Dual-pronged approach to diabetes and COPD needed

Researchers from the USA have found that patients with diabetes and a history of smoking have significantly impaired lung function, even in the absence of overt chronic obstructive pulmonary disease (COPD).

In such patients, the team observed decreases in almost all measures of pulmonary function alongside decreased exercise capacity and poorer quality of life, leading them to call for treatment approaches that tackle both diseases together.

The authors analyzed data from the COPDGene study on 4484 former and current smokers with COPD, 4388 smoking controls without COPD, and 1257 patients with unclassified spirometric abnormalities (reduced forced expiratory volume in 1 second [FEV1] but preserved FEV1 to forced vital capacity [FVC] ratio). Overall, 13%, 12%, and 22% from each group, respectively, had diabetes, and all participants had a minimum 10 pack–year smoking history.

FVC, FEV1% predicted, and FVC% predicted were all significantly lower, while the FEV1/ FVC ratio was significantly increased, in patients with diabetes overall, and in those with unclassified spirometric abnormalities and smoking controls with diabetes. Among those with COPD, FEV1 was unaffected by diabetes status; however, diabetes was related to FVC in Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 2 patients, with a reduction in FVC% predicted and a significant increase in FEV1/FVC seen in both GOLD stages 2 and 3 patients.

The team observed a significant decrease in distance achieved in the 6-minute walk test (6-MWT) in all patients with diabetes, at a mean reduction of 27.5 m compared with patients without the condition, a difference large enough to imply a significantly increased risk for death, they note.

They also report that patients with diabetes had significantly decreased quality of life by a mean of 3.3 points, measured on the St George’s Respiratory Questionnaire, except for those with GOLD stage 1 or 4 COPD.

“The overall picture of the effect of diabetes on pulmonary function is of small reductions exhibiting important effects on functional capacity and quality of life,” the authors, led by Gregory Kinney (University of Colorado, Denver), comment.

Writing in Diabetes Care, the team says the findings “underscore the importance of diabetes on the pulmonary system which may not be appreciated using spirometry alone.”

They suggest that performing an annual 6-MWT for smokers with diabetes could be a cost-effective method to identify clinically relevant lung function impairment in such patients.

“Additional work is needed to understand the influence of the biological pathways linking diabetes and reduced pulmonary function in order to identify appropriate treatments that consider both diabetes and COPD,” they conclude.

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