Purpose <p>Currently, there is a lack of early biomarkers to identify the risk of dysglycemia in patients with concurrent hypertension and obstructive sleep apnea (OSA). The aim of our study is to evaluate the efficacy of the recently proposed Body Mass Index (BMI)-Glucose (ByG) index in identifying the risk of dysglycemia in patients with hypertension and OSA.</p> Methods <p>A retrospective cohort study of 1,759 adults with hypertension and OSA from the Urumqi Research on Sleep Apnea and Hypertension study (UROSAH) was conducted. Cox proportional hazards models were used to assess the associations between the ByG index and new-onset dysglycemia, diabetes, and prediabetes. Time-dependent receiver operating characteristic (ROC) curves were constructed to compare the efficacy of the ByG index with traditional insulin resistance indicators.</p> Results <p>During a median follow-up of 7.25 years, 212 cases of dysglycemia (157 diabetes, 55 prediabetes) were identified. Participants in the highest ByG tertile had a significantly increased risk of dysglycemia (HR 3.20; 95% CI: 2.13–4.80), diabetes (HR 3.38; 95% CI: 2.02–5.66), and prediabetes (HR 2.95; 95% CI: 1.44–6.06) compared to the lowest tertile, after full adjustment. Time-dependent ROC showed the ByG index was more discriminative in predicting dysglycemia (including diabetes and prediabetes) events at 3, 5 and 7 years compared to BMI, TyG, TyG-BMI indices, waist circumference, and waist-to-height ratio.</p> Conclusion <p>The ByG index serves as an independent predictor of dysglycemia, encompassing diabetes and prediabetes, among patients with hypertension and OSA. As a simple, accessible, and reliable tool for early risk stratification, it demonstrates application potential but requires validation through prospective studies.</p> Trial registration <p>Not applicable.</p>