Comorbidities of patients in tiotropium clinical trials: comparison with observational studies of patients with chronic obstructive pulmonary disease

Acknowledgments The authors are fully responsible for all content and editorial decisions made, were involved at all stages of manuscript development, and have approved the final version for publication. Editorial assistance, supported financially by Boehringer Ingelheim and Pfizer, was provided by Godfrey Lisk of PAREXEL International during the preparation of this manuscript. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution - Non Commercial (unported, v3.0) License. The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. Permissions beyond the scope of the License are administered by Dove Medical Press Limited.