Pulmonary-Glycemic Coupling: A Correlation Analysis Of Hba1c Thresholds And Forced Vital Capacity (FVC) In Asymptomatic Chronic Type 2 Diabetics: A Cross-Sectional Study In South India

Abstract

Background:Type 2 Diabetes Mellitus (T2DM) is increasingly recognized as a systemic disorder affecting multiple organs, including the lungs. Chronic hyperglycemia may induce pulmonary microangiopathy, connective tissue glycation, and reduced lung compliance, resulting in subclinical restrictive pulmonary dysfunction. However, limited data exist regarding the pulmonary-glycemic relationship among South Indian diabetic populations.

Objective:To evaluate the correlation between Glycated Hemoglobin (HbA1c) levels and Forced Vital Capacity (FVC) among asymptomatic chronic T2DM patients in South India.

Methods:This hospital-based cross-sectional observational study included 136 asymptomatic T2DM patients aged 30–65 years. Participants underwent anthropometric assessment, HbA1c estimation using High-Performance Liquid Chromatography (HPLC), and spirometric evaluation following ATS/ERS guidelines. Based on HbA1c levels, subjects were categorized into optimal (<7.0%), sub-optimal (7.1–8.5%), and poor control (>8.5%) groups. Pulmonary parameters including FVC, FEV1, FEV1/FVC ratio, and PEFR were recorded. Statistical analysis included One-way ANOVA, Pearson’s correlation, and multiple linear regression.

Results:Pulmonary function parameters progressively declined with worsening glycemic control. Mean FVC (% predicted) was significantly reduced in the poor glycemic control group compared to the optimal control group (78.5 ± 8.7 vs. 92.6 ± 8.4; p < 0.001). HbA1c demonstrated a significant negative correlation with FVC (r = -0.48, p < 0.001) and FEV1 (r = -0.44, p < 0.001). Multiple regression analysis identified HbA1c as an independent predictor of reduced FVC after adjusting for age, BMI, and disease duration.

Conclusion:Poor glycemic control is significantly associated with reduced pulmonary function among asymptomatic chronic T2DM patients, suggesting early subclinical restrictive lung involvement. Routine spirometric screening may aid in early detection of pulmonary impairment in diabetes.