Malnutrition and its multidimensional determinants in institutionalized older adults: a cross-sectional study from resource-limited nursing homes in China

China’s rapidly aging population faces disproportionate malnutrition risks in under-resourced nursing homes, particularly in Southwest regions with fragmented healthcare systems. To assess the nutritional status and its influencing factors among older adult residents in nursing homes in Nan Chong, Southwest China.A cross-sectional study was conducted from February 2023 to March 2024, involving 205 older adult participants aged ≥ 60 years. Nutritional status was evaluated using the Mini-Nutritional Assessment Short-Form (MNA-SF), while sarcopenia, sleep quality, depression, and social support were assessed using validated scales. Descriptive statistics, correlation analysis, and multiple linear regression were performed. Among participants, 19.02% were malnourished, and 42.44% were at risk of malnutrition. Lower BMI (B = 0.256, P < 0.001), higher sarcopenia risk (B = -0.385, P < 0.001), and lower social support (B = -0.076, P = 0.008) were significant predictors of malnutrition. Malnutrition is prevalent among nursing home residents in Southwest China, with BMI, sarcopenia, and social support being key determinants. Targeted interventions should focus on improving dietary intake, muscle health, and social engagement.