ObjectiveTo describe and compare demographic and clinical profile of patients newly initiated on aclidinium (ACL) or tiotropium (TIO) and identify factors associated with newly initiated ACL in real-life clinical practice during 2013 in Catalonia.DesignWe performed a population-based, retrospective, observational study with data obtained from the Information System for Research Development in Primary Care, a population database that contains information of 5.8 million inhabitants (more than 80% of the Catalan population). Patients over 40 years old, with a recorded diagnosis of COPD and newly initiated treatment with either ACL or TIO during the study period (January to December 2013), were selected. A descriptive analysis of demographic and clinical characteristics was performed, and treatment adherence was also assessed for both cohorts.ResultsA total of 8,863 individuals were identified, 4,293 initiated with ACL and 4,570 with TIO. They had a mean age of 69.4 years (standard deviation: 11.3), a median COPD duration of 3 years (interquartile range: 0–8), and 71% were males. Patients treated with ACL were older, with more respiratory comorbidities, a longer time since COPD diagnosis, worse forced expiratory volume in 1 second (% predicted), and with a higher rate of exacerbations during the previous year compared with TIO. It was found that 41.3% of patients with ACL and 62.3% of patients with TIO had no previous COPD treatment. Inhaled corticosteroid and long-acting β2-agonist were the most frequent concomitant medications (32.9% and 32.6%, respectively). Approximately 75% of patients were persistent with ACL or TIO at 3 months from the beginning of treatment, and more than 50% of patients remained persistent at 9 months.ConclusionPatients initiated with ACL had more severe COPD and were taking more concomitant respiratory medications than patients initiated with TIO. ACL was more frequently initiated as part of triple therapy, while TIO was more frequently initiated as monotherapy.