<qa>  What is the most effective medication for long-term treatment of persistent asthma?Asthma is a chronic, potentially life-threatening disease that affects 17 million people in the United States. Asthma leads to millions of lost work days and thousands of hospitalizations annually. For the millions of people with this disease, it is chronic but controllable. Corticosteroids are the most effective medication for the long-term treatment of persistent asthma, and inhaling the medication minimizes the potential for systemic side effects. Despite convincing evidence of the benefits of inhaled corticosteroids ICS, both patients and doctors seem reluctant to use them regularly. Many people who are prescribed ICS either never take them, or take them less frequently e.g., once rather than twice daily, less regularly e.g., as needed rather than daily, or at lower doses than prescribed. Doctors agree that at least 50 of people who are prescribed ICS fail to benefit fully because of poor adherence. The many reasons for non-adherence are not fully understood. The relationship between the doctor and patient, an area in which potential impact can be made, is believed to be the strongest predictor of medication adherence. Providing pertinent information about asthma related lung function should prompt communication between the patient and doctor to improve adherence to ICS. 