Allostatic Load as a Correlate of Aging
Allostatic load is the concept of wear and tear on the body that emerges from stresses via overactivation of the neuroendocrine system. Causative stresses can range from starvation to psychological stress to a high burden of age-related dysfunction. At some point reactions to stress that are compensatory tip over into being themselves damaging. Thus one could expect allostatic load to correlate with degenerative aging and risk of mortality to at least some degree. In practice, however, there is little agreement on how to measure allostatic load, particularly in human patients, which makes it hard to compare results from study to study, and hard to form a unified body of work from the research on the topic.
Allostatic load (AL) refers to the activation of physiological regulatory systems in response to chronic stress and the long-term effects on the body and brain. AL reflects cumulative, multisystem physiological dysregulation, which is the result of repeated cycles over the lifespan in response to stressful life evens events. A literature review of AL and health reported that older and disadvantaged groups exhibited a higher risk of high AL. The primary mediators of AL include stress hormones and cytokines that influence the secondary outcomes of systematic dysregulation of metabolic, cardiovascular, and second-order inflammatory biomarkers over time.
Importantly, adults aged over 40 years old had a more than 2-fold higher risk of high AL than adults aged 18-29 years old. The effect of increased AL varies according to age, as well as multiple health-related and clinical factors. The aims of this study were to explore 1) the association of age and depressive symptoms with allostatic load and 2) whether socioeconomic (e.g., birth-assigned sex, educational level, marital status) and/or lifestyle factors (e.g., current smoking, high alcohol consumption, no physical exercise) are associated with high AL.
Thirteen biomarkers were used to construct AL. High AL was defined as scoring highly in ≥4 items. AL scores of 4 and above were exceeded in the age group of 45-54 years in men and 65-74 years in women. Age was the strongest predictor for belonging to the high AL score group. In addition, elevated depressive symptoms (BDI-6 ≥ 4), male sex, not engaging in physical exercise, high alcohol use, and a low level of education were associated with an increased likelihood of belonging to the high AL group.
Interesting concept. One wonders if this effect is made more significant and long-lasting by the suddenness, unpredictability, time-spacing since the last, and the nature of the target system (head injury, emotional trauma, etc.,) I suppose when one hears the 'simplism': '...what doesn't kill you, makes you stronger..." and then sees that the cumulative effect or extreme nature of the incident leads to a more lasting dysfunction. In engineering, oversimply, we refer to this as a 'plastic' response over an 'elastic' response, when the target can no longer return to 'normal', when subject to a type of loading that permanently deforms. This is often exacerbated by the surrounding conditions: temperature, pressure, state/age of the 'inanimate' target, etc.
Assumedly, this is minimized by having outstanding robustness and resilience in the system - likely from pre-conditioning (already being notably healthy) -or- by having gone through occasional smaller allostatic episodes and thus 'developed a resistance?'. Can one develop a resistance to attacks not immune-related above and beyond the regular injury responses??
Speaking of chaotic events affecting aging-resistance, I also posit that 'regularness' of lifestyle, that is regimented, standardized, and repetitive behaviours, possibly on the diurnal cycle; including eating, sleeping, exercising, and other activities creates an exceptional robustness - though not ideal, since periodic, positively-disruptive behaviours - fasting, intense workout, power naps, etc., is assumedly a beneficial and reinforcing 'shock' to the system. My point being that a person with an 80% regularized life (same breakfast and timing, etc.,) otherwise healthy, is more age-resilient than a person with a 20% regularized life (though similar diet and exercise, but very little standardization in scale and timing). This would be almost be the antithesis to sudden event 'damage' having an excessive effect in long-term - a simplification of some of the points in this article.
My 2c.