The Correlation between Red Blood Cell Distribution Width Level and Hypertension in Patients with Obstructive Sleep Apnea

Abstract

Background Hypertension and obstructive sleep apnea (OSA) often coexist, posing challenges in the management of blood pressure in these patients. A reliable and objective predictor is needed to anticipate the occurrence of hypertension and assess the status of blood pressure control in OSA patients, which would facilitate their blood pressure management. Objective To explore the correlation between red blood cell distribution width (RDW) and hypertension in patients with OSA. Methods A retrospective study was conducted at the Sleep Center of Peking University International Hospital, involving 510 patients who were diagnosed with OSA using polysomnography between January 2019 and September 2022. The derivation cohort comprised of 370 enrolled patients between January 2019 and December 2021, while the validation cohort included the remaining 140 patients enrolled between January and September 2022. Within the derivation cohort, patients were categorized into two groups based on their adherence to the definition of hypertension: hypertension group (n=211) and non-hypertension group (n=159). Subsequently, the hypertension group was further divided into two subgroups: blood pressure control subgroup (n=107) and blood pressure uncontrolled subgroup (n=104). The clinical characteristics and laboratory examination results of patients in the hypertension group and non-hypertension group, as well as those in the blood pressure control subgroup and blood pressure uncontrolled subgroup, were analyzed. Univariate and multivariate Logistic regression analyses were employed to investigate the predictors of hypertension in OSA patients and the status of blood pressure control in OSA patients with combined hypertension. The receiver operating characteristic (ROC) curve was plotted to evaluate the sensitivity and specificity of RDW in predicting the occurrence of hypertension among OSA patients, with its validity confirmed in the validation cohort. Results The multivariate Logistic regression analysis revealed that an increased BMI (OR=1.087, 95%CI=1.007-1.174, P=0.032), diabetes (OR=3.310, 95%CI=1.484-7.380, P=0.003), and a decreased RDW (OR=0.598, 95%CI=0.507-0.704, P<0.001) were independent predictors of hypertension in OSA patients. Furthermore, an increased hemoglobin level (OR=1.027, 95%CI=1.005-1.050, P=0.016) and a decreased RDW (OR=0.804, 95%CI=0.669-0.965, P=0.019) were identified as independent predictors of poor blood pressure control status in OSA patients with combined hypertension. The results of ROC curve analysis for RDW in predicting hypertension in OSA patients showed that the area under the ROC curve was 0.779 (95%CI=0.732-0.826, P<0.001), with an optimal cut-off value identified at 39.9 fL. Considering the clinical usability, when using an RDW≤40 fL as the threshold value, the sensitivity and specificity for predicting hypertension in OSA patients were 70.14% and 81.76%, respectively. The validation cohort, utilizing an RDW cutoff value of ≤40 fL, demonstrated that RDW predicted the hypertension in OSA patients with a sensitivity of 63.64% and a specificity of 80.95%. The area under the ROC curve was 0.757 (95%CI=0.678-0.835, P<0.001) . Conclusion The reduction of RDW is associated with the occurrence of hypertension and poor blood pressure control status in patients with OSA. OSA patients exhibiting decreased RDW level are at an elevated risk for hypertension.

Keywords

• sleep apnea, obstructive|hypertension|red cell distribution width|forecast|correlation