Background: Inhaled corticosteroid (ICS) used in chronic obstructive pulmonary disease (COPD) is linked to an increased risk of pneumonia.

Aims and objectives: To identify clusters within ICS treatment and pneumonia in patients with COPD.

Methods: A register-based cohort study using nationwide Danish registers. We included all patients ?40 years of age with an ICD-10 diagnosis J44 and a first-time registration of pulmonary function (index date) in the Danish register for COPD between 2008 and 2015. Patients were followed for 3 years, and we identified clusters using sequence analysis (SA) with four possible monthly states (dead, pneumonia, ICS, no ICS).

Results: We included 44.912 patients and identified eight clusters (3 manually gathered, and 5 using SA). Cluster 1 (n=7.135): Patients who received no ICS treatment and had infrequent pneumonia. Cluster 2 (n=1.800): Patients who discontinued ICS treatment during follow-up. Cluster 3 (n=924): Patients who initiated ICS treatment during follow-up. Cluster 4 (n=13.981): Patients in constant ICS treatment and with infrequent pneumonia. Cluster 5 (n=5.310): Patients in constant ICS treatment and with frequent pneumonia. Manually gathered clusters were patients who had the state of ?ICS? (n=1.958) or ?no ICS? (n=2.067) in all months, and patients who died during follow-up (n=11.737).

Conclusions: We have identified distinct clusters of patients with COPD based on ICS treatment patterns and pneumonia incidence. Of special interest for further exploration is cluster 4 (patients in constant ICS treatment and with infrequent pneumonia) and 5 (Patients in constant ICS treatment and with frequent pneumonia).