超越静态负荷：非裔美国老年人慢性压力的重点生物学测量

分享智慧共同成长

Full textIntroduction

African American older adults have experienced the chronic stress of health inequity and socioeconomic injustice across decades. Indeed, over a lifetime, African American individuals experience 60% more stressful events, from adverse childhood events to loss of employment, than White individuals (Zuelsdorff et al., 2020). These stressful events are also associated with poorer later-in-life cognition (Zuelsdorff et al., 2020). Likewise, scholars have long known that exposure to chronic stress from racism and unfair or unjust treatment presents challenges to our physical and mental health (Jackson et al., 2010; Williams et al., 1997). Despite African American individuals' psychological resilience, the impact of chronic stress is devastating to their health outcomes.

The accumulation of chronic stress over the life course puts African American older adults at a distinct disadvantage (Forde et al., 2019). For African American and White older adults, exposure to chronic stress leads to illnesses, such as cardiovascular disease, hypertension, and stroke in later life, but the incidence of these diseases is greater in African American than White older adults (August & Sorkin, 2010). Chronic stress accelerates normal age-related immune dysregulation. As the brain ages, older adults are more vulnerable to effects of prolonged chronic stress (McEwen, 2002).

Prolonged stress requires our bodies to adapt through the regulation of physiological responses that include the hypothalamic-pituitary-axis (HPA), sympathetic nervous system, parasympathetic nervous system, and cardiovascular and immune systems. This constant activation of the biological regulatory systems results in increased adiposity, atrophy of nerve cells in the hippocampus, and bone mineral loss.

Allostatic Load

Cardiovascular, metabolic, and immune biomarkers reflect the resulting wear on the body, which is called allostatic load (McEwen, 2002). To capture the impact of chronic psychological stress on health in African American older adults, there is a need to accurately measure allostatic load burden across this population. In turn, we can target psychosocial, behavioral, and health policy interventions that reduce allostatic load to improve health outcomes in this underrepresented population.

Problem

Three major challenges affect our systematic measurement of allostatic load. First, measurements vary widely. A review of 21 National Health and Nutrition Examination Survey studies found 18 different calculations of allostatic load (e.g., factor analysis, summation of parameters, averaging z-scores for each parameter) based on 26 different biomarkers (e.g., cortisol, adrenalin, noradrenalin, systolic and diastolic blood pressure) (Duong et al., 2017).

The second problem is that many studies use cortisol measured in blood, saliva, and urine, which only reflect stress in the past 24 hours. Thus, they do not capture the long-term activation of the HPA that increases allostatic load or a return to normal cortisol levels over a prolonged period of time (allostasis).

Finally, most studies use measures of allostatic load that are burdensome for research participants, such as the requirements of 24-hour urine collection. In gerontological research, such burdens are particularly limiting. As a result, allostatic load is understudied particularly in African American older adults and African American caregiving populations (Potier et al., 2018). Alternative measures and simplified data collection are needed to reduce participant burden and advance the science of allostatic load.

Solution

Focusing on a single biological marker of HPA function (central neuroendocrine of response to stress) provides an alternative to the complexity of measuring allostatic load. Scalp hair cortisol provides a reliable, noninvasive measure of cortisol exposure over a 3-month period and HPA function (Stalder et al., 2017). Hair cortisol can be used in research to quantify the relationship between chronic stress and multiple chronic diseases. For example, elevated hair cortisol is associated with cardiovascular disease, diabetes, and cognitive decline. Our pilot study (Wright et al., 2016) of urban African American older adults in low-income neighborhoods demonstrated a significantly positive correlation between hair cortisol and (a) depressive symptoms (correlation coefficient [r] = 0.416, p = 0.031) and (b) unexpected stress (r = 0.407, p = 0.035) over the preceding month. Low hair cortisol was significantly associated with elevated high-sensitivity C-reactive protein (r = −0.446, p = 0.020). Hair cortisol is an emerging biomarker that can aid in the description of the impact of chronic stress on mental and physical health.

Another less invasive alternative method to measure the impact of chronic stress on health outcomes is the use of dried blood spotting. Through dried blood spotting, researchers can obtain common measures used to calculate allostatic load, such as cholesterol and cortisol. This minimally invasive collection of whole blood through finger stick can be performed in the home by study participants, thereby reducing the need for specially trained personnel (Miller et al., 2015; Williams & McDade, 2009). Thus, the multiple systems/biomarkers represented (i.e., immune, cardiovascular, metabolic, and HPA) to quantify allostatic load are reduced to a single spot of blood.

Conclusion

Allostatic load is a well-studied methodology that describes the impact of wear and tear on the body resulting from chronic stress, but existing measures have limitations. Given the deleterious impact of chronic stress, incorporating convenient and accurate measures are critical to capture vital indicators of health for African American older adults. Hair cortisol or dried blood spotting techniques offer alternative metrics to examine the impact of chronic stress on health outcomes. By using established approaches in innovative ways, we will usher in a new era of population health—targeting and evaluating the impact of interventions on chronic stress to transform current research in underrepresented and overlooked populations.

