Abstract
<jats:p>Background Adults aged 80 years and older are the fastest-growing segment of the stroke population. Whether contemporary advances in stroke care have produced sustained outcome gains in this group during the past decade, including the post-pandemic era, has not been examined in nationwide longitudinal data with concurrent age-specific comparison. Methods Using the Clinical Research Collaboration for Stroke in Korea-National Institutes of Health (CRCS-K-NIH) registry, we analyzed consecutive adults with acute ischemic stroke admitted within 7 days of symptom onset between 2011 and 2022. Patients aged 80 years and older formed the primary cohort; those aged 18-79 years served as comparators. Primary outcomes were 3-month utility-weighted modified Rankin Scale (UW-mRS) and 1-year all-cause mortality. Non-linear trends and age-group-by-year interaction were modeled using restricted cubic splines adjusted for sex, age, and baseline NIHSS. Results Of 83,953 patients, 18,514 (22.1%) were aged 80 years and older; their proportion rose from 17.4% to 27.3%. Despite treatment intensification (endovascular thrombectomy 4.2% to 10.6%; oral anticoagulation for atrial fibrillation 52.5% to 76.9%), 1-year mortality in this group fell from 27.5% in 2011 to 19.4% in 2019, then rose to 23.7% by 2022; 3-month UW-mRS improved from 0.47 to 0.51 over the same period, then stagnated at 0.48. Restricted cubic splines confirmed significant nonlinearity in both outcomes after adjustment for sex, age, and NIHSS (P < 0.01 for both). Younger patients showed no comparable functional deterioration. Age-group-by-year interaction was significant for 3-month UW-mRS (P < 0.001) but not for 1-year mortality (P = 0.058), which showed a similar direction in both age groups. Conclusion In this nationwide registry, patients aged 80 years and older experienced an age-specific inflection of functional recovery gains after 2019 despite continued intensification of acute stroke care. Sustaining outcome gains in this population may require attention to post-acute care infrastructure.</jats:p>