Impact of lean body mass index on short-term outcomes in patients with ischemic stroke: an observational cohort study

The influence of muscle mass on post-stroke outcomes remains unclear. This study aimed to investigate whether lean body mass index (LBMI), a surrogate for muscle mass, is independently associated with 3-month outcomes after acute ischemic stroke. We analyzed data of 10,735 patients with acute ischemic stroke enrolled in the Fukuoka Stroke Registry between June 2007 and September 2019. LBMI and fat mass index (FMI) were calculated using validated anthropometric prediction equations. Patients were categorized into sex-specific LBMI quartiles. Outcomes included poor functional outcomes (modified Rankin Scale [mRS] score, 3-6), functional dependency (mRS score, 3-5), and mortality at 3 months. Multivariable logistic regression was used to assess associations between LBMI and outcomes, after adjusting for clinical covariates and FMI. As LBMI increased, proportions of poor functional outcomes, functional dependency, and mortality decreased. After multivariable adjustment, higher LBMI was associated with lower odds of poor functional outcome and mortality. These associations remained significant even after further adjustment for FMI. In the subgroup analysis, a significant interaction was observed between LBMI and diabetes for poor functional outcomes (P-value for interaction = 0.03). Thus, higher LBMI was independently associated with better short-term outcomes after ischemic stroke, indicating that skeletal muscle mass may be a crucial prognostic factor distinct from fat mass.