmHg; CV: 11.4±2.1 vs.10.1±2.0%; p<0.01) and HRV (SD: 8.8±3.2 vs. 11.3±3.4 beats/min; CV: 12.7±4.5 vs. 15.1±4.3%; p<0.01). Conclusions: Increased BPV was associated with decreased HRV in older compared to younger individuals, both in a hypertensive cohort and in a general population sample. The respective contribution to these changes of age-related dysfunction of autonomic cardiovascular modulation and increased arterial stiffness and their prognostic implications deserve further investigation.