Differential effects of premorbid functional dependency on mortality in patients with anterior and posterior circulation stroke

Background: This study investigated the impact of premorbid functional dependency on post-stroke mortality in patients with anterior circulation stroke (ACS) and posterior circulation stroke (PCS). Methods: This study enrolled 9,698 patients who experienced ischemic stroke between January 2011 and December 2022. The patients were classified into the ACS and PCS groups. Premorbid functional dependency was defined as modified Rankin Scale of ≥3. The risks of premorbid functional dependency and mortality at 3 months and 1-year post-stroke were assessed. A subgroup analysis was further performed to evaluate the risk of premorbid functional dependency in patients who underwent intravenous thrombolysis and endovascular treatment (EVT). Results: Among 6,358 patients with ACS and 3,340 with PCS, those with premorbid dependency were older, predominantly female, and had a higher proportion of vascular risk factors and stroke severity. Premorbid functional dependency was associated with increased mortality at both 3 months and 1 year in the PCS (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.00–3.13; P=0.04 and OR, 2.87; 95% CI, 1.86–4.38; P<0.001, respectively), but not in the ACS (OR, 1.08; 95% CI, 0.77–1.51; P=0.639 and OR, 1.22; 95% CI, 0.93–1.59; P=0.140, respectively) group. Among patients who underwent EVT, premorbid functional dependency increased the risk of mortality at 1 year in the ACS group (OR, 1.80; 95% CI, 1.04–3.08; P=0.034), but was not associated with the risk in the PCS group (OR, 2.56; 95% CI, 0.64–10.15; P=0.176). Conclusion: Premorbid functional dependency increases the risk of mortality in patients with PCS.