Higher allostatic load at hospitalization is linked to worse outcome 90 days after stroke

When a patient arrives at the hospital with an acute ischemic stroke, clinicians rapidly assess the damage with brain imaging and stroke scales, then decide on reperfusion therapy. What those assessments rarely capture is the cumulative physiological burden the patient carried into the emergency department: years of chronic stress that have quietly worn down the metabolic, inflammatory, and vascular systems. A new study suggests that this hidden burden, quantified as allostatic load, may shape who survives and who recovers after a stroke.

Allostatic load is a concept introduced in the early 1990s to describe the wear and tear that chronic stress inflicts on the body. Sustained activation of neuroendocrine and autonomic systems, the physiological machinery of the stress response, gradually promotes hypertension, atherosclerosis, increased coagulability, and low-grade inflammation. Over time, this multisystem dysregulation leaves the body and brain more vulnerable to injury. Researchers have linked high allostatic load to cardiovascular disease, all-cause and cardiovascular mortality, and disability in the general population, yet relatively little work has examined it directly in the context of stroke itself.

That gap is what motivated a team led by Eva Birgitte Aamodt of Oslo University Hospital, working with colleagues at Houston Methodist and TIRR Memorial Hermann in Texas, to investigate whether allostatic load measured at hospitalization predicts outcomes after acute ischemic stroke. Their findings, published in Frontiers in Stroke, indicate that patients with higher allostatic load at admission face longer hospital stays, higher mortality, and greater dependency 90 days after their stroke.

The study drew on the Houston Methodist Registry of Neurological Endpoint Assessments among Patients with Ischemic and Hemorrhagic Stroke, known as REINAH, an observational registry spanning seven certified stroke centers in and around Houston. From this registry, the researchers included 4,103 patients with acute ischemic stroke. For a sub-cohort of 2,244 patients, 90-day functional outcomes were available through the modified Rankin Scale, a standard measure of post-stroke disability ranging from 0 to 6, with higher scores indicating greater disability.

To construct the allostatic load score, the researchers used ten routinely collected clinical parameters representing three physiological systems. The metabolic system was captured by body mass index, glycated hemoglobin, total cholesterol, triglycerides, and high-density lipoprotein cholesterol. The inflammatory system was represented by C-reactive protein and white blood cell count. The vascular system was captured by systolic and diastolic blood pressure and pulse. Each parameter was scored by quartiles, with a point assigned if the value fell in the highest-risk quartile, and the points were summed to yield a score from 0 to 10. A score of 4 or higher was considered high allostatic load, a threshold the researchers chose because of the heavy comorbidity burden typical of stroke populations. Notably, no neuroendocrine parameters, such as cortisol, were available, so the score reflects metabolic, inflammatory, and vascular dysregulation rather than the full four-system conceptualization of allostatic load.

The results were striking. Patients with high allostatic load spent an average of 8.69 days in the hospital compared with 6.61 days for those with moderate-low load. Mortality at 90 days was 8.17 percent in the high-load group versus 3.08 percent in the moderate-low group. Among patients with 90-day follow-up, 57.06 percent of those with high allostatic load were dependent, defined as a modified Rankin Scale score of 3 or higher including death, compared with 41.85 percent of those with moderate-low load. These associations persisted after statistical adjustment for age, sex, race, stroke severity measured with the National Institutes of Health Stroke Scale at 6 and 24 hours, reperfusion therapies, and medications. In the fully adjusted models, high allostatic load remained associated with mortality with an odds ratio of 2.90, and with dependency with an odds ratio of 1.64, indicating that the burden was not simply a proxy for stroke severity or age.

The researchers also examined which factors were independently associated with high allostatic load. Younger age, Black race, higher area deprivation index, being single, illegal drug use, diabetes mellitus, sepsis, higher Charlson comorbidity index, anticoagulation reversal therapy, antihypertensive therapy, and higher stroke severity at 6 and 24 hours all predicted high load. Conversely, being a woman, hypercholesterolemia, atrial fibrillation, anticoagulant therapy, intravenous tissue plasminogen activator treatment, and endovascular thrombectomy were associated with moderate-low load. The inverse relationship between age and allostatic load was unexpected and likely reflects a survivorship effect, with older adults carrying high physiological burden being underrepresented in the registry.

A key sensitivity analysis added an important nuance. Because C-reactive protein and white blood cell count may partly reflect the acute inflammatory response to the stroke itself rather than chronic physiological burden, the researchers repeated their analyses using an alternative eight-biomarker score excluding these inflammatory parameters. The association between allostatic load and 90-day mortality disappeared in these models, suggesting that the inflammatory components contributed substantially to the observed mortality link. By contrast, the association with functional dependency remained essentially unchanged, and the association with length of stay persisted in partially adjusted models. This pattern implies that the prognostic value of allostatic load reflects both chronic multisystem dysregulation and acute inflammatory responses, and that the score may be particularly informative for functional outcomes.

The biological interpretation is compelling. Elevated allostatic load in this study primarily reflected chronic cardiometabolic and inflammatory dysregulation, including elevated blood pressure, glycemia, lipid levels, and C-reactive protein. Such long-standing vascular and systemic burden could reduce cerebrovascular reserve, impair circulation, and diminish ischemic tolerance, predisposing individuals to larger infarcts and more severe neurological deficits. The finding that higher allostatic load was linked to higher stroke severity at both 6 and 24 hours is consistent with this framework, although the researchers caution that some score components were measured during acute hospitalization and may themselves have been influenced by the stroke, so a causal relationship cannot be established from this observational design.

The authors suggest that allostatic load may serve as a clinically accessible marker of biological resilience, helping identify patients at increased risk of poor post-stroke outcomes. If validated in future studies, it could support risk stratification and guide closer monitoring or more individualized post-stroke care, particularly for functional recovery. However, the study has limitations: the allostatic load index lacked neuroendocrine measures central to the original concept, complete-case analyses may have introduced selection bias, roughly half the cohort had 90-day functional data, and the study did not evaluate whether allostatic load provides incremental prognostic value beyond established predictors such as age and stroke severity using discrimination metrics. Future work incorporating pre-stroke measures of allostatic load and testing its added value in prospective models will be needed to determine whether this composite marker of cumulative stress can move from research into clinical decision making after stroke.

Subject of Research: Neuroscience

Article Title: Higher allostatic load at hospitalization is linked to worse outcome 90 days after stroke

Article References: Aamodt, E. B., Borei, K., Potter, T., & Vahidy, F. (2026). Higher allostatic load at hospitalization is linked to worse outcome 90 days after stroke. Frontiers in Stroke, 5, Article 1847419. https://doi.org/10.3389/fstro.2026.1847419

Image Credits: AI Generated

DOI: 10.3389/fstro.2026.1847419

Keywords: allostatic load, stroke, ischemic stroke, mortality, dependency, length of stay, stress, modified Rankin Scale, Higher, allostatic, load, hospitalization