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ALLOSTATIC LOAD



Allostatic load, a concept popularized by neuroscientist Bruce McEwen, refers to the cumulative physiological toll on the body due to chronic stress. Calculating allostatic load involves assessing various biomarkers across different physiological systems that indicate stress-related wear and tear on the body. While there isn't a single formula for calculating allostatic load, it typically involves a composite score based on multiple biomarkers.


Here's a generalized approach to calculating allostatic load:

  1. Select Relevant Biomarkers: Identify a set of biomarkers across different physiological systems that are indicative of stress-related dysfunction. These may include measures of cardiovascular function (e.g., blood pressure, heart rate variability), metabolic function (e.g., glucose levels, insulin resistance), immune function (e.g., inflammatory markers such as C-reactive protein), and neuroendocrine function (e.g., cortisol levels).

  2. Assign Scores: For each biomarker, establish cutoff points that indicate dysregulation or dysfunction. These cutoff points can be based on clinical guidelines, population norms, or previous research findings. Assign scores to each biomarker based on whether they fall within normal ranges or indicate dysfunction. For example, a higher score may be assigned to biomarkers outside of normal ranges.

  3. Calculate Total Score: Sum up the scores across all biomarkers to obtain a total allostatic load score for an individual. This score reflects the overall burden of stress-related physiological dysregulation across multiple systems.

  4. Interpretation: Higher allostatic load scores indicate greater physiological dysregulation and are associated with increased risk for various health problems, including cardiovascular disease, metabolic disorders, and mental health conditions. Lower scores suggest better physiological resilience and adaptive stress responses.

  5. Consider Context: It's important to interpret allostatic load scores in the context of individual differences, including age, sex, genetic factors, and life circumstances. What constitutes a high allostatic load may vary depending on these factors.

  6. Longitudinal Assessment: Allostatic load can also be assessed longitudinally to track changes in physiological functioning over time in response to stressors or interventions. This longitudinal approach provides insights into the dynamic nature of stress-related biological adaptation and resilience.


Researchers have developed various methods and scoring systems based on sets of biomarkers to assess the physiological toll of chronic stress on the body. These methods often involve selecting a combination of biomarkers from different physiological systems and assigning scores based on deviations from normal ranges or established thresholds.


One of the pioneering approaches to measuring allostatic load is the one developed by Bruce McEwen and colleagues. This method typically includes a selection of biomarkers representing cardiovascular, metabolic, immune, and neuroendocrine systems. These biomarkers may include blood pressure, heart rate variability, cholesterol levels, glucose levels, inflammatory markers (such as C-reactive protein), and cortisol levels.


McEwen's method assigns a score of 1 for each biomarker falling outside of normal ranges or predefined thresholds, with the total allostatic load score representing the sum of these scores across all biomarkers. Higher scores indicate greater physiological dysregulation and cumulative stress burden.


Other researchers have developed modified versions of McEwen's method or alternative approaches to assessing allostatic load. These variations may include different sets of biomarkers, scoring systems, or statistical methods for aggregating biomarker data.


While these methods provide valuable insights into the physiological consequences of chronic stress, they are primarily used in research settings and may not be widely available for clinical use. Additionally, the interpretation of allostatic load scores requires careful consideration of individual differences and contextual factors.

Overall, while there are established methods for measuring allostatic load based on biomarkers, they may not be standardized or universally accepted. Researchers continue to refine and validate these methods to better understand the complex interplay between stress, physiological functioning, and health outcomes.



SEE ALSO: Allostatic load biomarkers of chronic stress and impact on health and cognition

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