Weight reduction drives improvement in insulin resistance independent of OSA phenotype and CPAP treatment in the RICCADSA cohort

Abstract

Insulin resistance is common in adults with obstructive sleep apnoea (OSA), yet the extent to which longitudinal metabolic improvement is driven by OSA phenotype, continuous positive airway pressure (CPAP) treatment, or changes in body weight remains unclear. We examined 1-year changes in insulin resistance across OSA and non-OSA subgroups in the non-diabetic RICCADSA cohort. Methods In the RICCADSA study, non-diabetic participants (n = 332) were categorized into four predefined subgroups: non-sleepy OSA randomized to CPAP (n = 72), non-sleepy OSA randomized to no CPAP (n = 81), sleepy OSA treated with CPAP (n = 98), and non-OSA controls (n = 81). Insulin resistance was assessed using log-transformed homeostasis model assessment of insulin resistance (ln-HOMA-IR) at baseline and 12 months. Longitudinal changes were analysed using linear mixed-effects models including subgroup, time, and subgroup-by-time interaction, with adjustment for age, sex, body mass index (BMI), hypertension, and cardiovascular medications. Secondary linear regression analyses were performed to identify independent predictors of change in insulin resistance (Δln-HOMA-IR). Results Ln-HOMA-IR decreased significantly over time across the entire cohort (p