Type 2 diabetes impairs pulmonary function in morbidly obese women: a case-control study

To determine whether the presence of type 2 diabetes and the degree of metabolic control are related to reduced pulmonary function in obese individuals. Seventy-five morbidly obese women (25 with type 2 diabetes [cases]-and 50 without diabetes [controls]) with a history of non-smoking and without prior cardiovascular or respiratory disease were prospective recruited for a case-control study in the outpatient obesity unit of a referral centre. Both groups were closely matched by age, BMI and waist circumference. Pulmonary function test included forced spirometry and static pulmonary volume measurements. Type 2 diabetic patients showed lower forced expiratory volume at 1 s (FEV1) (mean difference -11.6% of predicted [95% CI -20.4 to -2.8]; p = 0.011), and FEV1/forced vital capacity (FEV1/FVC) ratio (mean difference -4.4% [95% CI -8.1 to -0.7]; p = 0.049), but a greater residual volume (RV) (mean difference 19.5% of predicted [95% CI 10.8-28.3]; p < 0.001). In addition, an obstructive ventilatory pattern was more frequent in diabetic patients. Significant negative correlations between FEV1 and fasting glucose, HbA(1c) and HOMA insulin resistance (HOMA-IR) were detected. By contrast, RV was positively correlated with fasting glucose, HbA(1c) and HOMA-IR. Multiple linear regression analyses showed that fasting glucose and HbA(1c) independently predicted FEV1 and RV. The presence of diabetes and the degree of glycaemic control are related to respiratory function impairment in morbidly obese women. Therefore, the impact of type 2 diabetes on pulmonary function should be taken into consideration by those providing care for obese people.