Allostatic Load & Health Disparities

I. Homeostasis & The Stress Response

We take for granted that homeostasis, our normal state of equilibrium, keeps our bodies and minds at or near steady levels of physiologic function despite a spectrum of change in our external environments. We sweat when it’s warm, shiver when cold, and breathe faster at high altitudes to compensate for lower levels of oxygen in the air. We also take in sensory data about our environment on a regular basis, processing sights, sounds, and other sensory data through a part of our brain called the thalamus and send that information on for higher order processing in our brain’s cerebral cortex. But what happens when our environment presents us with immediate threats to survival or stress?

The mechanism we evolved for responding to acute, potentially lethal, stress is lighting quick, fundamental to our make-up, and extremely difficult to interrupt. Imagine our genetic predecessors out foraging for food or on a hunt, encountering a predator or member of a competing tribe, an enemy. They had two choices: prepare to eliminate the threat or get out fast. The well-known “fight or flight” response is fundamental to our physiology and the opposite of slow and considered decision-making since more time means dead in critical situations.

Emergency states trigger the emotional core of the brain, our amygdala, and the perceived threat detonates an outburst of hormones and neurotransmitters that bypass the thalamic-cortical loop, and go directly from stimulus to the hypothalamus and pituitary which activate our adrenals to pump out blasts of cortisol and adrenaline, hormones that initiate a cascade of physiologic responses resulting in: increased heart rate, blood pressure, breathing, redirection of blood flow to the brain and muscles, increased muscle tension, blood shunts away from skin and internal organs, liver conversion of glycogen to glucose ramps up to supply more fuel for quick energy, blood clots faster, pupils dilate and our field of vision narrows on the source of the threat to the point that we even diminish focus on details such as facial expressions: great in an emergency, terrible when predetermined biases are informing what constitutes an actual threat (more on that later). Furthermore, these high levels of cortisol also short-circuit our memory center in the hippocampus, making it difficult to form memories based on the details of the event and while allowing us only to learn how to become more sensitive to similar events in the future, which also served as the basis for a post-traumatic stress disorder. This hypothalamic-pituitary-adrenal (HPA) or neuroendocrine axis, involves our entire make-up and affects every physiologic component of our being. More than at any other time, humans are bio-psycho-social-spiritual beings and our entire system is never more integrated than when we are thus transformed in these critical stress states.

Once a threat is past, and the stressor eliminated, we need rest to recover. This period of recovery has been well-studied and requires about 20 minutes to resolve. Serious long-term problems arise if we experience recurrent stress states without allowance for those recuperation periods.

II. Allostasis & Resiliency:

Allostasis is the process by which our bodies recover from critical stress responses and return to homeostasis and each stressful event adds to a total we call our allostatic load. Homeostasis, or stability, and allostasis, the variability allowing for response to stress, are complimentary internal or “endogenous” mechanisms for maintaining inner stability. The greater the allostatic load, the more likely we are to overwhelm our system and exceed our ability to overcome the burden of that cumulative stress.

Resiliency is our ability to withstand and recover from stressors, or the sum total of all the adjustments we, as vulnerable organisms, must make to counteract stress. It represents our ability to maintain health when taxed by the total allostatic load we experience. Humans raised in nurturing environments have greater stores and have more durable mechanisms for resiliency. This is particularly important since as long as resiliency is greater than the allostatic load, we remain in relatively good health. Repeated stress unrelieved by such mechanisms during periods of recovery, causes the allostatic load to overwhelm resiliency making disease states more likely to prevail.

III. Acute vs. Chronic Stress:

Stressors not only range from mild to severe but from acute to chronic which can also trigger maladaptive or dysfunctional responses, particularly when constant, as implied above. Our brains and bodies are vulnerable to misinterpretation of the degree of threat in our modern worlds and our responses are often inappropriately triggered. In turn, the pathology of chronic stress daily, weekly, and yearly basis over decades lead to dangerous physiological effects. In a typical day sustained stress that begins with an alarm clock in the morning, continues with commuter traffic, unwelcome interactions at work, and / or challenging relationship interactions with family and friends can result in similar amygdale hijack that not only represent maladaptive responses to threats, but sustained allostatic load from with no provision made for periods of recovery can become overwhelming even in the most resilient among us. What if in addition, we consider the additional stressors of economic disadvantage or differences in culture that give you less access to support? What impact might added stressors like discrimination based on sex or race have on factors that are already known to predispose us to atherosclerosis, diabetes, cardiovascular disease, depressed immune function, low birth weight, maternal and infant mortality, and premature death?

