Supplemental material, Reviewer_2,_v.1. for The impact of comorbidities on mortality among men and women with COPD: report from the OLIN COPD study by Sami Sawalha, Linnea Hedman, Helena Backman, Nikolai Stenfors, Eva Rönmark, Bo Lundbäck and Anne Lindberg in Therapeutic Advances in Respiratory Disease</p