全文翻译（仅供参考）

介绍

几十年来，非裔美国老年人经历了健康不平等和社会经济不公正的长期压力。事实上，在一生中，非裔美国人经历的压力事件比白人多 60%（Zuelsdorff 等人，2020 年）。

这些压力事件也与晚年认知能力较差有关（Zuelsdorff 等人，2020 年）。同样，学者们早就知道，种族主义和不公平或不公正待遇带来的长期压力会给我们的身心健康带来挑战（Jackson 等人，2010 年；Williams 等人，1997 年））。尽管非裔美国人具有心理弹性，但慢性压力的影响对他们的健康结果是毁灭性的。

生命过程中慢性压力的累积使非裔美国老年人处于明显的劣势（Forde 等人，2019 年）。对于非洲裔美国人和白人老年人来说，长期承受压力会导致晚年患心血管疾病、高血压和中风等疾病，但这些疾病在非洲裔美国人中的发病率高于白人老年人（August & Sorkin, 2010）。

慢性压力会加速正常的与年龄相关的免疫失调。随着大脑年龄的增长，老年人更容易受到长期慢性压力的影响（McEwen，2002）。

长时间的压力需要我们的身体通过调节生理反应来适应，这些反应包括下丘脑-垂体轴 (HPA)、交感神经系统、副交感神经系统以及心血管和免疫系统。

这种生物调节系统的持续激活导致肥胖增加、海马神经细胞萎缩和骨矿物质流失。

静载荷

心血管、代谢和免疫生物标志物反映了对身体的磨损，称为异静负荷( McEwen, 2002 )。为了捕捉慢性心理压力对非裔美国老年人健康的影响，有必要准确测量这一人群的动态负荷负担。反过来，我们可以针对减少压力负荷的社会心理、行为和健康政策干预措施来改善这一代表性不足的人群的健康结果。

问题

三个主要挑战影响我们对静力载荷的系统测量。首先，测量值差异很大。对 21 项全国健康和营养检查调查研究的回顾发现，基于 26 种不同的生物标志物（例如皮质醇、肾上腺素、去甲肾上腺素、收缩压和舒张压）（Duong 等人，2017 年）。

第二个问题是，许多研究使用血液、唾液和尿液中测量的皮质醇，这只能反映过去 24 小时内的压力。因此，它们不能捕获 HPA 的长期激活，这种激活会增加动态负荷或长时间恢复正常的皮质醇水平（动态平衡）。

最后，大多数研究使用对研究参与者来说很繁重的异压负荷测量，例如 24 小时尿液收集的要求。在老年学研究中，这种负担特别有限。因此，对非裔美国人老年人和非裔美国人看护人群的动态负荷研究不足（Potier 等人，2018 年）。需要替代措施和简化数据收集来减轻参与者的负担并推进分配负荷的科学。

解决方案

专注于 HPA 功能的单一生物标志物（应激反应的中枢神经内分泌）提供了一种替代测量异压负荷的复杂性的方法。头皮毛发皮质醇提供了一种可靠的、无创的测量 3 个月内皮质醇暴露和 HPA 功能的方法（Stalder 等人，2017 年）。头发皮质醇可用于研究量化慢性压力与多种慢性疾病之间的关系。

例如，头发皮质醇升高与心血管疾病、糖尿病和认知能力下降有关。我们对低收入社区的城市非裔美国老年人进行的试点研究 ( Wright et al., 2016 ) 表明，头发皮质醇与 (a) 抑郁症状（相关系数 [r ] = 0.416, p = 0.031) 和 (b)上个月的意外压力 ( r = 0.407, p = 0.035)。低毛发皮质醇与升高的高敏 C 反应蛋白显着相关（r = -0.446，p = 0.020）。

头发皮质醇是一种新兴的生物标志物，可以帮助描述慢性压力对身心健康的影响。

衡量慢性压力对健康结果影响的另一种侵入性较小的替代方法是使用干血点。通过干血点，研究人员可以获得用于计算异压负荷的常用指标，例如胆固醇和皮质醇。研究参与者可以在家中通过手指穿刺进行全血微创采集，从而减少对受过专门训练的人员的需求（Miller 等人，2015 年；Williams & McDade，2009 年）。

因此，用于量化自律负荷的多个系统/生物标志物（即免疫、心血管、代谢和 HPA）被减少到单个血液点。

结论

Allostatic load 是一种经过充分研究的方法，用于描述慢性压力导致的身体磨损和撕裂的影响，但现有的测量方法存在局限性。鉴于慢性压力的有害影响，采用方便和准确的措施对于获取非裔美国老年人的重要健康指标至关重要。头发皮质醇或干血点技术提供了替代指标来检查慢性压力对健康结果的影响。

通过以创新方式使用既定方法，我们将迎来人口健康的新时代——针对和评估干预措施对慢性压力的影响，以改变目前对代表性不足和被忽视人群的研究。