Relationship between heart rate variability and differential patterns of cortisol response to acute stressors in mid‐life adults: A data‐driven investigation

Abstract

Cortisol and heart rate variability (HRV) are well‐established biomarkers of the human stress response system. While a relationship between cortisol and HRV is assumed, few studies have found evidence of their correlation within single study designs. One complication for isolating such a relationship may lie in individual variability in the cortisol response to stress such that atypical cortisol responding (i.e., elevated or blunted) occurs. To‐date, studies on the cortisol response have employed traditional mean‐difference‐based approaches to examine average magnitude change in cortisol over time. Alternatively, data‐driven trajectory modelling, such as latent growth mixture modelling, may be advantageous for quantifying cortisol based on patterns of response over time. Latent growth mixture modelling was used in N = 386 adults to identify subgroups based on trajectories of cortisol responses to stress. The relationship between cortisol and HRV was tested within subgroups. Results revealed a ‘prototypical’ subgroup characterised by expected rise and fall in cortisol response to stress (n = 309), a ‘decline’ subgroup (n = 28) that declined in cortisol after stress, and a ‘rise’ subgroup (n = 49) that increased in cortisol after stress. Within the ‘prototypical’ subgroup, greater HRV during stress was associated with decline in cortisol after stress from its maximum (r (306) = 0.19, p < 0.001). This relationship failed to emerge in the ‘decline’ and ‘rise’ subgroups (p > 0.271). Results document different patterns of cortisol response to stress; among those who exhibit a ‘prototypical’ response, changes in HRV during stress are related to changes in cortisol after stress.