The inverse and non-linear association between central augmentation index and heart rate variability in a cohort of male British combat personnel- findings from the ADVANCE study

Abstract: AbstractPurposeMethodResultsConclusion\nPlain Language SummaryThe central augmentation index (cAIx) is an indirect measure of arterial stiffness. The influence of heart rate variability (HRV) on cAIx remains unexplored in a military cohort and was the aim of this analysis.The first follow-up data from the ArmeD serVices trAuma rehabilitatioN outComE (ADVANCE) study were analysed. Participants were male British servicemen who served in Afghanistan (2003-2014) and were divided into two groups at recruitment: injured (who sustained severe combat injury) and uninjured. The uninjured were frequency-matched to the injured by age, rank, role-in-theatre and deployment. HRV was reported as root-mean-square-of-successive-differences (RMSSD) using a five-minute single-lead electrocardiogram. The cAIx was measured using pulse waveform analysis and was adjusted for heart rate at 60 beats/minute (cAIx@60). Effect modification by injury was assessed via interaction analysis. Linear models reported the association between RMSSD (HRV) and cAIx@60 adjusting for a priori confounders.1052 participants (injured n = 526; uninjured 526; median age at follow-up 37.4 years) were examined. Effect modification by injury was not statistically significant; therefore, was adjusted for along with other confounders. RMSSD and cAIx@60 exhibited a moderate inverse correlation (-0.40; p < 0.001). The association between natural log-transformed RMSSD (LnRMSSD) and cAIx@60 was non-linear and statistically significant, suggesting that a 10% decrease in LnRMSSD would be associated with 0.30% increase in cAIx@60.Lower RMSSD (HRV) is associated with an increase in cAIx@60, independent of injury status and other traditional cardiovascular risk factors. The efficacy of positive HRV modification on cardiovascular risk in military populations needs to be examined.The hardening of arteries can lead to serious cardiovascular sequelae and adversely affect health and wellbeing of an individual. One way to measure hardening of arteries (also known as arterial stiffness) is through the use of central augmentation index (cAIx). The cAIx measures the extra ‘workload’ the heart faces due to ‘augmented pressure’ or the ‘extra pressure’ exerted on the heart due to hardening of arteries. Previous research has not investigated whether there is a relationship between cAIx and heart rate variability (a measure of autonomic function), especially in a contemporary military cohort. This is crucial as servicemen may have an increased cardiovascular disease risk due to combat exposure and combat injuries, and studying this association may have important implications for their recovery. Therefore, the goal of this analysis was to explore the association between cAIx and HRV. With multivariable regression analysis and after controlling for confounders, we found an inverse and non-linear association between cAIx and HRV in a sample of British military cohort. It suggests that an increase in cAIx leads to a decrease in HRV but not in a linear way. Leveraging on this association, the results suggest the need to explore HRV elevating activities to mitigate the risk of arterial stiffness in military populations. [ABSTRACT FROM AUTHOR] — Copyright of Blood Pressure is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)