Introduction

The prevalence of asthma has increased in most countries since the 1970s. Levels may have plateaued in developed countries but as prevalence is associated with urbanisation and a western lifestyle the problem worldwide is likely to increase over the next two decades (fig 1). About 300 million people worldwide have asthma and by 2025 it has been estimated that a further 100 million will be affected.1 Asthma accounts for one in every 250 deaths worldwide and 1% of all disability adjusted life years. In overall health terms chronic symptoms of asthma account for 8% of self reported poor health in 18-64 year olds and 3.5% of days of limited activity, putting asthma above diabetes but below arthritis as a chronic health problem.^w1 Psychological distress and feelings of decreased control are high in people with asthma and strongly associated with physical health.^w2 Well controlled asthma reduces the burden for patients and health services.

Control of asthma may mean minimal symptoms and freedom from exacerbations for patients, normal peak flow or low scores on standard questionnaires for doctors, or composite measures in clinical trials. As definitions vary an American Thoracic Society taskforce is considering standard definitions for control and exacerbations.^w3 This review looks at important issues in definition and control of asthma in adults.

Sources and selection criteria

I searched Medline for articles on asthma in adults using the terms “asthma control” for 2004-6. I also searched Cochrane reviews, hand searched reference lists and conference proceedings, and discussed important current issues in asthma control with colleagues.

How do asthma guidelines define control?

Control is usually defined by severity of symptoms, simple tests such as peak expiratory flow, and prevention of exacerbations. Current guidelines …