The Obstructive Lung Disease in Northern Sweden Chronic Obstructive Pulmonary Disease Study: design, the first year participation and mortality.

BACKGROUND: Most epidemiological data on chronic obstructive pulmonary disease (COPD) are cross-sectional, and the longitudinal course of disease on population bases is incompletely described. AIM: To describe an epidemiological study designed to follow the longitudinal course of disease in chronic obstructive lung disease, COPD, including co-morbidity and mortality and further, to evaluate the impact of COPD on quality of life and health economics.
MATERIALS AND METHODS: From the Obstructive Lung Disease in Northern Sweden studies database cohorts I-IV, all subjects with COPD according to the Global Initiative for Chronic Obstructive Lung Disease spirometric criteria, FEV(1)/FVC < 0.70 (n = 993), were identified together with a similar size age- and gender-matched control group. The study population was invited to a yearly examination starting in year 2005. The examinations included structured interview, spirometry with reversibility testing, oxygen saturation and health-related quality of life questionnaires.
RESULTS: On the first year, 83% of the population was examined, and the subjects unable to attend the examination were interviewed by telephone. Altogether, 91% of the original study population participated (95% of all subjects were alive at the end of the first year). Mortality was significantly higher among subjects with COPD, 5.1%, compared with controls, 3.0% (P = 0.018).
CONCLUSION: The study design including cases of COPD representative of COPD by disease severity in the general population and a similar sized control group, together with a high participation rate in the first study year, creates excellent conditions for evaluating the impact of COPD on population bases, and to follow the longitudinal course of disease in COPD.