Diabetes and Lung Function: Response

Abstract

In response to the letter from Ahmad et al, we would like to clarify how we carefully dealt with BMI in our metaanalysis on pulmonary function in diabetes in our recent article in CHEST (August 2010).1van den Borst B Gosker HR Zeegers MP Schols AM Pulmonary function in diabetes: a metaanalysis.Chest. 2010; 138: 393-406Abstract Full Text Full Text PDF PubMed Scopus (155) Google Scholar All the studies we included in our metaanalysis had a control group, and in almost every study BMI was already closely matched between the diabetes patients and control subjects by the original authors. Still, to exclude the potential influence of a relatively small difference in mean BMI between diabetes patients and control subjects, we analyzed whether the delta of the mean BMI between the groups was a source for between-study heterogeneity, which was proven not to be the case. Therefore, we concluded that the observed differences in pulmonary function indices between diabetes patients and controls were independent of BMI. This finding from our quantitative review is also supported by a recent narrative systematic review on pulmonary function specifically in type 2 diabetes.2Klein OL Krishnan JA Glick S Smith LJ Systematic review of the association between lung function and Type 2 diabetes mellitus.Diabet Med. 2010; 27: 977-987Crossref PubMed Scopus (147) Google Scholar Ahmad et al directly link the lower pulmonary function in type 2 diabetes patients to systemic inflammation, for which no direct evidence exists. To the contrary, as we discussed, two large studies that sought a systemic inflammatory explanation for lower pulmonary function in diabetes failed to provide significant findings.3Yeh HC Punjabi NM Wang NY et al.Cross-sectional and prospective study of lung function in adults with type 2 diabetes: the Atherosclerosis Risk in Communities (ARIC) study.Diabetes Care. 2008; 31: 741-746Crossref PubMed Scopus (183) Google Scholar, 4Lee HM Le TV Lopez VA Wong ND Association of C-reactive protein with reduced forced vital capacity in a nonsmoking U.S. population with metabolic syndrome and diabetes.Diabetes Care. 2008; 31: 2000-2002Crossref PubMed Scopus (19) Google Scholar It has yet to be elucidated whether the subclinically lower lung function associated with diabetes indeed forms a risk of progressive decline. Diabetes and Lung Function: Part of a Wider SpectrumCHESTVol. 139Issue 1PreviewThe metaanalysis by van den Borst et al1 in a recent issue of CHEST (August 2010) importantly provided further indication that, similar to the cardiovascular system, the lung is a target organ in the systemic inflammatory process among subjects with type 2 diabetes. The International Diabetes Association suggests that 80% of these patients are overweight or obese, and because there is already a well-established relationship between obesity and abnormal lung function, the findings reported are not unexpected. Full-Text PDF