Objective To investigate the occurrence and influencing factors of carotid atherosclerosis (CAS) in the elderly patients with obstructive sleep apnea hypopnea syndrome (OSAHS)-related hypertension. Methods A total of 1 290 consecutive elderly patients (≥60 years old) with polysomnography-diagnosed OSAHS admitted from January 2015 to October 2017 were enrolled in this multi-center study. After exclusion of secondary hypertension caused by diabetes, other causes and serious cardiovascular and cerebrovascular diseases (such as atrial fibrillation, heart failure and stroke), 755 elderly OSAHS patients were finally included. According to whether they met the OSAHS related hypertension diagnostic criteria formulated by the Chinese Medical Doctor Association in 2012, they were divided into hypertension group (n=415) and non-hypertension group (n=340). Based on the occurrence of CAS or not, those patients were further assigned into CAS subgroup (n=74) and non-CAS subgroup (n=341). The demographic characteristics, sleep parameters, blood biochemical and blood routine indexes and medical history were compared between the 2 groups. SPSS statistics 20.0 was used for data analysis. Spearman correlation analysis and logistic regression analysis were employed to explore the influencing factors for CAS in elderly patients with OSAHS-related hypertension. Results The incidence of CAS was significantly higher in elderly OSAHS-related hypertension patients than the non-hypertension group [17.8% (74/415) vs 12.1% (41/340); P<0.05], the incidence was also higher in the female OSAHS-related hypertension patients than the male ones[21.0% (34/162) vs 15.8% (40/253); P<0.05], and the prevalence was mainly concentrated in the patients aged 70~80 years, followed by those of 60~70 and ≥80 years old [29.7% (30/101) vs 13.9% (41/296) and 16.7% (3/18); P<0.05]. Age, body mass, body mass index (BMI), waist circumference, smoking history, drinking history, systolic blood pressure, total sleep time (TST), mean pulse oxygen saturation (MSpO₂), triglyceride, creatinine, uric acid, mean corpuscular hemoglobin concentration (MCHC), platelet count (PLT), white blood cell count (WBC), peptic ulcer and chronic obstructive pulmonary disease (COPD) differed between the CAS subgroup and non-CAS subgroup (all P<0.05). Spearman correlation analysis showed that age, smoking history, drinking history, systolic blood pressure, TST, gastroesophageal reflux disease, peptic ulcer and COPD were positively correlated with CAS in elderly patients with OSAHS-related hypertension (r=0.158,0.185,0.237,0.108,0.116,0.104,0.147,0.266; P<0.05), while, body weight, BMI, waist circumference, MSpO₂, triglycerides, creatinine, uric acid, MCHC, PLT and WBC were negatively correlated (r=-0.206, -0.210, -0.110, -0.263, -0.144, -0.166, -0.175, -0.205, -0.211, -0.100; P<0.05). Logistic regression analysis indicated that BMI, smoking history, drinking history, systolic blood pressure, MSpO2 and creatinine were independent influencing factors of CAS in elderly patients with OSAHS related hypertension (OR=0.811,3.243,3.271,1.020,0.810,0.978; P<0.05). Conclusion The elderly patients with OSAHS-related hypertension have generally high prevalence of CAS, and it is more common in those aged 70-80 years and in women than men. Smoking history, drinking history and systolic blood pressure are independent risk factors for CAS, while BMI, MSpO₂ and creatinine concentration are independent protective factors in the population.