BACKGROUND/OBJECTIVES: Asthma in older individuals is poorly understood. We aimed to characterize the older asthma phenotype and test its association with obstructive sleep apnea (OSA). DESIGN: Cross-sectional. SETTING: Pulmonary and Asthma/Allergy clinics. PARTICIPANTS: 659 asthma subjects aged 18-59 years (younger) and 154 aged 60-75 (older). MEASUREMENTS: Sleep Apnea scale of Sleep Disorders Questionnaire (SA-SDQ), asthma severity step (1-4, severe if step 3 or 4), established OSA diagnosis, continuous positive airway pressure (CPAP) use, and comorbidities. RESULTS: Older versus younger had worse control, as assessed by asthma step, lung function, and inhaled corticosteroid use. Among older subjects, after controlling for known asthma aggravators, OSA diagnosis was the only factor robustly associated with severe asthma: on average, OSA was associated with nearly 7 times greater likelihood of severe asthma in an older individual (OR = 6.67). This relationship was of greater magnitude than in younger subjects (OR = 2.16). CPAP use attenuated the likelihood of severe asthma in older subjects by 91% (P = 0.005), much more than in the younger asthmatics. CONCLUSION: Diagnosed OSA increases the risk for worse asthma control in older patients, while CPAP therapy may have greater impact on asthma outcomes. Unrecognized OSA may be a reason for poor asthma control, particularly among older patients.