Biochemical Correlates of the Respiratory Disturbance Index Among Patients With Obstructive Sleep Apnea in a Tertiary Care Setting

Abstract

Background: Obstructive Sleep Apnea (OSA) is marked by recurrent upper airway obstruction during sleep, leading to intermittent hypoxia and oxidative stress. The Respiratory Disturbance Index (RDI) a measure of OSA severity, may influence metabolic homeostasis through biochemical alterations. This study aimed to assess the biochemical profile of OSA patients and examine associations between RDI and biochemical parameters.

Materials and methods: A cross-sectional study was conducted at the Department of Respiratory Medicine, Bangladesh Medical University (BMU). Seventy-four OSA patients were included and categorized as severe OSA (RDI  ³30) and non-severe OSA (RDI <30). Ater overnight  fasting, venous blood samples were collected for Fasting Blood Glucose (FBG) serum lipid profile [Total cholesterol, triglycerides, Low Density Lipoprotein-Cholesterol (LDLC)  High Density Lipoprotein-Cholesterol (HDL-C)] serum creatinine, serum electrolytes, serum Alanine Aminotransferase (ALT) and calcium.

Results: Patients with RDI ³30 showed significantly higher FBG (120.2 vs. 110.4 mg/dl, p=0.016), triglycerides (257.1 vs. 204.6 mg/dl, p=0.002) LDL-C (159.8 vs. 130.4 mg/dl, p<0.001) and total cholesterol (276.9 vs. 195.8 mg/dl, p<0.001) along with elevated serum potassium (4.6 vs. 4.4 mmol/L, p=0.008) and calcium (8.8 vs. 8.5 mg/dl, p=0.013). HDL-C was lower in this group (37.9 vs. 39.9 mg/dl, p=0.056). RDI correlated positively with FBG (r=0.325, p=0.005), triglycerides (r=0.351, p=0.002) LDL-C (r=0.430, p<0.001) total cholesterol (r=0.588, p<0.001) potassium (r=0.315, p=0.006) and ALT (r=0.241, p=0.039). Regression analysis identified RDI as an independent predictor of fasting glucose (b=0.250, p=0.011), triglycerides (b=0.368, p=0.001), and LDL-C (b=0.382, p<0.001).

Conclusion: Higher RDI is strongly associated with dyslipidemia, hyperglycemia, and selected biochemical disturbances in OSA patients. RDI may serve as a predictor of metabolic dysfunction, emphasizing the importance of biochemical monitoring alongside respiratory evaluation.

JCMCTA 2026 ; 37 (1) : 32-37