Nutritional risk, cold exposure, and stroke severity in older adults: an exploratory analysis of the “collapsed furnace” hypothesis

Vollständiger Abstract

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Objective To evaluate the exploratory “Collapsed Furnace” hypothesis that nutritional depletion and sarcopenia-related frailty may alter responses to ambient cold in older adults with stroke. Methods We integrated Global Burden of Disease (GBD) 2023 estimates for China (1990–2021), exploratory physiological data from the China Health and Retirement Longitudinal Study (CHARLS) 2015, and a retrospective clinical stroke cohort. The primary clinical analysis included patients aged ≥70 years; the full cohort aged ≥67 years was retained for sensitivity analysis. Nutritional risk was assessed using admission serum albumin as a nutritional-inflammatory marker, with the body mass index (BMI)-adjusted modified Geriatric Nutritional Risk Index (mGNRI) used as a sensitivity measure. Multivariable models examined nutritional risk, cold exposure, and their interaction in relation to admission National Institutes of Health Stroke Scale (NIHSS) score, adjusting for prespecified demographic, vascular, lifestyle, stroke-type, BMI, and C-reactive protein (CRP) covariates. Results Sodium-attributable stroke burden peaked at ages 70–79 years, whereas cold-attributable burden increased in the oldest groups. In the GBD analysis, the malnutrition × low-temperature interaction was negative ( β = −12.20, 95% confidence interval [CI], −18.52 to −5.88; p < 0.001). In the clinical cohort, nutritional risk was strongly associated with higher admission NIHSS scores. Cold exposure was associated with only a small additional NIHSS increase among patients with normal albumin and no measurable increase among those with low albumin; however, the interaction was not statistically significant. mGNRI- and CRP-based sensitivity analyses were directionally similar. CHARLS suggested different seasonal blood-pressure patterns by physiological status, but interpretation was limited by sparse cold-season interviews. Only 7 cold-exposed patients with low albumin aged ≥70 years and 4 CHARLS participants aged ≥70 years with cold-season interviews were available. Conclusion Nutritional depletion was strongly associated with stroke severity, but its role in modifying cold-related vulnerability remains uncertain. Because the clinical interaction was not significant and mortality, pre-stroke albumin, individual cold exposure, and core temperature were unavailable, the proposed ceiling-like effect should be considered hypothesis-generating and requires prospective validation.