A 68-year-old woman presents with a 3-day history of worsening shortness of breath, cough productive of purulent sputum, and pleuritic chest pain. Her observations are: RR 28/min, HR 110/min, BP 105/65 mmHg, SpO2 91% on air, Temp 38.2°C. Chest auscultation reveals crackles and bronchial breathing in the right lower zone. Her CURB-65 score is calculated. Which single factor contributes most significantly to her immediate management decision regarding hospital admission vs. community management?