Type 2 diabetes: a protective factor for COPD?

BACKGROUND: Chronic obstructive pulmonary disease (COPD) and type 2 diabetes (T2DM) are common comorbidities. COPD is a known risk factor for incident T2DM, however few studies have examined the relationship in reverse. The primary aim of this study was to compare the incidence of COPD in people with and without T2DM. MATERIALS AND METHODS: We conducted a retrospective case-control study using a long-established English general practice network database (n=894,646). We matched 29,217 cases of T2DM with controls, adjusting for age, gender, smoking status, BMI and social deprivation, to achieve 1:1 propensity matching and compared the rate of incident COPD over eight years of follow-up. We performed a secondary analysis to investigate the effect of insulin, metformin and sulphonylureas on COPD incidence. RESULTS: People with T2DM had a reduced risk of COPD compared to matched controls over the follow-up period (HR 0.89, 95%CI 0.79-0.93). 48.5% of those with T2DM were ex-smokers compared with 27.3% of those without T2DM. Active smoking rates were 20.4% and 23.7% respectively. Insulin, metformin and sulphonylureas were not associated with incident COPD. CONCLUSIONS: People with T2DM are less likely to be diagnosed with COPD than matched controls. This may be due to positive lifestyle changes, such as smoking cessation in those with T2DM.