IMPORTANCEThe benefits and harms of adding long-acting muscarinic antagonists (LAMAs) to inhaled corticosteroids (ICS) and long-acting β 2 -agonists (LABAs) for moderate to severe asthma remain unclear.OBJECTIVE To systematically synthesize the outcomes and adverse events associated with triple therapy (ICS, LABA, and LAMA) vs dual therapy (ICS plus LABA) in children and adults with persistent uncontrolled asthma.