Lung function or physiologic, objective impairment can be measured by spirometry, mainly forced expiratory volume in 1 second (FEV1) and the ratio of FEV1 to forced vital capacity (FVC), which correlate strongly with subjective components of asthma control that includes symptoms and clinical features such as How often symptoms are experienced How often the patient awakens at night How often the patient uses a short-acting beta-2 agonist for symptom relief How often asthma interferes with normal activity Risk Risk refers to the likelihood of future exacerbations or decline in lung function and the risk of adverse drug effects.