Pulmonary Function in Adults With Type 2 Diabetes With and Without Obesity

Background

Existing reports show a bidirectional association between type 2 diabetes (T2D) and pulmonary dysfunction. Obesity, which is causally related to both T2D and pulmonary dysfunction, could play an important role in this association. However, this has not been reported.

Research Question

What are the associations of measures of obesity with pulmonary function in T2D?

Study Design and Methods

This was a cross-sectional study among 464 adults with T2D. Spirometry was performed according to the American Thoracic Society/European Respiratory Society guidelines. The predicted values of the spirometric indices were determined using the Global Lung Function Initiative 2012 equations. The values of FEV₁/FVC and FVC were used to categorize pulmonary function patterns as normal, obstructive, restrictive, or mixed. Waist circumference (WC) was measured at the midpoint between the lower margin of the lowest palpable rib and the top of the iliac crest.

Results

The mean age, diabetes duration, and female/male ratio of the participants were 55.09 ± 10.45 years, 10.00 ± 7.36 years, and 2:1, respectively. In a multiple linear regression model, WC was a significant predictor of FVC (P = .018) and FEV₁/FVC ratio (P = .005), but not FEV₁ (P = .472). BMI was a significant predictor of FEV₁/FVC ratio (P = .031), but not FEV₁ (P = .802) or FVC (P = .129). In a multivariable logistic regression model adjusted for age, sex, socioeconomic status, diabetes duration, glycated hemoglobin, statin use, and smoking pack-years, increasing z score WC was associated with higher odds of restrictive spirometry (OR, 1.32; 95% CI, 1.05-1.66; P = .019) but not airway obstruction (OR, 0.65; 95% CI, 0.42-1.03; P = .067). There were no significant associations of increasing z score BMI with restrictive spirometry (OR, 1.24; 95% CI, 0.98-1.58; P = .075) or airway obstruction (OR, 0.79; 95% CI, 0.51-1.24; P = .305).

Interpretation

Increasing WC is associated with restrictive spirometry, independent of conventional diabetes and pulmonary risk factors. Future research could explore the role of the reversal of central obesity on pulmonary function in T2D.