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Heart Rate Variability in Psychiatric Disorders, Methodological Considerations, and Recommendations for Future Research
Published in Herbert F. Jelinek, David J. Cornforth, Ahsan H. Khandoker, ECG Time Series Variability Analysis, 2017
There is now a significant body of theoretical and experimental evidence for an important regulatory role of vagal function over a variety of allostatic systems including inflammatory processes (Huston and Tracey 2010), the hypothalamic–pituitary–adrenal (HPA) axis (Porges 2011), and glucose metabolism (Pocai et al. 2005; Wang et al. 2008; see also Thayer and Sternberg 2006a). Allostasis is a term that describes multisystemic adaptations to maintain homeostasis, allowing the body to cope with environmental challenges (McEwen 1998). Vagal dysfunction will therefore lead to overstimulation of these allostatic systems, a condition that has been labeled “allostatic load” (McEwen 1998), increasing risk for medical morbidity (McEwen 2012). Chronic reductions in HRV may therefore provide an early marker of ill health in psychiatric patients without comorbid medical illness that precedes other more established risk factors for medical illness.
The interplay between DNA methylation and cardiac autonomic system functioning: a systematic review
Published in International Journal of Environmental Health Research, 2023
Nayara Cristina Dos Santos Oliveira, Fernanda Serpeloni, Simone Gonçalves de Assis
The cardiovascular, digestive, metabolic, and respiratory systems are controlled and regulated by the autonomic nervous systems (ANS) (Carlson 2007). Many biological modulators (e.g. autonomic neurotransmitters, cytokines, and metabolic hormones) operate as an interactive network to maintain allostasis in these systems (McEwen and Tucker 2011). Allostasis refers to a dynamic regulatory process that maintains homeostasis and recognizes the “set points’ in response short-term response to predictable and unpredictable environmental conditions (McEwen 2016). For example, autonomic reflexes happen in seconds; catecholamines, adrenaline (released by the adrenal medulla) and noradrenaline (released by the sympathetic nerve terminals), increase the heart rate and decrease heart rate variability, control blood flow to muscle tissues, and elevate body temperature (Chrousos 1992; Ulrich-Lai and Herman 2009). The heart’s neural regulation involves complex interaction and responsiveness between the sympathetic and parasympathetic (vagal) ANS branches (Carlson 2007).
Exploring homeostatic value of space to prevent maladaptive behaviours of people living with dementia: a narrative study
Published in Architectural Science Review, 2021
Such a statement calls for knowledge concerning P-E relationships related to stressful conditions to understand how one may find an acceptable balance in an institutional facility. The former homeostasis concept introduced by Claude Bernard and revisited by Cannon (1932) and by Selye (1956) first comes to mind. According to Selye (1956), when faced with stressful situations the physiological system seeks for balance through the endocrine system in order to maintain homeostasis: an optimal physiological balance essential for life. More recently, however, Sterling and Eyer (1988) introduced the concept of allostasis that enables to understand dynamic processes that maintain these systems in balance beyond the limits of homeostatic mechanisms (McEwen 2002; Sterling and Eyer 1988). Allostasis therefore refers to regulation processes and coping strategies in order to maintain homeostasis. Regulation processes involved in allostasis are challenged by the amount of stress drawn in by environmental stressors and their adaptive cost: the allostatic load. Allostatic overload leads to exhaustion of stress response systems, thus resulting in homeostatic imbalance or failure.
The impaired healing hypothesis: a mechanism by which psychosocial stress and personal characteristics increase MSD risk?
Published in Ergonomics, 2022
Another theory that has been increasingly used to understand how psychological stressors lead to pathophysiological responses in workers is Allostatic Load (i.e. the cost of maintaining Allostasis), proposed by McEwen in 1998 (McEwan 1998). Allostasis (literally “maintaining stability, or homeostasis, through change”) refers the process of adaptation of an organism to acute stress across all biological systems, as a means to restore homeostasis after a challenge (McEwen 2000). Biological systems promote and coordinate adaptation using systemic mediators (cortisol, sympathetic and parasympathetic mediators, pro- and anti-inflammatory cytokines, metabolic mediators, and hormones), via a non-linear network in which each mediator regulates other mediators, often in a reciprocal fashion, with the brain typically coordinating these efforts (Karatsoreos and McEwen 2011; Sterling 2012). While adaptive acutely, chronic overactivity of a system, such as, cardiovascular, metabolic, immune, hypothalamus-pituitary-adrenal (HPA) axis, sympathetic-adrenal-medullary (SAM) system, and cognitive centres of the brain, in response to chronic or severe stressors (McEwen 1998; Karatsoreos and McEwen 2011) can induce a domino effect on the interconnected systems, leading one or more to overcompensate or become dysregulated, and can lead to the eventual disruption of a system, leaving the organism open to stress-related diseases (McEwen and Gianaros 2011; Juster, McEwen, and Lupien 2010). For example, pro-inflammatory cytokines released from injured cells or macrophages can enter the blood stream and become systemic. This can stimulate production of corticosteroids by the brain that then, in turn, reduce inflammatory cytokine production, as seen in Figure 1. Sympathetic and parasympathetic nervous systems (fight or flight systems) exert differential effects on pro-inflammatory cytokines, with the former stimulating production and the latter inhibiting them. When these responses are unbalanced, appropriate inflammatory responses may be inhibited, or vice versa. Allostatic Load is the accumulated burden (“wear and tear”) on the brain and other systems from trying to re-establish allostasis after exposure to repeated or chronic stressors (McEwen 1998; McEwen 2000), while Allostatic Overload occurs when the demands of the stressor exceed the body’s ability to repeatedly adapt, leading to disordered and diseased endpoints (Juster, McEwen, and Lupien 2010). In the current context, an allostatic overload due to psychological stress may result in a diminished healing capacity, which when paired with the physical process of tissue damage (fatigue failure) may result in increased MSD risk. The following sections will examine the effects of psychological stress and certain personal characteristics on healing kinetics and how these factors might influence the development of MSDs.