sentence: Patient informed consent was not required because the study used retrospective de-identified data.The prespecified study period ranged from 1 April 2015 to 31 March 2019 ( Fig. 1 ) and included the cohort entry date ( index date ; first prescription for fixed-dose tiotropium / olodaterol [ Spiolto ® Respimat ® , Boehringer Ingelheim International GmbH , Ingelheim , Germany ] or tiotropium monotherapy administered as an inhalation Soft mist inhaler or powder [ Spiriva ® Respimat ® or Spiriva ® Handihaler ® , Boehringer Ingelheim International GmbH , Ingelheim , Germany ] ) , a 180-day baseline period ( ie , 180 days before the cohort entry date and at least 180 days after approval of fixed-dose tiotropium / olodaterol ) , and a follow-up period , starting at the second prescription for tiotropium / olodaterol or tiotropium within 60 days of the first prescription and ending at the earliest use of any triple therapy , patient death , discontinuation , end of the study period , or a maximum follow-up of 1 year , whichever occurred first .