IV. Allostatic Load & Racial Disparities

It’s been almost two decades since the Institutes of Health published a preliminary review “Unequal Treatment: Confronting Racial and Ethnic Disparities in Health.” Since then, research on health disparities has focused less on racism in the current U.S healthcare system and more on the quality of care differences. Mounting evidence supports what is with increasing frequency referred to as ‘the social determinants of health’ and ‘cultural dissonance and concordance’ have been broadly studied as major contributors to inequities. This includes attention to socioeconomic factors such: wealth, influence and power, including lack of health insurance and preventative and routine medical care. A second major issue is the patient-clinician ethnic concordance and how it can enhance or interfere with communication and compliance. However, the IOM study also pointed to personally mediated biases from healthcare providers, which has received relatively less attention. It is much more challenging to approach the analysis of the effect of institutionalized, interpersonal and internalized racism on health outcomes measures. Despite this fact, several good studies have established that health disparities in cardiovascular disease and infant mortality persist even after adjustment for socioeconomic status and health behaviors due to allostatic load and chronic life stressors.

A majority of studies exist in psychology and sociology journals with a virtual alphabet soup of titles and degrees among researchers, yet the word racism itself appears infrequently on review of the past decade of research in Journal of the American Medical Association (JAMA) or New England Journal of Medicine (NEJM) based on PubMed and Medline and others. Yet, mounting studies in other journals strongly support that increased allostatic load is predictive of cardiovascular disease and all-cause mortality and correlated with poor health practices including decreased rates of exercise and social behavior such as smoking, alcohol, and rates of depression. Increasingly, studies show racial discrimination plays a critical role in explaining racial based health disparities. At least one large meta-analysis provides the perspective that ethnicity has a significant effect on health states due to racism and includes negative mental health effects on Asian American and Latino American, as well as African American participants. Not surprisingly, a strong relationship has been made between allostatic load and concomitant adverse pathophysiological processes in these populations who also have diminished participation in healthy behaviors known to contribute to resiliency, such as sleep and exercise and decreased alcohol consumption, known coping mechanisms for stress reduction.

V. Mitigating the Cost of Allostatic Load and Health Disparities:

Research has shown that remaining in a state of constant stress leads to a plethora of negative health effects. Interrupting the sources of stress would logically be more challenging in the case of people who are subject to discrimination. The cost of stress to our health care system is clearly astronomical. I have suggested it might be mitigated to some extent by providing for periods of rest and recovery. But even if we cannot realistically redesign our national take on work-life balance, a critical issue remains: does the disparity in allostatic load account for some significant portion of what we measurably quantify as health disparities based on race. If so, simply attaching those differences to the inherent culture of a racial group is a woefully inadequate approach to solving the problem and tantamount to victim-blaming.

Once we acknowledge stress has a significantly different effect on us based on our self-perception as well as perceived threats, we may be more apt to negotiate allostatic load successfully. Acknowledging this mechanism as a source of healing as well as the disease process gives us a powerful tool for using our knowledge about internalized racism as a mechanism for mitigating harm.

Health psychologists are now recognizing there are adaptive stress responses and that mild to moderate stress, is not inherently bad. The most negative lasting impacts arise when our response to perceived threats are disproportionate, sustained and maladaptive. We, therefore, may be able to enlist protective functions such as positive cultural identity. In one example, preliminary research suggests that a positive racial identity is associated with decreased blood pressure.

If we are consciously aware that stressful stimuli stacked on top of other insults occurring before the aforementioned 20 minute recovery period, we might purposely seek out partners for mutual support, take time-outs to as to interrupt the periods of sustained levels of stress hormones that lead to permanent disease through tissue remodeling. Another approach may be to take proactive steps, such as identify culture champions, allies and mentors to help distinguish between serious threats and relatively minor ones. Microaggressions need not lead to sustained levels of stress hormones if the prior experience does not sensitize victims to future events and interfere with rest and sleep. We are more apt to interrupt maladaptive behaviors such as self-medication that can lead to depression.

Another way to avoid this adrenal fatigue is to build our own virtual and physical spaces to rest and recover. For example, can breathe deeply, affirm positive experiences, listen to music, exercise, eat well and get outside ourselves. If you are a non-conformist, find others like yourself to create alliances.

You probably realize the mechanisms to counter-act the negative forces of chronic and critical stress, fall into two major categories in order to promote healing and health: decreasing allostatic load or increasing resiliency. What may not be as obvious is that the same mechanisms that can mitigate health disparities in stress in minority populations are inherently beneficial to all of us.

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