ABSTRACT
The epidemiology of exacerbations in chronic obstructive pulmonary disease
(COPD) does not differ from the epidemiology of other disorders. It attempts to
describe the characteristics of this feature of COPD in the population and relies on
usual epidemiological methodology. More than any other research area, however,
epidemiology is set back by the lack of a simple definition of an exacerbation easily
applied to larger population surveys. The recently proposed definition of an
exacerbation as ‘‘a sustained worsening of the patient’s condition, from the stable
state and beyond normal day-to-day variations, that is acute in onset and necessitates
a change in regular medication in a patient with underlying COPD’’ (1) needs to be
made operational to be included in epidemiology. To be useful in epidemiology,
information on exacerbations must be collected using questionnaires and=or diaries. In the initial testing of what later became the British Medical Research Council
(MRC) questionnaire, Fletcher et al. included questions on ‘‘chest illness which has
kept you in bed, off work, or indoors’’ and this phrasing presumably captures most
moderate-to-severe exacerbations whereas its specificity is unknown. Before their
systematic testing (2), it had been reported that ‘‘out-patients with chronic bronchitis
tended to exaggerate the number and duration of past sickness absences,’’ but
purposes.
