Allostatic load and its connection to the brain

Abstract

Although individual stress reactions are adaptive, chronic stress hasnegative effects onpsychological andphysiological functioning. It is therefore important to investigate the dysregulation associated with chronic stress – in the brain and in the rest of the body. Oneway to conceptualize the causes and effects of chronic stress is “allostatic load”, which describes the bodily cost an organism has to carry for adapting to changing environments (McEwen, 1998). Allostatic load can be quantified through a multi-systemic and cumulative measurement, an allostatic load index. We collected data from 96 young (45 female; age: 24.8±3.3, range: 20–35) and 74 elderly (37 female; age: 67.6±4.7, range: 59–77) healthy participants that were part of the Leipzig Cohort for Mind-BodyEmotion Interactions (LEMON). In addition to blood samples, we acquired psychoand anthropometric information as well as measures of the central and the autonomic nervous system, through 3T-MRI and 3-lead ECG recordings, respectively. Neuroendocrine, immune, and metabolic markers were combined with cardiovascular and anthropometric measures to yield individual allostatic load indices. In between-subject analyses, we find that such a composite marker of allostatic load can be related to subjective stress reports, measures of heart rate variability during a 5-min resting period, brain structure (i.e., regional differences in greymatter density) as well as brain function (i.e., network connectivity during task-free resting-state fMRI).We show that an allostatic load index can help investigate inter-individual differences in psychophysiological markers of chronic stress and the brain’s adaptation to it.