Association between carotid arterial strain and heart rate variability in older age

BackgroundLoss of the normal heart rate variability (HRV) predicts death. We hypothesised that impaired arterial compliance and increased vascular stiffness, could inhibit the baroreceptor reflex, resulting in cardiac autonomic dysfunction and loss of the normal HRV. AimsTo investigate the association between carotid arterial strain (CAS) and HRV in an older age population-based cohort. MethodParticipants (60-64 years) were from the 1946 Medical Research Council, National Survey of Health and Development British birth cohort. Carotid intima media thickness (cIMT) and CAS (exposures) were measured by ultrasound and time- and frequency-domain HRV indices (outcomes) by a resting 5-minute 12-lead tachogram. Generalized linear models were used, adjusted for relevant clinic-demographic confounders and subjected to sensitivity analysis in which we re-analyzed associations after additional adjustment for cIMT and after removing participants with known cardiovascular disease. Results896 participants were included. On univariate analysis CAS was associated with HRV markers: standard deviation of normal-to-normal beats (SDNN), root mean square of successive differences (RMSDD), HRV triangular index, high- and low-frequency (H/LF) normalised high-frequency power (all p<0.05). Associations persisted in fully confounder-adjusted models: SDNN {beta}=0.52 [confidence interval: 0.2,0.8] p<0.001; RMSDD {beta}=0.59 [0.3,0.9], p<0.001; HRV triangular index {beta}=-0.34 [-0.5,-0.1], p<0.001; HF power {beta}=8.33 [2.2,14.4], p=0.007; LF power {beta}=8.47 [1.0,15.9], p=0.026; normalised HF power {beta}=0.55 [0.2,0.9], p=0.006. Key associations persisted in the sensitivity analysis. ConclusionRegardless of carotid atherosclerotic vascular disease (indicated by cIMT), hypertension or stroke, increased carotid arterial function in older age associates with a loss of HRV, potentially through an impaired baroreceptor response.