Short-term change in self-reported COPD symptoms after smoking cessation in an internet sample

Smoking is the first risk factor for chronic obstructive pulmonary disease (COPD). Some recent reports suggest that, unexpectedly, some respiratory symptoms may increase transiently after smoking cessation, but there is a dearth of short-term data to test this hypothesis. The aim of the present study was to assess the validity of an online screening tool and to describe short-term associations between smoking behaviour and self-reported respiratory symptoms, in cross-sectional and longitudinal data. An internet survey was conducted in 2003-2009, on a smoking cessation website, with a follow-up survey after 30 days. There were 15,916 participants at baseline and 1,831 at follow-up. In the 252 baseline smokers who had quit smoking at 30-day follow-up, there was a substantial decrease in the proportion of participants who declared that they often coughed even without a cold (from 51.6% at baseline to 15.5% at follow-up), expectorated when they coughed in the morning (from 47.6% to 19.4%), were out of breath after climbing stairs or after a quick walk (from 75.0% to 48.4%), and who had a wheezing respiration (from 33.7% to 10.3%) (p<0.001 for all before/after comparisons). In participants who did not change their smoking behaviour between assessments, the test-retest reliability was r=0.87 for a score summing these four symptoms. Smoking cessation was followed by a rapid and substantial improvement in self-reported respiratory symptoms. COPD is largely underdiagnosed and undertreated. Internet screening is reliable and may allow for the early detection of COPD symptoms at a large scale, in patients who may otherwise have no access to COPD case-finding efforts.