Prevalence of obstructive lung disease in a general population sample: the NICECOPD study

There are little data available on the prevalence of chronic obstructive pulmonary disease (COPD) in the United Kingdom. The Northern Ireland Cost and Epidemiology of Chronic Obstructive Pulmonary Disease (NICECOPD) study is a two-stage survey to examine the prevalence of obstructive lung disease in a general population sample in the Greater Belfast area.

In stage one 4000 subjects aged 40-69 years were selected at random from the general population. They were posted a short screening questionnaire concerning respiratory symptoms. Respondents were divided into 'symptomatic' and 'asymptomatic' groups according to their responses. In stage two, a sample of symptomatic and asymptomatic subjects completed a more intensive assessment that included a detailed questionnaire on medical history, spirometry, skin allergy testing and serial peak flow measurements. Spirometric criteria for airflow obstruction were FEV1/FVC ratio of <70% with FEV1 < 80% predicted. Subjects were assigned diagnoses according to a pre-arranged protocol.

The survey was conducted from May 1999 to May 2001. There was a 67% response rate to the stage 1 screening questionnaire and 1330 responders were identified as being eligible to take part in stage 2. In total, 722 subjects completed a detailed assessment (50.8% Male, symptomatic, n = 326; asymptomatic, n = 396). COPD was diagnosed in 12.3% (8.8, 15.8) of the symptomatic and 2.2% (0.8, 3.6) of the asymptomatic group. The estimated prevalence of obstructive lung disease in the total population age 40-69 years was 14.4%: 6.3% COPD; 7.2% asthma; 0.9% with indeterminate airflow obstruction. In men, the prevalence of COPD varied from 4.9% in those aged 40-49 years to 12.3% in those aged 60-69 years and in women, varied from 1.4% in 40-49 years of age to 4.5% in 60-69 years.

The data suggest that COPD and asthma are common conditions in the general population and should inform future plans to address the burden of disease.