Chronic obstructive pulmonary disease (COPD): introduction

The World Health Organization (WHO) defines chronic obstructive pulmonary disease (COPD) as: 'a lung disease characterised by chronic obstruction of lung airflow that interferes with normal breathing and is not fully reversible'. This is in contrast to the variable airways obstruction seen in asthma which can be reversed by drug treatment. The airflow obstruction in COPD is due to damage to the lung structure and destruction of lung tissue (emphysema). This is normally due to smoking, but recurrent infection also contributes to the process. Whilst preventable (COPD is mainly caused by smoking) and increasingly treatable, the airflow obstruction seen in COPD is usually progressive. More recently the systemic effects of more severe COPD have been recognised, including weight loss, nutritional disturbances and abnormal skeletal muscle function. COPD is also frequently associated with, and may contribute towards, numerous co-existing diseases such as heart disease, osteoporosis and diabetes, which influence morbidity and mortality.

Common symptoms of COPD include chronic cough, sputum production and shortness of breath. People with COPD are at increased risk of chest infections, some of which will be severe enough to require hospitalisation. Measurement of lung function using spirometry confirms the diagnosis and helps to classify the severity of the disease. Spirometry measures the amount (volume) and speed (flow) of air that can be inhaled and exhaled, and is also useful to monitor the progress of the disease and the response to treatment.

COPD is an important cause of morbidity and mortality in Scotland and worldwide. It is estimated that it was the fourth most common cause of years of life lost in Scotland in 2015, ranked after ischaemic heart disease, lung cancer and cerebrovascular disease. (Global Burden of Disease 2015).

It is widely accepted that estimates of COPD prevalence underestimate the true burden of the disease. A cross-sectional study in Northern Sweden (Lindberg 2006) found that only 20 - 30% of people fulfilling the criteria for COPD had been correctly diagnosed. Underdiagnosis is more likely in patients with mild disease than in those with severe disease (5% diagnosed versus 50% diagnosed respectively). These findings are consistent with other studies in the literature which highlight the extent of COPD underdiagnosis.

Acknowledgments: ScotPHO would like to thank Dr Philip Conaglen, who prepared these pages on COPD. We also acknowledge the very helpful comments of the University of Edinburgh's Allergy and Respiratory Research Group.