Decline of the lung function and quality of glycemic control in type 2 diabetes mellitus

Objective: The aim of this study was to verify to which extent in type 2 diabetes mellitus respiratory function and respiratory muscle efficiency decline over time in relation to the quality of glycemic control (GC).

Methods: Forty-five non-smoker diabetic patients without pulmonary diseases performed a complete respiratory function assessment at baseline and after a follow-up of 4.9±0.6 years. The respiratory muscle efficiency was assessed by maximal inspiratory pressure (MIP) and maximum voluntary ventilation (MVV). Patients with an average yearly value of glycosylated hemoglobin≥7.5% at least in two years during follow-up were considered to have a poor GC.

Results: Residual volume and pulmonary diffusing capacity significantly declined over time in the whole sample of patients (p=0.049 and 0.025, respectively), but without difference between patients with poor (n. 12) and good (n. 33) GC. MIP declined in patients with poor GC (from 83.75±32.42 to 71.16±30.43% pred), and increased in those with good GC (from 76.22±26.00 to 82.42±30.34% pred), but the difference between groups was not significant (p=0.091). Finally, MVV significantly declined in patients with poor GC (from 70.60±25.49 to 68.10±18.82% pred) and increased in those with good GC (from 66.40±20.39 to 84.00±23.09% pred) with a significant difference between the two groups (p=0.003).

Conclusion: These results show that, in type 2 diabetic patients, respiratory muscle efficiency, but not lung volumes and diffusing capacity, might suffer from a poor GC over time.