Aims: To describe the association between lung function and Type 2 diabetes mellitus.
Methods: We identified English language studies evaluating the association between lung function and diabetes mellitus in the MEDLINE database from 1 January 1975 to 31 December 2009. We evaluated study quality based on established criteria (54 studies were reviewed, 34 met the inclusion criteria).
Results: Cross-sectional studies showed that adults with diabetes mellitus have lower forced vital capacity (FVC) and forced expiratory volume in one second (FEV1), with reductions in FVC more consistent than FEV1 and lower diffusion capacity (DLCO) compared with their non-diabetic counterparts. The reduced lung function in patients with diabetes is inversely related to blood glucose levels, duration of diabetes and its severity and is independent of smoking or obesity. Findings in cohort studies have been less consistent, with only a few studies identifying an increased rate of lung function decline in adults with diabetes. In addition, other cohort studies have reported an association between decreased lung function and incident insulin resistance and diabetes. Studies evaluating biological mechanisms to explain the association between lung impairment and diabetes identified microangiopathy of the alveolar capillaries and pulmonary arterioles, chronic inflammation, autonomic neuropathy involving the respiratory muscles, loss of elastic recoil secondary to collagen glycosylation of lung parenchyma, hypoxia-induced insulin resistance and low birthweight, as being associated with both insulin resistance and impaired lung function.
Conclusions: There is an association between diabetes mellitus and decreased lung function, but the definitive direction as well as the exact pathophysiological mechanism to explain this association requires further investigation.