Association between type 2 diabetes, prediabetes and lung function: Results from the KORA cohort

Some of the available data indicate a tendency towards reductions of lung volumes and CO diffusing capacity (TLCO) in lung-healthy subjects with type 2 diabetes (T2D). Whether such changes occur already in prediabetes (PD) patients, is unknown. We therefore examined the association of both T2D and PD with lung function in a population-based sample. Spirometric indices, TLCO and alveolar volume (VA) were determined in 1628 adults (48-93y; 49% male). The presence and duration of T2D were determined via questionnaires. In participants aged 48-68y, additionally the presence of PD (WHO 1999) was assessed via an oral glucose tolerance test. The association of lung function with T2D/PD was quantified by regression models adjusting for anthropometric measures. Compared to subjects with normal glucose tolerance, those with T2D or PD had lower values of FEV₁ (∆=-0.12L; -0.09L; p<0.05 each) and FVC (∆=-0.16L; -0.14L; p<0.05 each), while FEV₁/FVC was not different. TLCO, TLCO/VA and VA were reduced in T2D, reaching statistical significance in participants aged 60-74y (∆=-0.36mmol/min/kPa; -0,06mmol/min/kPa/L; -0.16L; p<0.05 each). T2D subjects with diabetes duration of ≥10y showed lower values of FVC, FEV₁ and TLCO (∆=-0.33L; -0.26L; -0.37mmol/min/kPa; p<0.05 each) compared to those with duration <10y. Even patients with PD showed a slight reduction in lung volumes, without signs of airflow obstruction, while TLCO was reduced only in T2D patients. This suggests subtle mechanical alterations in the lung periphery early in the development of diabetes, prior to effects on the pulmonary capillary bed. Such changes, however, may be detectable by more sensitive methods than standard CO diffusing capacity.