Comparative study of spirometry parameters in chronic smokers with and without Type 2 Diabetes Mellitus (T2DM)

The study aimed to know the changes in spirometry parameters in chronic smokers and evaluate how the presence of type 2 diabetes mellitus (T2DM) affects their lung function.

A prospective, cross-sectional, observational study was done for 12 months at a tertiary care hospital in the western region of Maharashtra State in India. Two groups of patients and one group of healthy volunteers aged 18 years or more were studied (with 50 in each group, n = 150). Group A consisted of smokers with T2DM, Group B- smokers without T2DM and Group 3- healthy controls who were non-smokers and non-diabetic. Spirometry was done for the following parameters: forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), FEV1/FVC ratio, and peak expiratory flow (PEF) and results compared between the three groups.

The mean age of the participants was 51.13 ± 10.74 years. There were 137 (91.3%) males and 13 (8.6%) females. Among the enrolled subjects, 66% had smoked for more than ten years. All spirometry parameters were significantly different across all three groups. When the spirometry parameters were compared between smokers with and without T2DM, all the parameters were significantly decreased (P < 0.05). FEV1 and FEV1/FVC were significantly decreased in T2DM patients with HbA1c >7%.

The presence of T2DM in smokers significantly affects their pulmonary function tests. Uncontrolled T2DM (HbA1c >7%) can result in increased abnormality in the spirometry parameters studied. Thus, adequate glycemic control and cessation of smoking can be beneficial for the improvement of lung functions in smokers.