Background and Objectives Obstructive sleep apnea (OSA) is an independent risk factor for stroke. Furthermore, intracranial arterial calcification (IAC) has been validated as a marker for subclinical cerebrovascular disease. However, the relationship between OSA with IAC was less studied compared with its established association with coronary artery calcification (CAC). In this study, we aimed to investigate the association between the severity of OSA and the degree of IAC in hospitalized patients without pre-existing cardiovascular disease. Methods This hospital-based observational study was conducted from June 1, 2017, to May 1, 2019. In total, 901 consecutive patients who underwent head computed tomography (CT) scans and portable sleep monitoring were included. Based on the apnea-hypopnea index (AHI), patients were divided into four OSA severity groups (normal: AHI <5/h; mild: 5≤ AHI <15/h; moderate: 15≤ AHI <30/h; severe: AHI ≥30/h). Associations of OSA with IAC scores were assessed by using multivariate logistic regression analysis. Results Of the 901 patients, 484 (53.7%) were men; the mean (SD) age was 66.1 (10.0) years. The non-OSA group included 207 (23.0%) patients; mild OSA, 209 (23.2%); moderate OSA, 235 (26.1%); and severe OSA, 169 (18.8%). Mean IAC scores were higher in the severe OSA group compared with non, mild, and moderate OSA groups (4.79 vs. 2.58; 4.79 vs. 2.94; 4.79 vs. 3.39, p<0.001). Multivariate analysis adjusted for confounding factors revealed that only severe OSA was associated with a higher IAC score (odds ratio [OR] 1.65; 95% confidence interval [CI], 1.43-1.91; p<0.001). In stratified analyses by BMI, among participants with a BMI <25kg/m2, the positive association between AHI values and IAC scores was found in the moderate OSA group (OR, 1.23; 95% CI 1.05, 1.43, p=0.01) and severe OSA group (OR, 1.96; 95% CI 1.55, 2.48, p<0.001). When stratified by gender, in women, the positive association was found in moderate OSA group (adjusted OR=1.21, 95% CI: 1.02-1.51, p=0.016) and severe OSA group (adjusted OR=1.76, 95% CI: 1.36-2.25, p<0.001). For the men group, a positive association between IAC scores and AHI was only observed in the severe OSA group. Discussion These findings suggest that OSA, in particular severe OSA (AHI ≥ 30), is independently associated with higher IAC scores. Women and no-obesity individuals appeared more susceptible to adverse OSA-related subclinical cerebrovascular disease as measured by IAC scores.The Author(s). Published by S. Karger AG, Basel.