Objective To explore the effect of obesity on obstructive sleep apnea (OSA) combined with hypertension and the associated risks, to clarify the value of different obesity assessment indicators (body mass index BMI, neck circumference NC, waist circumference WC, body fat percentage BF%, and visceral adiposity index VAI) in predicting hypertension risk in OSA patients, and to provide regional evidence for hypertension risk stratification of OSA patients in Southwest China.

Methods A total of 299 OSA patients were enrolled at the Sleep Medicine Center, West China Fourth Hospital, Sichuan University in 2024. The participants were divided into a simple OSA group (179 cases) and a group of those with OSA combined with hypertension (120 cases) according to their hypertension diagnosis. Logistic regression was performed to assess the risk association between obesity indicators and OSA combined with hypertension. Receiver operating characteristic (ROC) curves were plotted to evaluate the predictive performance of each indicator, and age stratification (≤ 45 years or > 45 years) was performed to analyze risk differences.

Results Significant differences were observed between the two groups (the OSA combined with hypertension group and the OSA-only group) in terms of age (the proportion of middle-aged and older adults, 65.0% and 38.5%, respectively), educational attainment (high school or below, 37.5% and 22.9%, respectively), and family history of hypertension (60.0% and 33.0%, respectively) (P < 0.01). All obesity indicators were positively correlated with the risk of OSA combined with hypertension, with progressively increasing risk observed across higher indicator categories. VAI exhibited the most pronounced risk gradient: the risk for participants with VAI ≥ P₇₅ was 45.96 times that for those with VAI < P₂₅ (odds ratio OR = 45.96, 95% CI: 15.46-136.59), and the risk for participants with VAI between P₅₀ and P₇₅ was 8.06 times that for those with VAI < P₂₅ (OR = 8.06, 95% CI: 2.86-22.73). VAI demonstrated the best predictive performance (area under the curve AUC = 0.856; 95% CI: 0.819-0.893), outperforming traditional indicators (AUC_BMI = 0.821, 95% CI: 0.782-0.860; AUC_WC = 0.799, 95% CI: 0.760-0.838). The hypertension risk associated with each obesity indicator in the middle-aged and older adult group was higher than that in the younger group.

Conclusion Obesity is a key risk factor for OSA combined with hypertension. VAI demonstrates the best predictive performance for the risk of OSA combined with hypertension and can be used as a priority indicator for hypertension screening in OSA patients in Southwest China. Age and obesity indicators exhibit a cumulative risk effect, which highlights the need to strengthen obesity management in middle-aged and older populations with OSA.