Data are presented as mean±sd or n (%), unless otherwise stated. Percentages may not sum to 100 because of rounding. Tie COPD: Tiotropium in Early COPD (chronic obstructive pulmonary disease); BMI: body mass index; FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; GOLD: Global Initiative for Chronic Obstructive Lung Disease; CAT: COPD Assessment Test; mMRC: modified Medical Research Council; CCQ: Clinical COPD Questionnaire. ^#: there were no significant between-group differences for characteristics at enrolment. The analysis set included patients who underwent both Tie-COPD and post-Tie-COPD follow-up and had at least one available spirometric data measurement after bronchodilator use at Tie-COPD and at least one measurement at post-Tie-COPD follow-up; ^¶: p-values for continuous variables were calculated using t-test or the Wilcoxon rank-sum test, and p-values for categorical variables were calculated using the Chi-squared test; ⁺: defined as an FEV₁ value obtained after bronchodilator use that increased by ≥200 mL and by ≥12% from the measurement obtained before bronchodilator use; ^§: the GOLD staging system is used to assess the severity of lung disease. Stages range from 1 to 4, with higher stages indicating more severe disease. Stage 1 (mild disease) is defined as FEV₁ ≥80% of the predicted value, and stage 2 (moderate disease) as FEV₁ 50–79% pred; ^ƒ: scores on the CAT range from 0 to 40, with higher scores indicating more severe disease; ^##: the mMRC dyspnoea scale ranges from 0 to 4, with higher scores indicating more severe breathlessness; ^¶¶: CCQ scores range from 0 to 6, with higher scores indicating worse clinical control.